Glossary of Environmental Health & Safety Terms
Click here for EHSO's Acronym's List
This page has a master list, in alphabetical order of U.S. EPA Terminology
with an explanation or definition of each.
Click here to search on a keyword (i.e., pollution) or text string (i.e., regulated substance) in either the term or definition.
- Abandoned Well: A well whose use has been permanently
discontinued or which is in a state of such disrepair that it cannot be used
for its intended purpose.
Abatement: Reducing the degree or intensity of, or eliminating,
Abatement Debris: Waste from remediation activities.
Absorbed Dose: In exposure assessment, the amount of a substance
that penetrates an exposed organism's absorption barriers (e.g. skin, lung
tissue, gastrointestinal tract) through physical or biological processes.
The term is synonymous with
Absorption: The uptake of water , other fluids, or dissolved
chemicals by a cell or an organism (as tree roots absorb dissolved nutrients
Absorption Barrier: Any of the exchange sites of the body that
permit uptake of various substances at different rates (e.g. skin, lung
tissue, and gastrointestinal-tract wall)
Accident Site: The location of an unexpected occurrence, failure
or loss, either at a plant or along a transportation route, resulting in a
release of hazardous materials.
Acclimatization: The physiological and behavioral adjustments of
an organism to changes in its environment.
Acid: A corrosive solution with a pH less than 7.
Acid Aerosol: Acidic liquid or solid particles small enough to
become airborne. High concentrations can irritate the lungs and have been
associated with respiratory diseases like asthma.
Acid Deposition: A complex chemical and atmospheric phenomenon
that occurs when emissions of sulfur and nitrogen compounds and other
substances are transformed by chemical processes in the atmosphere, often
far from the original sources, and then deposited on earth in either wet or
dry form. The wet forms, popularly called "acid rain," can fall to earth as
rain, snow, or fog. The dry forms are acidic gases or particulates.
Acid Mine Drainage: Drainage of water from areas that have been
mined for coal or other mineral ores. The water has a low pH because of its
contact with sulfur-bearing material and is harmful to aquatic organisms.
Acid Neutralizing Capacity: Measure of ability of a base (e.g.
water or soil) to resist changes in pH.
Acid Rain: (See:
Acidic: The condition of water or soil that contains a sufficient
amount of acid substances to lower the pH below 7.0.
Action Levels: 1. Regulatory levels recommended by EPA for
enforcement by FDA and USDA when pesticide residues occur in food or feed
commodities for reasons other than the direct application of the pesticide.
As opposed to "tolerances" which are established for residues occurring as a
direct result of proper usage, action levels are set for inadvertent
residues resulting from previous legal use or accidental contamination. 2.
In the Superfund program, the existence of a contaminant concentration in
the environment high enough to warrant action or trigger a response under
SARA and the National Oil and Hazardous Substances Contingency Plan. The
term is also used in other regulatory programs. (See:
Activated Carbon: A highly adsorbent form of carbon used to remove
odors and toxic substances from liquid or gaseous emissions. In waste
treatment, it is used to remove dissolved organic matter from waste drinking
water. It is also used in motor vehicle evaporative control systems.
Activated Sludge: Product that results when primary effluent is
mixed with bacteria-laden sludge and then agitated and aerated to promote
biological treatment, speeding the breakdown of organic matter in raw sewage
undergoing secondary waste treatment.
Activator: A chemical added to a pesticide to increase its
Active Ingredient: In any pesticide product, the component that
kills, or otherwise controls, target pests. Pesticides are regulated
primarily on the basis of active ingredients.
Activity Plans: Written procedures in a school's
asbestos-management plan that detail the steps a Local Education Agency
(LEA) will follow in performing the initial and additional cleaning,
operation and maintenance-program tasks; periodic surveillance; and
reinspection required by the Asbestos Hazard Emergency Response Act (AHERA).
Acute Effect: An adverse effect on any living organism
which results in severe symptoms that develop rapidly; symptoms often
subside after the exposure stops.
Acute Exposure: A single exposure to a toxic substance which may
result in severe biological harm or death. Acute exposures are usually
characterized as lasting no longer than a day, as compared to longer,
continuing exposure over a period of time.
Acute Toxicity: The ability of a substance to cause severe
biological harm or death soon after a single exposure or dose. Also, any
poisonous effect resulting from a single short-term exposure to a toxic
substance. (See: chronic
Adaptation: Changes in an organism's physiological structure or
function or habits that allow it to survive in new surroundings.
Add-on Control Device: An air pollution control device such as
carbon absorber or incinerator that reduces the pollution in an exhaust gas.
The control device usually does not affect the process being controlled and
thus is "add-on" technology, as opposed to a scheme to control pollution
through altering the basic process itself.
Adequately Wet: Asbestos containing material that is sufficiently
mixed or penetrated with liquid to prevent the release of particulates.
Administered Dose: In exposure assessment, the amount of a
substance given to a test subject (human or animal) to determine
dose-response relationships. Since exposure to chemicals is usually
inadvertent, this quantity is often called potential dose.
Administrative Order: A legal document signed by EPA directing an
individual, business, or other entity to take corrective action or refrain
from an activity. It describes the violations and actions to be taken, and
can be enforced in court. Such orders may be issued, for example, as a
result of an administrative complaint whereby the respondent is ordered to
pay a penalty for violations of a statute.
Administrative Order On Consent: A legal agreement signed by EPA
and an individual, business, or other entity through which the violator
agrees to pay for correction of violations, take the required corrective or
cleanup actions, or refrain from an activity. It describes the actions to be
taken, may be subject to a comment period, applies to civil actions, and can
be enforced in court.
Administrative Procedures Act: A law that spells out procedures
and requirements related to the promulgation of regulations.
Administrative Record: All documents which EPA considered or
relied on in selecting the response action at a Superfund site, culminating
in the record of decision for remedial action or, an action memorandum for
Adsorption: Removal of a pollutant from air or water by collecting
the pollutant on the surface of a solid material; e.g., an advanced method
of treating waste in which activated carbon removes organic matter from
Adulterants: Chemical impurities or substances that by law do not
belong in a food, or pesticide.
Adulterated: 1. Any pesticide whose strength or purity falls below
the quality stated on its label. 2. A food, feed, or product that contains
illegal pesticide residues.
Advanced Treatment: A level of wastewater treatment more stringent
than secondary treatment; requires an 85-percent reduction in conventional
pollutant concentration or a significant reduction in non-conventional
pollutants. Sometimes called
Advanced Wastewater Treatment: Any treatment of sewage that goes
beyond the secondary or biological water treatment stage and includes the
removal of nutrients such as phosphorus and nitrogen and a high percentage
of suspended solids. (See
Adverse Effects Data: FIFRA requires a pesticide registrant to
submit data to EPA on any studies or other information regarding
unreasonable adverse effects of a pesticide at any time after its
Advisory: A non-regulatory document that communicates risk
information to those who may have to make risk management decisions.
Aerated Lagoon: A holding and/or treatment pond that speeds up the
natural process of biological decomposition of organic waste by stimulating
the growth and activity of bacteria that degrade organic waste.
Aeration: A process which promotes biological degradation of
organic matter in water. The process may be passive (as when waste is
exposed to air), or active (as when a mixing or bubbling device introduces
Aeration Tank: A chamber used to inject air into water.
Aerobic: Life or processes that require, or are not destroyed by,
the presence of oxygen. (See:
Aerobic Treatment: Process by which microbes decompose complex
organic compounds in the presence of oxygen and use the liberated energy for
reproduction and growth. (Such processes include extended aeration,
trickling filtration, and rotating biological contactors.)
Aerosol: 1. Small droplets or particles suspended in the
atmosphere, typically containing sulfur. They are usually emitted naturally
(e.g. in volcanic eruptions) and as the result of anthropogenic (human)
activities such as burning fossil fuels. 2. The pressurized gas used to
propel substances out of a container.
Aerosol: A finely divided material suspended in air or other
Affected Landfill: Under the Clean Air Act, landfills that meet
criteria for capacity, age, and emissions rates set by the EPA. They are
required to collect and combust their gas emissions.
Affected Public: 1.The people who live and/or work near a
hazardous waste site. 2. The human population adversely impacted following
exposure to a toxic pollutant in food, water, air, or soil.
Afterburner: In incinerator technology, a burner located so that
the combustion gases are made to pass through its flame in order to remove
smoke and odors. It may be attached to or be separated from the incinerator
Age Tank: A tank used to store a chemical solution of known
concentration for feed to a chemical feeder. Also called a day tank.
Agent: Any physical, chemical, or biological entity that can be
harmful to an organism (synonymous with
Agent Orange: A toxic herbicide and defoliant used in the Vietnam
conflict, containing 2,4,5-trichlorophen-oxyacetic acid (2,4,5-T) and 2-4
dichlorophenoxyacetic acid (2,4-D) with trace amounts of dioxin.
Agricultural Pollution: Farming wastes, including runoff and
leaching of pesticides and fertilizers; erosion and dust from plowing;
improper disposal of animal manure and carcasses; crop residues, and debris.
Agricultural Waste: Poultry and livestock manure, and
residual materials in liquid or solid form generated from the production and
marketing of poultry, livestock or fur-bearing animals; also includes grain,
vegetable, and fruit harvest residue.
Agroecosystem: Land used for crops, pasture, and livestock; the
adjacent uncultivated land that supports other vegetation and wildlife; and
the associated atmosphere, the underlying soils, groundwater, and drainage
AHERA Designated Person (ADP): A person designated by a Local
Education Agency to ensure that the AHERA requirements for asbestos
management and abatement are properly implemented.
Air Binding: Situation where air enters the filter media and harms
both the filtration and backwash processes.
Air Changes Per Hour (ACH): The movement of a volume of air in a
given period of time; if a house has one air change per hour, it means that
the air in the house will be replaced in a one-hour period.
Air Cleaning: Indoor-air quality-control strategy to remove
various airborne particulates and/or gases from the air. Most common methods
are particulate filtration, electrostatic precipitation, and gas sorption.
Air Contaminant: Any particulate matter, gas, or combination
thereof, other than water vapor. (See:
Air Curtain: A method of containing oil spills. Air bubbling
through a perforated pipe causes an upward water flow that slows the spread
of oil. It can also be used to stop fish from entering polluted water.
Air Exchange Rate: The rate at which outside air replaces indoor
air in a given space.
Air Gap: Open vertical gap or empty space that separates drinking
water supply to be protected from another water system in a treatment plant
or other location. The open gap protects the drinking water from
contamination by backflow or back siphonage.
Air Handling Unit: Equipment that includes a fan or blower,
heating and/or cooling coils, regulator controls, condensate drain pans, and
Air Mass: A large volume of air with certain meteorological or
polluted characteristics--e.g., a heat inversion or smogginess--while in one
location. The characteristics can change as the air mass moves away.
Air Monitoring: (See:
Air/Oil Table: The surface between the vadose zone and ambient
oil; the pressure of oil in the porous medium is equal to atmospheric
Air Padding: Pumping dry air into a container to assist with the
withdrawal of liquid or to force a liquefied gas such as chlorine out of the
Air Permeability: Permeability of soil with respect to air.
Important to the design of soil-gas surveys. Measured in darcys or
Air Plenum: Any space used to convey air in a building, furnace,
or structure. The space above a suspended ceiling is often used as an air
Air Pollutant: Any substance in air that could, in high enough
concentration, harm man, other animals, vegetation, or material. Pollutants
may include almost any natural or artificial composition of airborne matter
capable of being airborne. They may be in the form of solid particles,
liquid droplets, gases, or in combination thereof. Generally, they fall into
two main groups: (1) those emitted directly from identifiable sources and
(2) those produced in the air by interaction between two or more primary
pollutants, or by reaction with normal atmospheric constituents, with or
without photoactivation. Exclusive of pollen, fog, and dust, which are of
natural origin, about 100 contaminants have been identified. Air pollutants
are often grouped in categories for ease in classification; some of he
categories are: solids, sulfur compounds, volatile organic chemicals,
particulate matter, nitrogen compounds, oxygen compounds, halogen compounds,
radioactive compound, and odors.
Air Pollution: The presence of contaminants or pollutant
substances in the air that interfere with human health or welfare, or
produce other harmful environmental effects.
Air Pollution Control Device: Mechanism or equipment that cleans
emissions generated by a source (e.g. an incinerator, industrial smokestack,
or an automobile exhaust system) by removing pollutants that would otherwise
be released to the atmosphere.
Air Pollution Episode: A period of abnormally high concentration
of air pollutants, often due to low winds and temperature inversion, that
can cause illness and death. (See:
Air Quality Control Region:
Air Quality Criteria: The levels of pollution and lengths of
exposure above which adverse health and welfare effects may occur.
Air Quality Standards: The level of pollutants prescribed by
regulations that are not be exceeded during a given time in a defined area.
Air Sparging: Injecting air or oxygen into an aquifer to strip or
flush volatile contaminants as air bubbles up through The ground water and
is captured by a vapor extraction system.
Air Stripping: A treatment system that removes volatile organic
compounds (VOCs) from contaminated ground water or surface water by forcing
an airstream through the water and causing the compounds to evaporate.
Air Toxics: Any air pollutant for which a national ambient air
quality standard (NAAQS) does not exist (i.e. excluding ozone, carbon
monoxide, PM-10, sulfur dioxide, nitrogen oxide) that may reasonably be
anticipated to cause cancer; respiratory, cardiovascular, or developmental
effects; reproductive dysfunctions, neurological disorders, heritable gene
mutations, or other serious or irreversible chronic or acute health effects
Airborne Particulates: Total suspended particulate matter found in
the atmosphere as solid particles or liquid droplets. Chemical composition
of particulates varies widely, depending on location and time of year.
Sources of airborne particulates include: dust, emissions from industrial
processes, combustion products from the burning of wood and coal, combustion
products associated with motor vehicle or non-road engine exhausts, and
reactions to gases in the atmosphere.
Airborne Release: Release of any pollutant into the air.
Alachlor: A herbicide, marketed under the trade name Lasso, used
mainly to control weeds in corn and soybean fields.
Alar: Trade name for daminozide, a pesticide that makes apples
redder, firmer, and less likely to drop off trees before growers are ready
to pick them. It is also used to a lesser extent on peanuts, tart cherries,
concord grapes, and other fruits.
Aldicarb: An insecticide sold under the trade name Temik. It is
made from ethyl isocyanate.
Algae: Simple rootless plants that grow in sunlit waters in
proportion to the amount of available nutrients. They can affect water
quality adversely by lowering the dissolved oxygen in the water. They are
food for fish and small aquatic animals.
Algal Blooms: Sudden spurts of algal growth, which can affect
water quality adversely and indicate potentially hazardous changes in local
Algicide: Substance or chemical used specifically to kill or
Aliquot: A measured portion of a sample taken for analysis. One or
more aliquots make up a sample. (See:
Alkaline: The condition of water or soil which contains a
sufficient amount of alkali substance to raise the pH above 7.0.
Alkalinity: The capacity of bases to neutralize acids. An example
is lime added to lakes to decrease acidity.
Allergen: A substance that causes an allergic reaction in
individuals sensitive to it.
Alluvial: Relating to and/or sand deposited by flowing water.
Alternate Method: Any method of sampling and analyzing for an air
or water pollutant that is not a reference or equivalent method but that has
been demonstrated in specific cases-to EPA's satisfaction-to produce results
adequate for compliance monitoring.
Alternative Compliance: A policy that allows facilities to choose
among methods for achieving emission-reduction or risk-reduction instead of
command-and control regulations that specify standards and how to meet them.
Use of a theoretical emissions bubble over a facility to cap the amount of
pollution emitted while allowing the company to choose where and how (within
the facility) it complies.(See:
Alternative Fuels: Substitutes for traditional liquid, oil-derived
motor vehicle fuels like gasoline and diesel. Includes mixtures of
alcohol-based fuels with gasoline, methanol, ethanol, compressed natural
gas, and others.
Alternative Remedial Contract Strategy Contractors: Government
contractors who provide project management and technical services to support
remedial response activities at National Priorities List sites.
Ambient Air: Any unconfined portion of the atmosphere: open air,
Ambient Air Quality Standards: (See:
Criteria Pollutants and
National Ambient Air Quality Standards.)
Ambient Measurement: A measurement of the concentration of a
substance or pollutant within the immediate environs of an organism; taken
to relate it to the amount of possible exposure.
Ambient Medium: Material surrounding or contacting an organism
(e.g. outdoor air, indoor air, water, or soil, through which chemicals or
pollutants can reach the organism. (See:
Ambient Temperature: Temperature of the surrounding air or other
Amprometric Titration: A way of measuring concentrations of
certain substances in water using an electric current that flows during a
Anaerobic: A life or process that occurs in, or is not destroyed
by, the absence of oxygen.
Anaerobic Decomposition: Reduction of the net energy level and
change in chemical composition of organic matter caused by microorganisms in
an oxygen-free environment.
Animal Dander: Tiny scales of animal skin, a common indoor air
Animal Studies: Investigations using animals as surrogates for
humans with the expectation that the results are pertinent to humans.
Anisotropy: In hydrology, the conditions under which one or more
hydraulic properties of an aquifer vary from a reference point.
Annular Space, Annulus: The space between two concentric tubes or
casings, or between the casing and the borehole wall.
Antagonism: Interference or inhibition of the effect of one
chemical by the action of another.
Antarctic "Ozone Hole": Refers to the seasonal depletion of ozone
in the upper atmosphere above a large area of Antarctica. (See:
Anti-Degradation Clause: Part of federal air quality and water
quality requirements prohibiting deterioration where pollution levels are
above the legal limit.
Anti-Microbial: An agent that kills microbes.
Applicable or Relevant and Appropriate Requirements (ARARs): Any
state or federal statute that pertains to protection of human life and the
environment in addressing specific conditions or use of a particular cleanup
technology at a Superfund site,
Applied Dose: In exposure assessment, the amount of a substance in
contact with the primary absorption boundaries of an organism (e.g. skin,
lung tissue, gastrointestinal track) and available for absorption.
Aqueous: Something made up of water.
Aqueous Solubility: The maximum concentration of a chemical that
will dissolve in pure water at a reference temperature.
Aquifer: An underground geological formation, or group of
formations, containing water. Are sources of groundwater for wells and
Aquifer Test: A test to determine hydraulic properties of an
Aquitard: Geological formation that may contain groundwater but is
not capable of transmitting significant quantities of it under normal
hydraulic gradients. May function as confining bed.
Architectural Coatings: Coverings such as paint and roof tar that
are used on exteriors of buildings.
Area of Contamination (AOC) Policy: EPA interprets RCRA to allow
certain discrete areas of generally dispersed contamination to be considered
RCRA units. Therefore consolidation of material within an AOC and treatment of
material, in situ, within an AOC does NOT CREATE A POINT OF HAZARDOUS WASTE
GENERATION FOR PURPOSES OF RCRA.
Area of Review: In the UIC program, the area surrounding an
injection well that is reviewed during the permitting process to determine
if flow between aquifers will be induced by the injection operation.
Area Source: Any source of air pollution that is released over a
relatively small area but which cannot be classified as a point source. Such
sources may include vehicles and other small engines, small businesses and
household activities, or biogenic sources such as a forest that releases
Aromatics: A type of hydrocarbon, such as benzene or toluene, with
a specific type of ring structure. Aromatics are sometimes added to gasoline
in order to increase octane. Some aromatics are toxic.
Arsenicals: Pesticides containing arsenic.
Artesian (Aquifer or Well): Water held under pressure in porous
rock or soil confined by impermeable geological formations.
Asbestos: A mineral fiber that can pollute air or water and cause
cancer or asbestosis when inhaled. EPA has banned or severely restricted its
use in manufacturing and construction.
Asbestos Abatement: Procedures to control fiber release from
asbestos-containing materials in a building or to remove them entirely,
including removal, encapsulation, repair, enclosure, encasement, and
operations and maintenance programs.
Asbestos Assessment: In the asbestos-in-schools program, the
evaluation of the physical condition and potential for damage of all friable
asbestos containing materials and thermal insulation systems.
Asbestos Program Manager: A building owner or designated
representative who supervises all aspects of the facility asbestos
management and control program.
Asbestos-Containing Waste Materials (ACWM): Mill tailings or any
waste that contains commercial asbestos and is generated by a source covered
by the Clean Air Act Asbestos NESHAPS.
Asbestosis: A disease associated with inhalation of asbestos
fibers. The disease makes breathing progressively more difficult and can be
Ash: The mineral content of a product remaining after complete
Assay: A test for a specific chemical, microbe, or effect.
Assessment Endpoint: In ecological risk assessment, an explicit
expression of the environmental value to be protected; includes both an
ecological entity and specific attributed thereof. entity (e.g. salmon are a
valued ecological entity; reproduction and population maintenance--the
attribute--form an assessment endpoint.)
Assimilation: The ability of a body of water to purify itself of
Assimilative Capacity: The capacity of a natural body of water to
receive wastewaters or toxic materials without deleterious effects and
without damage to aquatic life or humans who consume the water.
Association of Boards of Certification: An international
organization representing boards which certify the operators of waterworks
and wastewater facilities.
Attainment Area: An area considered to have air quality as good as
or better than the national ambient air quality standards as defined in the
Clean Air Act. An area may be an attainment area for one pollutant and a
non-attainment area for others.
Attenuation: The process by which a compound is reduced in
concentration over time, through absorption, adsorption, degradation,
dilution, and/or transformation. an also be the decrease with distance of
sight caused by attenuation of light by particulate pollution.
Attractant: A chemical or agent that lures insects or other pests
by stimulating their sense of smell.
Attrition: Wearing or grinding down of a substance by friction.
Dust from such processes contributes to air pollution.
Availability Session: Informal meeting at a public location where
interested citizens can talk with EPA and state officials on a one-to-one
Available Chlorine: A measure of the amount of chlorine available
in chlorinated lime, hypochlorite compounds, and other materials used as a
source of chlorine when compared with that of liquid or gaseous chlorines.
Avoided Cost: The cost a utility would incur to generate the next
increment of electric capacity using its own resources; many landfill gas
projects' buy back rates are based on avoided costs.
A-Scale Sound Level: A measurement of sound approximating the
sensitivity of the human ear, used to note the intensity or annoyance level
Back Pressure: A pressure that can cause water to backflow into
the water supply when a user's waste water system is at a higher pressure
than the public system.
Backflow/Back Siphonage: A reverse flow condition created by a
difference in water pressures that causes water to flow back into the
distribution pipes of a drinking water supply from any source other than the
Background Level: 1. The concentration of a substance in an
environmental media (air, water, or soil) that occurs naturally or is not
the result of human activities. 2. In exposure assessment the concentration
of a substance in a defined control area, during a fixed period of time
before, during, or after a data-gathering operation..
Backwashing: Reversing the flow of water back through the filter
media to remove entrapped solids.
Backyard Composting: Diversion of organic food waste and yard
trimmings from the municipal waste stream by composting hem in one's yard
through controlled decomposition of organic matter by bacteria and fungi
into a humus-like product. It is considered source reduction, not recycling,
because the composted materials never enter the municipal waste stream.
Barrel Sampler: Open-ended steel tube used to collect soil
BACT - Best Available Control Technology: An emission limitation
based on the maximum degree of emission reduction (considering energy,
environmental, and economic impacts) achievable through application of
production processes and available methods, systems, and techniques. BACT
does not permit emissions in excess of those allowed under any applicable
Clean Air Act provisions. Use of the BACT concept is allowable on a case by
case basis for major new or modified emissions sources in attainment areas
and applies to each regulated pollutant.
Bacteria: (Singular: bacterium) Microscopic living organisms that
can aid in pollution control by metabolizing organic matter in sewage, oil
spills or other pollutants. However, bacteria in soil, water or air can also
cause human, animal and plant health problems.
Bactericide: A pesticide used to control or destroy
bacteria, typically in the home, schools, or hospitals.
Baffle: A flat board or plate, deflector, guide, or similar device
constructed or placed in flowing water or slurry systems to cause more
uniform flow velocities to absorb energy and to divert, guide, or agitate
Baffle Chamber: In incinerator design, a chamber designed to
promote the settling of fly ash and coarse particulate matter by changing
the direction and/or reducing the velocity of the gases produced by the
combustion of the refuse or sludge.
Baghouse Filter: Large fabric bag, usually made of glass fibers,
used to eliminate intermediate and large (greater than 20 PM in diameter)
particles. This device operates like the bag of an electric vacuum cleaner,
passing the air and smaller particles while entrapping the larger ones.
Bailer: A pipe with a valve at the lower end, used to remove
slurry from the bottom or side of a well as it is being drilled, or to
collect groundwater samples from wells or open boreholes. 2. A tube of
Baling: Compacting solid waste into blocks to reduce volume and
Ballistic Separator: A machine that sorts organic from inorganic
matter for composting.
Band Application: The spreading of chemicals over, or next to,
each row of plants in a field.
Banking: A system for recording qualified air emission reductions
for later use in bubble, offset, or netting transactions. (See:
Bar Screen: In wastewater treatment, a device used to remove large
Barrier Coating(s): A layer of a material that obstructs or
prevents passage of something through a surface that is to be protected;
e.g., grout, caulk, or various sealing compounds; sometimes used with
polyurethane membranes to prevent corrosion or oxidation of metal surfaces,
chemical impacts on various materials, or, for example, to prevent radon
infiltration through walls, cracks, or joints in a house.
Basal Application: In pesticides, the application of a chemical on
plant stems or tree trunks just above the soil line.
Basalt: Consistent year-round energy use of a facility; also
refers to the minimum amount of electricity supplied continually to a
Bean Sheet: Common term for a pesticide data package record.
Bed Load: Sediment particles resting on or near the channel bottom
that are pushed or rolled along by the flow of water.
BEN: EPA's computer model for analyzing a violator's economic gain
from not complying with the law.
Bench-scale Tests: Laboratory testing of potential cleanup
Benefit-Cost Analysis: An economic method for assessing the
benefits and costs of achieving alternative health-based standards at given
levels of health protection.
Benthic/Benthos: An organism that feeds on the sediment at the bottom of
a water body such as an ocean, lake, or river.
Bentonite: A colloidal clay, expansible when moist, commonly used
to provide a tight seal around a well casing.
Beryllium: An metal hazardous to human health when inhaled as an
airborne pollutant. It is discharged by machine shops, ceramic and
propellant plants, and foundries.
Best Available Control Measures (BACM): A term used to refer to
the most effective measures (according to EPA guidance) for controlling
small or dispersed particulates and other emissions from sources such as
roadway dust, soot and ash from woodstoves and open burning of rush, timber,
grasslands, or trash.
Best Available Control Technology (BACT): For any specific source,
the currently available technology producing the greatest reduction of air
pollutant emissions,taking into account energy, environmental, economic, and
Best Available Control Technology (BACT): The most stringent
technology available for controlling emissions; major sources are required
to use BACT, unless it can be demonstrated that it is not feasible for
energy, environmental, or economic reasons.
Best Demonstrated Available Technology (BDAT): As identified by
EPA, the most effective commercially available means of treating specific
types of hazardous waste. The BDATs may change with advances in treatment
Best Management Practice (BMP): Methods that have been determined
to be the most effective, practical means of preventing or reducing
pollution from non-point sources.
Bimetal: Beverage containers with steel bodies and aluminum tops;
handled differently from pure aluminum in recycling.
Bioaccumulants: Substances that increase in concentration in
living organisms as they take in contaminated air, water, or food because
the substances are very slowly metabolized or excreted. (See:
Bioassay: A test to determine te relative strength of a substance
by comparing its effect on a test organism with that of a standard
Bioavailabiliity: Degree of ability to be absorbed and ready to
interact in organism metabolism.
Biochemical Oxygen Demand (BOD): A measure of the amount of oxygen
consumed in the biological processes that break down organic matter in
water. The greater the BOD, the greater the degree of pollution.
Bioconcentration: The accumulation of a chemical in tissues of a
fish or other organism to levels greater than in the surrounding medium.
Biodegradable: Capable of decomposing under natural conditions.
Biodiversity: Refers to the variety and variability among living
organisms and the ecological complexes in which they occur. Diversity can be
defined as the number of different items and their relative frequencies. For
biological diversity, these items are organized at many levels, ranging from
complete ecosystems to the biochemical structures that are the molecular
basis of heredity. Thus, the term encompasses different ecosystems, species,
Biological Contaminants: Living organisms or derivates (e.g.
viruses, bacteria, fungi, and mammal and bird antigens) that can cause
harmful health effects when inhaled, swallowed, or otherwise taken into the
Biological Control: In pest control, the use of animals and
organisms that eat or otherwise kill or out-compete pests.
Biological Integrity: The ability to support and maintain
balanced, integrated, functionality in the natural habitat of a given
region. Concept is applied primarily in drinking water management.
Biological Magnification: Refers to the process whereby certain
substances such as pesticides or heavy metals move up the food chain, work
their way into rivers or lakes, and are eaten by aquatic organisms such as
fish, which in turn are eaten by large birds, animals or humans. The
substances become concentrated in tissues or internal organs as they move up
the chain. (See:
Biological Measurement: A measurement taken in a biological
medium. For exposure assessment, it is related to the measurement is taken
to related it to the established internal dose of a compound.
Biological Medium: One of the major component of an organism; e.g.
blood, fatty tissue, lymph nodes or breath, in which chemicals can be stored
or transformed. (See:
Biological Oxidation: Decomposition of complex organic materials
by microorganisms. Occurs in self-purification of water bodies and in
activated sludge wastewater treatment.
Biological Oxygen Demand (BOD): An indirect measure of the
concentration of biologically degradable material present in organic wastes.
It usually reflects the amount of oxygen consumed in five days by biological
processes breaking down organic waste.
Biological pesticides: Certain microorganism, including
bacteria, fungi, viruses, and protozoa that are effective in controlling
pests. These agents usually do not have toxic effects on animals and people
and do not leave toxic or persistent chemical residues in the environment.
Biological Stressors: Organisms accidentally or intentionally
dropped into habitats in which they do not evolve naturally; e.g. gypsy
moths, Dutch elm disease, certain types of algae, and bacteria.
Biological Treatment: A treatment technology that uses bacteria to
consume organic waste.
Biologically Effective Dose: The amount of a deposited or absorbed
compound reaching the cells or target sites where adverse effect occur, or
where the chemical interacts with a membrane.
Biologicals: Vaccines, cultures and other preparations made from
living organisms and their products, intended for use in diagnosing,
immunizing, or treating humans or animals, or in related research.
Biomass: All of the living material in a given area; often refers
Biome: Entire community of living organisms in a single major
ecological area. (See:
Biomonitoring: 1. The use of living organisms to test the
suitability of effluents for discharge into receiving waters and to test the
quality of such waters downstream from the discharge. 2. Analysis of blood,
urine, tissues, etc. to measure chemical exposure in humans.
Bioremediation: Use of living organisms to clean up oil spills or
remove other pollutants from soil, water, or wastewater; use of organisms
such as non-harmful insects to remove agricultural pests or counteract
diseases of trees, plants, and garden soil.
Biosensor: Analytical device comprising a biological recognition
element (e.g. enzyme, receptor, DNA, antibody, or microorganism) in intimate
contact with an electrochemical, optical, thermal, or acoustic signal
transducer that together permit analyses of chemical properties or
quantities. Shows potential development in some areas, including
Biosphere: The portion of Earth and its atmosphere that can
Biostabilizer: A machine that converts solid waste into compost by
grinding and aeration.
Biota: The animal and plant life of a given region.
Biotechnology: Techniques that use living organisms or parts of
organisms to produce a variety of products (from medicines to industrial
enzymes) to improve plants or animals or to develop microorganisms to remove
toxics from bodies of water, or act as pesticides.
Biotic Community: A naturally occurring assemblage of plants and
animals that live in the same environment and are mutually sustaining and
Biotransformation: Conversion of a substance into other compounds
by organisms; includes biodegredation.
Blackwater: Water that contains animal, human, or food waste.
Blood Products: Any product derived from human blood, including
but not limited to blood plasma, platelets, red or white corpuscles, and
derived licensed products such as interferon.
Bloom: A proliferation of algae and/or higher aquatic plants in a
body of water; often related to pollution, especially when pollutants
BOD5: The amount of dissolved oxygen consumed in five days by
biological processes breaking down organic matter.
Body Burden: The amount of a chemical stored in the body at a
given time, especially a potential toxin in the body as the result of
Bog: A type of wetland that accumulates appreciable peat deposits.
Bogs depend primarily on precipitation for their water source, and are
usually acidic and rich in plant residue with a conspicuous mat of living
Boiler: A vessel designed to transfer heat produced by combustion
or electric resistance to water. Boilers may provide hot water or steam.
Boom: 1. A floating device used to contain oil on a body of water.
2. A piece of equipment used to apply pesticides from a tractor or truck.
Borehole: Hole made with drilling equipment.
Botanical Pesticide: A pesticide whose active ingredient is a
plant-produced chemical such as nicotine or strychnine. Also called a
Bottle Bill: Proposed or enacted legislation which requires a
returnable deposit on beer or soda containers and provides for retail store
or other redemption. Such legislation is designed to discourage use of
Bottom Ash: The non-airborne combustion residue from burning
pulverized coal in a boiler; the material which falls to the bottom of the
boiler and is removed mechanically; a concentration of non-combustible
materials, which may include toxics.
Bottom Land Hardwoods: Forested freshwater wetlands adjacent to
rivers in the southeastern United States, especially valuable for wildlife
breeding, nesting and habitat.
Bounding Estimate: An estimate of exposure, dose, or risk that is
higher than that incurred by the person in the population with the currently
highest exposure, dose, or risk. Bounding estimates are useful in developing
statements that exposures, doses, or risks are not greater than an estimated
Brackish: Mixed fresh and salt water.
Breakpoint Chlorination: Addition of chlorine to water until the
chlorine demand has been satisfied.
Breakthrough: A crack or break in a filter bed that allows the
passage of floc or particulate matter through a filter; will cause an
increase in filter effluent turbidity.
Breathing Zone: Area of air in which an organism inhales.
Brine Mud: Waste material, often associated with well-drilling or
mining, composed of mineral salts or other inorganic compounds.
British Thermal Unit: Unit of heat energy equal to the amount of
heat required to raise the temperature of one pound of water by one degree
Fahrenheit at sea level.
Broadcast Application: The spreading of pesticides over an entire
Brownfields: Abandoned, idled, or under used industrial and
commercial facilities/sites where expansion or redevelopment is complicated
by real or perceived environmental contamination. They can be in urban,
suburban, or rural areas. EPA's Brownfields initiative helps communities
mitigate potential health risks and restore the economic viability of such
areas or properties.
Bubble: A system under which existing emissions sources can
propose alternate means to comply with a set of emissions limitations; under
the bubble concept, sources can control more than required at one emission
point where control costs are relatively low in return for a comparable
relaxation of controls at a second emission point where costs are higher.
Bubble Policy: (See:
Buffer: A solution or liquid whose chemical makeup is such that it
minimizes changes in pH when acids or bases are added to it.
Buffer Strips: Strips of grass or other erosion-resisting
vegetation between or below cultivated strips or fields.
Building Cooling Load: The hourly amount of heat that must be
removed from a building to maintain indoor comfort (measured in British
thermal units (Btus).
Building Envelope: The exterior surface of a building's
construction--the walls, windows, floors, roof, and floor. Also called
Building Related Illness: Diagnosable illness whose cause and
symptoms can be directly attributed to a specific pollutant source within a
building (e.g. Legionnaire's disease, hypersensitivity, pneumonitis.) (See:
sick building syndrome.)
Bulk Sample: A small portion (usually thumbnail size) of a suspect
asbestos-containing building material collected by an asbestos inspector for
laboratory analysis to determine asbestos content.
Bulky Waste: Large items of waste materials, such as appliances,
furniture, large auto parts, trees, stumps.
Burial Ground (Graveyard): A disposal site for radioactive waste
materials that uses earth or water as a shield.
Buy-Back Center: Facility where individuals or groups bring
reyclables in return for payment.
By-product: Material, other than the principal product, generated
as a consequence of an industrial process or as a breakdown product in a
Cadmium (Cd): A heavy metal that accumulates in the
Cancellation: Refers to Section 6 (b) of the Federal Insecticide,
Fungicide and Rodenticide Act (FIFRA) which authorizes cancellation of a
pesticide registration if unreasonable adverse effects to the environment
and public health develop when a product is used according to widespread and
commonly recognized practice, or if its labeling or other material required
to be submitted does not comply with FIFRA provisions.
Cap: A layer of clay, or other impermeable material installed over
the top of a closed landfill to prevent entry of rainwater and minimize
Capacity Assurance Plan: A statewide plan which supports a state's
ability to manage the hazardous waste generated within its boundaries over a
twenty year period.
Capillary Action: Movement of water through very small spaces due
to molecular forces called capillary forces.
Capillary Fringe: The porous material just above the water table
which may hold water by capillarity (a property of surface tension that
draws water upwards) in the smaller void spaces.
Capillary Fringe: The zone above he water table within which the
porous medium is saturated by water under less than atmospheric pressure.
Capture Efficiency: The fraction of organic vapors generated by a
process that are directed to an abatement or recovery device.
Carbon Absorber: An add-on control device that uses activated
carbon to absorb volatile organic compounds from a gas stream. (The VOCs are
later recovered from the carbon.)
Carbon Adsorption: A treatment system that removes contaminants
from ground water or surface water by forcing it through tanks containing
activated carbon treated to attract the contaminants.
Carbon Monoxide (CO): A colorless, odorless, poisonous gas
produced by incomplete fossil fuel combustion.
Carbon Tetrachloride (CC14): Compound consisting of one carbon
atom ad four chlorine atoms, once widely used as a industrial raw material,
as a solvent, and in the production of CFCs. Use as a solvent ended when it
was discovered to be carcinogenic.
Carboxyhemoglobin: Hemoglobin in which the iron is bound to carbon
monoxide(CO) instead of oxygen.
Carcinogen: Any substance that can cause or aggravate cancer.
Carrier: 1.The inert liquid or solid material in a pesticide
product that serves as a delivery vehicle for the active ingredient.
Carriers do not have toxic properties of their own. 2. Any material or
system that can facilitate the movement of a pollutant into the body or
Carrying Capacity: 1. In recreation management, the amount of use
a recreation area can sustain without loss of quality. 2. In wildlife
management, the maximum number of animals an area can support during a given
CAS Registration Number: A number assigned by the Chemical
Abstract Service to identify a chemical.
Case Study: A brief fact sheet providing risk, cost, and
performance information on alternative methods and other pollution
prevention ideas, compliance initiatives, voluntary efforts, etc.
Cask: A thick-walled container (usually lead) used to transport
radioactive material. Also called a coffin.
Catalyst: A substance that changes the speed or yield of a
chemical reaction without being consumed or chemically changed by the
Catalytic Converter: An air pollution abatement device that
removes pollutants from motor vehicle exhaust, either by oxidizing them into
carbon dioxide and water or reducing them to nitrogen.
Catalytic Incinerator: A control device that oxidizes volatile
organic compounds (VOCs) by using a catalyst to promote the combustion
process. Catalytic incinerators require lower temperatures than conventional
thermal incinerators, thus saving fuel and other costs.
Categorical Exclusion: A class of actions which either
individually or cumulatively would not have a significant effect on the
human environment and therefore would not require preparation of an
environmental assessment or environmental impact statement under the
National Environmental Policy Act (NEPA).
Categorical Pretreatment Standard: A technology-based effluent
limitation for an industrial facility discharging into a municipal sewer
system. Analogous in stringency to Best Availability Technology (BAT) for
Cathodic Protection: A technique to prevent corrosion of a metal
surface by making it the cathode of an electrochemical cell.
Cavitation: The formation and collapse of gas pockets or bubbles
on the blade of an impeller or the gate of a valve; collapse of these
pockets or bubbles drives water with such force that it can cause pitting of
the gate or valve surface.
Cells: 1. In solid waste disposal, holes where waste is dumped,
compacted, and covered with layers of dirt on a daily basis. 2. The smallest
structural part of living matter capable of functioning as an independent
Cementitious: Densely packed and nonfibrous friable materials.
Central Collection Point: Location were a generator of regulated
medical waste consolidates wastes originally generated at various locations
in his facility. The wastes are gathered together for treatment on-site or
for transportation elsewhere for treatment and/or disposal. This term could
also apply to community hazardous waste collections, industrial and other
waste management systems.
Centrifugal Collector: A mechanical system using centrifugal force
to remove aerosols from a gas stream or to remove water from sludge.
CERCLIS: The federal Comprehensive Environmental
Response, Compensation, and Liability Information System is a database that
includes all sites which have been nominated for investigation by the
Channelization: Straightening and deepening streams so water will
move faster, a marsh-drainage tactic that can interfere with waste
assimilation capacity, disturb fish and wildlife habitats, and aggravate
Characteristic: Any one of the four categories used in defining
hazardous waste: ignitability, corrosivity, reactivity, and toxicity.
Characteristic Waste: Waste that is considered hazardous under
RCRA because it exhibits any four different properties: ignitability,
corrosivity, reactivity, and toxicity.
Characterization of Ecological Effects: Part of ecological risk
assessment that evaluates ability of a stressor to cause adverse effects
under given circumstances.
Characterization of Exposure: Portion of an ecological risk
assessment that evaluates interaction of a stressor with one or more
Check-Valve Tubing Pump: Water sampling tool also referred to as a
Chemical Case: For purposes of review and regulation, the grouping
of chemically similar pesticide active ingredients (e.g. salts and esters of
the same chemical) into chemical cases.
Chemical Compound: A distinct and pure substance formed by the
union or two or more elements in definite proportion by weight.
Chemical Element: A fundamental substance comprising one kind of
atom; the simplest form of matter.
Chemical Oxygen Demand (COD): A measure of the oxygen required to
oxidize all compounds, both organic and inorganic, in water.
Chemical Stressors: Chemicals released to the environment through
industrial waste, auto emissions, pesticides, and other human activity that
can cause illnesses and even death in plants and animals.
Chemical Treatment: Any one of a variety of technologies that use
chemicals or a variety of chemical processes to treat waste.
Chemnet: Mutual aid network of chemical shippers and contractors
that assigns a contracted emergency response company to provide technical
support if a representative of the firm whose chemicals are involved in an
incident is not readily available.
Chemosterilant: A chemical that controls pests by preventing
Chemtrec: The industry-sponsored Chemical Transportation Emergency
Center; provides information and/or emergency assistance to emergency
Child Resistant Packaging (CRP): Packaging that protects children
or adults from injury or illness resulting from accidental contact with or
ingestion of residential pesticides that meet or exceed specific toxicity
levels. Required by FIFRA regulations. Term is also used for protective
packaging of medicines.
Chiller: A device that generates a cold liquid that is circulated
through an air-handling unit's cooling coil to cool the air supplied to the
Chilling Effect: The lowering of the Earth's temperature because
of increased particles in the air blocking the sun's rays. (See:
Chisel Plowing: Preparing croplands by using a special implement
that avoids complete inversion of the soil as in conventional plowing.
Chisel plowing can leave a protective cover or crops residues on the soil
surface to help prevent erosion and improve filtration.
Chlorinated Hydrocarbons: 1. Chemicals containing only chlorine,
carbon, and hydrogen. These include a class of persistent, broad-spectrum
insecticides that linger in the environment and accumulate in the food
chain. Among them are DDT, aldrin, dieldrin, heptachlor, chlordane, lindane,
endrin, Mirex, hexachloride, and toxaphene. Other examples include TCE, used
as an industrial solvent. 2. Any chlorinated organic compounds including
chlorinated solvents such as dichloromethane, trichloromethylene,
Chlorinated Solvent: An organic solvent containing chlorine
atoms(e.g. methylene chloride and 1,1,1-trichloromethane). Uses of
chlorinated solvents are include aerosol spray containers, in highway paint,
and dry cleaning fluids.
Chlorination: The application of chlorine to drinking water,
sewage, or industrial waste to disinfect or to oxidize undesirable
Chlorinator: A device that adds chlorine, in gas or liquid form,
to water or sewage to kill infectious bacteria.
Chlorine-Contact Chamber: That part of a water treatment plant
where effluent is disinfected by chlorine.
Chlorofluorocarbons (CFCs): A family of inert, nontoxic, and
easily liquefied chemicals used in refrigeration, air conditioning,
packaging, insulation, or as solvents and aerosol propellants. Because CFCs
are not destroyed in the lower atmosphere they drift into the upper
atmosphere where their chlorine components destroy ozone. (See:
Chlorophenoxy: A class of herbicides that may be found in domestic
water supplies and cause adverse health effects.
Chlorosis: Discoloration of normally green plant parts caused by
disease, lack of nutrients, or various air pollutants.
Cholinesterase: An enzyme found in animals that regulates nerve
impulses by the inhibition of acetylcholine. Cholinesterase inhibition is
associated with a variety of acute symptoms such as nausea, vomiting,
blurred vision, stomach cramps, and rapid heart rate.
Chronic Effect: An adverse effect on a human or animal in which
symptoms recur frequently or develop slowly over a long period of time.
Chronic Exposure: Multiple exposures occurring over an extended
period of time or over a significant fraction of an animal's or human's
lifetime (Usually seven years to a lifetime.)
Chronic Toxicity: The capacity of a substance to cause long-term
poisonous health effects in humans, animals, fish, and other organisms.
(See: acute toxicity.)
Circle of Influence: The circular outer edge of a depression
produced in the water table by the pumping of water from a well. (See:
cone of depression.)
Cistern: Small tank or storage facility used to store water for a
home or farm; often used to store rain water.
Clarification: Clearing action that occurs during wastewater
treatment when solids settle out. This is often aided by centrifugal action
and chemically induced coagulation in wastewater.
Clarifier: A tank in which solids settle to the bottom and are
subsequently removed as sludge.
Class I Area: Under the Clean Air Act. a Class I area is one in
which visibility is protected more stringently than under the national
ambient air quality standards; includes national parks, wilderness areas,
monuments, and other areas of special national and cultural significance.
Class I Substance: One of several groups of chemicals with an
ozone depletion potential of 0.2 or higher, including CFCS, Halons, Carbon
Tetrachloride, and Methyl Chloroform (listed in the Clean Air Act), and
HBFCs and Ethyl Bromide (added by EPA regulations). (See:
Global warming potential.)
Class II Substance: A substance with an ozone depletion potential
of less than 0.2. All HCFCs are currently included in this classification.
(See: Global warming
Clay Soil: Soil material containing more than 40 percent clay,
less than 45 percent sand, and less than 40 percent silt.
Clean Coal Technology: Any technology not in widespread use prior
to the Clean Air Act Amendments of 1990. This Act will achieve significant
reductions in pollutants associated with the burning of coal.
Clean Fuels: Blends or substitutes for gasoline fuels, including
compressed natural gas, methanol, ethanol, and liquified petroleum gas.
Cleaner Technologies Substitutes Assessment: A document that
systematically evaluates the relative risk, performance, and cost trade-offs
of technological alternatives; serves as a repository for all the technical
data (including methodology and results) developed by a DfE or other
pollution prevention or education project.
Cleanup: Actions taken to deal with a release or threat of release
of a hazardous substance that could affect humans and/or the environment.
The term "cleanup" is sometimes used interchangeably with the terms remedial
action, removal action, response action, or corrective action.
Clear Cut: Harvesting all the trees in one area at one time, a
practice that can encourage fast rainfall or snowmelt runoff, erosion,
sedimentation of streams and lakes, and flooding, and destroys vital
Clear Well: A reservoir for storing filtered water of sufficient
quantity to prevent the need to vary the filtration rate with variations in
demand. Also used to provide chlorine contact time for disinfection.
Climate Change (also referred to as 'global climate change'):
The term 'climate change' is sometimes used to refer to all forms of
climatic inconsistency, but because the Earth's climate is never static,
the term is more properly used to imply a significant change from one
climatic condition to another. In some cases, 'climate change' has been
used synonymously with the term, 'global warming'; scientists however,
tend to use the term in the wider sense to also include natural changes
in climate. (See: global warming.)
Cloning: In biotechnology, obtaining a group of genetically
identical cells from a single cell; making identical copies of a gene.
Closed-Loop Recycling: Reclaiming or reusing wastewater for
non-potable purposes in an enclosed process.
Closure: The procedure a landfill operator must follow when a
landfill reaches its legal capacity for solid ceasing acceptance of solid
waste and placing a cap on the landfill site.
Co-fire: Burning of two fuels in the same combustion unit; e.g.,
coal and natural gas, or oil and coal.
Coagulation: Clumping of particles in wastewater to settle out
impurities, often induced by chemicals such as lime, alum, and iron salts.
Coal Cleaning Technology: A precombustion process by which coal is
physically or chemically treated to remove some of its sulfur so as to
reduce sulfur dioxide emissions.
Coal Gasification: Conversion of coal to a gaseous product by one
of several available technologies.
Coastal Zone: Lands and waters adjacent to the coast that exert an
influence on the uses of the sea and its ecology, or whose uses and ecology
are affected by the sea.
Code of Federal Regulations (CFR): Document that codifies all
rules of the executive departments and agencies of the federal government.
It is divided into fifty volumes, known as titles. Title 40 of the CFR
(referenced as 40 CFR) lists all environmental regulations.
Coefficient of Haze (COH): A measurement of visibility
interference in the atmosphere.
Cogeneration: The consecutive generation of useful thermal and
electric energy from the same fuel source.
Coke Oven: An industrial process which converts coal into coke,
one of the basic materials used in blast furnaces for the conversion of iron
ore into iron.
Cold Temperature CO: A standard for automobile emissions of carbon
monoxide (CO) emissions to be met at a low temperature (i.e. 20 degrees
Fahrenheit). Conventional automobile catalytic converters are not efficient
in cold weather until they warm up.
Coliform Index: A rating of the purity of water based on a count
of fecal bacteria.
Coliform Organism: Microorganisms found in the intestinal tract of
humans and animals. Their presence in water indicates fecal pollution and
potentially adverse contamination by pathogens.
Collector: Public or private hauler that collects nonhazardous
waste and recyclable materials from residential, commercial, institutional
and industrial sources. (See:
Collector Sewers: Pipes used to collect and carry wastewater from
individual sources to an interceptor sewer that will carry it to a treatment
Colloids: Very small, finely divided solids (that do not dissolve)
that remain dispersed in a liquid for a long time due to their small size
and electrical charge.
Combined Sewer Overflows: Discharge of a mixture of storm water
and domestic waste when the flow capacity of a sewer system is exceeded
Combined Sewers: A sewer system that carries both sewage and
storm-water runoff. Normally, its entire flow goes to a waste treatment
plant, but during a heavy storm, the volume of water may be so great as to
cause overflows of untreated mixtures of storm water and sewage into
receiving waters. Storm-water runoff may also carry toxic chemicals from
industrial areas or streets into the sewer system.
Combustion: 1. Burning, or rapid oxidation, accompanied by release
of energy in the form of heat and light. 2. Refers to controlled burning of
waste, in which heat chemically alters organic compounds, converting into
stable inorganics such as carbon dioxide and water.
Combustion Chamber: The actual compartment where waste is burned
in an incinerator.
Combustion Product: Substance produced during the burning or
oxidation of a material.
Command Post: Facility located at a safe distance upwind from an
accident site, where the on-scene coordinator, responders, and technical
representatives make response decisions, deploy manpower and equipment,
maintain liaison with news media, and handle communications.
Command-and-Control Regulations: Specific requirements prescribing
how to comply with specific standards defining acceptable levels of
Comment Period: Time provided for the public to review and comment
on a proposed EPA action or rulemaking after publication in the Federal
Commercial Waste: All solid waste emanating from business
establishments such as stores, markets, office buildings, restaurants,
shopping centers, and theaters.
Commercial Waste Management Facility: A treatment, storage,
disposal, or transfer facility which accepts waste from a variety of
sources, as compared to a private facility which normally manages a limited
waste stream generated by its own operations.
Commingled Recyclables: Mixed recyclables that are collected
Comminuter: A machine that shreds or pulverizes solids to make
waste treatment easier.
Comminution: Mechanical shredding or pulverizing of waste. Used in
both solid waste management and wastewater treatment.
Common Sense Initiative: Voluntary program to simplify
environmental regulation to achieve cleaner, cheaper, smarter results,
starting with six major industry sectors.
Community: In ecology, an assemblage of populations of different
species within a specified location in space and time. Sometimes, a
particular subgrouping may be specified, such as the fish community in a
lake or the soil arthropod community in a forest.
Community Relations: The EPA effort to establish two-way
communication with the public to create understanding of EPA programs and
related actions, to ensure public input into decision-making processes
related to affected communities, and to make certain that the Agency is
aware of and responsive to public concerns. Specific community relations
activities are required in relation to Superfund remedial actions.
Community Water System: A public water system which serves at
least 15 service connections used by year-round residents or regularly
serves at least 25 year-round residents.
Compact Fluorescent Lamp (CFL): Small fluorescent lamps used as
more efficient alternatives to incandescent lighting. Also called PL, CFL,
Twin-Tube, or BIAX lamps.
Compaction: Reduction of the bulk of solid waste by rolling and
Comparative Risk Assessment: Process that generally uses the
judgement of experts to predict effects and set priorities among a wide
range of environmental problems.
Complete Treatment: A method of treating water that consists of
the addition of coagulant chemicals, flash mixing, coagulation-flocculation,
sedimentation, and filtration. Also called conventional filtration.
Compliance Coal: Any coal that emits less than 1.2 pounds of
sulfur dioxide per million Btu when burned. Also known as low sulfur coal.
Compliance Coating: A coating whose volatile organic compound
content does not exceed that allowed by regulation.
Compliance Cycle: The 9-year calendar year cycle, beginning
January 1, 1993, during which public water systems must monitor. Each cycle
consists of three 3-year compliance periods.
Compliance Monitoring: Collection and evaluation of data,
including self-monitoring reports, and verification to show whether
pollutant concentrations and loads contained in permitted discharges are in
compliance with the limits and conditions specified in the permit.
Compliance Schedule: A negotiated agreement between a pollution
source and a government agency that specifies dates and procedures by which
a source will reduce emissions and, thereby, comply with a regulation.
Composite Sample: A series of water samples taken over a given
period of time and weighted by flow rate.
Compost: A humus or soil-like material created from aerobic,
microbial decomposition of organic materials such as food scraps, yard
trimmings, and manure
Composting: The controlled biological decomposition of organic
material in the presence of air to form a humus-like material. Controlled
methods of composting include mechanical mixing and aerating, ventilating
the materials by dropping them through a vertical series of aerated
chambers, or placing the compost in piles out in the open air and mixing it
or turning it periodically.
Composting Facilities: 1. An offsite facility where the organic
component of municipal solid waste is decomposed under controlled
conditions; 2.an aerobic process in which organic materials are ground or
shredded and then decomposed to humus in windrow piles or in mechanical
digesters, drums, or similar enclosures.
Compressed Natural Gas (CNG): An alternative fuel for motor
vehicles; considered one of the cleanest because of low hydrocarbon
emissions and its vapors are relatively non-ozone producing. However,
vehicles fueled with CNG do emit a significant quantity of nitrogen oxides.
Concentration: The relative amount of a substance mixed with
another substance. An example is five ppm of carbon monoxide in air or 1
mg/l of iron in water.
Condensate: 1.Liquid formed when warm landfill gas cools as it
travels through a collection system. 2. Water created by cooling steam or
Condensate Return System: System that returns the heated water
condensing within steam piping to the boiler and thus saves energy.
Conditional Registration: Under special circumstances, the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA) permits registration of
pesticide products that is "conditional" upon the submission of additional
data. These special circumstances include a finding by the EPA Administrator
that a new product or use of an existing pesticide will not significantly
increase the risk of unreasonable adverse effects. A product containing a
new (previously unregistered) active ingredient may be conditionally
registered only if the Administrator finds that such conditional
registration is in the public interest, that a reasonable time for
conducting the additional studies has not elapsed, and the use of the
pesticide for the period of conditional registration will not present an
Conditionally Exempt Generators (CE): Persons or enterprises which
produce less than 220 pounds of hazardous waste per month. Exempt from most
regulation, they are required merely to determine whether their waste is
hazardous, notify appropriate state or local agencies, and ship it by an
authorized transporter to a permitted facility for proper disposal. (See :
small quantity generator.)
Conductance: A rapid method of estimating the dissolved solids
content of water supply by determining the capacity of a water sample to
carry an electrical current. Conductivity is a measure of the ability of a
solution to carry and electrical current.
Conductivity: A measure of the ability of a solution to carry an
Cone of Depression: A depression in the water table that develops
around a pumped well.
Cone of Influence: The depression, roughly conical in shape,
produced in a water table by the pumping of water from a well.
Cone Penterometer Testing (CPT): A direct push system used to
measure lithology based on soil penetration resistance. Sensors in the tip
of the cone of the DP rod measure tip resistance and side-wall friction,
transmitting electrical signals to digital processing equipment on the
ground surface. (See:
Confidential Business Information (CBI): Material that contains
trade secrets or commercial or financial information that has been claimed
as confidential by its source (e.g. a pesticide or new chemical formulation
registrant). EPA has special procedures for handling such information.
Confidential Statement of Formula (CSF): A list of the ingredients
in a new pesticide or chemical formulation. The list is submitted at the
time for application for registration or change in formulation.
Confined Aquifer: An aquifer in which ground water is confined
under pressure which is significantly greater than atmospheric pressure.
Confluent Growth: A continuous bacterial growth covering all or
part of the filtration area of a membrane filter in which the bacteria
colonies are not discrete.
Consent Decree: A legal document, approved by a judge, that
formalizes an agreement reached between EPA and potentially responsible
parties (PRPs) through which PRPs will conduct all or part of a cleanup
action at a Superfund site; cease or correct actions or processes that are
polluting the environment; or otherwise comply with EPA initiated regulatory
enforcement actions to resolve the contamination at the Superfund site
involved. The consent decree describes the actions PRPs will take and may be
subject to a public comment period.
Conservation: Preserving and renewing, when possible, human and
natural resources. The use, protection, and improvement of natural resources
according to principles that will ensure their highest economic or social
Conservation Easement: Easement restricting a landowner to land
uses that that are compatible with long-term conservation and environmental
Constituent(s) of Concern: Specific chemicals that are identified
for evaluation in the site assessment process
Construction and Demolition Waste: Waste building materials,
dredging materials, tree stumps, and rubble resulting from construction,
remodeling, repair, and demolition of homes, commercial buildings and other
structures and pavements. May contain lead, asbestos, or other hazardous
Construction Ban: If, under the Clean Air Act, EPA disapproves an
area's planning requirements for correcting nonattainment, EPA can ban the
construction or modification of any major stationary source of the pollutant
for which the area is in nonattainment.
Consumptive Water Use: Water removed from available supplies
without return to a water resources system, e.g. water used in
manufacturing, agriculture, and food preparation.
Contact Pesticide: A chemical that kills pests when it touches
them, instead of by ingestion. Also, soil that contains the minute skeletons
of certain algae that scratch and dehydrate waxy-coated insects.
Contained-in Determination for Soil: Granted by EPA or an
authorized state that certifies that soil is no longer considered a
hazardous waste. You can apply for a contained-in determination if soil
should not be managed as a hazardous waste because:
(1) the soil does not
exhibit a characteristic of hazardous waste when generated, or
soil contaminated with a listed hazardous waste has concentrations of
hazardous constituents that are below health-based levels.
Contained-in Policy: The "contained-in" policy dates back to a
1986 memorandum which states that although groundwater is not a solid waste,
it can be considered a hazardous waste if it "contains" a hazardous waste.
This policy was then applied to soil and debris.
Contaminant: Any physical, chemical, biological, or radiological
substance or matter that has an adverse effect on air, water, or soil.
Contamination: Introduction into water, air, and soil of
microorganisms, chemicals, toxic substances, wastes, or wastewater in a
concentration that makes the medium unfit for its next intended use. Also
applies to surfaces of objects, buildings, and various household and
agricultural use products.
Contamination Source Inventory: An inventory of contaminant
sources within delineated State Water-Protection Areas. Targets likely
sources for further investigation.
Contingency Plan: A document setting out an organized, planned,
and coordinated course of action to be followed in case of a fire,
explosion, or other accident that releases toxic chemicals, hazardous waste,
or radioactive materials that threaten human health or the environment.
(See: National Oil and
Hazardous Substances Contingency Plan.)
Continuous Discharge: A routine release to the environment that
occurs without interruption, except for infrequent shutdowns for
maintenance, process changes, etc.
Continuous Sample: A flow of water, waste or other material from a
particular place in a plant to the location where samples are collected for
testing. May be used to obtain grab or composite samples.
Contour Plowing: Soil tilling method that follows the shape of the
land to discourage erosion.
Contour Strip Farming: A kind of contour farming in which row
crops are planted in strips, between alternating strips of close-growing,
erosion-resistant forage crops.
Contract Labs: Laboratories under contract to EPA, which analyze
samples taken from waste, soil, air, and water or carry out research
Control Technique Guidelines (CTG): EPA documents designed to
assist state and local pollution authorities to achieve and maintain air
quality standards for certain sources (e.g. organic emissions from solvent
metal cleaning known as degreasing) through reasonably available control
Controlled Reaction: A chemical reaction under temperature and
pressure conditions maintained within safe limits to produce a desired
product or process.
Conventional Filtration: (See:
Conventional Pollutants: Statutorily listed pollutants understood
well by scientists. These may be in the form of organic waste, sediment,
acid, bacteria, viruses, nutrients, oil and grease, or heat.
Conventional Site Assessment: Assessment in which most of the
sample analysis and interpretation of data is completed off-site; process
usually requires repeated mobilization of equipment and staff in order to
fully determine the extent of contamination.
Conventional Systems: Systems that have been traditionally used to
collect municipal wastewater in gravity sewers and convey it to a central
primary or secondary treatment plant prior to discharge to surface waters.
Conventional Tilling: Tillage operations considered standard for a
specific location and crop and that tend to bury the crop residues; usually
considered as a base for determining the cost effectiveness of control
Conveyance Loss: Water loss in pipes, channels, conduits, ditches
by leakage or evaporation.
Cooling Electricity Use: Amount of electricity used to meet the
building cooling load. (See:
building cooling load.)
Cooling Tower: A structure that helps remove heat from water used
as a coolant; e.g., in electric power generating plants.
Cooling Tower: Device which dissipates the heat from water-cooled
systems by spraying the water through streams of rapidly moving air.
Cooperative Agreement: An assistance agreement whereby EPA
transfers money, property, services or anything of value to a state,
university, non-profit, or not-for-profit organization for the
accomplishment of authorized activities or tasks.
Core: The uranium-containing heart of a nuclear reactor, where
energy is released.
Core Program Cooperative Agreement: An assistance agreement
whereby EPA supports states or tribal governments with funds to help defray
the cost of non-item-specific administrative and training activities.
Corrective Action: EPA can require treatment, storage and disposal
(TSDF) facilities handling hazardous waste to undertake corrective actions
to clean up spills resulting from failure to follow hazardous waste
management procedures or other mistakes. The process includes cleanup
procedures designed to guide TSDFs toward in spills.
Corrosion: The dissolution and wearing away of metal caused by a
chemical reaction such as between water and the pipes, chemicals touching a
metal surface, or contact between two metals.
Corrosive: A chemical agent that reacts with the surface of a
material causing it to deteriorate or wear away.
Cost/Benefit Analysis: A quantitative evaluation of the costs
which would have incurred by implementing an environmental regulation versus
the overall benefits to society of the proposed action.
Cost Recovery: A legal process by which potentially responsible
parties who contributed to contamination at a Superfund site can be required
to reimburse the Trust Fund for money spent during any cleanup actions by
the federal government.
Cost Sharing: A publicly financed program through which society,
as a beneficiary of environmental protection, shares part of the cost of
pollution control with those who must actually install the controls. In
Superfund, for example, the government may pay part of the cost of a cleanup
action with those responsible for the pollution paying the major share.
Cost-Effective Alternative: An alternative control or corrective
method identified after analysis as being the best available in terms of
reliability, performance, and cost. Although costs are one important
consideration, regulatory and compliance analysis does not require EPA to
choose the least expensive alternative. For example, when selecting or
approving a method for cleaning up a Superfund site, the Agency balances
costs with the long-term effectiveness of the methods proposed and the
potential danger posed by the site.
Cover Crop: A crop that provides temporary protection for delicate
seedlings and/or provides a cover canopy for seasonal soil protection and
improvement between normal crop production periods.
Cover Material: Soil used to cover compacted solid waste in a
Cradle-to-Grave or Manifest System: A procedure in which hazardous
materials are identified and followed as they are produced, treated,
transported, and disposed of by a series of permanent, linkable, descriptive
documents (e.g. manifests). Commonly referred to as the cradle-to-grave
Criteria: Descriptive factors taken into account by EPA in setting
standards for various pollutants. These factors are used to determine limits
on allowable concentration levels, and to limit the number of violations per
year. When issued by EPA, the criteria provide guidance to the states on how
to establish their standards.
Criteria Pollutants: The 1970 amendments to the Clean Air Act
required EPA to set National Ambient Air Quality Standards for certain
pollutants known to be hazardous to human health. EPA has identified and set
standards to protect human health and welfare for six pollutants: ozone,
carbon monoxide, total suspended particulates, sulfur dioxide, lead, and
nitrogen oxide. The term, "criteria pollutants" derives from the requirement
that EPA must describe the characteristics and potential health and welfare
effects of these pollutants. It is on the basis of these criteria that
standards are set or revised.
Critical Effect: The first adverse effect, or its known precursor,
that occurs as a dose rate increases. Designation is based on evaluation of
Crop Consumptive Use: The amount of water transpired during plant
growth plus what evaporated from the soil surface and foliage in the crop
Crop Rotation: Planting a succession of different crops on the
same land rea as opposed to planting the same crop time after time.
Cross Contamination: The movement of underground contaminants from
one level or area to another due to invasive subsurface activities.
Cross-Connection: Any actual or potential connection between a
drinking water system and an unapproved water supply or other source of
Crumb Rubber: Ground rubber fragments the size of sand or silt
used in rubber or plastic products, or processed further into reclaimed
rubber or asphalt products.
Cryptosporidium: A protozoan microbe associated with the disease
cryptosporidiosis in man. The disease can be transmitted through ingestion
of drinking water, person-to-person contact, or other pathways, and can
cause acute diarrhea, abdominal pain, vomiting, fever, and can be fatal as
it was in the Milwaukee episode.
Cubic Feet Per Minute (CFM): A measure of the volume of a
substance flowing through air within a fixed period of time. With regard to
indoor air, refers to the amount of air, in cubic feet, that is exchanged
with outdoor air in a minute's time; i.e. the air exchange rate.
Cullet: Crushed glass.
Cultural Eutrophication: Increasing rate at which water bodies
"die" by pollution from human activities.
Cultures and Stocks: Infectious agents and associated biologicals
including cultures from medical and pathological laboratories; cultures and
stocks of infectious agents from research and industrial laboratories; waste
from the production of biologicals; discarded live and attenuated vaccines;
and culture dishes and devices used to transfer, inoculate, and mix
regulated medical waste.)
Cumulative Ecological Risk Assessment: Consideration of the total
ecological risk from multiple stressors to a given eco-zone.
Cumulative Exposure: The sum of exposures of an organism to a
pollutant over a period of time.
Cumulative Working Level Months (CWLM): The sum of lifetime
exposure to radon working levels expressed in total working level months.
Curb Stop: A water service shutoff valve located in a water
service pipe near the curb and between the water main and the building.
Curbside Collection: Method of collecting recyclable materials at
homes, community districts or businesses.
Cutie-Pie: An instrument used to measure radiation levels.
Cuttings: Spoils left by conventional drilling with hollow stem
auger or rotary drilling equipment.
Cyclone Collector: A device that uses centrifugal force to remove
large particles from polluted air.
Data Call-In: A part of the Office of Pesticide Programs (OPP)
process of developing key required test data, especially on the long-term,
chronic effects of existing pesticides, in advance of scheduled Registration
Standard reviews. Data Call-In from manufacturers is an adjunct of the
Registration Standards program intended to expedite re-registration.
Data Quality Objectives (DQOs): Qualitative and quantitative
statements of the overall level of uncertainty that a decision-maker will
accept in results or decisions based on environmental data. They provide the
statistical framework for planning and managing environmental data
operations consistent with user's needs.
Day Tank: Another name for deaerating tank. (See:
DDT: The first chlorinated hydrocarbon insecticide chemical name:
Dichloro-Diphenyl-Trichloroethane. It has a half-life of 15 years and can
collect in fatty tissues of certain animals. EPA banned registration and
interstate sale of DDT for virtually all but emergency uses in the United
States in 1972 because of its persistence in the environment and
accumulation in the food chain.
Dead End: The end of a water main which is not connected to other
parts of the distribution system.
Deadmen: Anchors drilled or cemented into the ground to provide
additional reactive mass for DP sampling rigs.
Any solid material exceeding a 60 mm particle size that is intended for
disposal and that is a manufactured object, or plant or animal matter, or
natural geologic material.
Decant: To draw off the upper layer of liquid after the heaviest
material (a solid or another liquid) has settled.
Decay Products: Degraded radioactive materials, often referred to
as "daughters" or "progeny"; radon decay products of most concern from a
public health standpoint are polonium-214 and polonium-218.
Treat a characteristic waste so that it no longer exhibits a characteristic
property. For characteristic wastes treated in Clean Water Act and Safe Drinking
water Act systems, decharacterize means dilution.
Dechlorination: Removal of chlorine from a substance.
Decomposition: The breakdown of matter by bacteria and fungi,
changing the chemical makeup and physical appearance of materials.
Decontamination: Removal of harmful substances such as noxious
chemicals, harmful bacteria or other organisms, or radioactive material from
exposed individuals, rooms and furnishings in buildings, or the exterior
Deep-Well Injection: Deposition of raw or treated, filtered
hazardous waste by pumping it into deep wells, where it is contained in the
pores of permeable subsurface rock.
Deflocculating Agent: A material added to a suspension to prevent
Defluoridation: The removal of excess flouride in drinking water
to prevent the staining of teeth.
Defoliant: An herbicide that removes leaves from trees and growing
Degasification: A water treatment that removes dissolved gases
from the water.
Degree-Day: A rough measure used to estimate the amount of heating
required in a given area; is defined as the difference between the mean
daily temperature and 65 degrees Fahrenheit. Degree-days are also calculated
to estimate cooling requirements.
Delegated State: A state (or other governmental entity such as a
tribal government) that has received authority to administer an
environmental regulatory program in lieu of a federal counterpart. As used
in connection with NPDES, UIC, and PWS programs, the term does not connote
any transfer of federal authority to a state.
Delist: Use of the petition process to have a facility's toxic
Demand-side Waste Management: Prices whereby consumers use
purchasing decisions to communicate to product manufacturers that they
prefer environmentally sound products packaged with the least amount of
waste, made from recycled or recyclable materials, and containing no
Demineralization: A treatment process that removes dissolved
minerals from water.
Denitrification: The biological reduction of nitrate to nitrogen
gas by denitrifying bacteria in soil.
Dense Non-Aqueous Phase Liquid (DNAPL): Non-aqueous phase liquids
such as chlorinated hydrocarbon solvents or petroleum fractions with a
specific gravity greater than 1.0 that sink through the water column until
they reach a confining layer. Because they are at the bottom of aquifers
instead of floating on the water table, typical monitoring wells do not
indicate their presence.
Density: A measure of how heavy a specific volume of a solid,
liquid, or gas is in comparison to water. depending on the chemical.
Depletion Curve: In hydraulics, a graphical representation of
water depletion from storage-stream channels, surface soil, and groundwater.
A depletion curve can be drawn for base flow, direct runoff, or total flow.
Depressurization: A condition that occurs when the air pressure
inside a structure is lower that the air pressure outdoors. Depressurization
can occur when household appliances such as fireplaces or furnaces, that
consume or exhaust house air, are not supplied with enough makeup air. Radon
may be drawn into a house more rapidly under depressurized conditions.
Dermal Absorption/Penetration: Process by which a chemical
penetrates the skin and enters the body as an internal dose.
Dermal Exposure: Contact between a chemical and the skin.
Dermal Toxicity: The ability of a pesticide or toxic chemical to
poison people or animals by contact with the skin. (See:
DES: A synthetic estrogen, diethylstilbestrol is used as a growth
stimulant in food animals. Residues in meat are thought to be carcinogenic.
Desalination: [Desalinization] (1) Removing salts from ocean or
brackish water by using various technologies. (2) Removal of salts from soil
by artificial means, usually leaching.
Desiccant: A chemical agent that absorbs moisture; some desiccants
are capable of drying out plants or insects, causing death.
Design Capacity: The average daily flow that a treatment plant or
other facility is designed to accommodate.
Design Value: The monitored reading used by EPA to determine an
area's air quality status; e.g., for ozone, the fourth highest reading
measured over the most recent three years is the design value.
Designated Pollutant: An air pollutant which is neither a criteria
nor hazardous pollutant, as described in the Clean Air Act, but for which
new source performance standards exist. The Clean Air Act does require
states to control these pollutants, which include acid mist, total reduced
sulfur (TRS), and fluorides.
Designated Uses: Those water uses identified in state water
quality standards that must be achieved and maintained as required under the
Clean Water Act. Uses can include cold water fisheries, public water supply,
Designer Bugs: Popular term for microbes developed through
biotechnology that can degrade specific toxic chemicals at their source in
toxic waste dumps or in ground water.
Destination Facility: The facility to which regulated medical
waste is shipped for treatment and destruction, incineration, and/or
Destratification: Vertical mixing within a lake or reservoir to
totally or partially eliminate separate layers of temperature, plant, or
Destroyed Medical Waste: Regulated medical waste that has been
ruined, torn apart, or mutilated through thermal treatment, melting,
shredding, grinding, tearing, or breaking, so that it is no longer generally
recognized as medical waste, but has not yet been treated (excludes
compacted regulated medical waste).
Destruction and Removal Efficiency (DRE): A percentage that
represents the number of molecules of a compound removed or destroyed in an
incinerator relative to the number of molecules entering the system (e.g. a
DRE of 99.99 percent means that 9,999 molecules are destroyed for every
10,000 that enter; 99.99 percent is known as "four nines." For some
pollutants, the RCRA removal requirement may be as stringent as "six
Destruction Facility: A facility that destroys regulated medical
Desulfurization: Removal of sulfur from fossil fuels to reduce
Detectable Leak Rate: The smallest leak (from a storage tank),
expressed in terms of gallons- or liters-per-hour, that a test can reliably
discern with a certain probability of detection or false alarm.
Detection Criterion: A predetermined rule to ascertain whether a
tank is leaking or not. Most volumetric tests use a threshold value as the
detection criterion. (See:
volumetric tank tests.)
Detection Limit: The lowest concentration of a chemical that can
reliably be distinguished from a zero concentration.
Detention Time: 1. The theoretical calculated time required for a
small amount of water to pass through a tank at a given rate of flow. 2. The
actual time that a small amount of water is in a settling basin,
flocculating basin, or rapid-mix chamber. 3. In storage reservoirs, the
length of time water will be held before being used.
Detergent: Synthetic washing agent that helps to remove dirt and
oil. Some contain compounds which kill useful bacteria and encourage algae
growth when they are in wastewater that reaches receiving waters.
of Equivalent Treatment (DET): A type of variance from the treatment
standards in 40 CFR 268.40; applicable when a technology is specified as the
treatment standard. Allows an alternative technology to be used in lieu of the
specified technology, if the petitioner can demonstrate that the alternative
technology can achieve a measure of performance equivalent to that of the
Development Effects: Adverse effects such as altered growth,
structural abnormality, functional deficiency, or death observed in a
Dewater: 1. Remove or separate a portion of the water in a sludge
or slurry to dry the sludge so it can be handled and disposed of. 2. Remove
or drain the water from a tank or trench.
Diatomaceous Earth (Diatomite): A chalk-like material (fossilized
diatoms) used to filter out solid waste in wastewater treatment plants; also
used as an active ingredient in some powdered pesticides.
Diazinon: An insecticide. In 1986, EPA banned its use on open
areas such as sod farms and golf courses because it posed a danger to
migratory birds. The ban did not apply to agricultural, home lawn or
commercial establishment uses.
Dibenzofurans: A group of organic compounds, some of which are
Dicofol: A pesticide used on citrus fruits.
Diffused Air: A type of aeration that forces oxygen into sewage by
pumping air through perforated pipes inside a holding tank.
Diffusion: The movement of suspended or dissolved particles (or
molecules) from a more concentrated to a less concentrated area. The process
tends to distribute the particles or molecules more uniformly.
Digester: In wastewater treatment, a closed tank; in solid-waste
conversion, a unit in which bacterial action is induced and accelerated in
order to break down organic matter and establish the proper carbon to
Digestion: The biochemical decomposition of organic matter,
resulting in partial gasification, liquefaction, and mineralization of
Dike: A low wall that can act as a barrier to prevent a spill from
Diluent: Any liquid or solid material used to dilute or carry an
Dilution Ratio: The relationship between the volume of water in a
stream and the volume of incoming water. It affects the ability of the
stream to assimilate waste.
Dimictic: Lakes and reservoirs that freeze over and normally go
through two stratifications and two mixing cycles a year.
Dinocap: A fungicide used primarily by apple growers to control
summer diseases. EPA proposed restrictions on its use in 1986 when
laboratory tests found it caused birth defects in rabbits.
Dinoseb: A herbicide that is also used as a fungicide and
insecticide. It was banned by EPA in 1986 because it posed the risk of birth
defects and sterility.
Dioxin: Any of a family of compounds known chemically as
dibenzo-p-dioxins. Concern about them arises from their potential toxicity
as contaminants in commercial products. Tests on laboratory animals indicate
that it is one of the more toxic anthropogenic (man-made) compounds.
Direct Discharger: A municipal or industrial facility which
introduces pollution through a defined conveyance or system such as outlet
pipes; a point source.
Direct Filtration: A method of treating water which consists of
the addition of coagulent chemicals, flash mixing, coagulation, minimal
flocculation, and filtration. Sedimentation is not uses.
Direct Push: Technology used for performing subsurface
investigations by driving, pushing, and/or vibrating small-diameter hollow
steel rods into the ground/ Also known as direct drive, drive point, or push
Direct Runoff: Water that flows over the ground surface or through
the ground directly into streams, rivers, and lakes.
Discharge: Flow of surface water in a stream or canal or the
outflow of ground water from a flowing artesian well, ditch, or spring. Can
also apply tp discharge of liquid effluent from a facility or to chemical
emissions into the air through designated venting mechanisms.
Disinfectant: A chemical or physical process that kills pathogenic
organisms in water, air, or on surfaces. Chlorine is often used to disinfect
sewage treatment effluent, water supplies, wells, and swimming pools.
Disinfectant By-Product: A compound formed by the reaction of a
disinfenctant such as chlorine with organic material in the water supply; a
chemical byproduct of the disinfection process..
Disinfectant Time: The time it takes water to move from the point
of disinfectant application (or the previous point of residual disinfectant
measurement) to a point before or at the point where the residual
disinfectant is measured. In pipelines, the time is calculated by dividing
the internal volume of the pipe by he maximum hourly flow rate; within
mixing basins and storage reservoirs it is determined by tracer studies of
an equivalent demonstration.
Dispersant: A chemical agent used to break up concentrations of
organic material such as spilled oil.
Displacement Savings: Saving realized by displacing purchases of
natural gas or electricity from a local utility by using landfill gas for
power and heat.
Disposables: Consumer products, other items, and packaging used
once or a few times and discarded.
Disposal: Final placement or destruction of toxic, radioactive, or
other wastes; surplus or banned pesticides or other chemicals; polluted
soils; and drums containing hazardous materials from removal actions or
accidental releases. Disposal may be accomplished through use of approved
secure landfills, surface impoundments, land farming, deep-well injection,
ocean dumping, or incineration.
Disposal Facilities: Repositories for solid waste, including
landfills and combustors intended for permanent containment or destruction
of waste materials. Excludes transfer stations and composting facilities.
Dissolved Oxygen (DO): The oxygen freely available in water, vital
to fish and other aquatic life and for the prevention of odors. DO levels
are considered a most important indicator of a water body's ability to
support desirable aquatic life. Secondary and advanced waste treatment are
generally designed to ensure adequate DO in waste-receiving waters.
Dissolved Solids: Disintegrated organic and inorganic material in
water. Excessive amounts make water unfit to drink or use in industrial
Distillation: The act of purifying liquids through boiling, so
that the steam or gaseous vapors condense to a pure liquid. Pollutants and
contaminants may remain in a concentrated residue.
Disturbance: Any event or series of events that disrupt ecosystem,
community, or population structure and alters the physical environment.
Diversion: 1. Use of part of a stream flow as water supply. 2. A
channel with a supporting ridge on the lower side constructed across a slope
to divert water at a non-erosive velocity to sites where it can be used and
Diversion Rate: The percentage of waste materials diverted from
traditional disposal such as landfilling or incineration to be recycled,
composted, or re-used.
DNA Hybridization: Use of a segment of DNA, called a DNA probe, to
identify its complementary DNA; used to detect specific genes.
Dobson Unit (DU): Units of ozone level measurement. measurement of
ozone levels. If, for example, 100 DU of ozone were brought to the earth's
surface they would form a layer one millimeter thick. Ozone levels vary
geographically, even in the absence of ozone depletion.
Domestic Application: Pesticide application in and around houses,
office buildings, motels, and other living or working areas.(See:
Dosage/Dose: 1. The actual quantity of a chemical administered to
an organism or to which it is exposed. 2. The amount of a substance that
reaches a specific tissue (e.g. the liver). 3. The amount of a substance
available for interaction with metabolic processes after crossing the outer
boundary of an organism. (See:
Dose Equivalent: The product of the absorbed dose from ionizing
radiation and such factors as account for biological differences due to the
type of radiation and its distribution in the body in the body.
Dose Rate: In exposure assessment, dose per time unit (e.g.
mg/day), sometimes also called dosage.
Dose Response: Shifts in toxicological responses of an individual
(such as alterations in severity) or populations (such as alterations in
incidence) that are related to changes in the dose of any given substance.
Dose Response Curve: Graphical representation of the relationship
between the dose of a stressor and the biological response thereto.
Dose-Response Assessment: 1. Estimating the potency of a chemical.
2. In exposure assessment, the process of determining the relationship
between the dose of a stressor and a specific biological response. 3.
Evaluating the quantitative relationship between dose and toxicological
Dose-Response Relationship: The quantitative relationship between
the amount of exposure to a substance and the extent of toxic injury or
Dosimeter: An instrument to measure dosage; many so-called
dosimeters actually measure exposure rather than dosage. Dosimetry is the
process or technology of measuring and/or estimating dosage.
DOT Reportable Quantity: The quantity of a substance specified in
a U.S. Department of Transportation regulation that triggers labeling,
packaging and other requirements related to shipping such substances.
Downgradient: The direction that groundwater flows; similar to
"downstream" for surface water.
Downstream Processors: Industries dependent on crop production
(e.g. canneries and food processors).
DP Hole: Hole in the ground made with DP equipment. (See:
Draft: 1. The act of drawing or removing water from a tank or
reservoir. 2. The water which is drawn or removed.
Draft Permit: A preliminary permit drafted and published by EPA;
subject to public review and comment before final action on the application.
Drainage: Improving the productivity of agricultural land by
removing excess water from the soil by such means as ditches or subsurface
Drainage Basin: The area of land that drains water, sediment, and
dissolved materials to a common outlet at some point along a stream channel.
Drainage Well: A well drilled to carry excess water off
agricultural fields. Because they act as a funnel from the surface to the
groundwater below. Drainage wells can contribute to groundwater pollution.
Drawdown: 1. The drop in the water table or level of water in the
ground when water is being pumped from a well. 2. The amount of water used
from a tank or reservoir. 3. The drop in the water level of a tank or
Dredging: Removal of mud from the bottom of water bodies. This can
disturb the ecosystem and causes silting that kills aquatic life. Dredging
of contaminated muds can expose biota to heavy metals and other toxics.
Dredging activities may be subject to regulation under Section 404 of the
Clean Water Act.
Drilling Fluid: Fluid used to lubricate the bit and convey drill
cuttings to the surface with rotary drilling equipment. Usually composed of
bentonite slurry or muddy water. Can become contaminated, leading to cross
contamination, and may require special disposal. Not used with DP methods
Drinking Water Equivalent Level: Protective level of exposure
related to potentially non-carcinogenic effects of chemicals that are also
known to cause cancer.
Drinking Water State Revolving Fund: The Fund provides
capitalization grants to states to develop drinking water revolving loan
funds to help finance system infrastructure improvements, assure
source-water protection, enhance operation and management of drinking-water
systems, and otherwise promote local water-system compliance and protection
of public health.
Drive Casing: Heavy duty steel casing driven along with the
sampling tool in cased DP systems. Keeps the hole open between sampling runs
and is not removed until last sample has been collected.
Drive Point Profiler: An exposed groundwater DP system used to
collect multiple depth-discrete groundwater samples. Ports in the tip of the
probe connect to an internal stainless steel or teflon tube that extends to
the surface. Samples are collected via suction or airlift methods. Deionized
water is pumped down through the ports to prevent plugging while driving the
tool to the next sampling depth.
Drop-off: Recyclable materials collection method in which
individuals bring them to a designated collection site.
Dual-Phase Extraction: Active withdrawal of both liquid and gas
phases from a well usually involving the use of a vacuum pump.
Dump: A site used to dispose of solid waste without environmental
Duplicate: A second aliquot or sample that is treated the same as
the original sample in order to determine the precision of the analytical
method. (See: aliquot.)
Dustfall Jar: An open container used to collect large particles
from the air for measurement and analysis.
device used to place a load on an engine and measure its performance.
Dystrophic Lakes: Acidic, shallow bodies of water that contain
much humus and/or other organic matter; contain many plants but few fish.
Ecological Entity: In ecological risk assessment, a general term
referring to a species, a group of species, an ecosystem function or
characteristic, or a specific habitat or biome.
Ecological/Environmental Sustainability: Maintenance of ecosystem
components and functions for future generations.
Ecological Exposure: Exposure of a non-human organism to a
Ecological Impact: The effect that a man-caused or natural
activity has on living organisms and their non-living (abiotic) environment.
Ecological Indicator: A characteristic of an ecosystem that is
related to, or derived from, a measure of biotic or abiotic variable, that
can provide quantitative information on ecological structure and function.
An indicator can contribute to a measure of integrity and sustainability.
Ecological Integrity: A living system exhibits integrity if, when
subjected to disturbance, it sustains and organizes self-correcting ability
to recover toward a biomass end-state that is normal for that system.
End-states other than the pristine or naturally whole may be accepted as
normal and good.
Ecological Risk Assessment: The application of a formal framework,
analytical process, or model to estimate the effects of human actions(s) on
a natural resource and to interpret the significance of those effects in
light of the uncertainties identified in each component of the assessment
process. Such analysis includes initial hazard identification, exposure and
dose-response assessments, and risk characterization.
Ecology: The relationship of living things to one another and
their environment, or the study of such relationships.
Economic Poisons: Chemicals used to control pests and to defoliate
cash crops such as cotton.
Ecosphere: The "bio-bubble" that contains life on earth, in
surface waters, and in the air. (See:
Ecosystem: The interacting system of a biological community and
its non-living environmental surroundings.
Ecosystem Structure: Attributes related to the instantaneous
physical state of an ecosystem; examples include species population density,
species richness or evenness, and standing crop biomass.
Ecotone: A habitat created by the juxtaposition of distinctly
different habitats; an edge habitat; or an ecological zone or boundary where
two or more ecosystems meet.
Effluent: Wastewater--treated or untreated--that flows out of a
treatment plant, sewer, or industrial outfall. Generally refers to wastes
discharged into surface waters.
Effluent Guidelines: Technical EPA documents which set effluent
limitations for given industries and pollutants.
Effluent Limitation: Restrictions established by a state or EPA on
quantities, rates, and concentrations in wastewater discharges.
Effluent Standard: (See:
Ejector: A device used to disperse a chemical solution into water
Electrodialysis: A process that uses electrical current applied to
permeable membranes to remove minerals from water. Often used to desalinize
salty or brackish water.
Electromagnetic Geophysical Methods: Ways to measure subsurface
conductivity via low-frequency electromagnetic induction.
Electrostatic Precipitator (ESP): A device that removes particles
from a gas stream (smoke) after combustion occurs. The ESP imparts an
electrical charge to the particles, causing them to adhere to metal plates
inside the precipitator. Rapping on the plates causes the particles to fall
into a hopper for disposal.
Eligible Costs: The construction costs for wastewater treatment
works upon which EPA grants are based.
EMAP Data: Environmental monitoring data collected under the
auspices of the Environmental Monitoring and Assessment Program. All EMAP
data share the common attribute of being of known quality, having been
collected in the context of explicit data quality objectives (DQOs) and a
consistent quality assurance program.
Emergency and Hazardous Chemical Inventory: An annual
report by facilities having one or more extremely hazardous substances or
hazardous chemicals above certain weight limits.
Emergency (Chemical): A situation created by an accidental release
or spill of hazardous chemicals that poses a threat to the safety of
workers, residents, the environment, or property.
Emergency Episode: (See:
air pollution episode.)
Emergency Exemption: Provision in FIFRA under which EPA can grant
temporary exemption to a state or another federal agency to allow the use of
a pesticide product not registered for that particular use. Such actions
involve unanticipated and/or severe pest problems where there is not time or
interest by a manufacturer to register the product for that use.
(Registrants cannot apply for such exemptions.)
Emergency Removal Action: 1. Steps take to remove contaminated
materials that pose imminent threats to local residents (e.g. removal of
leaking drums or the excavation of explosive waste.) 2. The state record of
Emergency Response Values: Concentrations of chemicals, published
by various groups, defining acceptable levels for short-term exposures in
Emergency Suspension: Suspension of a pesticide product
registration due to an imminent hazard. The action immediately halts
distribution, sale, and sometimes actual use of the pesticide involved.
Emission: Pollution discharged into the atmosphere from
smokestacks, other vents, and surface areas of commercial or industrial
facilities; from residential chimneys; and from motor vehicle, locomotive,
or aircraft exhausts.
Emission Cap: A limit designed to prevent projected growth in
emissions from existing and future stationary sources from eroding any
mandated reductions. Generally, such provisions require that any emission
growth from facilities under the restrictions be offset by equivalent
reductions at other facilities under the same cap. (See:
Emission Factor: The relationship between the amount of pollution
produced and the amount of raw material processed. For example, an emission
factor for a blast furnace making iron would be the number of pounds of
particulates per ton of raw materials.
Emission Inventory: A listing, by source, of the amount of air
pollutants discharged into the atmosphere of a community; used to establish
Emission Standard: The maximum amount of air polluting discharge
legally allowed from a single source, mobile or stationary.
Emissions Trading: The creation of surplus emission reductions at
certain stacks, vents or similar emissions sources and the use of this
surplus to meet or redefine pollution requirements applicable to other
emissions sources. This allows one source to increase emissions when another
source reduces them, maintaining an overall constant emission level.
Facilities that reduce emissions substantially may "bank" their "credits" or
sell them to other facilities or industries.
Emulsifier: A chemical that aids in suspending one liquid in
another. Usually an organic chemical in an aqueous solution.
Encapsulation: The treatment of asbestos-containing material with
a liquid that covers the surface with a protective coating or embeds fibers
in an adhesive matrix to prevent their release into the air.
Enclosure: Putting an airtight, impermeable, permanent barrier
around asbestos-containing materials to prevent the release of asbestos
fibers into the air.
End User: Consumer of products for the purpose of recycling.
Excludes products for re-use or combustion for energy recovery.
End-of-the-pipe: Technologies such as scrubbers on smokestacks and
catalytic convertors on automobile tailpipes that reduce emissions of
pollutants after they have formed.
End-use Product: A pesticide formulation for field or other end
use. The label has instructions for use or application to control pests or
regulate plant growth. The term excludes products used to formulate other
Endangered Species: Animals, birds, fish, plants, or other living
organisms threatened with extinction by anthropogenic (man-caused) or other
natural changes in their environment. Requirements for declaring a species
endangered are contained in the Endangered Species Act.
Endangerment Assessment: A study to determine the nature and
extent of contamination at a site on the National Priorities List and the
risks posed to public health or the environment. EPA or the state conducts
the study when a legal action is to be taken to direct potentially
responsible parties to clean up a site or pay for it. An endangerment
assessment supplements a remedial investigation.
Endrin: A pesticide toxic to freshwater and marine aquatic life
that produces adverse health effects in domestic water supplies.
Energy Management System: A control system capable of monitoring
environmental and system loads and adjusting HVAC operations accordingly in
order to conserve energy while maintaining comfort.
Energy Recovery: Obtaining energy from waste through a variety of
processes (e.g. combustion).
Enforceable Requirements: Conditions or limitations in permits
issued under the Clean Water Act Section 402 or 404 that, if violated, could
result in the issuance of a compliance order or initiation of a civil or
criminal action under federal or applicable state laws. If a permit has not
been issued, the term includes any requirement which, in the Regional
Administrator's judgement, would be included in the permit when issued.
Where no permit applies, the term includes any requirement which the RA
determines is necessary for the best practical waste treatment technology to
meet applicable criteria.
Enforcement: EPA, state, or local legal actions to obtain
compliance with environmental laws, rules, regulations, or agreements and/or
obtain penalties or criminal sanctions for violations. Enforcement
procedures may vary, depending on the requirements of different
environmental laws and related implementing regulations. Under CERCLA, for
example, EPA will seek to require potentially responsible parties to clean
up a Superfund site, or pay for the cleanup, whereas under the Clean Air Act
the Agency may invoke sanctions against cities failing to meet ambient air
quality standards that could prevent certain types of construction or
federal funding. In other situations, if investigations by EPA and state
agencies uncover willful violations, criminal trials and penalties are
Enforcement Decision Document (EDD): A document that provides an
explanation to the public of EPA's selection of the cleanup alternative at
enforcement sites on the National Priorities List. Similar to a Record of
Engineered Controls: Method of managing environmental and health
risks by placing a barrier between the contamination and the rest of the
site, thus limiting exposure pathways.
Enhanced Inspection and Maintenance (I&M): An improved automobile
inspection and maintenance program--aimed at reducing automobile
emissions---that contains, at a minimum, more vehicle types and model years,
tighter inspection, and better management practices. It may also include
annual computerized or centralized inspections, under-the-hood
inspection--for signs of tampering with pollution control equipment--and
increased repair waiver cost.
Enrichment: The addition of nutrients (e.g. nitrogen, phosphorus,
carbon compounds) from sewage effluent or agricultural runoff to surface
water, greatly increases the growth potential for algae and other aquatic
Entrain: To trap bubbles in water either mechanically through
turbulence or chemically through a reaction.
Environment: The sum of all external conditions affecting the
life, development and survival of an organism.
Environmental Assessment: An environmental analysis prepared
pursuant to the National Environmental Policy Act to determine whether a
federal action would significantly affect the environment and thus require a
more detailed environmental impact statement.
Environmental Audit: An independent assessment of the current
status of a party's compliance with applicable environmental requirements or
of a party's environmental compliance policies, practices, and controls.
Environmental/Ecological Risk: The potential for adverse effects
on living organisms associated with pollution of the environment by
effluents, emissions, wastes, or accidental chemical releases; energy use;
or the depletion of natural resources.
Environmental Equity/Justice: Equal protection from environmental
hazards for individuals, groups, or communities regardless of race,
ethnicity, or economic status. This applies to the development,
implementation, and enforcement of environmental laws, regulations, and
policies, and implies that no population of people should be forced to
shoulder a disproportionate share of negative environmental impacts of
pollution or environmental hazard due to a lack of political or economic
Environmental Exposure: Human exposure to pollutants originating
from facility emissions. Threshold levels are not necessarily surpassed, but
low-level chronic pollutant exposure is one of the most common forms of
environmental exposure (See:
Environmental Fate: The destiny of a chemical or biological
pollutant after release into the environment.
Environmental Fate Data: Data that characterize a pesticide's fate
in the ecosystem, considering factors that foster its degradation (light,
water, microbes), pathways and resultant products.
Environmental Impact Statement: A document required of federal
agencies by the National Environmental Policy Act for major projects or
legislative proposals significantly affecting the environment. A tool for
decision making, it describes the positive and negative effects of the
undertaking and cites alternative actions.
Environmental Indicator: A measurement, statistic or value that
provides a proximate gauge or evidence of the effects of environmental
management programs or of the state or condition of the environment.
Environmental Justice: The fair treatment of people of
all races, cultures, incomes, and educational levels with respect to the
development and enforcement of environmental laws, regulations, and
Environmental Lien: A charge, security, or encumbrance on a
property's title to secure payment of cost or debt arising from response
actions, cleanup, or other remediation of hazardous substances or petroleum
Environmental Medium: A major environmental category that
surrounds or contacts humans, animals, plants, and other organisms (e.g.
surface water, ground water, soil or air) and through which chemicals or
pollutants move. (See:
Environmental Monitoring for Public Access and Community Tracking:
Joint EPA, NOAA, and USGS program to provide timely and effective
communication of environmental data and information through improved and
updated technology solutions that support timely environmental monitoring
reporting, interpreting, and use of the information for the benefit of the
public. (See: real-time
Environmental Response Team: EPA experts located in Edison, N.J.,
and Cincinnati, OH, who can provide around-the-clock technical assistance to
EPA regional offices and states during all types of hazardous waste site
emergencies and spills of hazardous substances.
Environmental Site Assessment: The process of determining whether
contamination is present on a parcel of real property.
Environmental Sustainability: Long-term maintenance of ecosystem
components and functions for future generations.
Environmental Tobacco Smoke: Mixture of smoke from the burning end
of a cigarette, pipe, or cigar and smoke exhaled by the smoker. (See:
Epidemiology: Study of the distribution of disease, or other
health-related states and events in human populations, as related to age,
sex, occupation, ethnicity, and economic status in order to identify and
alleviate health problems and promote better health.
Epilimnion: Upper waters of a thermally stratified lake subject to
Episode (Pollution): An air pollution incident in a given area
caused by a concentration of atmospheric pollutants under meteorological
conditions that may result in a significant increase in illnesses or deaths.
May also describe water pollution events or hazardous material spills.
Equilibrium: In relation to radiation, the state at which the
radioactivity of consecutive elements within a radioactive series is neither
increasing nor decreasing.
Equivalent Method: Any method of sampling and analyzing for air
pollution which has been demonstrated to the EPA Administrator's
satisfaction to be, under specific conditions, an acceptable alternative to
normally used reference methods.
Erosion: The wearing away of land surface by wind or water,
intensified by land-clearing practices related to farming, residential or
industrial development, road building, or logging.
Established Treatment Technologies: Technologies for which cost
and performance data are readily available. (See:
Estimated Environmental Concentration: The estimated pesticide
concentration in an ecosystem.
Estuary: Region of interaction between rivers and near-shore ocean
waters, where tidal action and river flow mix fresh and salt water. Such
areas include bays, mouths of rivers, salt marshes, and lagoons. These
brackish water ecosystems shelter and feed marine life, birds, and wildlife.
Ethanol: An alternative automotive fuel derived from grain and
corn; usually blended with gasoline to form gasohol.
Ethylene Dibromide (EDB): A chemical used as an agricultural
fumigant and in certain industrial processes. Extremely toxic and found to
be a carcinogen in laboratory animals, EDB has been banned for most
agricultural uses in the United States.
Eutrophic Lakes: Shallow, murky bodies of water with
concentrations of plant nutrients causing excessive production of algae.
(See: dystrophic lakes.)
Eutrophication: The slow aging process during which a lake,
estuary, or bay evolves into a bog or marsh and eventually disappears.
During the later stages of eutrophication the water body is choked by
abundant plant life due to higher levels of nutritive compounds such as
nitrogen and phosphorus. Human activities can accelerate the process.
Evaporation Ponds: Areas where sewage sludge is dumped and dried.
Evapotranspiration: The loss of water from the soil both by
evaporation and by transpiration from the plants growing in the soil.
Exceedance: Violation of the pollutant levels permitted by
environmental protection standards.
Exclusion: In the asbestos program, one of several situations that
permit a Local Education Agency (LEA) to delete one or more of the items
required by the Asbestos Hazard Emergency Response Act (AHERA); e.g. records
of previous asbestos sample collection and analysis may be used by the
accredited inspector in lieu of AHERA bulk sampling.
Exclusionary Ordinance: Zoning that excludes classes of persons or
businesses from a particular neighborhood or area.
Exempt Solvent: Specific organic compounds not subject to
requirements of regulation because they are deemed by EPA to be of
negligible photochemical reactivity.
Exempted Aquifer: Underground bodies of water defined in the
Underground Injection Control program as aquifers that are potential sources
of drinking water though not being used as such, and thus exempted from
regulations barring underground injection activities.
Exemption: A state (with primacy) may exempt a public water system
from a requirement involving a Maximum Contaminant Level (MCL), treatment
technique, or both, if the system cannot comply due to compelling economic
or other factors, or because the system was in operation before the
requirement or MCL was instituted; and the exemption will not create a
public health risk. (See:
Exotic Species: A species that is not indigenous to a region.
Experimental Use Permit: Obtained by manufacturers for testing new
pesticides or uses thereof whenever they conduct experimental field studies
to support registration on 10 acres or more of land or one acre or more of
Experimental Use Permit: A permit granted by EPA that allows a
producer to conduct tests of a new pesticide, product and/or use outside the
laboratory. The testing is usually done on ten or more acres of land or
Explosive Limits: The amounts of vapor in the air that form
explosive mixtures; limits are expressed as lower and upper limits and give
the range of vapor concentrations in air that will explode if an ignition
source is present.
Exports : In solid waste program, municipal solid waste and
recyclables transported outside the state or locality where they originated.
Exposure: The amount of radiation or pollutant present in a given
environment that represents a potential health threat to living organisms.
Exposure Assessment: Identifying the pathways by which toxicants
may reach individuals, estimating how much of a chemical an individual is
likely to be exposed to, and estimating the number likely to be exposed.
Exposure Concentration: The concentration of a chemical or other
pollutant representing a health threat in a given environment.
Exposure Indicator: A characteristic of the environment measured
to provide evidence of the occurrence or magnitude of a response indicator's
exposure to a chemical or biological stress.
Exposure Level: The amount (concentration) of a chemical at the
absorptive surfaces of an organism.
Exposure Pathway: The path from sources of pollutants via, soil,
water, or food to man and other species or settings.
Exposure Route: The way a chemical or pollutant enters an organism
after contact; i.e. by ingestion, inhalation, or dermal absorption.
Exposure-Response Relationship: The relationship between exposure
level and the incidence of adverse effects.
Extraction Procedure (EP Toxic): Determining toxicity by a
procedure which simulates leaching; if a certain concentration of a toxic
substance can be leached from a waste, that waste is considered hazardous,
Extraction Well: A discharge well used to remove groundwater or
Extremely Hazardous Substances: Any of 406 chemicals identified by
EPA as toxic, and listed under SARA Title III. The list is subject to
Fabric Filter: A cloth device that catches dust particles from
Facilities Plans: Plans and studies related to the construction of
treatment works necessary to comply with the Clean Water Act or RCRA. A
facilities plan investigates needs and provides information on the
cost-effectiveness of alternatives, a recommended plan, an environmental
assessment of the recommendations, and descriptions of the treatment works,
costs, and a completion schedule.
Facility Emergency Coordinator: Representative of a facility
covered by environmental law (e.g, a chemical plant) who participates in the
emergency reporting process with the Local Emergency Planning Committee
Facultative Bacteria: Bacteria that can live under aerobic or
Feasibility Study: 1. Analysis of the practicability of a
proposal; e.g., a description and analysis of potential cleanup alternatives
for a site such as one on the National Priorities List. The feasibility
study usually recommends selection of a cost-effective alternative. It
usually starts as soon as the remedial investigation is underway; together,
they are commonly referred to as the "RI/FS". 2. A small-scale investigation
of a problem to ascertain whether a proposed research approach is likely to
provide useful data.
Fecal Coliform Bacteria: Bacteria found in the intestinal tracts
of mammals. Their presence in water or sludge is an indicator of pollution
and possible contamination by pathogens.
Federal Implementation Plan: Under current law, a federally
implemented plan to achieve attainment of air quality standards, used when a
state is unable to develop an adequate plan.
Federal Motor Vehicle Control Program: All federal actions aimed
at controlling pollution from motor vehicles by such efforts as establishing
and enforcing tailpipe and evaporative emission standards for new vehicles,
testing methods development, and guidance to states operating inspection and
maintenance programs. Federally designated area that is required to meet and
maintain federal ambient air quality standards. May include nearby locations
in the same state or nearby states that share common air pollution problems.
Feedlot: A confined area for the controlled feeding of animals.
Tends to concentrate large amounts of animal waste that cannot be absorbed
by the soil and, hence, may be carried to nearby streams or lakes by
Fen: A type of wetland that accumulates peat deposits. Fens are
less acidic than bogs, deriving most of their water from groundwater rich in
calcium and magnesium. (See:
Ferrous Metals: Magnetic metals derived from iron or steel;
products made from ferrous metals include appliances, furniture, containers,
and packaging like steel drums and barrels. Recycled products include
processing tin/steel cans, strapping, and metals from appliances into new
FIFRA Pesticide Ingredient: An ingredient of a pesticide that must
be registered with EPA under the Federal Insecticide, Fungicide, and
Rodenticide Act. Products making pesticide claims must register under FIFRA
and may be subject to labeling and use requirements.
Fill: Man-made deposits of natural soils or rock products and
Filling: Depositing dirt, mud or other materials into aquatic
areas to create more dry land, usually for agricultural or commercial
development purposes, often with ruinous ecological consequences.
Filter Strip: Strip or area of vegetation used for removing
sediment, organic matter, and other pollutants from runoff and wastewater.
Filtration: A treatment process, under the control of qualified
operators, for removing solid (particulate) matter from water by means of
porous media such as sand or a man-made filter; often used to remove
particles that contain pathogens.
Financial Assurance for Closure: Documentation or proof that an
owner or operator of a facility such as a landfill or other waste repository
is capable of paying the projected costs of closing the facility and
monitoring it afterwards as provided in RCRA regulations.
Finding of No Significant Impact: A document prepared by a federal
agency showing why a proposed action would not have a significant impact on
the environment and thus would not require preparation of an Environmental
Impact Statement. An FNSI is based on the results of an environmental
Finished Water: Water is "finished" when it has passed through all
the processes in a water treatment plant and is ready to be delivered to
First Draw: The water that comes out when a tap is first opened,
likely to have the highest level of lead contamination from plumbing
Fix a Sample: A sample is "fixed" in the field by adding chemicals
that prevent water quality indicators of interest in the sample from
changing before laboratory measurements are made.
Fixed-Location Monitoring: Sampling of an environmental or ambient
medium for pollutant concentration at one location continuously or
Flammable: Any material that ignites easily and will burn rapidly.
Flare: A control device that burns hazardous materials to prevent
their release into the environment; may operate continuously or
intermittently, usually on top of a stack.
Flash Point: The lowest temperature at which evaporation of a
substance produces sufficient vapor to form an ignitable mixture with air.
Floc: A clump of solids formed in sewage by biological or chemical
Flocculation: Process by which clumps of solids in water or sewage
aggregate through biological or chemical action so they can be separated
from water or sewage.
Floodplain: The flat or nearly flat land along a river or stream
or in a tidal area that is covered by water during a flood.
Floor Sweep: Capture of heavier-than-air gases that collect at
Flow Rate: The rate, expressed in gallons -or liters-per-hour, at
which a fluid escapes from a hole or fissure in a tank. Such measurements
are also made of liquid waste, effluent, and surface water movement.
Flowable: Pesticide and other formulations in which the active
ingredients are finely ground insoluble solids suspended in a liquid. They
are mixed with water for application.
Flowmeter: A gauge indicating the velocity of wastewater moving
through a treatment plant or of any liquid moving through various industrial
Flue Gas: The air coming out of a chimney after combustion in the
burner it is venting. It can include nitrogen oxides, carbon oxides, water
vapor, sulfur oxides, particles and many chemical pollutants.
Flue Gas Desulfurization: A technology that employs a sorbent,
usually lime or limestone, to remove sulfur dioxide from the gases produced
by burning fossil fuels. Flue gas desulfurization is current state-of-the
art technology for major SO2 emitters, like power plants.
Fluidized: A mass of solid particles that is made to flow like a
liquid by injection of water or gas is said to have been fluidized. In water
treatment, a bed of filter media is fluidized by backwashing water through
Fluidized Bed Incinerator: An incinerator that uses a bed of hot
sand or other granular material to transfer heat directly to waste. Used
mainly for destroying municipal sludge.
Flume: A natural or man-made channel that diverts water.
Fluoridation: The addition of a chemical to increase the
concentration of fluoride ions in drinking water to reduce the incidence of
Fluorides: Gaseous, solid, or dissolved compounds containing
fluorine that result from industrial processes. Excessive amounts in food
can lead to fluorosis.
Fluorocarbons (FCs): Any of a number of organic compounds
analogous to hydrocarbons in which one or more hydrogen atoms are replaced
by fluorine. Once used in the United States as a propellant for domestic
aerosols, they are now found mainly in coolants and some industrial
processes. FCs containing chlorine are called chlorofluorocarbons (CFCs).
They are believed to be modifying the ozone layer in the stratosphere,
thereby allowing more harmful solar radiation to reach the Earth's surface.
Flush: 1. To open a cold-water tap to clear out all the water
which may have been sitting for a long time in the pipes. In new homes, to
flush a system means to send large volumes of water gushing through the
unused pipes to remove loose particles of solder and flux. 2. To force large
amounts of water through a system to clean out piping or tubing, and storage
or process tanks.
Flux: 1. A flowing or flow. 2. A substance used to help metals
Fly Ash: Non-combustible residual particles expelled by flue gas.
Fogging: Applying a pesticide by rapidly heating the liquid
chemical so that it forms very fine droplets that resemble smoke or fog.
Used to destroy mosquitoes, black flies, and similar pests.
Food Chain: A sequence of organisms, each of which uses the next,
lower member of the sequence as a food source.
Food Processing Waste: Food residues produced during agricultural
and industrial operations.
Food Waste: Uneaten food and food preparation wastes from
residences and commercial establishments such as grocery stores,
restaurants, and produce stands, institutional cafeterias and kitchens, and
industrial sources like employee lunchrooms.
Food Web: The feeding relationships by which energy and nutrients
are transferred from one species to another.
Formaldehyde: A colorless, pungent, and irritating gas, CH20, used
chiefly as a disinfectant and preservative and in synthesizing other
compounds like resins.
Formulation: The substances comprising all active and inert
ingredients in a pesticide.
Fossil Fuel: Fuel derived from ancient organic remains; e.g. peat,
coal, crude oil, and natural gas.
Fracture: A break in a rock formation due to structural stresses;
e.g. faults, shears, joints, and planes of fracture cleavage.
Free Product: A petroleum hydrocarbon in the liquid free or non
aqueous phase. (See:
non-aqueous phase liquid.)
Freeboard: 1. Vertical distance from the normal water surface to
the top of a confining wall. 2. Vertical distance from the sand surface to
the underside of a trough in a sand filter.
Fresh Water: Water that generally contains less than 1,000
milligrams-per-liter of dissolved solids.
Friable: Capable of being crumbled, pulverized, or reduced to
powder by hand pressure.
Friable Asbestos: Any material containing more than one-percent
asbestos, and that can be crumbled or reduced to powder by hand pressure.
(May include previously non-friable material which becomes broken or damaged
by mechanical force.)
Fuel Economy Standard: The Corporate Average Fuel Economy Standard
(CAFE) effective in 1978. It enhanced the national fuel conservation effort
imposing a miles-per-gallon floor for motor vehicles.
Fuel Efficiency: The proportion of energy released by fuel
combustion that is converted into useful energy.
Fuel Switching: 1. A precombustion process whereby a low-sulfur
coal is used in place of a higher sulfur coal in a power plant to reduce
sulfur dioxide emissions. 2. Illegally using leaded gasoline in a motor
vehicle designed to use only unleaded.
Fugitive Emissions: Emissions not caught by a capture system.
Fume: Tiny particles trapped in vapor in a gas stream.
Fumigant: A pesticide vaporized to kill pests. Used in buildings
Functional Equivalent: Term used to describe EPA's decision-making
process and its relationship to the environmental review conducted under the
National Environmental Policy Act (NEPA). A review is considered
functionally equivalent when it addresses the substantive components of a
Fungicide: Pesticides which are used to control, deter, or destroy
Fungistat: A chemical that keeps fungi from growing.
Fungus (Fungi): Molds, mildews, yeasts, mushrooms, and puffballs,
a group of organisms lacking in chlorophyll (i.e. are not photosynthetic)
and which are usually non-mobile, filamentous, and multicellular. Some grow
in soil, others attach themselves to decaying trees and other plants whence
they obtain nutrients. Some are pathogens, others stabilize sewage and
digest composted waste.
Furrow Irrigation: Irrigation method in which water travels
through the field by means of small channels between each groups of rows.
Future Liability: Refers to potentially responsible parties'
obligations to pay for additional response activities beyond those specified
in the Record of Decision or Consent Decree.
Game Fish: Species like trout, salmon, or bass, caught for sport.
Many of them show more sensitivity to environmental change than "rough"
Garbage: Animal and vegetable waste resulting from the handling,
storage, sale, preparation, cooking, and serving of foods.
Gas Chromatograph/Mass Spectrometer: Instrument that identifies
the molecular composition and concentrations of various chemicals in water
and soil samples.
Gasahol: Mixture of gasoline and ethanol derived from fermented
agricultural products containing at least nine percent ethanol. Gasohol
emissions contain less carbon monoxide than those from gasoline.
Gasification: Conversion of solid material such as coal into a gas
for use as a fuel.
Gasoline Volatility: The property of gasoline whereby it
evaporates into a vapor. Gasoline vapor is a mixture of volatile organic
General Permit: A permit applicable to a class or category of
General Reporting Facility: A facility having one or more
hazardous chemicals above the 10,000 pound threshold for planning
quantities. Such facilities must file MSDS and emergency inventory
information with the SERC, LEPC, and local fire departments.
Generally Recognized as Safe (GRAS): Designation by the FDA that a
chemical or substance (including certain pesticides) added to food is
considered safe by experts, and so is exempted from the usual FFDCA food
additive tolerance requirements.
Generator: 1. A facility or mobile source that emits pollutants
into the air or releases hazardous waste into water or soil. 2. Any person,
by site, whose act or process produces regulated medical waste or whose act
first causes such waste to become subject to regulation. Where more than one
person (e.g. doctors with separate medical practices) are located in the
same building, each business entity is a separate generator.
Any person whose act first creates or produces hazardous waste.
Genetic Engineering: A process of inserting new genetic
information into existing cells in order to modify a specific organism for
the purpose of changing one of its characteristics.
Damaging to DNA; pertaining to agents known to damage DNA.
Geographic Information System (GIS): A computer system designed
for storing, manipulating, analyzing, and displaying data in a geographic
Geological Log: A detailed description of all underground features
(depth, thickness, type of formation) discovered during the drilling of a
Geophysical Log: A record of the structure and composition of the
earth encountered when drilling a well or similar type of test hold or
Geothermal/Ground Source Heat Pump: These heat pumps are
underground coils to transfer heat from the ground to the inside of a
building. (See: heat
pump; water source
Germicide: Any compound that kills disease-causing microorganisms.
Giardia Lamblia: Protozoan in the feces of humans and animals that
can cause severe gastrointestinal ailments. It is a common contaminant of
Glass Containers: For recycling purposes, containers like bottles
and jars for drinks, food, cosmetics and other products. When being
recycled, container glass is generally separated into color categories for
conversion into new containers, construction materials or fiberglass
Global Warming: An increase in the near surface temperature of the
Earth. Global warming has occurred in the distant past as the result of
natural influences, but the term is most often used to refer to the warming
predicted to occur as a result of increased emissions of greenhouse gases.
Scientists generally agree that the Earth's surface has warmed by about 1
degree Fahrenheit in the past 140 years. The Intergovernmental Panel on
Climate Change (IPCC) recently concluded that increased concentrations of
greenhouse gases are causing an increase in the Earth's surface temperature
and that increased concentrations of sulfate aerosols have led to relative
cooling in some regions, generally over and downwind of heavily
industrialized areas. (See:
Global Warming Potential: The ratio of the warming caused by a
substance to the warming caused by a similar mass of carbon dioxide. CFC-12,
for example, has a GWP of 8,500, while water has a GWP of zero. (See:
Class I Substance
and Class II Substance.)
Glovebag: A polyethylene or polyvinyl chloride bag-like enclosure
affixed around an asbestos-containing source (most often thermal system
insulation) permitting the material to be removed while minimizing release
of airborne fibers to the surrounding atmosphere.
Gooseneck: A portion of a water service connection between the
distribution system water main and a meter. Sometimes called a pigtail.
Grab Sample: A single sample collected at a particular time and
place that represents the composition of the water, air, or soil only at
that time and place.
Grain Loading: The rate at which particles are emitted from a
pollution source. Measurement is made by the number of grains per cubic foot
of gas emitted.
Granular Activated Carbon Treatment: A filtering system often used
in small water systems and individual homes to remove organics. Also used by
municipal water treatment plantsd. GAC can be highly effective in lowering
elevated levels of radon in water.
Grasscycling: Source reduction activities in which grass clippings
are left on the lawn after mowing.
Grassed Waterway: Natural or constructed watercourse or outlet
that is shaped or graded and established in suitable vegetation for the
disposal of runoff water without erosion.
Gray Water: Domestic wastewater composed of wash water from
kitchen, bathroom, and laundry sinks, tubs, and washers.
Greenhouse Effect: The warming of the Earth's atmosphere
attributed to a buildup of carbon dioxide or other gases; some scientists
think that this build-up allows the sun's rays to heat the Earth, while
making the infra-red radiation atmosphere opaque to infra-red radiation,
thereby preventing a counterbalancing loss of heat.
Greenhouse Gas: A gas, such as carbon dioxide or methane, which
contributes to potential climate change.
Grinder Pump: A mechanical device that shreds solids and raises
sewage to a higher elevation through pressure sewers.
Gross Alpha/Beta Particle Activity: The total radioactivity due to
alpha or beta particle emissions as inferred from measurements on a dry
Gross Power-Generation Potential: The installed power generation
capacity that landfill gas can support.
Ground Cover: Plants grown to keep soil from eroding.
Ground Water: The supply of fresh water found beneath the Earth's
surface, usually in aquifers, which supply wells and springs. Because ground
water is a major source of drinking water, there is growing concern over
contamination from leaching agricultural or industrial pollutants or leaking
underground storage tanks.
Ground Water Under the Direct Influence (UDI) of Surface Water:
Any water beneath the surface of the ground with: 1. significant occurence
of insects or other microorganisms, algae, or large-diameter pathogens; 2.
significant and relatively rapid shifts in water characteristics such as
turbidity, temperature, conductivity, or pH which closely correlate to
climatological or surface water conditions. Direct influence is determined
for individual sources in accordance with criteria established by a state.
Ground-Penetrating Radar: A geophysical method that uses high
frequency electromagnetic waves to obtain subsurface information.
Ground-Water Discharge: Ground water entering near coastal waters
which has been contaminated by landfill leachate, deep well injection of
hazardous wastes, septic tanks, etc.
Ground-Water Disinfection Rule: A 1996 amendment of the Safe
Drinking Water Act requiring EPA to promulgate national primary drinking
water regulations requiring disinfection as for all public water systems,
including surface waters and ground water systems.
Gully Erosion: Severe erosion in which trenches are cut to a depth
greater than 30 centimeters (a foot). Generally, ditches deep enough to
cross with farm equipment are considered gullies.
Habitat: The place where a population (e.g. human, animal, plant,
microorganism) lives and its surroundings, both living and non-living.
Habitat Indicator: A physical attribute of the environment
measured to characterize conditions necessary to support an organism,
population, or community in the absence of pollutants; e.g. salinity of
estuarine waters or substrate type in streams or lakes.
Half-Life: 1. The time required for a pollutant to lose one-half
of its original coconcentrationor example, the biochemical half-life of DDT
in the environment is 15 years. 2. The time required for half of the atoms
of a radioactive element to undergo self-transmutation or decay (half-life
of radium is 1620 years). 3. The time required for the elimination of half a
total dose from the body.
Halogen: A type of incandescent lamp with higher energy-efficiency
that standard ones.
Halon: Bromine-containing compounds with long atmospheric
lifetimes whose breakdown in the stratosphere causes depletion of ozone.
Halons are used in firefighting.
Hammer Mill: A high-speed machine that uses hammers and cutters to
crush, grind, chip, or shred solid waste.
Hard Water: Alkaline water containing dissolved salts that
interfere with some industrial processes and prevent soap from sudsing.
Hauler: Garbage collection company that offers complete refuse
removal service; many will also collect recyclables.
Hazard: 1. Potential for radiation, a chemical or other pollutant
to cause human illness or injury. 2. In the pesticide program, the inherent
toxicity of a compound. Hazard identification of a given substances is an
informed judgment based on verifiable toxicity data from animal models or
Hazard Assessment: Evaluating the effects of a stressor or
determining a margin of safety for an organism by comparing the
concentration which causes toxic effects with an estimate of exposure to the
Hazard Communication Standard: An OSHA regulation that requires
chemical manufacturers, suppliers, and importers to assess the hazards of
the chemicals that they make, supply, or import, and to inform employers,
customers, and workers of these hazards through MSDS information.
Hazard Evaluation: A component of risk evaluation that involves
gathering and evaluating data on the types of health injuries or diseases
that may be produced by a chemical and on the conditions of exposure under
which such health effects are produced.
Hazard Identification: Determining if a chemical or a microbe can
cause adverse health effects in humans and what those effects might be.
Hazard Quotient: The ratio of estimated site-specific exposure to
a single chemical from a site over a specified period to the estimated daily
exposure level, at which no adverse health effects are likely to occur.
Hazard Ratio: A term used to compare an animal's daily dietary
intake of a pesticide to its LD 50 value. A ratio greater than 1.0 indicates
that the animal is likely to consume an a dose amount which would kill 50
percent of animals of the same species. (See:
LD 50 /Lethal Dose.)
and Solid Waste Amendments (HSWA): Amendments to RCRA, enacted in 1984.
Hazardous Air Pollutants: Air pollutants which are not covered by
ambient air quality standards but which, as defined in the Clean Air Act,
may present a threat of adverse human health effects or adverse
environmental effects.Such pollutants include asbestos, beryllium, mercury,
benzene, coke oven emissions, radionuclides, and vinyl chloride.
Hazardous Chemical: An EPA designation for any hazardous material
requiring an MSDS under OSHA's Hazard Communication Standard. Such
substances are capable of producing fires and explosions or adverse health
effects like cancer and dermatitis. Hazardous chemicals are distinct from
Hazardous Ranking System: The principal screening tool used by EPA
to evaluate risks to public health and the environment associated with
abandoned or uncontrolled hazardous waste sites. The HRS calculates a score
based on the potential of hazardous substances spreading from the site
through the air, surface water, or ground water, and on other factors such
as density and proximity of human population. This score is the primary
factor in deciding if the site should be on the National Priorities List
and, if so, what ranking it should have compared to other sites on the list.
Hazardous Substance: 1. Any material that poses a threat to human
health and/or the environment. Typical hazardous substances are toxic,
corrosive, ignitable, explosive, or chemically reactive. 2. Any substance
designated by EPA to be reported if a designated quantity of the substance
is spilled in the waters of the United States or is otherwise released into
Hazardous Waste: By-products of society that can pose a
substantial or potential hazard to human health or the environment when
improperly managed. Possesses at least one of four characteristics
(ignitability, corrosivity, reactivity, or toxicity), or appears on special
Hazardous Waste Landfill: An excavated or engineered site where
hazardous waste is deposited and covered.
Hazardous Waste Minimization: Reducing the amount of toxicity or
waste produced by a facility via source reduction or environmentally sound
Hazards Analysis: Procedures used to (1) identify potential
sources of release of hazardous materials from fixed facilities or
transportation accidents; (2) determine the vulnerability of a geographical
area to a release of hazardous materials; and (3) compare hazards to
determine which present greater or lesser risks to a community.
Hazards Identification: Providing information on which facilities
have extremely hazardous substances, what those chemicals are, how much
there is at each facility, how the chemicals are stored, and whether they
are used at high temperatures.
Headspace: The vapor mixture trapped above a solid or liquid in a
Health Advisory Level: A non-regulatory health-based reference
level of chemical traces (usually in ppm) in drinking water at which there
are no adverse health risks when ingested over various periods of time. Such
levels are established for one day, 10 days, long-term and life-time
exposure periods. They contain a wide margin of safety.
Health Assessment: An evaluation of available data on existing or
potential risks to human health posed by a Superfund site. The Agency for
Toxic Substances and Disease Registry (ATSDR) of the Department of Health
and Human Services (DHHS) is required to perform such an assessment at every
site on the National Priorities List.
Heat Island Effect: A "dome" of elevated temperatures over an
urban area caused by structural and pavement heat fluxes, and pollutant
Heat Pump: An electric device with both heating and cooling
capabilities. It extracts heat from one medium at a lower (the heat source)
temperature and transfers it to another at a higher temperature (the heat
sink), thereby cooling the first and warming the second. (See:
water source heat pump.)
Heavy Metals: Metallic elements with high atomic weights; (e.g.
mercury, chromium, cadmium, arsenic, and lead); can damage living things at
low concentrations and tend to accumulate in the food chain.
Heptachlor: An insecticide that was banned on some food products
in 1975 and in all of them 1978. It was allowed for use in seed treatment
until 1983. More recently it was found in milk and other dairy products in
Arkansas and Missouri where dairy cattle were illegally fed treated seed.
Herbicide: A chemical pesticide designed to control or destroy
plants, weeds, or grasses.
Herbivore: An animal that feeds on plants.
Heterotrophic Organisms: Species that are dependent on organic
matter for food.
High End Exposure (dose) Estimate: An estimate of exposure, or
dose level received anyone in a defined population that is greater than the
90th percentile of all individuals in that population, but less than the
exposure at the highest percentile in that population. A high end risk
descriptor is an estimate of the risk level for such individuals. Note that
risk is based on a combination of exposure and susceptibility to the
High Intensity Discharge: A generic term for mercury vapor, metal
halide, and high pressure sodium lamps and fixtures.
High-Density Polyethylene: A material used to make plastic bottles
and other products that produces toxic fumes when burned.
High-Level Nuclear Waste Facility: Plant designed to handle
disposal of used nuclear fuel, high-level radioactive waste, and plutonium
High-Level Radioactive Waste (HLRW): Waste generated in core fuel
of a nuclear reactor, found at nuclear reactors or by nuclear fuel
reprocessing; is a serious threat to anyone who comes near the waste without
low-level radioactive waste.)
High-Line Jumpers: Pipes or hoses connected to fire hydrants and
laid on top of the ground to provide emergency water service for an isolated
portion of a distribution system.
High-Risk Community: A community located within the vicinity of
numerous sites of facilities or other potential sources of envienvironmental
exposure/health hazards which may result in high levels of exposure to
contaminants or pollutants.
High-to-Low-Dose Extrapolation: The process of prediction of low
exposure risk to humans and animals from the measured
high-exposure-high-risk data involving laboratory animals.
Highest Dose Tested: The highest dose of a chemical or substance
tested in a study.
Holding Pond: A pond or reservoir, usually made of earth, built to
store polluted runoff.
Holding Time: The maximum amount of time a sample may be stored
Hollow Stem Auger Drilling: Conventional drilling method that uses
augurs to penetrate the soil. As the augers are rotated, soil cuttings are
conveyed to the ground surface via augur spirals. DP tools can be used
inside the hollow augers.
Homeowner Water System: Any water system which supplies piped
water to a single residence.
Homogeneous Area: In accordance with Asbestos Hazard and Emergency
Response Act (AHERA) definitions, an area of surfacing materials, thermal
surface insulation, or miscellaneous material that is uniform in color and
Hood Capture Efficiency: Ratio of the emissions captured by a hood
and directed into a control or disposal device, expressed as a percent of
Host: 1. In genetics, the organism, typically a bacterium, into
which a gene from another organism is transplanted. 2. In medicine, an
animal infected or parasitized by another organism.
Household Hazardous Waste: Hazardous products used and disposed of
by residential as opposed to industrial consumers. Includes paints, stains,
varnishes, solvents, pesticides, and other materials or products containing
volatile chemicals that can catch fire, react or explode, or that are
corrosive or toxic.
Household Waste (Domestic Waste): Solid waste, composed of garbage
and rubbish, which normally originates in a private home or apartment house.
Domestic waste may contain a significant amount of toxic or hazardous waste.
Human Equivalent Dose: A dose which, when administered to humans,
produces an effect equal to that produced by a dose in animals.
Human Exposure Evaluation: Describing the nature and size of the
population exposed to a substance and the magnitude and duration of their
Human Health Risk: The likelihood that a given exposure or series
of exposures may have damaged or will damage the health of individuals.
Hydraulic Conductivity: The rate at which water can move through a
permeable medium. (i.e. the coefficient of permeability.)
Hydraulic Gradient: In general, the direction of groundwater flow
due to changes in the depth of the water table.
Hydrocarbons (HC): Chemical compounds that consist entirely of
carbon and hydrogen.
Hydrogen Sulfide (H2S): Gas emitted during organic
decomposition. Also a by-product of oil refining and burning. Smells like
rotten eggs and, in heavy concentration, can kill or cause illness.
Hydrogeological Cycle: The natural process recycling water from
the atmosphere down to (and through) the earth and back to the atmosphere
Hydrogeology: The geology of ground water, with particular
emphasis on the chemistry and movement of water.
Hydrologic Cycle: Movement or exchange of water between the
atmosphere and earth.
Hydrology: The science dealing with the properties, distribution,
and circulation of water.
Hydrolysis: The decomposition of organic compounds by interaction
Hydronic: A ventilation system using heated or cooled water pumped
through a building.
Hydrophilic: Having a strong affinity for water.
Hydrophobic: Having a strong aversion for water.
Hydropneumatic: A water system, usually small, in which a water
pump is automatically controlled by the pressure in a compressed air tank.
Hypersensitivity Diseases: Diseases characterized by allergic
responses to pollutants; diseases most clearly associated with indoor air
quality are asthma, rhinitis, and pneumonic hypersensitivity.
Hypolimnion: Bottom waters of a thermally stratified lake. The
hypolimnion of a eutrophic lake is usually low or lacking in oxygen.
Hypoxia/Hypoxic Waters: Waters with dissolved oxygen
concentrations of less than 2 ppm, the level generally accepted as the
minimum required for most marine life to survive and reproduce.
Identification Code or EPA I.D. Number: The unique code assigned
to each generator, transporter, and treatment, storage, or disposal facility
by regulating agencies to facilitate identification and tracking of
chemicals or hazardous waste.
Ignitable: Capable of burning or causing a fire.
IM240: A high-tech, transient dynamometer automobile emissions
test that takes up to 240 seconds.
Imhoff Cone: A clear, cone-shaped container used to measure the
volume of settleable solids in a specific volume of water.
Immediately Dangerous to Life and Health (IDLH): The maximum level
to which a healthy individual can be exposed to a chemical for 30 minutes
and escape without suffering irreversible health effects or impairing
symptoms. Used as a "level of concern." (See:
level of concern.)
Imminent Hazard: One that would likely result in unreasonable
adverse effects on humans or the environment or risk unreasonable hazard to
an endangered species during the time required for a pesticide registration
Imminent Threat: A high probability that exposure is occurring.
Immiscibility: The inability of two or more substances or liquids
to readily dissolve into one another, such as soil and water. Immiscibility
The inability of two or more substances or liquids to readily dissolve into
one another, such as soil and water.
Impermeable: Not easily penetrated. The property of a material or
soil that does not allow, or allows only with great difficulty, the movement
or passage of water.
Imports: Municipal solid waste and recyclables that have been
transported to a state or locality for processing or final disposition (but
that did not originate in that state or locality).
Impoundment: A body of water or sludge confined by a dam, dike,
floodgate, or other barrier.
In Situ: In its original place; unmoved unexcavated; remaining at
the site or in the subsurface.
In-Line Filtration: Pre-treattment method in which chemicals are
mixed by the flowing water; commonly used in pressure filtration
installations. Eliminates need for flocculation and sedimentation.
In-Situ Flushing: Introduction of large volumes of water, at times
supplemented with cleaning compounds, into soil, waste, or ground water to
flush hazardous contaminants from a site.
In-Situ Oxidation: Technology that oxidizes contaminants dissolved
in ground water, converting them into insoluble compounds.
In-Situ Stripping: Treatment system that removes or "strips"
volatile organic compounds from contaminated ground or surface water by
forcing an airstream through the water and causing the compounds to
In-Situ Vitrification: Technology that treats contaminated soil in
place at extremely high temperatures, at or more than 3000 degrees
In Vitro: Testing or action outside an organism (e.g. inside a
test tube or culture dish.)
In Vivo: Testing or action inside an organism.
Incident Command Post: A facility located at a safe distance from
an emergency site, where the incident commander, key staff, and technical
representatives can make decisions and deploy emergency manpower and
Incident Command System (ICS): The organizational arrangement
wherein one person, normally the Fire Chief of the impacted district, is in
charge of an integrated, comprehensive emergency response organization and
the emergency incident site, backed by an Emergency Operations Center staff
with resources, information, and advice.
Incineration: A treatment technology involving destruction of
waste by controlled burning at high temperatures; e.g., burning sludge to
remove the water and reduce the remaining residues to a safe, non-burnable
ash that can be disposed of safely on land, in some waters, or in
Incineration at Sea: Disposal of waste by burning at sea on
specially-designed incinerator ships.
Incinerator: A furnace for burning waste under controlled
Incompatible Waste: A waste unsuitable for mixing with another
waste or material because it may react to form a hazard.
Indemnification: In the pesticide program, legal requirement that
EPA pay certain end-users, dealers, and distributors for the cost of stock
on hand at the time a pesticide registration is suspended.
Indicator: In biology, any biological entity or processes, or
community whose characteristics show the presence of specific environmental
conditions. 2. In chemistry, a substance that shows a visible change,
usually of color, at a desired point in a chemical reaction. 3.A device that
indicates the result of a measurement; e.g. a pressure gauge or a moveable
Indirect Discharge: Introduction of pollutants from a non-domestic
source into a publicly owned waste-treatment system. Indirect dischargers
can be commercial or industrial facilities whose wastes enter local sewers.
Indirect Source: Any facility or building, property, road or
parking area that attracts motor vehicle traffic and, indirectly, causes
Indoor Air: The breathable air inside a habitable structure or
Indoor Air Pollution: Chemical, physical, or biological
contaminants in indoor air.
Indoor Climate: Temperature, humidity, lighting, air flow and
noise levels in a habitable structure or conveyance. Indoor climate can
affect indoor air pollution.
Industrial Pollution Prevention: Combination of industrial source
reduction and toxic chemical use substitution.
Industrial Process Waste: Residues produced during manufacturing
Industrial Sludge: Semi-liquid residue or slurry remaining from
treatment of industrial water and wastewater.
Industrial Source Reduction: Practices that reduce the amount of
any hazardous substance, pollutant, or contaminant entering any waste stream
or otherwise released into the environment. Also reduces the threat to
public health and the environment associated with such releases. Term
includes equipment or technology modifications, substitution of raw
materials, and improvements in housekeeping, maintenance, training or
Industrial Waste: Unwanted materials from an industrial operation;
may be liquid, sludge, solid, or hazardous waste.
Inert Ingredient: Pesticide components such as solvents, carriers,
dispersants, and surfactants that are not active against target pests. Not
all inert ingredients are innocuous.
Inertial Separator: A device that uses centrifugal force to
separate waste particles.
Infectious Agent: Any organism, such as a pathogenic virus,
parasite, or or bacterium, that is capable of invading body tissues,
multiplying, and causing disease.
Infectious Waste: Hazardous waste capable of causing infections in
humans, including: contaminated animal waste; human blood and blood
products; isolation waste, pathological waste; and discarded sharps
(needles, scalpels or broken medical instruments).
Infiltration: 1. The penetration of water through the ground
surface into sub-surface soil or the penetration of water from the soil into
sewer or other pipes through defective joints, connections, or manhole
walls. 2. The technique of applying large volumes of waste water to land to
penetrate the surface and percolate through the underlying soil. (See:
Infiltration Gallery: A sub-surface groundwater collection system,
typically shallow in depth, constructed with open-jointed or perforated
pipes that discharge collected water into a watertight chamber from which
the water is pumped to treatment facilities and into the distribution
system. Usually located close to streams or ponds.
Infiltration Rate: The quantity of water that can enter the soil
in a specified time interval.
Inflow: Entry of extraneous rain water into a sewer system from
sources other than infiltration, such as basement drains, manholes, storm
drains, and street washing.
Influent: Water, wastewater, or other liquid flowing into a
reservoir, basin, or treatment plant.
Information Collection Request (ICR): A description of information
to be gathered in connection with rules, proposed rules, surveys, and
guidance documents that contain information-gathering requirements. The ICR
describes what information is needed, why it is needed, how it will be
collected, and how much collecting it will cost. The ICR is submitted by the
EPA to the Office of Management and Budget (OMB) for approval.
Information File: In the Superfund program, a file that contains
accurate, up-to-date documents on a Superfund site. The file is usually
located in a public building (school, library, or city hall) convenient for
Inhalable Particles: All dust capable of entering the human
Initial Compliance Period (Water): The first full three-year
compliance period which begins at least 18 months after promulgation.
Injection Well: A well into which fluids are injected for purposes
such as waste disposal, improving the recovery of crude oil, or solution
Injection Zone: A geological formation receiving fluids through a
Innovative Technologies: New or inventive methods to treat
effectively hazardous waste and reduce risks to human health and the
Innovative Treatment Technologies: Technologies whose routine use
is inhibited by lack of data on performance and cost. (See:
Inoculum: 1. Bacteria or fungi injected into compost to start
biological action. 2. A medium containing organisms, usually bacteria or a
virus, that is introduced into cultures or living organisms.
Inorganic Chemicals: Chemical substances of mineral origin, not of
basically carbon structure.
Insecticide: A pesticide compound specifically used to kill or
prevent the growth of insects.
Inspection and Maintenance (I/M): 1. Activities to ensure that
vehicles' emission controls work properly. 2. Also applies to wastewater
treatment plants and other anti-pollution facilities and processes.
Institutional Waste: Waste generated at institutions such as
schools, libraries, hospitals, prisons, etc.
Instream Use: Water use taking place within a stream channel;
e.g., hydro-electric power generation, navigation, water quality
improvement, fish propagation, recreation.
Integrated Exposure Assessment: Cumulative summation (over time)
of the magnitude of exposure to a toxic chemical in all media.
Integrated Pest Management (IPM): A mixture of chemical and other,
non-pesticide, methods to control pests.
Integrated Waste Management: Using a variety of practices to
handle municipal solid waste; can include source reduction, recycling,
incineration, and landfilling.
Interceptor Sewers: Large sewer lines that, in a combined system,
control the flow of sewage to the treatment plant. In a storm, they allow
some of the sewage to flow directly into a receiving stream, thus keeping it
from overflowing onto the streets. Also used in separate systems to collect
the flows from main and trunk sewers and carry them to treatment points.
Interface: The common boundary between two substances such as a
water and a solid, water and a gas, or two liquids such as water and oil.
Interfacial Tension: The strength of the film separating two
immiscible fluids (e.g. oil and water) measured in dynes per, or millidynes
Interim (Permit) Status: Period during which treatment, storage
and disposal facilities coming under RCRA in 1980 are temporarily permitted
to operate while awaiting a permanent permit. Permits issued under these
circumstances are usually called "Part A" or "Part B" permits.
Internal Dose: In exposure assessment, the amount of a substance
penetrating the absorption barriers (e.g. skin, lung tissue,
gastrointestinal tract) of an organism through either physical or biological
Interstate Carrier Water Supply: A source of water for drinking
and sanitary use on planes, buses, trains, and ships operating in more than
one state. These sources are federally regulated.
Interstate Commerce Clause: A clause of the U.S. Constitution
which reserves to the federal government the right to regulate the conduct
of business across state lines. Under this clause, for example, the U.S.
Supreme Court has ruled that states may not inequitably restrict the
disposal of out-of-state wastes in their jurisdictions.
Interstate Waters: Waters that flow across or form part of state
or international boundaries; e.g. the Great Lakes, the Mississippi River, or
Interstitial Monitoring: The continuous surveillance of the space
between the walls of an underground storage tank.
Intrastate Product: Pesticide products once registered by states
for sale and use only in the state. All intrastate products have been
converted to full federal registration or canceled.
Inventory (TSCA): Inventory of chemicals produced pursuant to
Section 8 (b) of the Toxic Substances Control Act.
Inversion: A layer of warm air that prevents the rise of cooling
air and traps pollutants beneath it; can cause an air pollution episode.
Ion: An electrically charged atom or group of atoms.
Ion Exchange Treatment: A common water-softening method often
found on a large scale at water purification plants that remove some
organics and radium by adding calcium oxide or calcium hydroxide to increase
the pH to a level where the metals will precipitate out.
Ionization Chamber: A device that measures the intensity of
Ionizing Radiation: Radiation that can strip electrons from atoms;
e.g. alpha, beta, and gamma radiation.
IRIS: EPA's Integrated Risk Information System, an electronic data
base containing the Agency's latest descriptive and quantitative regulatory
information on chemical constituents.
Irradiated Food: Food subject to brief radioactivity, usually
gamma rays, to kill insects, bacteria, and mold, and to permit storage
Irradiation: Exposure to radiation of wavelengths shorter than
those of visible light (gamma, x-ray, or ultra- violet), for medical
purposes, to sterilize milk or other foodstuffs, or to induce polymerization
of monomers or vulcanization of rubber.
Irreversible Effect: Effect characterized by the inability of the
body to partially or fully repair injury caused by a toxic agent.
Irrigation: Applying water or wastewater to land areas to supply
the water and nutrient needs of plants.
Irrigation Efficiency: The amount of water stored in the crop root
zone compared to the amount of irrigation water applied.
Irrigation Return Flow: Surface and subsurface water which leaves
the field following application of irrigation water.
Irritant: A substance that can cause irritation of the skin, eyes,
or respiratory system. Effects may be acute from a single high level
exposure, or chronic from repeated low-level exposures to such compounds as
chlorine, nitrogen dioxide, and nitric acid.
Isoconcentration: More than one sample point exhibiting the same
Isopleth: The line or area represented by an isoconcentration.
Isotope: A variation of an element that has the same atomic number
of protons but a different weight because of the number of neutrons. Various
isotopes of the same element may have different radioactive behaviors, some
are highly unstable..
Isotropy: The condition in which the hydraulic or other properties
of an aquifer are the same in all directions.
Jar Test: A laboratory procedure that simulates a water treatment
plant's coagulation/flocculation units with differing chemical doses, mix
speeds, and settling times to estimate the minimum or ideal coagulant dose
required to achieve certain water quality goals.
Joint and Several Liability: Under CERCLA, this legal concept
relates to the liability for Superfund site cleanup and other costs on the
part of more than one potentially responsible party (i.e. if there were
several owners or users of a site that became contaminated over the years,
they could all be considered potentially liable for cleaning up the site.)
Karst: A geologic formation of irregular limestone deposits with
sinks, underground streams, and caverns.
Kinetic Energy: Energy possessed by a moving object or water body.
Kinetic Rate Coefficient: A number that describes the rate at
which a water constituent such as a biochemical oxygen demand or dissolved
oxygen rises or falls, or at which an air pollutant reacts.
Laboratory Animal Studies: Investigations using animals as
surrogates for humans.
Lagoon: 1. A shallow pond where sunlight, bacterial action, and
oxygen work to purify wastewater; also used for storage of wastewater or
spent nuclear fuel rods. 2. Shallow body of water, often separated from the
sea by coral reefs or sandbars.
Land Application: Discharge of wastewater onto the ground for
treatment or reuse. (See:
Land Ban: Phasing out of land disposal of most untreated hazardous
wastes, as mandated by the 1984 RCRA amendments.
Land Disposal Restrictions: Rules that require hazardous wastes to
be treated before disposal on land to destroy or immobilize hazardous
constituents that might migrate into soil and ground water.
Land Farming (of Waste): A disposal process in which hazardous
waste deposited on or in the soil is degraded naturally by microbes.
Landfills: 1. Sanitary landfills are disposal sites for
non-hazardous solid wastes spread in layers, compacted to the smallest
practical volume, and covered by material applied at the end of each
operating day. 2. Secure chemical landfills are disposal sites for hazardous
waste, selected and designed to minimize the chance of release of hazardous
substances into the environment.
Landscape: The traits, patterns, and structure of a specific
geographic area, including its biological composition, its physical
environment, and its anthropogenic or social patterns. An area where
interacting ecosystems are grouped and repeated in similar form.
Landscape Characterization: Documentation of the traits and
patterns of the essential elements of the landscape.
Landscape Ecology: The study of the distribution patterns of
communities and ecosystems, the ecological processes that affect those
patterns, and changes in pattern and process over time.
Landscape Indicator: A measurement of the landscape, calculated
from mapped or remotely sensed data, used to describe spatial patterns of
land use and land cover across a geographic area. Landscape indicators may
be useful as measures of certain kinds of environmental degradation such as
Langelier Index (LI): An index reflecting the equilibrium pH of a
water with respect to calcium and alkalinity; used in stabilizing water to
control both corrosion and scale deposition.
Large Quantity Generator: Person or facility generating more than
2200 pounds of hazardous waste per month. Such generators produce about 90
percent of the nation's hazardous waste, and are subject to all RCRA
Large Water System: A water system that services more than 50,000
Laser Induced Fluorescence: A method for measuring the relative
amount of soil and/or groundwater with an in-situ sensor.
Latency: Time from the first exposure of a chemical until the
appearance of a toxic effect.
Lateral Sewers: Pipes that run under city streets and receive the
sewage from homes and businesses, as opposed to domestic feeders and main
Laundering Weir: Sedimention basin overflow weir.
LC 50/Lethal Concentration: Median level concentration, a standard
measure of toxicity. It tells how much of a substance is needed to kill half
of a group of experimental organisms in a given time. (See:
LD 50/ Lethal Dose: The dose of a toxicant or microbe that will
kill 50 percent of the test organisms within a designated period. The lower
the LD 50, the more toxic the compound.
Ldlo: Lethal dose low; the lowest dose in an animal study at which
Leachate: Water that collects contaminants as it trickles through
wastes, pesticides or fertilizers. Leaching may occur in farming areas,
feedlots, and landfills, and may result in hazardous substances entering
surface water, ground water, or soil.
Leachate Collection System: A system that gathers leachate and
pumps it to the surface for treatment.
Leaching: The process by which soluble constituents are dissolved
and filtered through the soil by a percolating fluid. (See:
Lead (Pb): A heavy metal that is hazardous to health if breathed
or swallowed. Its use in gasoline, paints, and plumbing compounds has been
sharply restricted or eliminated by federal laws and regulations. (See:
Lead Service Line: A service line made of lead which connects the
water to the building inlet and any lead fitting connected to it.
Legionella: A genus of bacteria, some species of which have caused
a type of pneumonia called Legionaires Disease.
Lethal Concentration 50: Also referred to as LC50, a
concentration of a pollutant or effluent at which 50 percent of the test
organisms die; a common measure of acute toxicity.
Lethal Dose 50: Also referred to as LD50, the dose of a
toxicant that will kill 50 percent of test organisms within a designated
period of time; the lower the LD 50, the more toxic the compound.
Level of Concern (LOC): The concentration in air of an extremely
hazardous substance above which there may be serious immediate health
effects to anyone exposed to it for short periods
Life Cycle of a Product: All stages of a product's development,
from extraction of fuel for power to production, marketing, use, and
Lifetime Average Daily Dose: Figure for estimating excess lifetime
Lifetime Exposure: Total amount of exposure to a substance that a
human would receive in a lifetime (usually assumed to be 70 years).
Lift: In a sanitary landfill, a compacted layer of solid waste and
the top layer of cover material.
Lifting Station: (See:
Light Non-Aqueous Phase Liquid (LNAPL): A non-aqueous phase liquid
with a specific gravity less than 1.0. Because the specific gravity of water
is 1.0, most LNAPLs float on top of the water table. Most common petroleum
hydrocarbon fuels and lubricating oils are LNAPLs.
Light-Emitting Diode: A long-lasting illumination technology used
for exit signs which requires very little power
Limestone Scrubbing: Use of a limestone and water solution to
remove gaseous stack-pipe sulfur before it reaches the atmosphere.
Limit of Detection (LOD): The minimum concentration of a substance
being analyzed test that has a 99 percent probability of being identified.
Limited Degradation: An environmental policy permitting some
degradation of natural systems but terminating at a level well beneath an
established health standard.
Limiting Factor: A condition whose absence or excessive
concentration, is incompatible with the needs or tolerance of a species or
population and which may have a negative influence on their ability to
Limnology: The study of the physical, chemical, hydrological, and
biological aspects of fresh water bodies.
Lindane: A pesticide that causes adverse health effects in
domestic water supplies and is toxic to freshwater fish and aquatic life.
Liner: 1. A relatively impermeable barrier designed to keep
leachate inside a landfill. Liner materials include plastic and dense clay.
2. An insert or sleeve for sewer pipes to prevent leakage or infiltration.
Lipid Solubility: The maximum concentration of a chemical that
will dissolve in fatty substances. Lipid soluble substances are insoluble in
water. They will very selectively disperse through the environment via
uptake in living tissue.
Liquefaction: Changing a solid into a liquid.
Liquid Injection Incinerator: Commonly used system that relies on
high pressure to prepare liquid wastes for incineration by breaking them up
into tiny droplets to allow easier combustion.
List: Shorthand term for EPA list of violating facilities or firms
debarred from obtaining government contracts because they violated certain
sections of the Clean Air or Clean Water Acts. The list is maintained by The
Office of Enforcement and Compliance Monitoring.
Listed Waste: Wastes listed as hazardous under RCRA but which have
not been subjected to the Toxic Characteristics Listing Process because the
dangers they present are considered self-evident.
Lithology: Mineralogy, grain size, texture, and other physical
properties of granular soil, sediment, or rock.
Litter: 1. The highly visible portion of solid waste carelessly
discarded outside the regular garbage and trash collection and disposal
system. 2. leaves and twigs fallen from forest trees.
Littoral Zone: 1. That portion of a body of fresh water extending
from the shoreline lakeward to the limit of occupancy of rooted plants. 2. A
strip of land along the shoreline between the high and low water levels.
Local Education Agency (LEA): In the asbestos program, an
educational agency at the local level that exists primarily to operate
schools or to contract for educational services, including primary and
secondary public and private schools. A single, unaffiliated school can be
considered an LEA for AHERA purposes.
Local Emergency Planning Committee (LEPC): A committee appointed
by the state emergency response commission, as required by SARA Title III,
to formulate a comprehensive emergency plan for its jurisdiction.
Low Density Polyethylene (LOPE): Plastic material used for both
rigid containers and plastic film applications.
Low Emissivity (low-E) Windows: New window technology that lowers
the amount of energy loss through windows by inhibiting the transmission of
radiant heat while still allowing sufficient light to pass through.
Low NOx Burners: One of several combustion technologies
used to reduce emissions of Nitrogen Oxides (NOx.)
Low-Level Radioactive Waste (LLRW): Wastes less hazardous than
most of those associated with a nuclear reactor; generated by hospitals,
research laboratories, and certain industries. The Department of Energy,
Nuclear Regulatory Commission, and EPA share responsibilities for managing
them. (See: high-level
Lower Detection Limit: The smallest signal above background noise
an instrument can reliably detect.
Lower Explosive Limit (LEL): The concentration of a compound in
air below which the mixture will not catch on fire.
Lowest Acceptable Daily Dose: The largest quantity of a chemical
that will not cause a toxic effect, as determined by animal studies.
Lowest Achievable Emission Rate: Under the Clean Air Act, the rate
of emissions that reflects (1) the most stringent emission limitation in the
implementation plan of any state for such source unless the owner or
operator demonstrates such limitations are not achievable; or (2) the most
stringent emissions limitation achieved in practice, whichever is more
stringent. A proposed new or modified source may not emit pollutants in
excess of existing new source standards.
Lowest Observed Adverse Effect Level (LOAEL): The lowest level of
a stressor that causes statistically and biologically significant
differences in test samples as compared to other samples subjected to no
Macropores: Secondary soil features such as root holes or
desiccation cracks that can create significant conduits for movement of NAPL
and dissolved contaminants, or vapor-phase contaminants.
Magnetic Separation: Use of magnets to separate ferrous materials
from mixed municipal waste stream.
Major Modification: This term is used to define modifications of
major stationary sources of emissions with respect to Prevention of
Significant Deterioration and New Source Review under the Clean Air Act.
Major Stationary Sources: Term used to determine the applicability
of Prevention of Significant Deterioration and new source regulations. In a
nonattainment area, any stationary pollutant source with potential to emit
more than 100 tons per year is considered a major stationary source. In PSD
areas the cutoff level may be either 100 or 250 tons, depending upon the
Majors: Larger publicly owned treatment works (POTWs) with flows
equal to at least one million gallons per day (mgd) or servicing a
population equivalent to 10,000 persons; certain other POTWs having
significant water quality impacts. (See:
Man-Made (Anthropogenic) Beta Particle and Photon Emitters: All
radionuclides emitting beta particles and/or photons listed in Maximum
Permissible Body Burdens and Maximum Permissible Concentrations of
Radonuclides in Air and Water for Occupational Exposure.
Management Plan: Under the Asbestos Hazard Emergency Response Act
(AHERA), a document that each Local Education Agency is required to prepare,
describing all activities planned and undertaken by a school to comply with
AHERA regulations, including building inspections to identify
asbestos-containing materials, response actions, and operations and
maintenance programs to minimize the risk of exposure.
Managerial Controls: Methods of nonpoint source pollution control
based on decisions about managing agricultural wastes or application times
or rates for agrochemicals.
Mandatory Recycling: Programs which by law require consumers to
separate trash so that some or all recyclable materials are recovered for
recycling rather than going to landfills.
Manifest: A one-page form used by haulers transporting waste that
lists EPA identification numbers, type and quantity of waste, the generator
it originated from, the transporter that shipped it, and the storage or
disposal facility to which it is being shipped. It includes copies for all
participants in the shipping process.
Manifest System: Tracking of hazardous waste from
"cradle-to-grave" (generation through disposal) with accompanying documents
known as manifests.(See:
cradle to grave.)
Manual Separation: Hand sorting of recyclable or compostable
materials in waste.
Manufacturer's Formulation: A list of substances or component
parts as described by the maker of a coating, pesticide, or other product
containing chemicals or other substances.
Manufacturing Use Product: Any product intended (labeled) for
formulation or repackaging into other pesticide products.
Margin of Safety: Maximum amount of exposure producing no
measurable effect in animals (or studied humans) divided by the actual
amount of human exposure in a population.
Margin of Exposure (MOE): The ratio of the no-observed
adverse-effect-level to the estimated exposure dose.
Marine Sanitation Device: Any equipment or process installed on
board a vessel to receive, retain, treat, or discharge sewage.
Marsh: A type of wetland that does not accumulate appreciable peat
deposits and is dominated by herbaceous vegetation. Marshes may be either
fresh or saltwater, tidal or non-tidal. (See:
Material Category: In the asbestos program, broad classification
of materials into thermal surfacing insulation, surfacing material, and
Material Safety Data Sheet (MSDS): A compilation of information
required under the OSHA Communication Standard on the identity of hazardous
chemicals, health, and physical hazards, exposure limits, and precautions.
Section 311 of SARA requires facilities to submit MSDSs under certain
Material Type: Classification of suspect material by its specific
use or application; e.g., pipe insulation, fireproofing, and floor tile.
Materials Recovery Facility (MRF): A facility that processes
residentially collected mixed recyclables into new products available for
Maximally (or Most) Exposed Individual: The person with the
highest exposure in a given population.
Maximum Acceptable Toxic Concentration: For a given ecological
effects test, the range (or geometric mean) between the No Observable
Adverse Effect Level and the Lowest Observable Adverse Effects Level.
Maximum Available Control Technology (MACT): The emission standard
for sources of air pollution requiring the maximum reduction of hazardous
emissions, taking cost and feasibility into account. Under the Clean Air Act
Amendments of 1990, the MACT must not be less than the average emission
level achieved by controls on the best performing 12 percent of existing
sources, by category of industrial and utility sources.
Maximum Contaminant Level: The maximum permissible level of a
contaminant in water delivered to any user of a public system. MCLs are
Maximum Contaminant Level Goal (MCLG): Under the Safe Drinking
Water Act, a non-enforceable concentration of a drinking water contaminant,
set at the level at which no known or anticipated adverse effects on human
health occur and which allows an adequate safety margin. The MCLG is usually
the starting point for determining the regulated Maximum Contaminant Level.
Maximum Exposure Range: Estimate of exposure or dose level
received by an individual in a defined population that is greater than the
98th percentile dose for all individuals in that population, but less than
the exposure level received by the person receiving the highest exposure
Maximum Residue Level: Comparable to a U.S. tolerance level, the
Maximum Residue Level the enforceable limit on food pesticide levels in some
countries. Levels are set by the Codex Alimentarius Commission, a United
Nations agency managed and funded jointly by the World Health Organization
and the Food and Agriculture Organization.
Maximum Tolerated Dose: The maximum dose that an animal species
can tolerate for a major portion of its lifetime without significant
impairment or toxic effect other than carcinogenicity.
Measure of Effect/ Measurement Endpoint: A measurable
characteristic of ecological entity that can be related to an assessment
endpoint; e.g. a laboratory test for eight species meeting certain
requirements may serve as a measure of effect for an assessment endpoint,
such as survival of fish, aquatic, invertebrate or algal species under acute
Measure of Exposure: A measurable characteristic of a stressor
(such as the specific amount of mercury in a body of water) used to help
quantify the exposure of an ecological entity or individual organism.
Mechanical Aeration: Use of mechanical energy to inject air into
water to cause a waste stream to absorb oxygen.
Mechanical Separation: Using mechanical means to separate waste
into various components.
Mechanical Turbulence: Random irregularities of fluid motion in
air caused by buildings or other nonthermal, processes.
Media: Specific environments--air, water, soil--which are the
subject of regulatory concern and activities.
Medical Surveillance: A periodic comprehensive review of a
worker's health status; acceptable elements of such surveillance program are
listed in the Occupational Safety and Health Administration standards for
Medical Waste: Any solid waste generated in the diagnosis,
treatment, or immunization of human beings or animals, in research
pertaining thereto, or in the production or testing of biologicals,
excluding hazardous waste identified or listed under 40 CFR Part 261 or any
household waste as defined in 40 CFR Sub-section 261.4 (b)(1).
Medium-size Water System: A water system that serves 3,300 to
Meniscus: The curved top of a column of liquid in a small tube.
Mercury (Hg): Heavy metal that can accumulate in the environment
and is highly toxic if breathed or swallowed. (See:heavy
Mesotrophic: Reservoirs and lakes which contain moderate
quantities of nutrients and are moderately productive in terms of aquatic
animal and plant life.
Metabolites: Any substances produced by biological processes, such
as those from pesticides.
Metalimnion: The middle layer of a thermally stratified lake or
reservoir. In this layer there is a rapid decrease in temperature with
depth. Also called thermocline.
Methane: A colorless, nonpoisonous, flammable gas created by
anaerobic decomposition of organic compounds. A major component of natural
gas used in the home.
Methanol: An alcohol that can be used as an alternative fuel or as
a gasoline additive. It is less volatile than gasoline; when blended with
gasoline it lowers the carbon monoxide emissions but increases hydrocarbon
emissions. Used as pure fuel, its emissions are less ozone-forming than
those from gasoline. Poisonous to humans and animals if ingested.
Method 18: An EPA test method which uses gas chromatographic
techniques to measure the concentration of volatile organic compounds in a
Method 24: An EPA reference method to determine density, water
content and total volatile content (water and VOC) of coatings.
Method 25: An EPA reference method to determine the VOC
concentration in a gas stream.
Method Detection Limit (MDL): See limit of detection.
Methoxychlor: Pesticide that causes adverse health effects in
domestic water supplies and is toxic to freshwater and marine aquatic life.
Methyl Orange Alkalinity: A measure of the total alkalinity in a
water sample in which the color of methyl orange reflects the change in
Microbial Growth: The amplification or multiplication of
microorganisms such as bacteria, algae, diatoms, plankton, and fungi.
Microbial Pesticide: A microorganism that is used to kill a pest,
but is of minimum toxicity to humans.
Microclimate: 1. Localized climate conditions within an urban area
or neighborhood. 2. The climate around a tree or shrub or a stand of trees.
Microenvironmental Method: A method for sequentially assessing
exposure for a series of microenvironments that can be approximated by
constant concentrations of a stressor.
Microenvironments: Well-defined surroundings such as the home,
office, or kitchen that can be treated as uniform in terms of stressor
Million-Gallons Per Day (MGD): A measure of water flow.
Minimization: A comprehensive program to minimize or eliminate
wastes, usually applied to wastes at their point of origin. (See:
Mining of an Aquifer: Withdrawal over a period of time of ground
water that exceeds the rate of recharge of the aquifer.
Mining Waste: Residues resulting from the extraction of raw
materials from the earth.
Minor Source: New emissions sources or modifications to existing
emissions sources that do not exceed NAAQS emission levels.
Minors: Publicly owned treatment works with flows less than 1
million gallons per day. (See:
Miscellaneous ACM: Interior asbestos-containing building material
or structural components, members or fixtures, such as floor and ceiling
tiles; does not include surfacing materials or thermal system insulation.
Miscellaneous Materials: Interior building materials on structural
components, such as floor or ceiling tiles.
Miscible Liquids: Two or more liquids that can be mixed and will
remain mixed under normal conditions.
Missed Detection: The situation that occurs when a test indicates
that a tank is "tight" when in fact it is leaking.
Mist: Liquid particles measuring 40 to 500 micrometers (pm), are
formed by condensation of vapor. By comparison, fog particles are smaller
than 40 micrometers (pm).
Mitigation: Measures taken to reduce adverse impacts on the
Mixed Funding: Settlements in which potentially responsible
parties and EPA share the cost of a response action.
Mixed Glass: Recovered container glass not sorted into categories
(e.g. color, grade).
Mixed Liquor: A mixture of activated sludge and water containing
organic matter undergoing activated sludge treatment in an aeration tank.
Mixed Metals: Recovered metals not sorted into categories such as
aluminum, tin, or steel cans or ferrous or non-ferrous metals.
Mixed Municipal Waste: Solid waste that has not been sorted into
specific categories (such as plastic, glass, yard trimmings, etc.)
Mixed Paper: Recovered paper not sorted into categories such as
old magazines, old newspapers, old corrugated boxes, etc.
Mixed Plastic: Recovered plastic unsorted by category.
Waste: Radioactive waste that is also a hazardous waste under RCRA. Such
wastes are jointly regulated by RCRA and Atomic Energy Act.
Mobile Incinerator Systems: Hazardous waste incinerators that can
be transported from one site to another.
Mobile Source: Any non-stationary source of air pollution such as
cars, trucks, motorcycles, buses, airplanes, and locomotives.
Model Plant: A hypothetical plant design used for developing
economic, environmental, and energy impact analyses as support for
regulations or regulatory guidelines; first step in exploring the economic
impact of a potential NSPS.
Modified Bin Method: Way of calculating the required heating or
cooling for a building based on determining how much energy the system would
use if outdoor temperatures were within a certain temperature interval and
then multiplying the energy use by the time the temperature interval
Modified Source: The enlargement of a major stationary pollutant
sources is often referred to as modification, implying that more emissions
Moisture Content: 1.The amount of water lost from soil upon drying
to a constant weight, expressed as the weight per unit of dry soil or as the
volume of water per unit bulk volume of the soil. For a fully saturated
medium, moisture content indicates the porosity. 2. Water equivalent of snow
on the ground; an indicator of snowmelt flood potential.
Molecule: The smallest division of a compound that still retains
or exhibits all the properties of the substance.
Molten Salt Reactor: A thermal treatment unit that rapidly heats
waste in a heat-conducting fluid bath of carbonate salt.
Monitoring: Periodic or continuous surveillance or testing to
determine the level of compliance with statutory requirements and/or
pollutant levels in various media or in humans, plants, and animals.
Monitoring Well: 1. A well used to obtain water quality samples or
measure groundwater levels. 2. A well drilled at a hazardous waste
management facility or Superfund site to collect ground-water samples for
the purpose of physical, chemical, or biological analysis to determine the
amounts, types, and distribution of contaminants in the groundwater beneath
Monoclonal Antibodies (Also called MABs and MCAs): 1. Man-made
(anthropogenic) clones of a molecule, produced in quantity for medical or
research purposes. 2. Molecules of living organisms that selectively find
and attach to other molecules to which their structure conforms exactly.
This could also apply to equivalent activity by chemical molecules.
Monomictic: Lakes and reservoirs which are relatively deep, do not
freeze over during winter, and undergo a single stratification and mixing
cycle during the year (usually in the fall).
Montreal Protocol: Treaty, signed in 1987, governs stratospheric
ozone protection and research, and the production and use of ozone-depleting
substances. It provides for the end of production of ozone-depleting
substances such as CFCS. Under the Protocol, various research groups
continue to assess the ozone layer. The Multilateral Fund provides resources
to developing nations to promote the transition to ozone-safe technologies.
Moratorium: During the negotiation process, a period of 60 to 90
days during which EPA and potentially responsible parties may reach
settlement but no site response activities can be conducted.
Morbidity: Rate of disease incidence.
Mortality: Death rate.
Most Probable Number: An estimate of microbial density per unit
volume of water sample, based on probability theory.
Muck Soils: Earth made from decaying plant materials.
Mudballs: Round material that forms in filters and gradually
increases in size when not removed by backwashing.
Mulch: A layer of material (wood chips, straw, leaves, etc.)
placed around plants to hold moisture, prevent weed growth, and enrich or
sterilize the soil.
Multi-Media Approach: Joint approach to several environmental
media, such as air, water, and land.
Multiple Chemical Sensitivity: A diagnostic label for people who
suffer multi-system illnesses as a result of contact with, or proximity to,
a variety of airborne agents and other substances.
Multiple Use: Use of land for more than one purpose; e.g., grazing
of livestock, watershed and wildlife protection, recreation, and timber
production. Also applies to use of bodies of water for recreational
purposes, fishing, and water supply.
Multistage Remote Sensing: A strategy for landscape
characterization that involves gathering and analyzing information at
several geographic scales, ranging from generalized levels of detail at the
national level through high levels of detail at the local scale.
Municipal Discharge: Discharge of effluent from waste water
treatment plants which receive waste water from households, commercial
establishments, and industries in the coastal drainage basin. Combined
sewer/separate storm overflows are included in this category.
Municipal Sewage: Wastes (mostly liquid) orginating from a
community; may be composed of domestic wastewaters and/or industrial
Municipal Sludge: Semi-liquid residue remaining from the treatment
of municipal water and wastewater.
Municipal Solid Waste: Common garbage or trash generated by
industries, businesses, institutions, and homes.
Mutagen/Mutagenicity: An agent that causes a permanent genetic
change in a cell other than that which occurs during normal growth.
Mutagenicity is the capacity of a chemical or physical agent to cause such
National Ambient Air Quality Standards (NAAQS):
Standards established by EPA that apply for outdoor air throughout the
country. (See: criteria
National Emissions Standards for Hazardous Air Pollutants (NESHAPS):
Emissions standards set by EPA for an air pollutant not covered by NAAQS
that may cause an increase in fatalities or in serious, irreversible, or
incapacitating illness. Primary standards are designed to protect human
health, secondary standards to protect public welfare (e.g. building
facades, visibility, crops, and domestic animals).
National Environmental Performance Partnership Agreements: System
that allows states to assume greater responsibility for environmental
programs based on their relative ability to execute them.
National Estuary Program: A program established under the Clean
Water Act Amendments of 1987 to develop and implement conservation and
management plans for protecting estuaries and restoring and maintaining
their chemical, physical, and biological integrity, as well as controlling
point and nonpoint pollution sources.
National Municipal Plan: A policy created in 1984 by EPA and the
states in 1984 to bring all publicly owned treatment works (POTWs) into
compliance with Clean Water Act requirements.
National Oil and Hazardous Substances Contingency Plan (NOHSCP/NCP):
The federal regulation that guides determination of the sites to be
corrected under both the Superfund program and the program to prevent or
control spills into surface waters or elsewhere.
National Pollutant Discharge Elimination System (NPDES): A
provision of the Clean Water Act which prohibits discharge of pollutants
into waters of the United States unless a special permit is issued by EPA, a
state, or, where delegated, a tribal government on an Indian reservation.
National Priorities List (NPL): EPA's list of the most serious
uncontrolled or abandoned hazardous waste sites identified for possible
long-term remedial action under Superfund. The list is based primarily on
the score a site receives from the Hazard Ranking System. EPA is required to
update the NPL at least once a year. A site must be on the NPL to receive
money from the Trust Fund for remedial action.
National Response Center: The federal operations center that
receives notifications of all releases of oil and hazardous substances into
the environment; open 24 hours a day, is operated by the U.S. Coast Guard,
which evaluates all reports and notifies the appropriate agency.
National Response Team (NRT): Representatives of 13 federal
agencies that, as a team, coordinate federal responses to nationally
significant incidents of pollution--an oil spill, a major chemical release,
or a - superfund response action--and provide advice and technical
assistance to the responding agency(ies) before and during a response
National Secondary Drinking Water Regulations: Commonly referred
to as NSDWRs.
Navigable Waters: Traditionally, waters sufficiently deep and wide
for navigation by all, or specified vessels; such waters in the United
States come under federal jurisdiction and are protected by certain
provisions of the Clean Water Act.
Necrosis: Death of plant or animal cells or tissues. In plants,
necrosis can discolor stems or leaves or kill a plant entirely.
Negotiations (Under Superfund): After potentially responsible
parties are identified for a site, EPA coordinates with them to reach a
settlement that will result in the PRP paying for or conducting the cleanup
under EPA supervision. If negotiations fail, EPA can order the PRP to
conduct the cleanup or EPA can pay for the cleanup using Superfund monies
and then sue to recover the costs.
Nematocide: A chemical agent which is destructive to nematodes.
Nephelometric: Method of of measuring turbidity in a water sample
by passing light through the sample and measuring the amount of the light
that is deflected.
Netting: A concept in which all emissions sources in the same area
that owned or controlled by a single company are treated as one large
source, thereby allowing flexibility in controlling individual sources in
order to meet a single emissions standard. (See:
Neutralization: Decreasing the acidity or alkalinity of a
substance by adding alkaline or acidic materials, respectively.
New Source: Any stationary source built or modified after
publication of final or proposed regulations that prescribe a given standard
New Source Performance Standards (NSPS): Uniform national EPA air
emission and water effluent standards which limit the amount of pollution
allowed from new sources or from modified existing sources.
New Source Review (NSR): A Clean Air Act requirement that State
Implementation Plans must include a permit review that applies to the
construction and operation of new and modified stationary sources in
nonattainment areas to ensure attainment of national ambient air quality
Nitrate: A compound containing nitrogen that can exist in the
atmosphere or as a dissolved gas in water and which can have harmful effects
on humans and animals. Nitrates in water can cause severe illness in infants
and domestic animals. A plant nutrient and inorganic fertilizer, nitrate is
found in septic systems, animal feed lots, agricultural fertilizers, manure,
industrial waste waters, sanitary landfills, and garbage dumps.
Nitric Oxide (NO): A gas formed by combustion under high
temperature and high pressure in an internal combustion engine; it is
converted by sunlight and photochemical processes in ambient air to nitrogen
oxide. NO is a precursor of ground-level ozone pollution, or smog..
Nitrification: The process whereby ammonia in wastewater is
oxidized to nitrite and then to nitrate by bacterial or chemical reactions.
Nitrilotriacetic Acid (NTA): A compound now replacing phosphates
Nitrite: 1. An intermediate in the process of nitrification. 2.
Nitrous oxide salts used in food preservation.
Nitrogen Dioxide (NO2): The result of nitric oxide
combining with oxygen in the atmosphere; major component of photochemical
Nitrogen Oxide (NOx): The result of photochemical
reactions of nitric oxide in ambient air; major component of photochemical
smog. Product of combustion from transportation and stationary sources and a
major contributor to the formation of ozone in the troposphere and to acid
Nitrogenous Wastes: Animal or vegetable residues that contain
significant amounts of nitrogen.
Nitrophenols: Synthetic organopesticides containing carbon,
hydrogen, nitrogen, and oxygen.
No Further Remedial Action Planned: Determination made by EPA
following a preliminary assessment that a site does not pose a significant
risk and so requires no further activity under CERCLA.
No Observable Adverse Effect Level (NOAEL): An exposure level at
which there are no statistically or biologically significant increases in
the frequency or severity of adverse effects between the exposed population
and its appropriate control; some effects may be produced at this level, but
they are not considered as adverse, or as precurors to adverse effects. In
an experiment with several NOAELs, the regulatory focus is primarily on the
highest one, leading to the common usage of the term NOAEL as the highest
exposure without adverse effects.
No Till: Planting crops without prior seedbed preparation, into an
existing cover crop, sod, or crop residues, and eliminating subsequent
No-Observed-Effect-Level (NOEL): Exposure level at which there are
no statistically or biological significant differences in the frequency or
severity of any effect in the exposed or control populations.
Noble Metal: Chemically inactive metal such as gold; does not
Noise: Product-level or product-volume changes occurring during a
test that are not related to a leak but may be mistaken for one.
Constituents: Constituents that lack appropriate test methods or chemical
standards and therefore cannot be properly measured to determine compliance with
LDR concentration-based standards in 268.40 and 268.48.
Non-Aqueous Phase Liquid (NAPL): Contaminants that remain
undiluted as the original bulk liquid in the subsurface, e.g. spilled oil.
(See: fee product.)
Non-Attainment Area: Area that does not meet one or more of the
National Ambient Air Quality Standards for the criteria pollutants
designated in the Clean Air Act.
Non-Binding Allocations of Responsibility (NBAR): A process for
EPA to propose a way for potentially responsible parties to allocate costs
Non-Community Water System: A public water system that is not a
community water system; e.g. the water supply at a camp site or national
Non-Compliance Coal: Any coal that emits greater than 3.0 pounds
of sulfur dioxide per million BTU when burned. Also known as high-sulfur
Non-Contact Cooling Water: Water used for cooling which does not
come into direct contact with any raw material, product, byproduct, or
Non-Conventional Pollutant: Any pollutant not statutorily listed
or which is poorly understood by the scientific community.
Non-Degradation: An environmental policy which disallows any
lowering of naturally occurring quality regardless of preestablished health
Non-Ferrous Metals: Nonmagnetic metals such as aluminum, lead, and
copper. Products made all or in part from such metals include containers,
packaging, appliances, furniture, electronic equipment and aluminum foil.
Non-ionizing Electromagnetic Radiation: 1. Radiation that does not
change the structure of atoms but does heat tissue and may cause harmful
biological effects. 2. Microwaves, radio waves, and low-frequency
electromagnetic fields from high-voltage transmission lines.
Non-Methane Hydrocarbon (NMHC): The sum of all hydrocarbon air
pollutants except methane; significant precursors to ozone formation.
Non-Methane Organic Gases (NMOG): The sum of all organic air
pollutants. Excluding methane; they account for aldehydes, ketones,
alcohols, and other pollutants that are not hydrocarbons but are precursors
Non-Point Sources: Diffuse pollution sources (i.e. without a
single point of origin or not introduced into a receiving stream from a
specific outlet). The pollutants are generally carried off the land by storm
water. Common non-point sources are agriculture, forestry, urban, mining,
construction, dams, channels, land disposal, saltwater intrusion, and city
Non-potable: Water that is unsafe or unpalatable to drink because
it contains pollutants, contaminants, minerals, or infective agents.
Non-Road Emissions: Pollutants emitted by combustion engines on
farm and construction equipment, gasoline-powered lawn and garden equipment,
and power boats and outboard motors.
Non-Transient Non-Community Water System: A public water system
that regularly serves at least 25 of the same non-resident persons per day
for more than six months per year.
Nondischarging Treatment Plant: A treatment plant that does not
discharge treated wastewater into any stream or river. Most are pond systems
that dispose of the total flow they receive by means of evaporation or
percolation to groundwater, or facilities that dispose of their effluent by
recycling or reuse (e.g. spray irrigation or groundwater discharge).
Nonfriable Asbestos-Containing Materials: Any material containing
more than one percent asbestos (as determined by Polarized Light Microscopy)
that, when dry, cannot be crumbled, pulverized, or reduced to powder by hand
Nonhazardous Industrial Waste: Industrial process waste in
wastewater not considered municipal solid waste or hazardous waste under
Nonwastewater (NWW): Wastes that do not meet the criteria for wastewaters
Notice of Deficiency: An EPA request to a facility owner or
operator requesting additional information before a preliminary decision on
a permit application can be made.
Notice of Intent to Cancel: Notification sent to registrants when
EPA decides to cancel registration of a product containing a pesticide.
Notice of Intent to Deny: Notification by EPA of its preliminary
intent to deny a permit application.
Notice of Intent to Suspend: Notification sent to a pesticide
registrant when EPA decides to suspend product sale and distribution because
of failure to submit requested data in a timely and/or acceptable manner, or
because of imminent hazard. (See:
Nuclear Reactors and Support Facilities: Uranium mills, commercial
power reactors, fuel reprocessing plants, and uranium enrichment facilities.
Nuclear Winter: Prediction by some scientists that smoke and
debris rising from massive fires of a nuclear war could block sunlight for
weeks or months, cooling the earth's surface and producing climate changes
that could, for example, negatively affect world agricultural and weather
Nuclide: An atom characterized by the number of protons, neturons,
and energy in the nucleus.
Nutrient: Any substance assimilated by living things that promotes
growth. The term is generally applied to nitrogen and phosphorus in
wastewater, but is also applied to other essential and trace elements.
Nutrient Pollution: Contamination of water resources by excessive
inputs of nutrients. In surface waters, excess algal production is a major
Ocean Discharge Waiver: A variance from Clean Water Act
requirements for discharges into marine waters.
Odor Threshold: The minimum odor of a water or air sample that can
just be detected after successive dilutions with odorless water. Also called
OECD Guidelines: Testing guidelines prepared by the Organization
of Economic and Cooperative Development of the United Nations. They assist
in preparation of protocols for studies of toxicology, environmental fate,
Off-Site Facility: A hazardous waste treatment, storage or
disposal area that is located away from the generating site.
Office Paper: High grade papers such as copier paper, computer
printout, and stationary almost entirely made of uncoated chemical pulp,
although some ground wood is used. Such waste is also generated in homes,
schools, and elsewhere.
Offsets: A concept whereby emissions from proposed new or modified
stationary sources are balanced by reductions from existing sources to
stabilize total emissions. (See:
Offstream Use: Water withdrawn from surface or groundwater sources
for use at another place.
Oil and Gas Waste: Gas and oil drilling muds, oil production
brines, and other waste associated with exploration for, development and
production of crude oil or natural gas.
Oil Desulfurization: Widely used precombustion method for reducing
sulfur dioxide emissions from oil-burning power plants. The oil is treated
with hydrogen, which removes some of the sulfur by forming hydrogen sulfide
Oil Fingerprinting: A method that identifies sources of oil and
allows spills to be traced to their source.
Oil Spill: An accidental or intentional discharge of oil which
reaches bodies of water. Can be controlled by chemical dispersion,
combustion, mechanical containment, and/or adsorption. Spills from tanks and
pipelines can also occur away from water bodies, contaminating the soil,
getting into sewer systems and threatening underground water sources.
Oligotrophic Lakes: Deep clear lakes with few nutrients, little
organic matter and a high dissolved-oxygen level.
On-Scene Coordinator (OSC): The predesignated EPA, Coast Guard, or
Department of Defense official who coordinates and directs Superfund removal
actions or Clean Water Act oil- or hazardous-spill response actions.
On-Site Facility: A hazardous waste treatment, storage or disposal
area that is located on the generating site.
Onboard Controls: Devices placed on vehicles to capture gasoline
vapor during refueling and route it to the engines when the vehicle is
starting so that it can be efficiently burned.
Onconogenicity: The capacity to induce cancer.
One-hit Model: A mathematical model based on the biological theory
that a single "hit" of some minimum critical amount of a carcinogen at a
cellular target such as DNA can start an irreversible series events leading
to a tumor.
Opacity: The amount of light obscured by particulate pollution in
the air; clear window glass has zero opacity, a brick wall is 100 percent
opaque. Opacity is an indicator of changes in performance of particulate
Open Burning: Uncontrolled fires in an open dump.
Open Dump: An uncovered site used for disposal of waste without
environmental controls. (See:
Operable Unit: Term for each of a number of separate activities
undertaken as part of a Superfund site cleanup. A typical operable unit
would be removal of drums and tanks from the surface of a site.
Operating Conditions: Conditions specified in a RCRA permit that
dictate how an incinerator must operate as it burns different waste types. A
trial burn is used to identify operating conditions needed to meet specified
Operation and Maintenance: 1. Activities conducted after a
Superfund site action is completed to ensure that the action is effective.
2. Actions taken after construction to ensure that facilities constructed to
treat waste water will be properly operated and maintained to achieve
normative efficiency levels and prescribed effluent limitations in an
optimum manner. 3. On-going asbestos management plan in a school or other
public building, including regular inspections, various methods of
maintaining asbestos in place, and removal when necessary.
Operator Certification: Certification of operators of community
and nontransient noncommunity water systems, asbestos specialists, pesticide
applicators, hazardous waste transporter, and other such specialists as
required by the EPA or a state agency implementing an EPA-approved
environmental regulatory program.
Optimal Corrosion Control Treatment: An erosion control treatment
that minimizes the lead and copper concentrations at users' taps while also
ensuring that the treatment does not cause the water system to violate any
national primary drinking water regulations.
Oral Toxicity: Ability of a pesticide to cause injury when
Organic: 1. Referring to or derived from living organisms. 2. In
chemistry, any compound containing carbon.
Organic Chemicals/Compounds: Naturally occuring (animal or
plant-produced or synthetic) substances containing mainly carbon, hydrogen,
nitrogen, and oxygen.
Organic Matter: Carbonaceous waste contained in plant or animal
matter and originating from domestic or industrial sources.
Organism: Any form of animal or plant life.
Organophosphates: Pesticides that contain phosphorus; short-lived,
but some can be toxic when first applied.
Organophyllic: A substance that easily combines with organic
Organotins: Chemical compounds used in anti-foulant paints to
protect the hulls of boats and ships, buoys, and pilings from marine
organisms such as barnacles.
Original AHERA Inspection/Original Inspection/Inspection:
Examination of school buildings arranged by Local Education Agencies to
identify asbestos-containing-materials, evaluate their condition, and take
samples of materials suspected to contain asbestos; performed by
Original Generation Point: Where regulated medical or other
material first becomes waste.
Osmosis: The passage of a liquid from a weak solution to a more
concentrated solution across a semipermeable membrane that allows passage of
the solvent (water) but not the dissolved solids.
Other Ferrous Metals: Recyclable metals from strapping, furniture,
and metal found in tires and consumer electronics but does not include
metals found in construction materials or cars, locomotives, and ships.
(See: ferrous metals.)
Other Glass: Recyclable glass from furniture, appliances, and
consumer electronics. Does not include glass from transportation products
(cars trucks or shipping containers) and construction or demolition debris.
Other Nonferrous Metals: Recyclable nonferrous metals such as
lead, copper, and zinc from appliances, consumer electronics, and
nonpackaging aluminum products. Does not include nonferrous metals from
industrial applications and construction and demolition debris. (See:
Other Paper: For Recyclable paper from books, third-class mail,
commercial printing, paper towels, plates and cups; and other nonpackaging
paper such as posters, photographic papers, cards and games, milk cartons,
folding boxes, bags, wrapping paper, and paperboard. Does not include
wrapping paper or shipping cartons.
Other Plastics: Recyclable plastic from appliances, eating
utensils, plates, containers, toys, and various kinds of equipment. Does not
include heavy-duty plastics such as yielding materials.
Other Solid Waste: Recyclable nonhazardous solid wastes, other
than municipal solid waste, covered under Subtitle D of RARA. (See:
Other Wood: Recyclable wood from furniture, consumer electronics
cabinets, and other nonpackaging wood products. Does not include lumber and
tree stumps recovered from construction and demolition activities, and
industrial process waste such as shavings and sawdust.
Outdoor Air Supply: Air brought into a building from outside.
Outfall: The place where effluent is discharged into receiving
Overburden: Rock and soil cleared away before mining.
Overdraft: The pumping of water from a groundwater basin or
aquifer in excess of the supply flowing into the basin; results in a
depletion or "mining" of the groundwater in the basin. (See:
Overfire Air: Air forced into the top of an incinerator or boiler
to fan the flames.
Overflow Rate: One of the guidelines for design of the settling
tanks and clarifers in a treatment plant; used by plant operators to
determine if tanks and clarifiers are over or under-used.
Overland Flow: A land application technique that cleanses waste
water by allowing it to flow over a sloped surface. As the water flows over
the surface, contaminants are absorbed and the water is collected at the
bottom of the slope for reuse.
Oversized Regulated Medical Waste: Medical waste that is too large
for plastic bags or standard containers.
Overturn: One complete cycle of top to bottom mixing of previously
stratified water masses. This phenomenon may occur in spring or fall, or
after storms, and results in uniformity of chemical and physical properties
of water at all depths.
Oxidant: A collective term for some of the primary constituents of
Oxidation Pond: A man-made (anthropogenic) body of water in which
waste is consumed by bacteria, used most frequently with other
waste-treatment processes; a sewage lagoon.
Oxidation: The chemical addition of oxygen to break down
pollutants or organizac waste; e.g., destruction of chemicals such as
cyanides, phenols, and organic sulfur compounds in sewage by bacterial and
Oxidation-Reduction Potential: The electric potential required to
transfer electrons from one compound or element (the oxidant) to another
compound (the reductant); used as a qualitative measure of the state of
oxidation in water treatment systems.
Oxygenated Fuels: Gasoline which has been blended with alcohols or
ethers that contain oxygen in order to reduce carbon monoxide and other
Oxygenated Solvent: An organic solvent containing oxygen as part
of the molecular structure. Alcohols and ketones are oxygenated compounds
often used as paint solvents.
Ozonation/Ozonator: Application of ozone to water for disinfection
or for taste and odor control. The ozonator is the device that does this.
Ozone (O3): Found in two layers of the atmosphere, the
stratosphere and the troposphere. In the stratosphere (the atmospheric layer
7 to 10 miles or more above the earth's surface) ozone is a natural form of
oxygen that provides a protective layer shielding the earth from ultraviolet
radiation.In the troposphere (the layer extending up 7 to 10 miles from the
earth's surface), ozone is a chemical oxidant and major component of
photochemical smog. It can seriously impair the respiratory system and is
one of the most wide- spread of all the criteria pollutants for which the
Clean Air Act required EPA to set standards. Ozone in the troposphere is
produced through complex chemical reactions of nitrogen oxides, which are
among the primary pollutants emitted by combustion sources; hydrocarbons,
released into the atmosphere through the combustion, handling and processing
of petroleum products; and sunlight.
Ozone Depletion: Destruction of the stratospheric ozone layer
which shields the earth from ultraviolet radiation harmful to life. This
destruction of ozone is caused by the breakdown of certain chlorine and/or
bromine containing compounds (chlorofluorocarbons or halons), which break
down when they reach the stratosphere and then catalytically destroy ozone
Ozone Hole: A thinning break in the stratospheric ozone layer.
Designation of amount of such depletion as an "ozone hole" is made when the
detected amount of depletion exceeds fifty percent. Seasonal ozone holes
have been observed over both the Antarctic and Arctic regions, part of
Canada, and the extreme northeastern United States.
Ozone Layer: The protective layer in the atmosphere, about 15
miles above the ground, that absorbs some of the sun's ultraviolet rays,
thereby reducing the amount of potentially harmful radiation that reaches
the earth's surface.
Packaging: The assembly of one or more containers and any other
components necessary to ensure minimum compliance with a program's storage
and shipment packaging requirements. Also, the containers, etc. involved.
Packed Bed Scrubber: An air pollution control device in which
emissions pass through alkaline water to neutralize hydrogen chloride gas.
Packed Tower: A pollution control device that forces dirty air
through a tower packed with crushed rock or wood chips while liquid is
sprayed over the packing material. The pollutants in the air stream either
dissolve or chemically react with the liquid.
Packer: An inflatable gland, or balloon, used to create a
temporary seal in a borehole, probe hole, well, or drive casing. It is made
of rubber or non-reactive materials.
Palatable Water: Water, at a desirable temperature, that is free
from objectionable tastes, odors, colors, and turbidity.
Pandemic: A widespread epidemic throughout an area, nation or the
Paper: In the recycling business, refers to products and
materials, including newspapers, magazines, office papers, corrugated
containers, bags and some paperboard packaging that can be recycled into new
Paper Processor/Plastics Processor: Intermediate facility where
recovered paper or plastic products and materials are sorted,
decontaminated, and prepared for final recycling.
Parameter: A variable, measurable property whose value is a
determinant of the characteristics of a system; e.g. temperature, pressure,
and density are parameters of the atmosphere.
Paraquat: A standard herbicide used to kill various types of
crops, including marijuana. Causes lung damage if smoke from the crop is
Parshall Flume: Device used to measure the flow of water in an
Part A Permit, Part B Permit: (See:
Interim Permit Status.)
Participation Rate: Portion of population participating in a
Particle Count: Results of a microscopic examination of treated
water with a special "particle counter" that classifies suspended particles
by number and size.
Particulate Loading: The mass of particulates per unit volume of
air or water.
Particulates: 1. Fine liquid or solid particles such as dust,
smoke, mist, fumes, or smog, found in air or emissions. 2. Very small solids
suspended in water; they can vary in size, shape, density and electrical
charge and can be gathered together by coagulation and flocculation.
Partition Coefficient: Measure of the sorption phenomenon, whereby
a pesticide is divided between the soil and water phase; also referred to as
adsorption partition coefficient.
Parts Per Billion (ppb)/Parts Per Million (ppm): Units commonly
used to express contamination ratios, as in establishing the maximum
permissible amount of a contaminant in water, land, or air.
Passive Smoking/Secondhand Smoke: Inhalation of others' tobacco
Passive Treatment Walls: Technology in which a chemical reaction
takes place when contaminated ground water comes in contact with a barrier
such as limestone or a wall containing iron filings.
Pathogens: Microorganisms (e.g., bacteria, viruses, or parasites)
that can cause disease in humans, animals and plants.
Pathway: The physical course a chemical or pollutant takes from
its source to the exposed organism.
Pay-As-You-Throw/Unit-Based Pricing: Systems under which residents
pay for municipal waste management and disposal services by weight or volume
collected, not a fixed fee.
Peak Electricity Demand: The maximum electricity used to meet the
cooling load of a building or buildings in a given area.
Peak Levels: Levels of airborne pollutant contaminants much higher
than average or occurring for short periods of time in response to sudden
Percent Saturatiuon: The amount of a substance that is dissolved
in a solution compared to the amount that could be dissolved in it.
Perched Water: Zone of unpressurized water held above the water
table by impermeable rock or sediment.
Percolating Water: Water that passes through rocks or soil under
the force of gravity.
Percolation: 1. The movement of water downward and radially
through subsurface soil layers, usually continuing downward to ground water.
Can also involve upward movement of water. 2. Slow seepage of water through
Performance Bond: Cash or securities deposited before a landfill
operating permit is issued, which are held to ensure that all requirements
for operating ad subsequently closing the landfill are faithful performed.
The money is returned to the owner after proper closure of the landfill is
completed. If contamination or other problems appear at any time during
operation, or upon closure, and are not addressed, the owner must forfeit
all or part of the bond which is then used to cover clean-up costs.
Performance Data (For Incinerators): Information collected, during
a trial burn, on concentrations of designated organic compounds and
pollutants found in incinerator emissions. Data analysis must show that the
incinerator meets performance standards under operating conditions specified
in the RCRA permit. (See:
Performance Standards: 1. Regulatory requirements limiting the
concentrations of designated organic compounds, particulate matter, and
hydrogen chloride in emissions from incinerators. 2. Operating standards
established by EPA for various permitted pollution control systems, asbestos
inspections, and various program operations and maintenance requirements.
Periphyton: Microscopic underwater plants and animals that are
firmly attached to solid surfaces such as rocks, logs, and pilings.
Permeability: The rate at which liquids pass through soil or other
materials in a specified direction.
Permissible Dose: The dose of a chemical that may be received by
an individual without the expectation of a significantly harmful result.
Permissible Exposure Limit: Also referred to as PEL,
federal limits for workplace exposure to contaminants as established by
Permit: An authorization, license, or equivalent control document
issued by EPA or an approved state agency to implement the requirements of
an environmental regulation; e.g. a permit to operate a wastewater treatment
plant or to operate a facility that may generate harmful emissions.
Persistence: Refers to the length of time a compound stays in the
environment, once introduced. A compound may persist for less than a second
Persistent Pesticides: Pesticides that do not break down
chemically or break down very slowly and remain in the environment after a
Personal Air Samples: Air samples taken with a pump that is
directly attached to the worker with the collecting filter and cassette
placed in the worker's breathing zone (required under OSHA asbestos
standards and EPA worker protection rule).
Personal Measurement: A measurement collected from an individual's
Personal Protective Equipment: Clothing and equipment worn by
pesticide mixers, loaders and applicators and re-entry workers, hazmat
emergency responders, workers cleaning up Superfund sites, et. al., which is
worn to reduce their exposure to potentially hazardous chemicals and other
Pest: An insect, rodent, nematode, fungus, weed or other form of
terrestrial or aquatic plant or animal life that is injurious to health or
Pest Control Operator: Person or company that applies pesticides
as a business (e.g. exterminator); usually describes household services, not
Pesticide: Substances or mixture there of intended for preventing,
destroying, repelling, or mitigating any pest. Also, any substance or
mixture intended for use as a plant regulator, defoliant, or desiccant.
Pesticide Regulation Notice: Formal notice to pesticide
registrants about important changes in regulatory policy, procedures,
Pesticide Tolerance: The amount of pesticide residue allowed by
law to remain in or on a harvested crop. EPA sets these levels well below
the point where the compounds might be harmful to consumers.
PETE (Polyethylene Terepthalate): Thermoplastic material used in
plastic soft drink and rigid containers.
Petroleum: Crude oil or any fraction thereof that is liquid under
normal conditions of temperature and pressure. The term includes
petroleum-based substances comprising a complex blend of hydrocarbons
derived from crude oil through the process of separation, conversion,
upgrading, and finishing, such as motor fuel, jet oil, lubricants, petroleum
solvents, and used oil.
Petroleum Derivatives: Chemicals formed when gasoline breaks down
in contact with ground water.
pH: An expression of the intensity of the basic or acid condition
of a liquid; may range from 0 to 14, where 0 is the most acid and 7 is
neutral. Natural waters usually have a pH between 6.5 and 8.5.
Pharmacokinetics: The study of the way that drugs move through the
body after they are swallowed or injected.
Phenolphthalein Alkalinity: The alkalinity in a water sample
measured by the amount of standard acid needed to lower the pH to a level of
8.3 as indicated by the change of color of the phenolphthalein from pink to
Phenols: Organic compounds that are byproducts of petroleum
refining, tanning, and textile, dye, and resin manufacturing. Low
concentrations cause taste and odor problems in water; higher concentrations
can kill aquatic life and humans.
Phosphates: Certain chemical compounds containing phosphorus.
Phosphogypsum Piles (Stacks): Principal byproduct generated in
production of phosphoric acid from phosphate rock. These piles may generate
radioactive radon gas.
Phosphorus: An essential chemical food element that can contribute
to the eutrophication of lakes and other water bodies. Increased phosphorus
levels result from discharge of phosphorus-containing materials into surface
Phosphorus Plants: Facilities using electric furnaces to produce
elemental phosphorous for commercial use, such as high grade phosphoric
acid, phosphate-based detergent, and organic chemicals use.
Photochemical Oxidants: Air pollutants formed by the action of
sunlight on oxides of nitrogen and hydrocarbons.
Photochemical Smog: Air pollution caused by chemical reactions of
various pollutants emitted from different sources. (See:
Photosynthesis: The manufacture by plants of carbohydrates and
oxygen from carbon dioxide mediated by chlorophyll in the presence of
Physical and Chemical Treatment: Processes generally used in
large-scale wastewater treatment facilities. Physical processes may include
air-stripping or filtration. Chemical treatment includes coagulation,
chlorination, or ozonation. The term can also refer to treatment of toxic
materials in surface and ground waters, oil spills, and some methods of
dealing with hazardous materials on or in the ground.
Phytoplankton: That portion of the plankton community comprised of
tiny plants; e.g. algae, diatoms.
Phytoremediation: Low-cost remediation option for sites with
widely dispersed contamination at low concentrations.
Phytotoxic: Harmful to plants.
Phytotreatment: The cultivation of specialized plants that absorb
specific contaminants from the soil through their roots or foliage. This
reduces the concentration of contaminants in the soil, but incorporates them
into biomasses that may be released back into the environment when the plant
dies or is harvested.
Picocuries Per Liter pCi/L): A unit of measure for levels of radon
gas; becquerels per cubic meter is metric equivalent.
Piezometer: A nonpumping well, generally of small diameter, for
measuring the elevation of a water table.
Pilot Tests: Testing a cleanup technology under actual site
conditions to identify potential problems prior to full-scale
Plankton: Tiny plants and animals that live in water.
Plasma Arc Reactors: devices that use an electric arc to
thermally decompose organic and inorganic materials at ultra-high
temperatures into gases and a vitrified slag residue. A plasma arc reactor
can operate as any of the following:
|integral component of chemical, fuel, or electricty production
systems, processing high or medium value organic compounds into a
synthetic gas used as a fuel
||materials recovery device, processing scrap to recover metal from
||destruction or incineration system, processing waste materials into
slag and gases ignited inside of a secondary combustion chamber that
follows the reactor
Plasmid: A circular piece of DNA that exists apart from the
chromosome and replicates independently of it. Bacterial plasmids carry
information that renders the bacteria resistant to antibiotics. Plasmids are
often used in genetic engineering to carry desired genes into organisms.
Plastics: Non-metallic chemoreactive compounds molded into rigid
or pliable construction materials, fabrics, etc.
Plate Tower Scrubber: An air pollution control device that
neutralizes hydrogen chloride gas by bubbling alkaline water through holes
in a series of metal plates.
Plug Flow: Type of flow the occurs in tanks, basins, or reactors
when a slug of water moves through without ever dispersing or mixing with
the rest of the water flowing through.
Plugging: Act or process of stopping the flow of water, oil, or
gas into or out of a formation through a borehole or well penetrating that
Plume: 1. A visible or measurable discharge of a contaminant from
a given point of origin. Can be visible or thermal in water, or visible in
the air as, for example, a plume of smoke. 2 The area of radiation leaking
from a damaged reactor. 3. Area downwind within which a release could be
dangerous for those exposed to leaking fumes.
Plutonium: A radioactive metallic element chemically similar to
PM-10/PM-2.5: PM 10 is measure of particles in the atmosphere with
a diameter of less than ten or equal to a nominal 10 micrometers. PM-2.5 is
a measure of smaller particles in the air. PM-10 has been the pollutant
particulate level standard against which EPA has been measuring Clean Air
Act compliance. On the basis of newer scientific findings, the Agency is
considering regulations that will make PM-2.5 the new "standard".
Pneumoconiosis: Health conditions characterized by permanent
deposition of substantial amounts of particulate matter in the lungs and by
the tissue reaction to its presence; can range from relatively harmless
forms of sclerosis to the destructive fibrotic effect of silicosis.
Point Source: A stationary location or fixed facility from which
pollutants are discharged; any single identifiable source of pollution; e.g.
a pipe, ditch, ship, ore pit, factory smokestack.
Point-of-Contact Measurement of Exposure: Estimating exposure by
measuring concentrations over time (while the exposure is taking place) at
or near the place where it is occurring.
Point-of-Disinfectant Application: The point where disinfectant is
applied and water downstream of that point is not subject to recontamination
by surface water runoff.
of generation (POG) of a Hazardous Waste: The point at which a waste is
first determined to be hazardous. For listed wastes this is the point at which
the waste first meets the listing description, and for characteristic wastes it
is the point the waste first exhibits the characteristic.
Point-of-Use Treatment Device: Treatment device applied to a
single tap to reduce contaminants in the drinking water at the one faucet.
Pollen: The fertilizing element of flowering plants; background
Pollutant: Generally, any substance introduced into the
environment that adversely affects the usefulness of a resource or the
health of humans, animals, or ecosystems..
Pollutant Pathways: Avenues for distribution of pollutants. In
most buildings, for example, HVAC systems are the primary pathways although
all building components can interact to affect how air movement distributes
Pollutant Standard Index (PSI): Indicator of one or more
pollutants that may be used to inform the public about the potential for
adverse health effects from air pollution in major cities.
Pollution: Generally, the presence of a substance in the
environment that because of its chemical composition or quantity prevents
the functioning of natural processes and produces undesirable environmental
and health effects.Under the Clean Water Act, for example, the term has been
defined as the man-made or man-induced alteration of the physical,
biological, chemical, and radiological integrity of water and other media.
Pollution Prevention: 1. Identifying areas, processes, and
activities which create excessive waste products or pollutants in order to
reduce or prevent them through, alteration, or eliminating a process. Such
activities, consistent with the Pollution Prevention Act of 1990, are
conducted across all EPA programs and can involve cooperative efforts with
such agencies as the Departments of Agriculture and Energy. 2. EPA has
initiated a number of voluntary programs in which industrial, or commercial
or "partners" join with EPA in promoting activities that conserve energy,
conserve and protect water supply, reduce emissions or find ways of
utilizing them as energy resources, and reduce the waste stream. Among these
are: Agstar, to reduce methane emissions through manure management. Climate
Wise, to lower industrial greenhouse-gas emissions and energy costs. Coalbed
Methane Outreach, to boost methane recovery at coal mines. Design for the
Environment, to foster including environmental considerations in product
design and processes. Energy Star programs, to promote energy efficiency in
commercial and residential buildings, office equipment, transformers,
computers, office equipment, and home appliances. Environmental Accounting,
to help businesses identify environmental costs and factor them into
management decision making. Green Chemistry, to promote and recognize
cost-effective breakthroughs in chemistry that prevent pollution. Green
Lights, to spread the use of energy-efficient lighting technologies. Indoor
Environments, to reduce risks from indoor-air pollution. Landfill Methane
Outreach, to develop landfill gas-to-energy projects. Natural Gas Star, to
reduce methane emissions from the natural gas industry. Ruminant Livestock
Methane, to reduce methane emissions from ruminant livestock. Transportation
Partners, to reduce carbon dioxide emissions from the transportation sector.
Voluntary Aluminum Industrial Partnership, to reduce perfluorocarbon
emissions from the primary aluminum industry. WAVE, to promote efficient
water use in the lodging industry. Wastewi$e, to reduce business-generated
solid waste through prevention, reuse, and recycling. (See:
Common Sense Initiative
and Project XL.)
Polychlorinated Biphenyls: A group of toxic, persistent
chemicals used in electrical transformers and capacitors for insulating
purposes, and in gas pipeline systems as lubricant. The sale and new use of
these chemicals, also known as PCBs, were banned by law in 1979.
Portal-of-Entry Effect: A local effect produced in the tissue or
organ of first contact between a toxicant and the biological system.
Polonium: A radioactive element that occurs in pitchblende and
other uranium-containing ores.
Polyelectrolytes: Synthetic chemicals that help solids to clump
during sewage treatment.
Polymer: A natural or synthetic chemical structure where two or
more like molecules are joined to form a more complex molecular structure
(e.g. polyethylene in plastic).
Polyvinyl Chloride (PVC): A tough, environmentally indestructible
plastic that releases hydrochloric acid when burned.
Population: A group of interbreeding organisms occupying a
particular space; the number of humans or other living creatures in a
Population at Risk: A population subgroup that is more likely to
be exposed to a chemical, or is more sensitive to the chemical, than is the
Porosity: Degree to which soil, gravel, sediment, or rock is
permeated with pores or cavities through which water or air can move.
Post-Chlorination: Addition of chlorine to plant effluent for
disinfectant purposes after the effluent has been treated.
Post-Closure: The time period following the shutdown of a waste
management or manufacturing facility; for monitoring purposes, often
considered to be 30 years.
Post-Consumer Materials/Waste: Recovered materials that are
diverted from municipal solid waste for the purpose of collection,
recycling, and disposition.
Post-Consumer Recycling: Use of materials generated from
residential and consumer waste for new or similar purposes; e.g. converting
wastepaper from offices into corrugated boxes or newsprint.
Potable Water: Water that is safe for drinking and cooking.
Potential Dose: The amount of a compound contained in material
swallowed, breathed, or applied to the skin.
Potentially Responsible Party (PRP): Any individual or
company--including owners, operators, transporters or
generators--potentially responsible for, or contributing to a spill or other
contamination at a Superfund site. Whenever possible, through administrative
and legal actions, EPA requires PRPs to clean up hazardous sites they have
Potentiation: The ability of one chemical to increase the effect
of another chemical.
Potentiometric Surface: The surface to which water in an aquifer
can rise by hydrostatic pressure.
Precautionary Principle: When information about potential risks is
incomplete, basing decisions about the best ways to manage or reduce risks
on a preference for avoiding unnecessary health risks instead of on
unnecessary economic expenditures.
Pre-Consumer Materials/Waste: Materials generated in manufacturing
and converting processes such as manufacturing scrap and trimmings and
cuttings. Includes print overruns, overissue publications, and obsolete
Pre-Harvest Interval: The time between the last pesticide
application and harvest of the treated crops.
Prechlorination: The addition of chlorine at the headworks of a
treatment plant prior to other treatment processes. Done mainly for
disinfection and control of tastes, odors, and aquatic growths, and to aid
in coagulation and settling,
Precipitate: A substance separated from a solution or suspension
by chemical or physical change.
Precipitation: Removal of hazardous solids from liquid waste to
permit safe disposal; removal of particles from airborne emissions as in
rain (e.g. acid precipitation).
Precipitator: Pollution control device that collects particles
from an air stream.
Precursor: In photochemistry, a compound antecedent to a
pollutant. For example, volatile organic compounds (VOCs) and nitric oxides
of nitrogen react in sunlight to form ozone or other photochemical oxidants.
As such, VOCs and oxides of nitrogen are precursors.
Preliminary Assessment: The process of collecting and reviewing
available information about a known or suspected waste site or release.
Prescriptive: Water rights which are acquired by diverting water
and putting it to use in accordance with specified procedures; e.g. filing a
request with a state agency to use unused water in a stream, river, or lake.
Pressed Wood Products: Materials used in building and furniture
construction that are made from wood veneers, particles, or fibers bonded
together with an adhesive under heat and pressure.
Pressure Sewers: A system of pipes in which water, wastewater, or
other liquid is pumped to a higher elevation.
Pressure, Static: In flowing air, the total pressure minus
velocity pressure, pushing equally in all directions.
Pressure, Total: In flowing air, the sum of the static and
Pressure, Velocity: In flowing air, the pressure due to velocity
and density of air.
Pretreatment: Processes used to reduce, eliminate, or alter the
nature of wastewater pollutants from non-domestic sources before they are
discharged into publicly owned treatment works (POTWs).
Prevalent Level Samples: Air samples taken under normal conditions
(also known as ambient background samples).
Prevalent Levels: Levels of airborne contaminant occurring under
Prevention of Significant Deterioration (PSD): EPA program in
which state and/or federal permits are required in order to restrict
emissions from new or modified sources in places where air quality already
meets or exceeds primary and secondary ambient air quality standards.
Primacy: Having the primary responsibility for administering and
Primary Drinking Water Regulation: Applies to public water systems
and specifies a contaminant level, which, in the judgment of the EPA
Administrator, will not adversely affect human health.
Primary Effect: An effect where the stressor acts directly on the
ecological component of interest, not on other parts of the ecosystem. (See:
Primary Standards: National ambient air quality standards designed
to protect human health with an adequate margin for safety. (See:
National Ambient Air
Primary Treatment: First stage of wastewater treatment
in which solids are removed by screening and settling.
Primary Waste Treatment: First steps in wastewater treatment;
screens and sedimentation tanks are used to remove most materials that float
or will settle. Primary treatment removes about 30 percent of carbonaceous
biochemical oxygen demand from domestic sewage.
Principal Organic Hazardous Constituents (POHCs): Hazardous
compounds monitored during an incinerator's trial burn, selected for high
concentration in the waste feed and difficulty of combustion.
Microscopic particles made of protein that can cause disease.
Prior Appropriation: A doctrine of water law that allocates the
rights to use water on a first-come, first-served basis.
Probability of Detection : The likelihood, expressed as a
percentage, that a test method will correctly identify a leaking tank.
Process Variable: A physical or chemical quantity which is usually
measured and controlled in the operation of a water treatment plant or
Process Verification: Verifying that process raw materials, water
usage, waste treatment processes, production rate and other facts relative
to quantity and quality of pollutants contained in discharges are
substantially described in the permit application and the issued permit.
Process Wastewater: Any water that comes into contact with any raw
material, product, byproduct, or waste.
Process Weight: Total weight of all materials, including fuel,
used in a manufacturing process; used to calculate the allowable particulate
Producers: Plants that perform photosynthesis and provide food to
Product Level: The level of a product in a storage tank.
Product Water: Water that has passed through a water treatment
plant and is ready to be delivered to consumers.
Products of Incomplete Combustion (PICs): Organic compounds formed
by combustion. Usually generated in small amounts and sometimes toxic, PICs
are heat-altered versions of the original material fed into the incinerator
(e.g. charcoal is a P.I.C. from burning wood).
Wastes: Wastes that have to meet their treatment standards before land
Project XL: An EPA initiative to give states and the regulated
community the flexibility to develop comprehensive strategies as
alternatives to multiple current regulatory requirements in order to exceed
compliance and increase overall environmental benefits.
Propellant: Liquid in a self-pressurized pesticide product that
expels the active ingredient from its container.
Proportionate Mortality Ratio (PMR): The number of deaths from a
specific cause in a specific period of time per 100 deaths from all causes
in the same time period.
Proposed Plan: A plan for a site cleanup that is available to the
public for comment.
Proteins: Complex nitrogenous organic compounds of high molecular
weight made of amino acids; essential for growth and repair of animal
tissue. Many, but not all, proteins are enzymes.
Protocol: A series of formal steps for conducting a test.
Protoplast: A membrane-bound cell from which the outer wall has
been partially or completely removed. The term often is applied to plant
Protozoa: One-celled animals that are larger and more complex than
bacteria. May cause disease.
Public Comment Period: The time allowed for the public to express
its views and concerns regarding an action by EPA (e.g. a Federal Register
Notice of proposed rule-making, a public notice of a draft permit, or a
Notice of Intent to Deny).
Public Health Approach: Regulatory and voluntary focus on
effective and feasible risk management actions at the national and community
level to reduce human exposures and risks, with priority given to reducing
exposures with the biggest impacts in terms of the number affected and
severity of effect.
Public Health Context: The incidence, prevalence, and severity of
diseases in communities or populations and the factors that account for
them, including infections, exposure to pollutants, and other exposures or
Public Hearing: A formal meeting wherein EPA officials hear the
public's views and concerns about an EPA action or proposal. EPA is required
to consider such comments when evaluating its actions. Public hearings must
be held upon request during the public comment period.
Public Notice: 1. Notification by EPA informing the public of
Agency actions such as the issuance of a draft permit or scheduling of a
hearing. EPA is required to ensure proper public notice, including
publication in newspapers and broadcast over radio and television stations.
2. In the safe drinking water program, water suppliers are required to
publish and broadcast notices when pollution problems are discovered.
Public Water System: A system that provides piped water for human
consumption to at least 15 service connections or regularly serves 25
Publicly Owned Treatment Works (POTWs): A waste-treatment works
owned by a state, unit of local government, or Indian tribe, usually
designed to treat domestic wastewaters.
Pumping Station: Mechanical device installed in sewer or water
system or other liquid-carrying pipelines to move the liquids to a higher
Pumping Test: A test conducted to determine aquifer or well
Purging: Removing stagnant air or water from sampling zone or
equipment prior to sample collection.
Putrefaction: Biological decomposition of organic matter;
associated with anaerobic conditions.
Putrescible: Able to rot quickly enough to cause odors and attract
Pyrolysis: Decomposition of a chemical by extreme heat.
Qualitative Use Assessment: Report summarizing the major uses of a
pesticide including percentage of crop treated, and amount of pesticide used
on a site.
Quality Assurance/Quality Control: A system of procedures, checks,
audits, and corrective actions to ensure that all EPA research design and
performance, environmental monitoring and sampling, and other technical and
reporting activities are of the highest achievable quality.
Quench Tank: A water-filled tank used to cool incinerator residues
or hot materials during industrial processes.
Radiation: Transmission of energy though space or any medium. Also
known as radiant energy.
Radiation Standards: Regulations that set maximum exposure limits
for protection of the public from radioactive materials.
Radio Frequency Radiation: (See
Radioactive Decay: Spontaneous change in an atom by emission of of
charged particles and/or gamma rays; also known as radioactive
disintegration and radioactivity.
Radioactive Substances: Substances that emit ionizing radiation.
Radioactive Waste: Any waste that emits energy as rays,
waves, streams or energetic particles. Radioactive materials are often mixed
with hazardous waste, from nuclear reactors, research institutions, or
Radioisotopes: Chemical variants of radioactive elements with
potentially oncogenic, teratogenic, and mutagenic effects on the human body.
Radionuclide: Radioactive particle, man-made (anthropogenic) or
natural, with a distinct atomic weight number. Can have a long life as soil
or water pollutant.
Radius of Vulnerability Zone: The maximum distance from the point
of release of a hazardous substance in which the airborne concentration
could reach the level of concern under specified weather conditions.
Radius of Influence: 1. The radial distance from the center of a
wellbore to the point where there is no lowering of the water table or
potentiometric surface (the edge of the cone of depression); 2. the radial
distance from an extraction well that has adequate air flow for effective
removal of contaminants when a vacuum is applied to the extraction well.
Radon: A colorless naturally occurring, radioactive, inert gas
formed by radioactive decay of radium atoms in soil or rocks.
Radon Daughters/Radon Progeny: Short-lived radioactive decay
products of radon that decay into longer-lived lead isotopes that can attach
themselves to airborne dust and other particles and, if inhaled, damage the
linings of the lungs.
Radon Decay Products: A term used to refer collectively to the
immediate products of the radon decay chain. These include Po-218, Pb-214,
Bi-214, and Po-214, which have an average combined half-life of about 30
Rainbow Report: Comprehensive document giving the status of all
pesticides now or ever in registration or special reviews. Known as the
"rainbow report" because chapters are printed on different colors of paper.
Rasp: A machine that grinds waste into a manageable material and
helps prevent odor.
Raw Agricultural Commodity: An unprocessed human food or animal
feed crop (e.g., raw carrots, apples, corn, or eggs.)
Raw Sewage: Untreated wastewater and its contents.
Raw Water: Intake water prior to any treatment or use.
Re-entry: (In indoor air program) Refers to air exhausted from a
building that is immediately brought back into the system through the air
intake and other openings.
Reactivity: Refers to those hazardous wastes that are
normally unstable and readily undergo violent chemical change but do not
Reaeration: Introduction of air into the lower layers of a
reservoir. As the air bubbles form and rise through the water, the oxygen
dissolves into the water and replenishes the dissolved oxygen. The rising
bubbles also cause the lower waters to rise to the surface where they take
on oxygen from the atmosphere.
Real-Time Monitoring: Monitoring and measuring environmental
developments with technology and communications systems that provide
time-relevant information to the public in an easily understood format
people can use in day-to-day decision-making about their health and the
Reasonable Further Progress: Annual incremental reductions in air
pollutant emissions as reflected in a State Implementation Plan that EPA
deems sufficient to provide for the attainment of the applicable national
ambient air quality standards by the statutory deadline.
Reasonable Maximum Exposure: The maximum exposure reasonably
expected to occur in a population.
Reasonable Worst Case: An estimate of the individual dose,
exposure, or risk level received by an individual in a defined population
that is greater than the 90th percentile but less than that received by
anyone in the 98th percentile in the same population.
Reasonably Available Control Measures (RACM): A broadly defined
term referring to technological and other measures for pollution control.
Reasonably Available Control Technology (RACT): Control technology
that is reasonably available, and both technologically and economically
feasible. Usually applied to existing sources in nonattainment areas; in
most cases is less stringent than new source performance standards.
Recarbonization: Process in which carbon dioxide is bubbled into
water being treated to lower the pH.
Receiving Waters: A river, lake, ocean, stream or other
watercourse into which wastewater or treated effluent is discharged.
Receptor: Ecological entity exposed to a stressor.
Recharge: The process by which water is added to a zone of
saturation, usually by percolation from the soil surface; e.g., the recharge
of an aquifer.
Recharge Area: A land area in which water reaches the zone of
saturation from surface infiltration, e.g., where rainwater soaks through
the earth to reach an aquifer.
Recharge Rate: The quantity of water per unit of time that
replenishes or refills an aquifer.
Reclamation: (In recycling) Restoration of materials found in the
waste stream to a beneficial use which may be for purposes other than the
Recombinant Bacteria: A microorganism whose genetic makeup has
been altered by deliberate introduction of new genetic elements. The
offspring of these altered bacteria also contain these new genetic elements;
i.e. they "breed true."
Recombinant DNA: The new DNA that is formed by combining pieces of
DNA from different organisms or cells.
Recommended Maximum Contaminant Level (RMCL): The maximum level of
a contaminant in drinking water at which no known or anticipated adverse
effect on human health would occur, and that includes an adequate margin of
safety. Recommended levels are nonenforceable health goals. (See:
Reconstructed Source: Facility in which components are replaced to
such an extent that the fixed capital cost of the new components exceeds 50
percent of the capital cost of constructing a comparable brand-new facility.
New-source performance standards may be applied to sources reconstructed
after the proposal of the standard if it is technologically and economically
feasible to meet the standards.
Reconstruction of Dose: Estimating exposure after it has occurred
by using evidence within an organism such as chemical levels in tissue or
Record of Decision (ROD): A public document that explains which
cleanup alternative(s) will be used at National Priorities List sites where,
under CERCLA, Trust Funds pay for the cleanup.
Recovery Rate: Percentage of usable recycled materials that have
been removed from the total amount of municipal solid waste generated in a
specific area or by a specific business.
Recycle/Reuse: Minimizing waste generation by recovering and
reprocessing usable products that might otherwise become waste (.i.e.
recycling of aluminum cans, paper, and bottles, etc.).
Recycling and Reuse Business Assistance Centers: Located in state
solid-waste or economic-development agencies, these centers provide
recycling businesses with customized and targeted assistance.
Recycling Economic Development Advocates: Individuals hired by
state or tribal economic development offices to focus financial, marketing,
and permitting resources on creating recycling businesses.
Recycling Mill: Facility where recovered materials are
remanufactured into new products.
Recycling Technical Assistance Partnership National Network: A
national information-sharing resource designed to help businesses and
manufacturers increase their use of recovered materials.
Red Bag Waste: (See:
Red Border: An EPA document undergoing review before being
submitted for final management decision-making.
Red Tide: A proliferation of a marine plankton toxic and often
fatal to fish, perhaps stimulated by the addition of nutrients. A tide can
be red, green, or brown, depending on the coloration of the plankton.
Redemption Program: Program in which consumers are monetarily
compensated for the collection of recyclable materials, generally through
prepaid deposits or taxes on beverage containers. In some states or
localities legislation has enacted redemption programs to help prevent
roadside litter. (See:
Reduction: The addition of hydrogen, removal of oxygen, or
addition of electrons to an element or compound.
Reentry Interval: The period of time immediately following the
application of a pesticide during which unprotected workers should not enter
Reference Dose (RfD): The RfD is a numerical estimate of a daily
oral exposure to the human population, including sensitive subgroups such as
children, that is not likely to cause harmful effects during a lifetime.
RfDs are generally used for health effects that are thought to have a
threshold or low dose limit for producing effects.
Reformulated Gasoline: Gasoline with a different composition from
conventional gasoline (e.g., lower aromatics content) that cuts air
Refueling Emissions: Emissions released during vehicle re-fueling.
Refuse Reclamation: Conversion of solid waste into useful
products; e.g., composting organic wastes to make soil conditioners or
separating aluminum and other metals for recycling.
Regeneration: Manipulation of cells to cause them to develop into
Regional Response Team (RRT): Representatives of federal, local,
and state agencies who may assist in coordination of activities at the
request of the On-Scene Coordinator before and during a significant
pollution incident such as an oil spill, major chemical release, or
Registrant: Any manufacturer or formulator who obtains
registration for a pesticide active ingredient or product.
Registration: Formal listing with EPA of a new pesticide before it
can be sold or distributed. Under the Federal Insecticide, Fungicide, and
Rodenticide Act, EPA is responsible for registration (pre-market licensing)
of pesticides on the basis of data demonstrating no unreasonable adverse
effects on human health or the environment when applied according to
approved label directions.
Registration Standards: Published documents which include summary
reviews of the data available on a pesticide's active ingredient, data gaps,
and the Agency's existing regulatory position on the pesticide.
Regulated Asbestos-Containing Material (RACM): Friable asbestos
material or nonfriable ACM that will be or has been subjected to sanding,
grinding, cutting, or abrading or has crumbled, or been pulverized or
reduced to powder in the course of demolition or renovation operations.
Regulated Medical Waste: Under the Medical Waste Tracking Act of
1988, any solid waste generated in the diagnosis, treatment, or immunization
of human beings or animals, in research pertaining thereto, or in the
production or testing of biologicals. Included are cultures and stocks of
infectious agents; human blood and blood products; human pathological body
wastes from surgery and autopsy; contaminated animal carcasses from medical
research; waste from patients with communicable diseases; and all used sharp
implements, such as needles and scalpels, and certain unused sharps. (See:
treated medical waste;
untreated medical waste;
destroyed medical waste.)
Relative Ecological Sustainability: Ability of an ecosystem to
maintain relative ecological integrity indefinitely.
Relative Permeability: The permeability of a rock to gas, NAIL, or
water, when any two or more are present.
Relative Risk Assessment: Estimating the risks associated with
different stressors or management actions.
Release: Any spilling, leaking, pumping, pouring, emitting,
emptying, discharging, injecting, escaping, leaching, dumping, or disposing
into the environment of a hazardous or toxic chemical or extremely hazardous
Remedial Action (RA): The actual construction or implementation
phase of a Superfund site cleanup that follows remedial design.
Remedial Design: A phase of remedial action that follows the
remedial investigation/feasibility study and includes development of
engineering drawings and specifications for a site cleanup.
Remedial Investigation: An in-depth study designed to gather data
needed to determine the nature and extent of contamination at a Superfund
site; establish site cleanup criteria; identify preliminary alternatives for
remedial action; and support technical and cost analyses of alternatives.
The remedial investigation is usually done with the feasibility study.
Together they are usually referred to as the "RI/FS".
Remedial Project Manager (RPM): The EPA or state
official responsible for overseeing on-site remedial action.
Remedial Response: Long-term action that stops or substantially
reduces a release or threat of a release of hazardous substances that is
serious but not an immediate threat to public health.
Remediation: 1. Cleanup or other methods used to remove or contain
a toxic spill or hazardous materials from a Superfund site; 2. for the
Asbestos Hazard Emergency Response program, abatement methods including
evaluation, repair, enclosure, encapsulation, or removal of greater than 3
linear feet or square feet of asbestos-containing materials from a building.
Remote Sensing: The collection and interpretation of information
about an object without physical contact with the object; e.g., satellite
imaging, aerial photography, and open path measurements.
Removal Action: Short-term immediate actions taken to address
releases of hazardous substances that require expedited response. (See:
Renewable Energy Production Incentive (REPI): Incentive
established by the Energy Policy Act available to renewable energy power
projects owned by a state or local government or nonprofit electric
Repeat Compliance Period: Any subsequent compliance period after
the initial one.
Reportable Quantity (RQ): Quantity of a hazardous substance that
triggers reports under CERCLA. If a substance exceeds its RQ, the release
must be reported to the National Response Center, the SERC, and community
emergency coordinators for areas likely to be affected.
Repowering: Rebuilding and replacing major components of a power
plant instead of building a new one.
Representative Sample: A portion of material or water that is as
nearly identical in content and consistency as possible to that in the
larger body of material or water being sampled.
Reregistration: The reevaluation and relicensing of existing
pesticides originally registered prior to current scientific and regulatory
standards. EPA reregisters pesticides through its Registration Standards
Reserve Capacity: Extra treatment capacity built into solid waste
and wastewater treatment plants and interceptor sewers to accommodate flow
increases due to future population growth.
Reservoir: Any natural or artificial holding area used to store,
regulate, or control water.
Residential Use: Pesticide application in and around houses,
office buildings, apartment buildings, motels, and other living or working
Residential Waste: Waste generated in single and multi-family
homes, including newspapers, clothing, disposable tableware, food packaging,
cans, bottles, food scraps, and yard trimmings other than those that are
diverted to backyard composting. (See:
Residual: Amount of a pollutant remaining in the environment after
a natural or technological process has taken place; e.g., the sludge
remaining after initial wastewater treatment, or particulates remaining in
air after it passes through a scrubbing or other process.
Residual Risk: The extent of health risk from air pollutants
remaining after application of the Maximum Achievable Control Technology
Residual Saturation: Saturation level below which fluid drainage
will not occur.
Residue: The dry solids remaining after the evaporation of a
sample of water or sludge.
Resistance: For plants and animals, the ability to withstand poor
environmental conditions or attacks by chemicals or disease. May be inborn
Resource Recovery: The process of obtaining matter or energy from
materials formerly discarded.
Response Action: 1. Generic term for actions taken in response to
actual or potential health-threatening environmental events such as spills,
sudden releases, and asbestos abatement/management problems. 2. A
CERCLA-authorized action involving either a short-term removal action or a
long-term removal response. This may include but is not limited to: removing
hazardous materials from a site to an EPA-approved hazardous waste facility
for treatment, containment or treating the waste on-site, identifying and
removing the sources of ground-water contamination and halting further
migration of contaminants. 3. Any of the following actions taken in school
buildings in response to AHERA to reduce the risk of exposure to asbestos:
removal, encapsulation, enclosure, repair, and operations and maintenance.
Responsiveness Summary: A summary of oral and/or written public
comments received by EPA during a comment period on key EPA documents, and
EPA's response to those comments.
Restoration: Measures taken to return a site to pre-violation
Restricted Entry Interval: The time after a pesticide application
during which entry into the treated area is restricted.
Restricted Use: A pesticide may be classified (under FIFRA
regulations) for restricted use if it requires special handling because of
its toxicity, and, if so, it may be applied only by trained, certified
applicators or those under their direct supervision.
Wastes: Wastes that have LDR treatment standards, but can be land disposed
without treatment because of an exemption (e.g., a capacity variance).
Restriction Enzymes: Enzymes that recognize specific regions of a
long DNA molecule and cut it at those points.
Retrofit: Addition of a pollution control device on an existing
facility without making major changes to the generating plant. Also called
Reuse: Using a product or component of municipal solid waste in
its original form more than once; e.g., refilling a glass bottle that has
been returned or using a coffee can to hold nuts and bolts.
Reverse Osmosis: A treatment process used in water systems by
adding pressure to force water through a semi-permeable membrane. Reverse
osmosis removes most drinking water contaminants. Also used in wastewater
treatment. Large-scale reverse osmosis plants are being developed.
Reversible Effect: An effect which is not permanent; especially
adverse effects which diminish when exposure to a toxic chemical stops.
Ribonucleic Acid (RNA): A molecule that carries the genetic
message from DNA to a cellular protein-producing mechanism.
Rill: A small channel eroded into the soil by surface runoff; can
be easily smoothed out or obliterated by normal tillage.
Ringlemann Chart: A series of shaded illustrations used to measure
the opacity of air pollution emissions, ranging from light grey through
black; used to set and enforce emissions standards.
Riparian Habitat: Areas adjacent to rivers and streams with a
differing density, diversity, and productivity of plant and animal species
relative to nearby uplands.
Riparian Rights: Entitlement of a land owner to certain uses of
water on or bordering the property, including the right to prevent diversion
or misuse of upstream waters. Generally a matter of state law.
Risk: A measure of the probability that damage to life, health,
property, and/or the environment will occur as a result of a given hazard.
Risk (Adverse) for Endangered Species: Risk to aquatic species if
anticipated pesticide residue levels equal one-fifth of LD10 or one-tenth of
LC50; risk to terrestrial species if anticipated pesticide residue levels
equal one-fifth of LC10 or one-tenth of LC50.
Risk Assessment: Qualitative and quantitative evaluation of the
risk posed to human health and/or the environment by the actual or potential
presence and/or use of specific pollutants.
Risk Characterization: The last phase of the risk assessment
process that estimates the potential for adverse health or ecological
effects to occur from exposure to a stressor and evaluates the uncertainty
Risk Communication: The exchange of information about health or
environmental risks among risk assessors and managers, the general public,
news media, interest groups, etc.
Risk Estimate: A description of the probability that organisms
exposed to a specific dose of a chemical or other pollutant will develop an
adverse response, e.g., cancer.
Risk Factor: Characteristics (e.g., race, sex, age, obesity) or
variables (e.g., smoking, occupational exposure level) associated with
increased probability of a toxic effect.
Risk for Non-Endangered Species: Risk to species if anticipated
pesticide residue levels are equal to or greater than LC50.
Risk Management: The process of evaluating and selecting
alternative regulatory and non-regulatory responses to risk. The selection
process necessarily requires the consideration of legal, economic, and
Risk-based Targeting: The direction of resources to those areas
that have been identified as having the highest potential or actual adverse
effect on human health and/or the environment.
Risk-Specific Dose: The dose associated with a specified risk
River Basin: The land area drained by a river and its tributaries.
Rodenticide: A chemical or agent used to destroy rats or other
rodent pests, or to prevent them from damaging food, crops, etc.
Rotary Kiln Incinerator: An incinerator with a rotating combustion
chamber that keeps waste moving, thereby allowing it to vaporize for easier
Rough Fish: Fish not prized for sport or eating, such as gar and
suckers. Most are more tolerant of changing environmental conditions than
are game or food species.
Route of Exposure: The avenue by which a chemical comes into
contact with an organism, e.g., inhalation, ingestion, dermal contact,
Rubbish: Solid waste, excluding food waste and ashes, from homes,
institutions, and workplaces.
Run-Off: That part of precipitation, snow melt, or irrigation
water that runs off the land into streams or other surface-water. It can
carry pollutants from the air and land into receiving waters.
Running Losses: Evaporation of motor vehicle fuel from the fuel
tank while the vehicle is in use.
Sacrifical Anode: An easily corroded material deliberately
installed in a pipe or intake to give it up (sacrifice it) to corrosion
while the rest of the water supply facility remains relatively
Safe: Condition of exposure under which there is a practical
certainty that no harm will result to exposed individuals.
Safe Water: Water that does not contain harmful bacteria, toxic
materials, or chemicals, and is considered safe for drinking even if it may
have taste, odor, color, and certain mineral problems.
Safe Yield: The annual amount of water that can be taken from a
source of supply over a period of years without depleting that source beyond
its ability to be replenished naturally in "wet years."
Safener: A chemical added to a pesticide to keep it from injuring
Salinity: The percentage of salt in water.
Salt Water Intrusion: The invasion of fresh surface or ground
water by salt water. If it comes from the ocean it may be called sea water
Salts: Minerals that water picks up as it passes through the air,
over and under the ground, or from households and industry.
Salvage: The utilization of waste materials.
Sampling Frequency: The interval between the collection of
Sanctions: Actions taken by the federal government for failure to
provide or implement a State Implementation Plan (SIP). Such action may
include withholding of highway funds and a ban on construction of new
sources of potential pollution.
Sand Filters: Devices that remove some suspended solids from
sewage. Air and bacteria decompose additional wastes filtering through the
sand so that cleaner water drains from the bed.
Sanitary Landfill: (See:
Sanitary Sewers: Underground pipes that carry off only domestic or
industrial waste, not storm water.
Sanitary Survey: An on-site review of the water sources,
facilities, equipment, operation and maintenance of a public water system to
evaluate the adequacy of those elements for producing and distributing safe
Sanitary Water (Also known as gray water): Water discharged from
sinks, showers, kitchens, or other non-industrial operations, but not from
Sanitation: Control of physical factors in the human environment
that could harm development, health, or survival.
Saprolite: A soft, clay-rich, thoroughly decomposed rock formed in
place by chemical weathering of igneous or metamorphic rock. Forms in humid,
tropical, or subtropical climates.
Saprophytes: Organisms living on dead or decaying organic matter
that help natural decomposition of organic matter in water.
Saturated Zone: The area below the water table where all open
spaces are filled with water under pressure equal to or greater than that of
Saturation: The condition of a liquid when it has taken into
solution the maximum possible quantity of a given substance at a given
temperature and pressure.
Science Advisory Board (SAB): A group of external scientists who
advise EPA on science and policy.
Scrap: Materials discarded from manufacturing operations that may
be suitable for reprocessing.
Scrap Metal Processor: Intermediate operating facility where
recovered metal is sorted, cleaned of contaminants, and prepared for
Screening: Use of screens to remove coarse floating and suspended
solids from sewage.
Screening Risk Assessment: A risk assessment performed with few
data and many assumptions to identify exposures that should be evaluated
more carefully for potential risk.
Scrubber: An air pollution device that uses a spray of water or
reactant or a dry process to trap pollutants in emissions.
Secondary Drinking Water Regulations: Non-enforceable regulations
applying to public water systems and specifying the maximum contamination
levels that, in the judgment of EPA, are required to protect the public
welfare. These regulations apply to any contaminants that may adversely
affect the odor or appearance of such water and consequently may cause
people served by the system to discontinue its use.
Secondary Effect: Action of a stressor on supporting components of
the ecosystem, which in turn impact the ecological component of concern.
(See: primary effect.)
Secondary Materials: Materials that have been manufactured and
used at least once and are to be used again.
Secondary Standards: National ambient air quality standards
designed to protect welfare, including effects on soils, water, crops,
vegetation, man-made (anthropogenic) materials, animals, wildlife, weather,
visibility, and climate; damage to property; transportation hazards;
economic values, and personal comfort and well-being.
Secondary Treatment: The second step in most publicly owned waste
treatment systems in which bacteria consume the organic parts of the waste.
It is accomplished by bringing together waste, bacteria, and oxygen in
trickling filters or in the activated sludge process. This treatment removes
floating and settleable solids and about 90 percent of the oxygen-demanding
substances and suspended solids. Disinfection is the final stage of
secondary treatment. (See:
Secure Chemical Landfill: (See:landfills.)
Secure Maximum Contaminant Level: Maximum permissible level of a
contaminant in water delivered to the free flowing outlet of the ultimate
user, or of contamination resulting from corrosion of piping and plumbing
caused by water quality.
Sediment: Topsoil, sand, and minerals washed from the
land into water, usually after rain or snow melt.
Sediment Yield: The quantity of sediment arriving at a specific
Sedimentation: Letting solids settle out of wastewater by gravity
Sedimentation Tanks: Wastewater tanks in which floating wastes are
skimmed off and settled solids are removed for disposal.
Sediments: Soil, sand, and minerals washed from land into water,
usually after rain. They pile up in reservoirs, rivers and harbors,
destroying fish and wildlife habitat, and clouding the water so that
sunlight cannot reach aquatic plants. Careless farming, mining, and building
activities will expose sediment materials, allowing them to wash off the
land after rainfall.
Seed Protectant: A chemical applied before planting to protect
seeds and seedlings from disease or insects.
Seepage: Percolation of water through the soil from unlined
canals, ditches, laterals, watercourses, or water storage facilities.
Selective Pesticide: A chemical designed to affect only certain
types of pests, leaving other plants and animals unharmed.
Semi-Confined Aquifer: An aquifer partially confined by soil
layers of low permeability through which recharge and discharge can still
Semivolatile Organic Compounds: Organic compounds that volatilize
slowly at standard temperature (20 degrees C and 1 atm pressure).
Senescence: The aging process. Sometimes used to describe lakes or
other bodies of water in advanced stages of eutrophication. Also used to
describe plants and animals.
Septic System: An on-site system designed to treat and dispose of
domestic sewage. A typical septic system consists of tank that receives
waste from a residence or business and a system of tile lines or a pit for
disposal of the liquid effluent (sludge) that remains after decomposition of
the solids by bacteria in the tank and must be pumped out periodically.
Septic Tank: An underground storage tank for wastes from homes not
connected to a sewer line. Waste goes directly from the home to the tank.
(See: septic system.)
Service Connector: The pipe that carries tap water from a public
water main to a building.
Service Line Sample: A one-liter sample of water that has been
standing for at least 6 hours in a service pipeline and is collected
according to federal regulations.
Service Pipe: The pipeline extending from the water main to the
building served or to the consumer's system.
Set-Back: Setting a thermometer to a lower temperature when the
building is unoccupied to reduce consumption of heating energy. Also refers
to setting the thermometer to a higher temperature during unoccupied periods
in the cooling season.
Settleable Solids: Material heavy enough to sink to the bottom of
a wastewater treatment tank.
Settling Chamber: A series of screens placed in the way of flue
gases to slow the stream of air, thus helping gravity to pull particles into
a collection device.
Settling Tank: A holding area for wastewater, where heavier
particles sink to the bottom for removal and disposal.
7Q10: Seven-day, consecutive low flow with a ten year return
frequency; the lowest stream flow for seven consecutive days that would be
expected to occur once in ten years.
Sewage: The waste and wastewater produced by residential and
commercial sources and discharged into sewers.
Sewage Lagoon: (See:
Sewage Sludge: Sludge produced at a Publicly Owned Treatment
Works, the disposal of which is regulated under the Clean Water Act.
Sewer: A channel or conduit that carries wastewater and
storm-water runoff from the source to a treatment plant or receiving stream.
"Sanitary" sewers carry household, industrial, and commercial waste. "Storm"
sewers carry runoff from rain or snow. "Combined" sewers handle both.
Sewerage: The entire system of sewage collection, treatment, and
Shading Coefficient: The amount of the sun's heat transmitted
through a given window compared with that of a standard 1/8- inch-thick
single pane of glass under the same conditions.
Sharps: Hypodermic needles, syringes (with or without the attached
needle), Pasteur pipettes, scalpel blades, blood vials, needles with
attached tubing, and culture dishes used in animal or human patient care or
treatment, or in medical, research or industrial laboratories. Also included
are other types of broken or unbroken glassware that were in contact with
infectious agents, such as used slides and cover slips, and unused
hypodermic and suture needles, syringes, and scalpel blades.
Shock Load: The arrival at a water treatment plant of raw water
containing unusual amounts of algae, colloidal matter. color, suspended
solids, turbidity, or other pollutants.
Short-Circuiting: When some of the water in tanks or basins flows
faster than the rest; may result in shorter contact, reaction, or settling
times than calculated or presumed.
Sick Building Syndrome: Building whose occupants experience acute
health and/or comfort effects that appear to be linked to time spent
therein, but where no specific illness or cause can be identified.
Complaints may be localized in a particular room or zone, or may spread
throughout the building. (See:
Signal: The volume or product-level change produced by a leak in a
Signal Words: The words used on a pesticide label--Danger,
Warning, Caution--to indicate level of toxicity.
Significant Deterioration: Pollution resulting from a new source
in previously "clean" areas. (See:
Significant Municipal Facilities: Those publicly owned sewage
treatment plants that discharge a million gallons per day or more and are
therefore considered by states to have the potential to substantially affect
the quality of receiving waters.
Significant Non-Compliance: (See
Significant Potential Source of Contamination: A facility or
activity that stores, uses, or produces compounds with potential for
significant contaminating impact if released into the source water of a
public water supply.
Significant Violations: Violations by point source dischargers of
sufficient magnitude or duration to be a regulatory priority.
Silt: Sedimentary materials composed of fine or intermediate-sized
Silviculture: Management of forest land for timber.
Single-Breath Canister: Small one-liter canister designed to
capture a single breath. Used in air pollutant ingestion research.
Sink: Place in the environment where a compound or material
Sinking: Controlling oil spills by using an agent to trap the oil
and sink it to the bottom of the body of water where the agent and the oil
SIP Call: EPA action requiring a state to resubmit all or part of
its State Implementation Plan to demonstrate attainment of the require
national ambient air quality standards within the statutory deadline. A SIP
Revision is a revision of a SIP altered at the request of EPA or on a
state's initiative. (See:
Site: An area or place within the jurisdiction of the EPA and/or a
Site Assessment Program: A means of evaluating hazardous waste
sites through preliminary assessments and site inspections to develop a
Hazard Ranking System score.
Site Inspection: The collection of information from a Superfund
site to determine the extent and severity of hazards posed by the site. It
follows and is more extensive than a preliminary assessment. The purpose is
to gather information necessary to score the site, using the Hazard Ranking
System, and to determine if it presents an immediate threat requiring prompt
Site Safety Plan: A crucial element in all removal actions, it
includes information on equipment being used, precautions to be taken, and
steps to take in the event of an on-site emergency.
Siting: The process of choosing a location for a facility.
Skimming: Using a machine to remove oil or scum from the surface
of the water.
Slow Sand Filtration: Passage of raw water through a bed of sand
at low velocity, resulting in substantial removal of chemical and biological
Sludge: A semi-solid residue from any of a number of air or water
treatment processes; can be a hazardous waste.
Sludge Digester: Tank in which complex organic substances like
sewage sludges are biologically dredged. During these reactions, energy is
released and much of the sewage is converted to methane, carbon dioxide, and
Slurry: A watery mixture of insoluble matter resulting from some
pollution control techniques.
Small Quantity Generator (SQG-sometimes referred to as "Squeegee"):
Persons or enterprises that produce 220-2200 pounds per month of hazardous
waste; they are required to keep more records than conditionally exempt
generators. The largest category of hazardous waste generators, SQGs,
include automotive shops, dry cleaners, photographic developers, and many
other small businesses. (See:
Smelter: A facility that melts or fuses ore, often with an
accompanying chemical change, to separate its metal content. Emissions cause
pollution. "Smelting" is the process involved.
Smog: Air pollution typically associated with oxidants. (See:
Smoke: Particles suspended in air after incomplete combustion.
Soft Detergents: Cleaning agents that break down in nature.
Soft Water: Any water that does not contain a significant amount
of dissolved minerals such as salts of calcium or magnesium.
Unconsolidated earth material composing the superficial geologic strata
(material overlying bedrock) consisting of clay, silt, sand or gravel size
particles as classified by the U.S. Soil Conservation Service, or a mixture of
such materials with liquids, sludges or solids which is inseparable by simple
mechanical removal processes and is made up primarily of soil by volume based on
Soil Adsorption Field: A sub-surface area containing a trench or
bed with clean stones and a system of piping through which treated sewage
may seep into the surrounding soil for further treatment and disposal.
Soil and Water Conservation Practices: Control measures consisting
of managerial, vegetative, and structural practices to reduce the loss of
soil and water.
Soil Conditioner: An organic material like humus or compost that
helps soil absorb water, build a bacterial community, and take up mineral
Soil Erodibility: An indicator of a soil's susceptibility to
raindrop impact, runoff, and other erosive processes.
Soil Gas: Gaseous elements and compounds in the small spaces
between particles of the earth and soil. Such gases can be moved or driven
out under pressure.
Soil Moisture: The water contained in the pore space of the
Soil Sterilant: A chemical that temporarily or permanently
prevents the growth of all plants and animals,
Solder: Metallic compound used to seal joints between pipes. Until
recently, most solder contained 50 percent lead. Use of solder containing
more than 0.2 percent lead in pipes carrying drinking water is now
Sole-Source Aquifer: An aquifer that supplies 50-percent or more
of the drinking water of an area.
Solid Waste: Non-liquid, non-soluble materials ranging from
municipal garbage to industrial wastes that contain complex and sometimes
hazardous substances. Solid wastes also include sewage sludge, agricultural
refuse, demolition wastes, and mining residues. Technically, solid waste
also refers to liquids and gases in containers.
Solid Waste Disposal: The final placement of refuse that is not
salvaged or recycled.
Solid Waste Management: Supervised handling of waste materials
from their source through recovery processes to disposal.
Solidification and Stabilization: Removal of wastewater from a
waste or changing it chemically to make it less permeable and susceptible to
transport by water.
Solubility: The amount of mass of a compound that will dissolve in
a unit volume of solution. Aqueous Solubility is the maximum concentration
of a chemical that will dissolve in pure water at a reference temperature.
Soot: Carbon dust formed by incomplete combustion.
Sorption: The action of soaking up or attracting substances;
process used in many pollution control systems.
Source Area: The location of liquid hydrocarbons or the zone of
highest soil or groundwater concentrations, or both, of the chemical of
Source Characterization Measurements: Measurements made to
estimate the rate of release of pollutants into the environment from a
source such as an incinerator, landfill, etc.
Source Reduction: Reducing the amount of materials entering the
waste stream from a specific source by redesigning products or patterns of
production or consumption (e.g., using returnable beverage containers).
Synonymous with waste reduction.
Source Separation: Segregating various wastes at the point of
generation (e.g., separation of paper, metal and glass from other wastes to
make recycling simpler and more efficient).
Source-Water Protection Area: The area delineated by a state for a
Public Water Supply or including numerous such suppliers, whether the source
is ground water or surface water or both.
Sparge or Sparging: Injection of air below the water table to
strip dissolved volatile organic compounds and/or oxygenate ground water to
facilitate aerobic biodegradation of organic compounds.
Special Local-Needs Registration: Registration of a pesticide
product by a state agency for a specific use that is not federally
registered. However, the active ingredient must be federally registered for
other uses. The special use is specific to that state and is often minor,
thus may not warrant the additional cost of a full federal registration
process. SLN registration cannot be issued for new active ingredients,
food-use active ingredients without tolerances, or for a canceled
registration. The products cannot be shipped across state lines.
Special Review: Formerly known as Rebuttable Presumption Against
Registration (RPAR), this is the regulatory process through which existing
pesticides suspected of posing unreasonable risks to human health,
non-target organisms, or the environment are referred for review by EPA.
Such review requires an intensive risk/benefit analysis with opportunity for
public comment. If risk is found to outweigh social and economic benefits,
regulatory actions can be initiated, ranging from label revisions and
use-restriction to cancellation or suspended registration.
Special Waste: Items such as household hazardous waste, bulky
wastes (refrigerators, pieces of furniture, etc.) tires, and used oil.
Species: 1. A reproductively isolated aggregate of interbreeding
organisms having common attributes and usually designated by a common
name.2. An organism belonging to belonging to such a category.
Specific Conductance: Rapid method of estimating the dissolved
solid content of a water supply by testing its capacity to carry an
Specific Yield: The amount of water a unit volume of saturated
permeable rock will yield when drained by gravity.
Spill Prevention, Containment, and Countermeasures Plan (SPCP):
Plan covering the release of hazardous substances as defined in the Clean
Spoil: Dirt or rock removed from its original location--destroying
the composition of the soil in the process--as in strip-mining, dredging, or
Sprawl: Unplanned development of open land.
Spray Tower Scrubber: A device that sprays alkaline water into a
chamber where acid gases are present to aid in neutralizing the gas.
Spring: Ground water seeping out of the earth where the water
table intersects the ground surface.
Spring Melt/Thaw: The process whereby warm temperatures melt
winter snow and ice. Because various forms of acid deposition may have been
stored in the frozen water, the melt can result in abnormally large amounts
of acidity entering streams and rivers, sometimes causing fish kills.
Stabilization: Conversion of the active organic matter in sludge
into inert, harmless material.
Stabilization Ponds: (See:
Stable Air: A motionless mass of air that holds, instead of
Stack: A chimney, smokestack, or vertical pipe that discharges
Stack Effect: Air, as in a chimney, that moves upward because it
is warmer than the ambient atmosphere.
Stack Effect: Flow of air resulting from warm air rising, creating
a positive pressure area at the top of a building and negative pressure area
at the bottom. This effect can overpower the mechanical system and disrupt
building ventilation and air circulation.
Stack Gas: (See:
Stage II Controls: Systems placed on service station gasoline
pumps to control and capture gasoline vapors during refuelling.
Stagnation: Lack of motion in a mass of air or water that holds
pollutants in place.
Stakeholder: Any organization, governmental entity, or individual
that has a stake in or may be impacted by a given approach to environmental
regulation, pollution prevention, energy conservation, etc.
Standard Industrial Classification Code: Also known as
SIC Codes, a method of grouping industries with similar products or services
and assigning codes to these groups.
Standard Sample: The part of finished drinking water that is
examined for the presence of coliform bacteria.
Standards: Norms that impose limits on the amount of pollutants or
emissions produced. EPA establishes minimum standards, but states are
allowed to be stricter.
Start of a Response Action: The point in time when there is a
guarantee or set-aside of funding by EPA, other federal agencies, states or
Principal Responsible Parties in order to begin response actions at a
State Emergency Response Commission (SERC): Commission appointed
by each state governor according to the requirements of SARA Title III. The
SERCs designate emergency planning districts, appoint local emergency
planning committees, and supervise and coordinate their activities.
State Environmental Goals and Indication Project: Program to
assist state environmental agencies by providing technical and financial
assistance in the development of environmental goals and indicators.
State Implementation Plans (SIP): EPA approved state plans for the
establishment, regulation, and enforcement of air pollution standards.
State Management Plan: Under FIFRA, a state management plan
required by EPA to allow states, tribes, and U.S. territories the
flexibility to design and implement ways to protect ground water from the
use of certain pesticides.
Static Water Depth: The vertical distance from the centerline of
the pump discharge down to the surface level of the free pool while no water
is being drawn from the pool or water table.
Static Water Level: 1. Elevation or level of the water table in a
well when the pump is not operating. 2. The level or elevation to which
water would rise in a tube connected to an artesian aquifer or basin in a
conduit under pressure.
Stationary Source: A fixed-site producer of pollution, mainly
power plants and other facilities using industrial combustion processes.
(See: point source.)
Sterilization: The removal or destruction of all microorganisms,
including pathogenic and other bacteria, vegetative forms, and spores.
Sterilizer: One of three groups of anti-microbials registered by
EPA for public health uses. EPA considers an antimicrobial to be a
sterilizer when it destroys or eliminates all forms of bacteria, viruses,
and fungi and their spores. Because spores are considered the most difficult
form of microorganism to destroy, EPA considers the term sporicide to be
synonymous with sterilizer.
Storage: Temporary holding of waste pending treatment or disposal,
as in containers, tanks, waste piles, and surface impoundments.
Storm Sewer: A system of pipes (separate from sanitary sewers)
that carries water runoff from buildings and land surfaces.
Stratification: Separating into layers.
Stratigraphy: Study of the formation, composition, and sequence of
sediments, whether consolidated or not.
Stratosphere: The portion of the atmosphere 10-to-25 miles above
the earth's surface.
Stressors: Physical, chemical, or biological entities that can
induce adverse effects on ecosystems or human health.
Strip-Cropping: Growing crops in a systematic arrangement of
strips or bands that serve as barriers to wind and water erosion.
Strip-Mining: A process that uses machines to scrape soil or rock
away from mineral deposits just under the earth's surface.
Structural Deformation: Distortion in walls of a tank after liquid
has been added or removed.
Subchronic: Of intermediate duration, usually used to describe
studies or periods of exposure lasting between 5 and 90 days.
Subchronic Exposure: Multiple or continuous exposures lasting for
approximately ten percent of an experimental species lifetime, usually over
a three-month period.
Submerged Aquatic Vegetation: Vegetation that lives at or below
the water surface; an important habitat for young fish and other aquatic
C Landfill: A landfill that accepts hazardous waste (including treated
D Landfill: A landfill that accepts nonhazardous waste.
Subwatershed: Topographic perimeter of the catchment area of a
Sulfur Dioxide (SO2): A pungent, colorless, gasformed primarily by
the combustion of fossil fuels; becomes a pollutant when present in large
Sump: A pit or tank that catches liquid runoff for drainage or
Superchlorination: Chlorination with doses that are deliberately
selected to produce water free of combined residuals so large as to require
Supercritical Water: A type of thermal treatment using moderate
temperatures and high pressures to enhance the ability of water to break
down large organic molecules into smaller, less toxic ones. Oxygen injected
during this process combines with simple organic compounds to form carbon
dioxide and water.
Superfund: The program operated under the legislative authority of
CERCLA and SARA that funds and carries out EPA solid waste emergency and
long-term removal and remedial activities. These activities include
establishing the National Priorities List, investigating sites for inclusion
on the list, determining their priority, and conducting and/or supervising
cleanup and other remedial actions.
Superfund Innovative Technology Evaluation (SITE) Program: EPA
program to promote development and use of innovative treatment and site
characterization technologies in Superfund site cleanups.
Supplemental Registration: An arrangement whereby a registrant
licenses another company to market its pesticide product under the second
Supplier of Water: Any person who owns or operates a public water
Surface Impoundment: Treatment, storage, or disposal of liquid
hazardous wastes in ponds.
Surface Runoff: Precipitation, snow melt, or irrigation water in
excess of what can infiltrate the soil surface and be stored in small
surface depressions; a major transporter of non-point source pollutants in
rivers, streams, and lakes..
Surface Uranium Mines: Strip mining operations for removal of
Surface Water: All water naturally open to the atmosphere (rivers,
lakes, reservoirs, ponds, streams, impoundments, seas, estuaries, etc.)
Surface-Water Treatment Rule: Rule that specifies maximum
contaminant level goals for Giardia lamblia, viruses, and Legionella and
promulgates filtration and disinfection requirements for public water
systems using surface-water or ground-water sources under the direct
influence of surface water. The regulations also specify water quality,
treatment, and watershed protection criteria under which filtration may be
Surfacing ACM: Asbestos-containing material that is sprayed or
troweled on or otherwise applied to surfaces, such as acoustical plaster on
ceilings and fireproofing materials on structural members.
Surfacing Material: Material sprayed or troweled onto structural
members (beams, columns, or decking) for fire protection; or on ceilings or
walls for fireproofing, acoustical or decorative purposes. Includes textured
plaster, and other textured wall and ceiling surfaces.
Surfactant: A detergent compound that promotes lathering.
Surrogate Data: Data from studies of test organisms or a test
substance that are used to estimate the characteristics or effects on
another organism or substance.
Surveillance System: A series of monitoring devices designed to
check on environmental conditions.
Susceptibility Analysis: An analysis to determine whether a Public
Water Supply is subject to significant pollution from known potential
Suspect Material: Building material suspected of containing
asbestos; e.g., surfacing material, floor tile, ceiling tile, thermal system
Suspended Loads: Specific sediment particles maintained in the
water column by turbulence and carried with the flow of water.
Suspended Solids: Small particles of solid pollutants that float
on the surface of, or are suspended in, sewage or other liquids. They resist
removal by conventional means.
Suspension: Suspending the use of a pesticide when EPA deems it
necessary to prevent an imminent hazard resulting from its continued use. An
emergency suspension takes effect immediately; under an ordinary suspension
a registrant can request a hearing before the suspension goes into effect.
Such a hearing process might take six months.
Suspension Culture: Cells growing in a liquid nutrient medium.
Swamp: A type of wetland dominated by woody vegetation but without
appreciable peat deposits. Swamps may be fresh or salt water and tidal or
Synergism: An interaction of two or more chemicals that results in
an effect greater than the sum of their separate effects.
Synthetic Organic Chemicals (SOCs): Man-made (anthropogenic)
organic chemicals. Some SOCs are volatile; others tend to stay dissolved in
water instead of evaporating.
System With a Single Service Connection: A system that supplies
drinking water to consumers via a single service line.
Systemic Pesticide: A chemical absorbed by an organism that
interacts with the organism and makes the organism toxic to pests.
Tail Water: The runoff of irrigation water from the lower end of
an irrigated field.
Tailings: Residue of raw material or waste separated out during
the processing of crops or mineral ores.
Tailpipe Standards: Emissions limitations applicable to mobile
source engine exhausts.
Tampering: Adjusting, negating, or removing pollution control
equipment on a motor vehicle.
Technical Assistance Grant (TAG): As part of the Superfund
program, Technical Assistance Grants of up to $50,000 are provided to
citizens' groups to obtain assistance in interpreting information related to
clean-ups at Superfund sites or those proposed for the National Priorities
List. Grants are used by such groups to hire technical advisors to help them
understand the site-related technical information for the duration of
Technical-Grade Active Ingredient (TGA): A pesticide chemical in
pure form as it is manufactured prior to being formulated into an end-use
product (e.g. wettable powders, granules, emulsifiable concentrates).
Registered manufactured products composed of such chemicals are known as
Technical Grade Products.
Technology-Based Limitations: Industry-specific effluent
limitations based on best available preventive technology applied to a
discharge when it will not cause a violation of water quality standards at
low stream flows. Usually applied to discharges into large rivers.
Technology-Based Standards: Industry-specific effluent limitations
applicable to direct and indirect sources which are developed on a
category-by-category basis using statutory factors, not including
Teratogen: A substance capable of causing birth defects.
Teratogenesis: The introduction of nonhereditary birth defects in
a developing fetus by exogenous factors such as physical or chemical agents
acting in the womb to interfere with normal embryonic development.
Terracing: Dikes built along the contour of sloping farm land that
hold runoff and sediment to reduce erosion.
Tertiary Treatment: Advanced cleaning of wastewater that goes
beyond the secondary or biological stage, removing nutrients such as
phosphorus, nitrogen, and most BOD and suspended solids.
Theoretical Maximum Residue Contribution: The theoretical maximum
amount of a pesticide in the daily diet of an average person. It assumes
that the diet is composed of all food items for which there are
tolerance-level residues of the pesticide. The TMRC is expressed as
milligrams of pesticide/kilograms of body weight/day.
Therapeutic Index: The ratio of the dose required to produce toxic
or lethal effects to the dose required to produce nonadverse or therapeutic
Thermal Pollution: Discharge of heated water from industrial
processes that can kill or injure aquatic organisms.
Thermal Stratification: The formation of layers of different
temperatures in a lake or reservoir.
Thermal System Insulation (TSI): Asbestos-containing material
applied to pipes, fittings, boilers, breeching, tanks, ducts, or other
interior structural components to prevent heat loss or gain or water
Thermal Treatment: Use of elevated temperatures to treat hazardous
Thermocline: The middle layer of a thermally stratified lake or
reservoir. In this layer, there is a rapid decrease in temperatures in a
lake or reservoir.
Threshold: The lowest dose of a chemical at which a specified
measurable effect is observed and below which it is not observed.
Threshold: The dose or exposure level below which a significant
adverse effect is not expected.
Threshold Level: Time-weighted average pollutant concentration
values, exposure beyond which is likely to adversely affect human health.
Threshold Limit Value (TLV): The concentration of an airborne
substance to which an average person can be repeatedly exposed without
adverse effects. TLVs may be expressed in three ways: (1) TLV-TWA--Time
weighted average, based on an allowable exposure averaged over a normal
8-hour workday or 40-hour work- week; (2) TLV-STEL--Short-term exposure
limit or maximum concentration for a brief specified period of time,
depending on a specific chemical (TWA must still be met); and (3)
TLV-C--Ceiling Exposure Limit or maximum exposure concentration not to be
exceeded under any circumstances. (TWA must still be met.)
Threshold Odor: (See:
Threshold Planning Quantity: A quantity designated for each
chemical on the list of extremely hazardous substances that triggers
notification by facilities to the State Emergency Response Commission that
such facilities are subject to emergency planning requirements under SARA
Thropic Levels: A functional classification of species that is
based on feeding relationships (e.g. generally aquatic and terrestrial green
plants comprise the first thropic level, and herbivores comprise the
Tidal Marsh: Low, flat marshlands traversed by channels and tidal
hollows, subject to tidal inundation; normally, the only vegetation present
is salt-tolerant bushes and grasses. (See:
Tillage: Plowing, seedbed preparation, and cultivation practices.
Time-weighted Average (TWA): In air sampling, the average air
concentration of contaminants during a given period.
Tire Processor: Intermediate operating facility where recovered
tires are processed in preparation for recycling.
Tires: As used in recycling, passenger car and truck tires
(excludes airplane, bus, motorcycle and special service military,
agricultural, off-the-road and-slow speed industrial tires). Car and truck
tires are recycled into rubber products such as trash cans, storage
containers, rubberized asphalt or used whole for playground and reef
Tolerance Petition: A formal request to establish a new tolerance
or modify an existing one.
Tolerances: Permissible residue levels for pesticides in raw
agricultural produce and processed foods. Whenever a pesticide is registered
for use on a food or a feed crop, a tolerance (or exemption from the
tolerance requirement) must be established. EPA establishes the tolerance
levels, which are enforced by the Food and Drug Administration and the
Department of Agriculture.
Tonnage: The amount of waste that a landfill accepts, usually
expressed in tons per month. The rate at which a landfill accepts waste is
limited by the landfill's permit.
Topography: The physical features of a surface area including
relative elevations and the position of natural and man-made (anthropogenic)
Total Dissolved Phosphorous: The total phosphorous content of all
material that will pass through a filter, which is determined as
orthophosphate without prior digestion or hydrolysis. Also called soluble P.
or ortho P.
Total Dissolved Solids (TDS): All material that passes the
standard glass river filter; now called total filtrable residue. Term is
used to reflect salinity.
Total Petroleum Hydrocarbons (TPH): Measure of the concentration
or mass of petroleum hydrocarbon constituents present in a given amount of
soil or water. The word "total" is a misnomer--few, if any, of the
procedures for quantifying hydrocarbons can measure all of them in a given
sample. Volatile ones are usually lost in the process and not quantified and
non-petroleum hydrocarbons sometimes appear in the analysis.
Total Recovered Petroleum Hydrocarbon: A method for measuring
petroleum hydrocarbons in samples of soil or water.
Total Suspended Particles (TSP): A method of monitoring airborne
particulate matter by total weight.
Total Suspended Solids (TSS): A measure of the suspended solids in
wastewater, effluent, or water bodies, determined by tests for "total
suspended non-filterable solids." (See:
Waste Analysis: Analytic test method used to measure compliance with most of
the organic treatment standards. Carbon disulfide, cyclohexanone, and methanol
treatment standards are measured using toxicity characteristic leaching
Characteristic Leaching Procedure (TCLP): Analytic test method used to
measure compliance with the metal treatment standards.
Toxaphene: Chemical that causes adverse health effects in domestic
water supplies and is toxic to fresh water and marine aquatic life.
Toxic Chemical: Any chemical listed in EPA rules as "Toxic
Chemicals Subject to Section 313 of the Emergency Planning and Community
Right-to-Know Act of 1986."
Toxic Chemical Release Form: Information form required of
facilities that manufacture, process, or use (in quantities above a specific
amount) chemicals listed under SARA Title III.
Toxic Chemical Use Substitution: Replacing toxic chemicals with
less harmful chemicals in industrial processes.
Toxic Cloud: Airborne plume of gases, vapors, fumes, or aerosols
containing toxic materials.
Toxic Concentration: The concentration at which a substance
produces a toxic effect.
Toxic Dose: The dose level at which a substance produces a toxic
Toxic Pollutants: Materials that cause death, disease, or birth
defects in organisms that ingest or absorb them. The quantities and
exposures necessary to cause these effects can vary widely.
Toxic Release Inventory: Database of toxic releases in the United
States compiled from SARA Title III Section 313 reports.
Toxic Substance: A chemical or mixture that may present an
unreasonable risk of injury to health or the environment.
Toxic Waste: A waste that can produce injury if inhaled,
swallowed, or absorbed through the skin.
Toxicant: A harmful substance or agent that may injure an exposed
Toxicity: The degree to which a substance or mixture of substances
can harm humans or animals. Acute toxicity involves harmful effects
in an organism through a single or short-term exposure. Chronic toxicity
is the ability of a substance or mixture of substances to cause harmful
effects over an extended period, usually upon repeated or continuous
exposure sometimes lasting for the entire life of the exposed organism.
Subchronic toxicity is the ability of the substance to cause effects for
more than one year but less than the lifetime of the exposed organism.
Toxicity Assessment: Characterization of the toxicological
properties and effects of a chemical, with special emphasis on establishment
of dose-response characteristics.
Toxicity Testing: Biological testing (usually with an
invertebrate, fish, or small mammal) to determine the adverse effects of a
compound or effluent.
Toxicological Profile: An examination, summary, and interpretation
of a hazardous substance to determine levels of exposure and associated
Transboundary Pollutants: Air pollution that travels from one
jurisdiction to another, often crossing state or international boundaries.
Also applies to water pollution.
Facilities: Any transportation-related facility such as loading docks,
parking areas, storage areas, or other similar areas where shipments of
hazardous waste are temporarily held during the normal course of transportation.
Transfer Station: Facility where solid waste is transferred from
collection vehicles to larger trucks or rail cars for longer distance
Transient Water System: A non-community water system that does not
serve 25 of the same nonresidents per day for more than six months per year.
Transmission Lines: Pipelines that transport raw water from its
source to a water treatment plant, then to the distribution grid system.
Transmissivity: The ability of an aquifer to transmit water.
Transpiration: The process by which water vapor is lost to the
atmosphere from living plants. The term can also be applied to the quantity
of water thus dissipated.
Any person engaged in the off-site transportation of hazardous waste by air,
rail, highway, or water.
Transportation Control Measures (TCMs): Steps taken by a locality
to reduce vehicular emission and improve air quality by reducing or changing
the flow of traffic; e.g. bus and HOV lanes, carpooling and other forms of
ride-shairing, public transit, bicycle lanes.
Transporter: Hauling firm that picks up properly packaged and
labeled hazardous waste from generators and transports it to designated
facilities for treatment, storage, or disposal. Transporters are subject to
EPA and DOT hazardous waste regulations.
Trash: Material considered worthless or offensive that is thrown
away. Generally defined as dry waste material, but in common usage it is a
synonym for garbage, rubbish, or refuse.
Trash-to-Energy Plan: Burning trash to produce energy.
Treatability Studies: Tests of potential cleanup technologies
conducted in a laboratory (See:
Treated Regulated Medical Waste: Medical waste treated to
substantially reduce or eliminate its pathogenicity, but that has not yet
Treated Wastewater: Wastewater that has been subjected to one or
more physical, chemical, and biological processes to reduce its potential of
being health hazard.
Treatment: (1) Any method, technique, or process designed to
remove solids and/or pollutants from solid waste, waste-streams, effluents,
and air emissions. (2) Methods used to change the biological character or
composition of any regulated medical waste so as to substantially reduce or
eliminate its potential for causing disease.
Group: A grouping of hazardous wastes that can be treated to similar
concentrations using identical technologies.
Treatment Plant: A structure built to treat wastewater before
discharging it into the environment.
Treatment, Storage, and Disposal Facility: Site where a hazardous
substance is treated, stored, or disposed of. TSD facilities are regulated
by EPA and states under RCRA.
Tremie: Device used to place concrete or grout under water.
Trial Burn: An incinerator test in which emissions are monitored
for the presence of specific organic compounds, particulates, and hydrogen
Trichloroethylene (TCE): A stable, low boiling-point colorless
liquid, toxic if inhaled. Used as a solvent or metal degreasing agent, and
in other industrial applications.
Trickle Irrigation: Method in which water drips to the soil from
perforated tubes or emitters.
Trickling Filter: A coarse treatment system in which wastewater is
trickled over a bed of stones or other material covered with bacteria that
break down the organic waste and produce clean water.
Trihalomethane (THM): One of a family of organic compounds named
as derivative of methane. THMs are generally by-products of chlorination of
drinking water that contains organic material.
Troposhpere: The layer of the atmosphere closest to the earth's
Trust Fund (CERCLA): A fund set up under the Comprehensive
Environmental Response, Compensation and Liability Act (CERCLA) to help pay
for cleanup of hazardous waste sites and for legal action to force those
responsible for the sites to clean them up.
Tube Settler: Device using bundles of tubes to let solids in water
settle to the bottom for removal by conventional sludge collection means;
sometimes used in sedimentation basins and clarifiers to improve particle
Tuberculation: Development or formation of small mounds of
corrosion products on the inside of iron pipe. These tubercules roughen the
inside of the pipe, increasing its resistance to water flow.
Tundra: A type of treeless ecosystem dominated by lichens, mosses,
grasses, and woody plants. Tundra is found at high latitudes (arctic tundra)
and high altitudes (alpine tundra). Arctic tundra is underlain by permafrost
and is usually water saturated. (See:
Turbidimeter: A device that measures the cloudiness of suspended
solids in a liquid; a measure of the quantity of suspended solids.
Turbidity: 1. Haziness in air caused by the presence of particles
and pollutants. 2. A cloudy condition in water due to suspended silt or
Ultra Clean Coal (UCC): Coal that is washed, ground into fine
particles, then chemically treated to remove sulfur, ash, silicone, and
other substances; usually briquetted and coated with a sealant made from
Ultraviolet Rays: Radiation from the sun that can be useful or
potentially harmful. UV rays from one part of the spectrum (UV-A) enhance
plant life. UV rays from other parts of the spectrum (UV-B) can cause skin
cancer or other tissue damage. The ozone layer in the atmosphere partly
shields us from ultraviolet rays reaching the earth's surface.
Uncertainty Factor: One of several factors used in calculating the
reference dose from experimental data. UFs are intended to account for (1)
the variation in sensitivity among humans; (2) the uncertainty in
extrapolating animal data to humans; (3) the uncertainty in extrapolating
data obtained in a study that covers less than the full life of the exposed
animal or human; and (4) the uncertainty in using LOAEL data rather than
Unconfined Aquifer: An aquifer containing water that is not under
pressure; the water level in a well is the same as the water table outside
Underground Injection Control (UIC): The program under the Safe
Drinking Water Act that regulates the use of wells to pump fluids into the
Underground Injection Wells: Steel- and concrete-encased shafts
into which hazardous waste is deposited by force and under pressure.
Underground Sources of Drinking Water: Aquifers currently being
used as a source of drinking water or those capable of supplying a public
water system. They have a total dissolved solids content of 10,000
milligrams per liter or less, and are not "exempted aquifers." (See:
Underground Storage Tank (UST): A tank located at least partially
underground and designed to hold gasoline or other petroleum products or
Hazardous Constituent (UHC): Any constituent listed in 40 CFR 268.48, “Table
UTS - Universal Treatment Standards”, except fluoride, selenium, sulfide,
vanadium, and zinc, which can reasonably be expected to be present at the point
of generation of the hazardous waste, at a concentration above the
constituent-specific universal treatment standard.
Treatment Standards (UTS): These are the constituent-specific treatment
standards found in §268.48.
Constituting Disposal: The direct placement of recycled materials, that is
wastes or waste derived-products, on the land. Note, remediation activities
involving replacement of treated soils onto the land is not a type of use
constituting disposal, in part, because it is a supervised remediation instead
of an unsupervised recycling activity.
Unreasonable Risk: Under the Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA), "unreasonable adverse effects" means any
unreasonable risk to man or the environment, taking into account the
medical, economic, social, and environmental costs and benefits of any
Unsaturated Zone: The area above the water table where soil pores
are not fully saturated, although some water may be present.
Upper Detection Limit: The largest concentration that an
instrument can reliably detect.
Uranium Mill Tailings Piles: Former uranium ore processing sites
that contain leftover radioactive materials (wastes), including radium and
Uranium Mill-Tailings Waste Piles: Licensed active mills with
tailings piles and evaporation ponds created by acid or alkaline leaching
Urban Runoff: Storm water from city streets and adjacent domestic
or commercial properties that carries pollutants of various kinds into the
sewer systems and receiving waters.
Urea-Formaldehyde Foam Insulation: A material once used to
conserve energy by sealing crawl spaces, attics, etc.; no longer used
because emissions were found to be a health hazard.
Use Cluster: A set of competing chemicals, processes, and/or
technologies that can substitute for one another in performing a particular
Used Oil: Spent motor oil from passenger cars and trucks collected
at specified locations for recycling (not included in the category of
municipal solid waste).
User Fee: Fee collected from only those persons who use a
particular service, as compared to one collected from the public in general.
Utility Load: The total electricity demand for a utility district.
Vadose Zone: The zone between land surface and the water table
within which the moisture content is less than saturation (except in the
capillary fringe) and pressure is less than atmospheric. Soil pore space
also typically contains air or other gases. The capillary fringe is included
in the vadose zone. (See:
Valued Environmental Attributes/Components: Those
aspects(components/processes/functions) of ecosystems, human health, and
environmental welfare considered to be important and potentially at risk
from human activity or natural hazards. Similar to the term "valued
environmental components" used in environmental impact assessment.
Vapor: The gas given off by substances that are solids
or liquids at ordinary atmospheric pressure and temperatures.
Vapor Capture System: Any combination of hoods and ventilation
system that captures or contains organic vapors so they may be directed to
an abatement or recovery device.
Vapor Dispersion: The movement of vapor clouds in air due to wind,
thermal action, gravity spreading, and mixing.
Vapor Plumes: Flue gases visible because they contain water
Vapor Pressure: A measure of a substance's propensity to
evaporate, vapor pressure is the force per unit area exerted by vapor in an
equilibrium state with surroundings at a given pressure. It increases
exponentially with an increase in temperature. A relative measure of
chemical volatility, vapor pressure is used to calculate water partition
coefficients and volatilization rate constants.
Vapor Recovery System: A system by which the volatile
gases from gasoline are captured instead of being released into the
Variance: Government permission for a delay or exception in the
application of a given law, ordinance, or regulation.
Vector: 1. An organism, often an insect or rodent, that carries
disease. 2. Plasmids, viruses, or bacteria used to transport genes into a
host cell. A gene is placed in the vector; the vector then "infects" the
Vegetative Controls: Non-point source pollution control practices
that involve vegetative cover to reduce erosion and minimize loss of
Vehicle Miles Travelled (VMT): A measure of the extent of motor
vehicle operation; the total number of vehicle miles travelled within a
specific geographic area over a given period of time.
Ventilation Rate: The rate at which indoor air enters and leaves a
building. Expressed as the number of changes of outdoor air per unit of time
(air changes per hour (ACH), or the rate at which a volume of outdoor air
enters in cubic feet per minute (CFM).
Ventilation/Suction: The act of admitting fresh air into a space
in order to replace stale or contaminated air; achieved by blowing air into
the space. Similarly, suction represents the admission of fresh air into an
interior space by lowering the pressure outside of the space, thereby
drawing the contaminated air outward.
Venturi Scrubbers: Air pollution control devices that use water to
remove particulate matter from emissions.
Vinyl Chloride: A chemical compound, used in producing some
plastics, that is believed to be oncogenic.
Virgin Materials: Resources extracted from nature in their raw
form, such as timber or metal ore.
Viscosity: The molecular friction within a fluid that produces
Volatile: Any substance that evaporates readily.
Volatile Liquids: Liquids which easily vaporize or evaporate at
Volatile Organic Compound (VOC): Any organic compound that
participates in atmospheric photochemical reactions except those designated
by EPA as having negligible photochemical reactivity.
Volatile Solids: Those solids in water or other liquids that are
lost on ignition of the dry solids at 550° centigrade.
Volatile Synthetic Organic Chemicals: Chemicals that tend to
volatilize or evaporate.
Volume Reduction: Processing waste materials to decrease the
amount of space they occupy, usually by compacting, shredding, incineration,
Volumetric Tank Test: One of several tests to determine the
physical integrity of a storage tank; the volume of fluid in the tank is
measured directly or calculated from product-level changes. A marked drop in
volume indicates a leak.
Vulnerability Analysis: Assessment of elements in the community
that are susceptible to damage if hazardous materials are released.
Vulnerable Zone: An area over which the airborne concentration of
a chemical accidentally released could reach the level of concern.
Waste: 1. Unwanted materials left over from a manufacturing
process. 2. Refuse from places of human or animal habitation.
Analysis Plan (WAP): A plan that outlines the procedures necessary to ensure
proper treatment, storage, or disposal of hazardous waste.
Waste Characterization: Identification of chemical and
microbiological constituents of a waste material.
Waste Exchange: Arrangement in which companies exchange their
wastes for the benefit of both parties.
Waste Feed: The continuous or intermittent flow of wastes into an
Waste Generation: The weight or volume of materials and products
that enter the waste stream before recycling, composting, landfilling, or
combustion takes place. Also can represent the amount of waste generated by
a given source or category of sources.
Waste Load Allocation: 1. The maximum load of pollutants each
discharger of waste is allowed to release into a particular waterway.
Discharge limits are usually required for each specific water quality
criterion being, or expected to be, violated. 2. The portion of a stream's
total assimilative capacity assigned to an individual discharge.
Waste Minimization: Measures or techniques that reduce the amount
of wastes generated during industrial production processes; term is also
applied to recycling and other efforts to reduce the amount of waste going
into the waste stream.
Waste Piles: Non-containerized, lined or unlined accumulations of
solid, nonflowing waste.
Waste Reduction: Using source reduction, recycling, or composting
to prevent or reduce waste generation.
Waste Stream: The total flow of solid waste from homes,
businesses, institutions, and manufacturing plants that is recycled, burned,
or disposed of in landfills, or segments thereof such as the "residential
waste stream" or the "recyclable waste stream."
Waste Treatment Lagoon: Impoundment made by excavation or earth
fill for biological treatment of wastewater.
Waste Treatment Plant: A facility containing a series of tanks,
screens, filters and other processes by which pollutants are removed from
Waste Treatment Stream: The continuous movement of waste from
generator to treater and disposer.
Waste-Heat Recovery: Recovering heat discharged as a byproduct of
one process to provide heat needed by a second process.
Waste-to-Energy Facility/Municipal-Waste Combustor: Facility where
recovered municipal solid waste is converted into a usable form of energy,
usually via combustion.
(WW): Wastes that contain less than 1% by weight total organic carbon (TOC)
and less than 1% by weight total suspended solids (TSS).
Wastewater: The spent or used water from a home, community, farm,
or industry that contains dissolved or suspended matter. Water Pollution: The
presence in water of enough harmful or objectionable material to damage the
Wastewater Infrastructure: The plan or network for the collection,
treatment, and disposal of sewage in a community. The level of treatment
will depend on the size of the community, the type of discharge, and/or the
designated use of the receiving water.
Wastewater Operations and Maintenance: Actions taken after
construction to ensure that facilities constructed to treat wastewater will
be operated, maintained, and managed to reach prescribed effluent levels in
an optimum manner.
Wastewater Treatment Plan: A facility containing a
series of tanks, screens, filters, and other processes by which pollutants
are removed from water. Most treatments include chlorination to attain safe
drinking water standards.
Water Purveyor: A public utility, mutual water company, county
water district, or municipality that delivers drinking water to customers.
Water Quality Criteria: Levels of water quality expected to render
a body of water suitable for its designated use. Criteria are based on
specific levels of pollutants that would make the water harmful if used for
drinking, swimming, farming, fish production, or industrial processes.
Water Quality Standards: State-adopted and EPA-approved ambient
standards for water bodies. The standards prescribe the use of the water
body and establish the water quality criteria that must be met to protect
Water Quality-Based Limitations: Effluent limitations applied to
dischargers when mere technology-based limitations would cause violations of
water quality standards. Usually applied to discharges into small streams.
Water Quality-Based Permit: A permit with an effluent limit more
stringent than one based on technology performance. Such limits may be
necessary to protect the designated use of receiving waters (e.g.
recreation, irrigation, industry or water supply).
Water Solubility: The maximum possible concentration of a chemical
compound dissolved in water. If a substance is water soluble it can very
readily disperse through the environment.
Water Storage Pond: An impound for liquid wastes designed to
accomplish some degree of biochemical treatment.
Water Supplier: One who owns or operates a public water system.
Water Supply System: The collection, treatment, storage, and
distribution of potable water from source to consumer.
Water Table: The level of groundwater.
Water Treatment Lagoon: An impound for liquid wastes designed to
accomplish some degree of biochemical treatment.
Water Well: An excavation where the intended use is for location,
acquisition, development, or artificial recharge of ground water.
Water-Soluble Packaging: Packaging that dissolves in water; used
to reduce exposure risks to pesticide mixers and loaders.
Water-Source Heat Pump: Heat pump that uses wells or heat
exchangers to transfer heat from water to the inside of a building. Most
such units use ground water. (See:
groundsource heat pump;
Waterborne Disease Outbreak: The significant occurence of acute
illness associated with drinking water from a public water system that is
deficient in treatment, as determined by appropriate local or state
Watershed: The land area that drains into a stream; the watershed
for a major river may encompass a number of smaller watersheds that
ultimately combine at a common point.
Watershed Approach: A coordinated framework for environmental
management that focuses public and private efforts on the highest priority
problems within hydrologically-defined geographic areas taking into
consideration both ground and surface water flow.
Watershed Area: A topographic area within a line drawn connecting
the highest points uphill of a drinking waterintake into which overland flow
Weight of Scientific Evidence: Considerations in assessing the
interpretation of published information about toxicity--quality of testing
methods, size and power of study design, consistency of results across
studies, and biological plausibility of exposure-response relationships and
Weir: 1. A wall or plate placed in an open channel to measure the
flow of water. 2. A wall or obstruction used to control flow from settling
tanks and clarifiers to ensure a uniform flow rate and avoid
Well: A bored, drilled, or driven shaft, or a dug hole whose depth
is greater than the largest surface dimension and whose purpose is to reach
underground water supplies or oil, or to store or bury fluids below ground.
Well Field: Area containing one or more wells that produce usable
amounts of water or oil.
Well Injection: The subsurface emplacement of fluids into a well.
Well Monitoring: Measurement by on-site instruments or laboratory
methods of well water quality.
Well Plug: A watertight, gastight seal installed in a bore hole or
well to prevent movement of fluids.
Well Point: A hollow vertical tube, rod, or pipe terminating in a
perforated pointed shoe and fitted with a fine-mesh screen.
Wellhead Protection Area: A protected surface and subsurface zone
surrounding a well or well field supplying a public water system to keep
contaminants from reaching the well water.
Wetlands: An area that is saturated by surface or ground water
with vegetation adapted for life under those soil conditions, as swamps,
bogs, fens, marshes, and estuaries.
Wettability: The relative degree to which a fluid will spread into
or coat a solid surface in the presence of other immiscible fluids.
Wettable Powder: Dry formulation that must be mixed with water or
other liquid before it is applied.
Wheeling: The transmission of electricity owned by one entity
through the facilities owned by another (usually a utility).
Whole-Effluent-Toxicity Tests: Tests to determine the toxicity
levels of the total effluent from a single source as opposed to a series of
tests for individual contaminants.
Wildlife Refuge: An area designated for the protection of wild
animals, within which hunting and fishing are either prohibited or strictly
Wire-to-Wire Efficiency: The efficiency of a pump and motor
Wood Packaging: Wood products such as pallets, crates, and
Wood Treatment Facility: An industrial facility that treats lumber
and other wood products for outdoor use. The process employs chromated
copper arsenate, which is regulated as a hazardous material.
Wood-Burning-Stove Pollution: Air pollution caused by emissions of
particulate matter, carbon monoxide, total suspended particulates, and
polycyclic organic matter from wood-burning stoves.
Working Level (WL): A unit of measure for documenting exposure to
radon decay products, the so-called "daughters." One working level is equal
to approximately 200 picocuries per liter.
Working Level Month (WLM): A unit of measure used to determine
cumulative exposure to radon.
Yard Waste: The part of solid waste composed of grass clippings,
leaves, twigs, branches, and other garden refuse.
Yellow-Boy: Iron oxide flocculant (clumps of solids in waste or
water); usually observed as orange-yellow deposits in surface streams with
excess iron content. (See:
Yield: The quantity of water (expressed as a rate of flow or total
quantity per year) that can be collected for a given use from surface or
Zero Air: Atmospheric air purified to contain less than 0.1 ppm
Small (often microscopic) free-floating aquatic plants or animals.
Zone of Saturation: The layer beneath the surface of
the land containing openings that may fill with water.
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