National Ambient Air Quality Standards

The U.S. National Ambient Air Quality Standards (NAAQS, pronounced /ˈnæks/ naks) are limits on atmospheric concentration of six pollutants that cause smog, acid rain, and other health hazards.

[1] Established by the United States Environmental Protection Agency (EPA) under authority of the Clean Air Act (42 U.S.C.

[4] The National Emissions Standards for Hazardous Air Pollutants cover many other chemicals, and require the maximum achievable reduction that the EPA determines is feasible.

[8] These sections require the EPA "(1) to list widespread air pollutants that reasonably may be expected to endanger public health or welfare; (2) to issue air quality criteria for them that assess the latest available scientific information on nature and effects of ambient exposure to them; (3) to set primary NAAQS to protect human health with adequate margin of safety and to set secondary NAAQS to protect against welfare effects (e.g., effects on vegetation, ecosystems, visibility, climate, manmade materials, etc); and (5) to periodically review and revise, as appropriate, the criteria and NAAQS for a given listed pollutant or class of pollutants.

Primary standards are designed to protect human health,[23] with an adequate margin of safety, including sensitive populations such as children, the elderly, and individuals suffering from respiratory diseases.

Secondary standards are designed to protect public welfare, damage to property, transportation hazards, economic values, and personal comfort and well-being from any known or anticipated adverse effects of a pollutant.