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Q: What is acid rain?
A: "Acid rain" is a broad term used to describe several ways that acids fall out of the
atmosphere. A more precise term is acid deposition, which has two parts: wet (rain,
fog, and snow) and dry (particles and gases). Acid rain's effects include:
The specific effects and their severity depends on several factors, including soil and surface water chemistry, the amount of air pollution that creates acid rain, and the specific species involved. For more information, see the acid rain home page.
Q: What is the difference between air pollutants and toxic air pollutants?
A: Toxic air pollutants (or Hazardous Air Pollutants, HAPs) are different from air pollutants. Air toxics are known or suspected to cause cancer or other serious heath effects, such as damage to respiratory or nervous systems. Toxic air pollutants may exist as particulate matter or as vapors (gases). Air toxics include metals, particles, and certain vapors from fuels and other sources. To find out more about toxic air pollutants visit the basic facts page.
Q: What causes indoor air quality problems and how can I tell whether I have a problem?
A: Indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home. High temperature and humidity levels can also increase concentrations of some pollutants. EPA has developed a Building Survey to help you determine if there's a problem.
Q: What are the two main issues related to ozone?
A: Ozone, a molecule with three oxygen atoms, is at the core of two very different issues: stratospheric ozone depletion and ground-level ozone formation.
Stratospheric Ozone Depletion
About 90% of all ozone occurs in the ozone layer, a region of high concentrations approximately 15-40 kilometers (10-25 miles) above the Earth's surface, in the stratosphere. The ozone layer protects all life from ultraviolet radiation (UV) from the sun. Unfortunately, several chemicals used in air conditioning and certain industrial uses damage the ozone layer, allowing more UV to reach the Earth's surface. Since UV causes skin cancer, cataracts, and other harmful effects, ozone depletion will lead to increases in these problems. Increased UV can also lead to reduced crop yield and disruptions in the marine food chain. The ozone depletion web site explains EPA's programs to protect the ozone layer and other information related to ozone depletion. In particular, the ozone science page offers much more detail on ozone depletion, its causes and effects, and what the world is doing to fix the problem.
Ground-Level Ozone Formation
The same ozone molecules that protect us from UV high in the stratosphere can cause health problems for people and animals when they form near the Earth's surface. Ground-level ozone is formed when vehicle exhaust and some other chemicals commonly used in industry mix in strong sunlight. When these ozone concentrations get high enough, they can make breathing difficult, especially for people with asthma and other respiratory diseases. EPA's ozone mapping site provides information on ozone levels in many US cities. If you hear an ozone alert on the news, it means ozone levels in your area are very high that day, and you should try to stay indoors and not exercise vigorously until ozone levels drop again. EPA has several programs to reduce air pollution and ozone concentrations.
"Ozone: Good Up High, Bad Nearby" is an EPA fact sheet that explains the difference between "good" ozone (stratospheric) and "bad" ozone (ground-level) in more detail.
Q: What can be done to prevent pollution?
A: Did you know that your home and office contribute to the greenhouse effect? Energy used in our everyday activities -- turning on electrical appliances, driving cars, and heating and cooling our homes -- is responsible for air pollution that contributes to climate change. Technologies are available today that can cut this energy use significantly and, at the same time, improve our quality of life.
Preventing pollution is as easy as looking for the ENERGY STAR Label. ENERGY STAR is already helping American homes, businesses, state and local governments and other organizations by reducing energy consumption, emissions of greenhouse gases and other harmful pollutants, and their associated energy costs.
Other things you can do:
For more information on Atmospheric Pollution Prevention Division's mission, click here.
Q: What is the definition for radiation?
A: Radiation is energy given off by atoms in the form of particles or electromagnetic rays. There are actually many different types of electromagnetic radiation that have a range of energy levels. They form the electromagnetic spectrum and include radio and microwaves, heat, light, and x-rays.
Common Questions, Clear Answers
Q: What pollutants affect air quality?
A: A few air pollutants, called criteria air pollutants, are common throughout the United States. These pollutants can injure health, harm the environment and cause property damage. The current criteria pollutants are: Carbon Monoxide (CO), Lead (Pb), Nitrogen Dioxide (NO2), Ozone (O3), Particulate matter with aerodynamic size less than or equal to 10 micrometers (PM-10), and Sulfur Dioxide (SO2). To find out more in depth information about the criteria air pollutants, visit the Green Book site.
Q: What kinds of air pollution are produced by mobile sources?
A: Combustion of fuels can cause the release of hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), particulate matter (PM), toxics, sulfur dioxide (SO2), and greenhouse gases such as carbon dioxide (CO2) and nitrous oxide (N2O). Mobile sources produce air pollution from exhaust emissions, as well as evaporative emissions and refueling losses from gasoline engines. The type and amount of pollution depends on many factors: the type of engine or vehicle (e.g., passenger car, heavy-duty truck, lawn mower, locomotive, etc.); the type of fuel used (e.g., gasoline, diesel, or alternative fuels); the type and condition of emission control devices (e.g., catalytic converters); and how the engine is used/run. For example, diesel engines used in trucks, buses, locomotives, and ships tend to emit more NOx and PM than gasoline engines. Engines with catalytic converters (e.g., passenger cars) emit much less HC, CO, NOx, and toxics than similar engines without catalysts (i.e., the catalytic converter is an important pollution control device to reduce exhaust emissions).
Additional information on air pollution from mobile sources is available on the Office of Mobile Sources Web site.
Q: How is pollution affecting what we see?
A:Visibility impairment occurs as a result of the scattering and absorption of light by particles and gases in the atmosphere. It is most simply described as the haze which obscures the clarity, color, texture, and form of what we see. The same particles which are linked to serious health effects [sulfates, nitrates, organic carbon, soot (elemental carbon), and soil dust] can significantly affect our ability to see.
Air Pollution Control
Air Pollution Monitoring
Air Pollution Legal Aspects
Why Be Concerned?
Effects of Air Pollution
What You Can Do!