US EPA National Drinking Water Standards

List of Drinking Water Contaminants & Maximum Contaminant Levels Allowed (MCL's)

Current Drinking Water Standards

glass of waterNational Primary Drinking Water Regulations

National Primary Drinking Water Regulations (NPDWRs or primary standards) are legally enforceable standards that apply to public water systems. Primary standards protect public health by limiting the levels of contaminants in drinking water. Vist the list of regulated contaminants with links for more details.

bulletList of Contaminants & their Maximum Contaminant Level (MCLs)
  • Setting Standards for Safe Drinking Water to learn about EPA's standard-setting process
  • EPA's Regulated Contaminant Timeline (PDF File)
  • National Primary Drinking Water Regulations - The complete regulations regarding these contaminants availible from the Code of Federal Regulations Website
  • National Secondary Drinking Water Regulations

    National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

    bulletList of National Secondary Drinking Water Regulations
  • National Secondary Drinking Water Regulations - The complete regulations regarding these contaminants availible from the Code of Federal Regulations Website.
  • Unregulated Contaminants

    This list of contaminants which, at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation (NPDWR), are known or anticipated to occur in public water systems, and may require regulations under SDWA. For more information check out the list, or vist the Drinking Water Contaminant Candidate List (CCL) website.

    bulletList of Unregulated Contaminants
  • Drinking Water Contaminant Candidate List (CCL) Website
  • Unregulated Contaminant Monitoring Rule (UCMR)
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    List of Contaminants & their MCLs

    EPA 816-F-02-013
    July 2002

    • The links provided below are to either Consumer Fact Sheet, Rule Implementation websites, or PDF files

    Microorganisms

    ContaminantMCLG1
    (mg/L)2
    MCL or TT1
    (mg/L)2
    Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
    Cryptosporidium
    zero
    TT 3
    Gastrointestinal illness (e.g., diarrhea, vomiting, cramps)Human and fecal animal waste
    Giardia lamblia
    zero
    TT3
    Gastrointestinal illness (e.g., diarrhea, vomiting, cramps)Human and animal fecal waste
    Heterotrophic plate count
    n/a
    TT3
    HPC has no health effects; it is an analytic method used to measure the variety of bacteria that are common in water. The lower the concentration of bacteria in drinking water, the better maintained the water system is.HPC measures a range of bacteria that are naturally present in the environment
    Legionella
    zero
    TT3
    Legionnaire's Disease, a type of pneumoniaFound naturally in water; multiplies in heating systems
    Total Coliforms (including fecal coliform and E. Coli)
    zero
    5.0%4
    Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present5Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste.
    Turbidity
    n/a
    TT3
    Turbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (e.g., whether disease-causing organisms are present). Higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches. Soil runoff
    Viruses (enteric)
    zero
    TT3
    Gastrointestinal illness (e.g., diarrhea, vomiting, cramps)Human and animal fecal waste

    Disinfection Byproducts

    ContaminantMCLG1
    (mg/L)2
    MCL or TT1
    (mg/L)2
    Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
    Bromate
    zero
    0.010
    Increased risk of cancerByproduct of drinking water disinfection
    Chlorite
    0.8
    1.0
    Anemia; infants & young children: nervous system effectsByproduct of drinking water disinfection
    Haloacetic acids (HAA5)
    n/a6
    0.060
    Increased risk of cancerByproduct of drinking water disinfection
    Total Trihalomethanes (TTHMs)
    none7
    ----------
    n/a6
    0.10
    ----------
    0.080
    Liver, kidney or central nervous system problems; increased risk of cancerByproduct of drinking water disinfection

    Disinfectants

    ContaminantMRDLG1
    (mg/L)2
    MRDL1
    (mg/L)2
    Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
    Chloramines (as Cl2)MRDLG=41
    MRDL=4.01
    Eye/nose irritation; stomach discomfort, anemiaWater additive used to control microbes
    Chlorine (as Cl2)MRDLG=41
    MRDL=4.01
    Eye/nose irritation; stomach discomfortWater additive used to control microbes
    Chlorine dioxide (as ClO2)MRDLG=0.81
    MRDL=0.81
    Anemia; infants & young children: nervous system effectsWater additive used to control microbes

    Inorganic Chemicals

    ContaminantMCLG1
    (mg/L)2
    MCL or TT1
    (mg/L)2
    Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
    Antimony
    0.006
    0.006
    Increase in blood cholesterol; decrease in blood sugarDischarge from petroleum refineries; fire retardants; ceramics; electronics; solder
    Arsenic
    07
    0.010
    as of 01/23/06
    Skin damage or problems with circulatory systems, and may have increased risk of getting cancerErosion of natural deposits; runoff from orchards, runoff from glass & electronicsproduction wastes
    Asbestos
    (fiber >10 micrometers)
    7 million fibers per liter
    7 MFL
    Increased risk of developing benign intestinal polypsDecay of asbestos cement in water mains; erosion of natural deposits
    Barium
    2
    2
    Increase in blood pressureDischarge of drilling wastes; discharge from metal refineries; erosion of natural deposits
    Beryllium
    0.004
    0.004
    Intestinal lesions Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries
    Cadmium
    0.005
    0.005
    Kidney damage Corrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints
    Chromium (total)
    0.1
    0.1
    Allergic dermatitisDischarge from steel and pulp mills; erosion of natural deposits
    Copper
    1.3
    TT8;
    Action Level=1.3
    Short term exposure: Gastrointestinal distress

    Long term exposure: Liver or kidney damage

    People with Wilson's Disease should consult their personal doctor if the amount of copper in their water exceeds the action level

    Corrosion of household plumbing systems; erosion of natural deposits
    Cyanide (as free cyanide)
    0.2
    0.2
    Nerve damage or thyroid problems Discharge from steel/metal factories; discharge from plastic and fertilizer factories
    Fluoride
    4.0
    4.0
    Bone disease (pain and tenderness of the bones); Children may get mottled teeth Water additive which promotes strong teeth; erosion of natural deposits; discharge from fertilizer and aluminum factories
    Lead
    zero
    TT8;
    Action Level=0.015
    Infants and children: Delays in physical or mental development; children could show slight deficits in attention span and learning abilities

    Adults: Kidney problems; high blood pressure

    Corrosion of household plumbing systems; erosion of natural deposits
    Mercury (inorganic)
    0.002
    0.002
    Kidney damageErosion of natural deposits; discharge from refineries and factories; runoff from landfills and croplands
    Nitrate (measured as Nitrogen)
    10
    10
    Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits
    Nitrite (measured as Nitrogen)
    1
    1
    Infants below the age of six months who drink water containing nitrite in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits
    Selenium
    0.05
    0.05
    Hair or fingernail loss; numbness in fingers or toes; circulatory problems Discharge from petroleum refineries; erosion of natural deposits; discharge from mines
    Thallium
    0.0005
    0.002
    Hair loss; changes in blood; kidney, intestine, or liver problems Leaching from ore-processing sites; discharge from electronics, glass, and drug factories

    Organic Chemicals

    ContaminantMCLG1
    (mg/L)2
    MCL or TT1
    (mg/L)2
    Potential Health Effects from Ingestion of Water
    Sources of Contaminant in Drinking Water
    Acrylamide
    zero
    TT9

    Nervous system or blood problems; increased risk of cancer

    Added to water during sewage/wastewater treatment
    Alachlor
    zero
    0.002

    Eye, liver, kidney or spleen problems; anemia; increased risk of cancer

    Runoff from herbicide used on row crops
    Atrazine
    0.003
    0.003

    Cardiovascular system or reproductive problems

    Runoff from herbicide used on row crops
    Benzene
    zero
    0.005

    Anemia; decrease in blood platelets; increased risk of cancer

    Discharge from factories; leaching from gas storage tanks and landfills
    Benzo(a)pyrene (PAHs)
    zero
    0.0002

    Reproductive difficulties; increased risk of cancer

    Leaching from linings of water storage tanks and distribution lines
    Carbofuran
    0.04
    0.04

    Problems with blood, nervous system, or reproductive system

    Leaching of soil fumigant used on rice and alfalfa
    Carbon
    tetrachloride
    zero
    0.005

    Liver problems; increased risk of cancer

    Discharge from chemical plants and other industrial activities
    Chlordane
    zero
    0.002

    Liver or nervous system problems; increased risk of cancer

    Residue of banned termiticide
    Chlorobenzene
    0.1
    0.1

    Liver or kidney problems

    Discharge from chemical and agricultural chemical factories
    2,4-D
    0.07
    0.07

    Kidney, liver, or adrenal gland problems

    Runoff from herbicide used on row crops
    Dalapon
    0.2
    0.2

    Minor kidney changes

    Runoff from herbicide used on rights of way
    1,2-Dibromo-3-chloropropane (DBCP)
    zero
    0.0002

    Reproductive difficulties; increased risk of cancer

    Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards
    o-Dichlorobenzene
    0.6
    0.6

    Liver, kidney, or circulatory system problems

    Discharge from industrial chemical factories
    p-Dichlorobenzene
    0.075
    0.075

    Anemia; liver, kidney or spleen damage; changes in blood

    Discharge from industrial chemical factories
    1,2-Dichloroethane
    zero
    0.005

    Increased risk of cancer

    Discharge from industrial chemical factories
    1,1-Dichloroethylene
    0.007
    0.007

    Liver problems

    Discharge from industrial chemical factories
    cis-1,2-Dichloroethylene
    0.07
    0.07

    Liver problems

    Discharge from industrial chemical factories
    trans-1,2-Dichloroethylene
    0.1
    0.1

    Liver problems

    Discharge from industrial chemical factories
    Dichloromethane
    zero
    0.005

    Liver problems; increased risk of cancer

    Discharge from drug and chemical factories
    1,2-Dichloropropane
    zero
    0.005

    Increased risk of cancer

    Discharge from industrial chemical factories
    Di(2-ethylhexyl) adipate
    0.4
    0.4

    Weight loss, liver problems, or possible reproductive difficulties.

    Discharge from chemical factories
    Di(2-ethylhexyl) phthalate
    zero
    0.006

    Reproductive difficulties; liver problems; increased risk of cancer

    Discharge from rubber and chemical factories
    Dinoseb
    0.007
    0.007

    Reproductive difficulties

    Runoff from herbicide used on soybeans and vegetables
    Dioxin (2,3,7,8-TCDD)
    zero
    0.00000003

    Reproductive difficulties; increased risk of cancer

    Emissions from waste incineration and other combustion; discharge from chemical factories
    Diquat
    0.02
    0.02

    Cataracts

    Runoff from herbicide use
    Endothall
    0.1
    0.1

    Stomach and intestinal problems

    Runoff from herbicide use
    Endrin
    0.002
    0.002

    Liver problems

    Residue of banned insecticide
    Epichlorohydrin
    zero
    TT9

    Increased cancer risk, and over a long period of time, stomach problems

    Discharge from industrial chemical factories; an impurity of some water treatment chemicals
    Ethylbenzene
    0.7
    0.7

    Liver or kidneys problems

    Discharge from petroleum refineries
    Ethylene dibromide
    zero
    0.00005

    Problems with liver, stomach, reproductive system, or kidneys; increased risk of cancer

    Discharge from petroleum refineries
    Glyphosate
    0.7
    0.7

    Kidney problems; reproductive difficulties

    Runoff from herbicide use
    Heptachlor
    zero
    0.0004

    Liver damage; increased risk of cancer

    Residue of banned termiticide
    Heptachlor epoxide
    zero
    0.0002

    Liver damage; increased risk of cancer

    Breakdown of heptachlor
    Hexachlorobenzene
    zero
    0.001

    Liver or kidney problems; reproductive difficulties; increased risk of cancer

    Discharge from metal refineries and agricultural chemical factories
    Hexachlorocyclopentadiene
    0.05
    0.05

    Kidney or stomach problems

    Discharge from chemical factories
    Lindane
    0.0002
    0.0002

    Liver or kidney problems

    Runoff/leaching from insecticide used on cattle, lumber, gardens
    Methoxychlor
    0.04
    0.04

    Reproductive difficulties

    Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock
    Oxamyl (Vydate)
    0.2
    0.2

    Slight nervous system effects

    Runoff/leaching from insecticide used on apples, potatoes, and tomatoes
    Polychlorinated
    biphenyls (PCBs)
    zero
    0.0005

    Skin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer

    Runoff from landfills; discharge of waste chemicals
    Pentachlorophenol
    zero
    0.001

    Liver or kidney problems; increased cancer risk

    Discharge from wood preserving factories
    Picloram
    0.5
    0.5

    Liver problems

    Herbicide runoff
    Simazine
    0.004
    0.004

    Problems with blood

    Herbicide runoff
    Styrene
    0.1
    0.1

    Liver, kidney, or circulatory system problems

    Discharge from rubber and plastic factories; leaching from landfills
    Tetrachloroethylene
    zero
    0.005

    Liver problems; increased risk of cancer

    Discharge from factories and dry cleaners
    Toluene
    1
    1

    Nervous system, kidney, or liver problems

    Discharge from petroleum factories
    Toxaphene
    zero
    0.003

    Kidney, liver, or thyroid problems; increased risk of cancer

    Runoff/leaching from insecticide used on cotton and cattle
    2,4,5-TP (Silvex)
    0.05
    0.05

    Liver problems

    Residue of banned herbicide
    1,2,4-Trichlorobenzene
    0.07
    0.07

    Changes in adrenal glands

    Discharge from textile finishing factories
    1,1,1-Trichloroethane
    0.20
    0.2

    Liver, nervous system, or circulatory problems

    Discharge from metal degreasing sites and other factories
    1,1,2-Trichloroethane
    0.003
    0.005

    Liver, kidney, or immune system problems

    Discharge from industrial chemical factories
    Trichloroethylene
    zero
    0.005

    Liver problems; increased risk of cancer

    Discharge from metal degreasing sites and other factories
    Vinyl chloride
    zero
    0.002

    Increased risk of cancer

    Leaching from PVC pipes; discharge from plastic factories
    Xylenes (total)
    10
    10

    Nervous system damage

    Discharge from petroleum factories; discharge from chemical factories

    Radioactives - Radionuclides

    ContaminantMCLG1
    (mg/L)2
    MCL or TT1
    (mg/L)2
    Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
    Alpha particles
    none7
    ----------
    zero
    15 picocuries per Liter (pCi/L)
    Increased risk of cancerErosion of natural deposits of certain minerals that are radioactive and may emit a form of radiation known as alpha radiation
    Beta particles and photon emitters
    none7
    ----------
    zero
    4 millirems per year
    Increased risk of cancerDecay of natural and man-made deposits of

    certain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation

    Radium 226 and Radium 228 (combined)
    none7
    ----------
    zero
    5 pCi/L
    Increased risk of cancer Erosion of natural deposits
    Uranium
    zero
    30 ug/L
    as of 12/08/03
    Increased risk of cancer, kidney toxicityErosion of natural deposits


    Notes

    1 Definitions:
    Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.
    Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.
    Maximum Residual Disinfectant Level (MRDL) - The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.
    Maximum Residual Disinfectant Level Goal (MRDLG) - The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.
    Treatment Technique - A required process intended to reduce the level of a contaminant in drinking water.

    2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.

    3 EPA's surface water treatment rules require systems using surface water or ground water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels:

    bulletCryptosporidium (as of1/1/02 for systems serving >10,000 and 1/14/05 for systems serving <10,000) 99% removal.
  • Giardia lamblia: 99.9% removal/inactivation
  • Viruses: 99.99% removal/inactivation
  • Legionella: No limit, but EPA believes that if Giardia and viruses are removed/inactivated, Legionella will also be controlled.
  • Turbidity: At no time can turbidity (cloudiness of water) go above 5 nephelolometric turbidity units (NTU); systems that filter must ensure that the turbidity go no higher than 1 NTU (0.5 NTU for conventional or direct filtration) in at least 95% of the daily samples in any month. As of January 1, 2002, turbidity may never exceed 1 NTU, and must not exceed 0.3 NTU in 95% of daily samples in any month.
  • HPC: No more than 500 bacterial colonies per milliliter.
  • Long Term 1 Enhanced Surface Water Treatment (Effective Date: January 14, 2005); Surface water systems or (GWUDI) systems serving fewer than 10,000 people must comply with the applicable Long Term 1 Enhanced Surface Water Treatment Rule provisions (e.g. turbidity standards, individual filter monitoring, Cryptosporidium removal requirements, updated watershed control requirements for unfiltered systems).
  • Filter Backwash Recycling; The Filter Backwash Recycling Rule requires systems that recycle to return specific recycle flows through all processes of the system's existing conventional or direct filtration system or at an alternate location approved by the state.
  • 4 more than 5.0% samples total coliform-positive in a month. (For water systems that collect fewer than 40 routine samples per month, no more than one sample can be total coliform-positive per month.) Every sample that has total coliform must be analyzed for either fecal coliforms or E. coli if two consecutive TC-positive samples, and one is also positive for E.coli fecal coliforms, system has an acute MCL violation.

    5 Fecal coliform and E. coli are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms. These pathogens may pose a special health risk for infants, young children, and people with severely compromised immune systems.

    6 Although there is no collective MCLG for this contaminant group, there are individual MCLGs for some of the individual contaminants:

    bulletTrihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/L). Chloroform is regulated with this group but has no MCLG.
  • Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.3 mg/L). Monochloroacetic acid, bromoacetic acid, and dibromoacetic acid are regulated with this group but have no MCLGs.
  • 7 MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no MCLG for this contaminant.

    8 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/L, and for lead is 0.015 mg/L.

    9 Each water system must certify, in writing, to the state (using third-party or manufacturer's certification) that when acrylamide and epichlorohydrin are used in drinking water systems, the combination (or product) of dose and monomer level does not exceed the levels specified, as follows:

    bulletAcrylamide = 0.05% dosed at 1 mg/L (or equivalent)
  • Epichlorohydrin = 0.01% dosed at 20 mg/L (or equivalent)
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    National Secondary Drinking Water Regulations

    National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

    Contaminant
    Secondary Standard
    Aluminum
    0.05 to 0.2 mg/L
    Chloride
    250 mg/L
    Color
    15 (color units)
    Copper
    1.0 mg/L
    Corrosivity
    noncorrosive
    Fluoride
    2.0 mg/L
    Foaming Agents
    0.5 mg/L
    Iron
    0.3 mg/L
    Manganese
    0.05 mg/L
    Odor
    3 threshold odor number
    pH
    6.5-8.5
    Silver
    0.10 mg/L
    Sulfate
    250 mg/L
    Total Dissolved Solids
    500 mg/L
    Zinc
    5 mg/L