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The U.S. Clean Air Act requires EPA to set National Ambient Air Quality Standards for six common air pollutants. These pollutants (known as "criteria pollutants") are found all over the United States. They are particulate matter (often referred to as particle pollution), ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen oxides, and lead.
These pollutants can harm human health, harm the environment, and cause property damage. Of the six pollutants, particle pollution and ground-level ozone are the most widespread health threats. EPA calls these six pollutants "criteria" air pollutants because it regulates them by developing limits that are based on human health and/or environmental criteria.
Learn more about criteria air pollutants.
Toxic air pollutants, also known as hazardous air pollutants (HAPs), are those pollutants that are known or suspected to cause cancer, other serious health effects (including reproductive effects or birth defects), or adverse environmental effects. EPA is working with state, local, and tribal governments to reduce air emissions of HAPs to the environment.
Examples of HAPs include benzene, which is found in gasoline; perchloroethylene, which is emitted from some dry cleaning facilities; and methylene chloride, which is used as a solvent and paint stripper by a number of industries. Other examples are dioxins, asbestos, toluene, and metals such as cadmium, mercury, chromium, and lead compounds.
Additional resources about air pollution
More information on air-related issues, including stratospheric ozone protection, acid rain, indoor air pollution and greenhouse gases can be found at: