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Reviewing National Ambient Air Quality Standards (NAAQS): Scientific and Technical Information

  • EPA sets NAAQS for six principal pollutants, called "criteria pollutants".

The Clean Air Act requires EPA to review the standards – and the science behind them – periodically to determine whether changes are warranted. Learn more about EPA's NAAQS review process.

The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for pollutants that are common in outdoor air, considered harmful to public health and the environment, and that come from numerous and diverse sources.  

The statute established two types of national air quality standards: primary standardsNational ambient air quality standards designed to protect public health with an adequate margin for safety. and secondary 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.. This website provides scientific and technical information about the current or prior review of the NAAQS for each of the six criteria pollutants.
 

Carbon Monoxide (CO)

  • CO Air Quality Standards

Lead (Pb)

  • Pb Air Quality Standards

Particulate Matter (PM)

  • PM Air Quality Standards

Ozone (O3)

  • O3 Air Quality Standards

Nitrogen Dioxide (NO2)

  • NO2 Primary Air Quality Standards
  • NO2 Secondary Air Quality Standards

Sulfur Dioxide (SO2)

  • SO2 Primary Air Quality Standards
  • SO2 Secondary Air Quality Standards

Related Links

  • Air Quality Research
  • Criteria Air Pollutants
  • Current NAAQS Table
  • Air Quality Analysis
  • Trends and Design Values
  • Air Quality Monitoring Sites
  • Ambient Air Monitoring Networks
Contact Us to ask a question, provide feedback, or report a problem.
Last updated on August 18, 2021
United States Environmental Protection Agency

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