The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS)National Ambient Air Quality StandardsNational Ambient Air Quality Standards established by EPA for six "criteria" pollutants in outdoor air. NAAQS are currently set for carbon monoxide, lead, ground-level ozone, nitrogen dioxide, particulate matter, and sulfur dioxide. for six common air pollutants (also known as "criteria air pollutantsCriteria Air PollutantsThese pollutants are particulate matter, photochemical oxidants (including ozone), carbon monoxide, sulfur oxides, nitrogen oxides and lead. EPA calls these pollutants “criteria” air pollutants because it sets NAAQS for them based on the criteria, which are characterizations of the latest scientific information regarding their effects on health or welfare."). These pollutants are found all over the U.S. They can harm your health and the environment, and cause property damage.

Learn how EPA sets, reviews and revises standards (primary standardsprimary standardsNational ambient air quality standards designed to protect public health with an adequate margin for safety. and secondary standardssecondary standardsNational ambient air quality standards designed to protect the public welfare from adverse effects, including those related to 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.), determines whether areas meet the standards, and works with areas to attain and maintain the standards.