Ambient Air Quality Standards (AAQS)

This page last reviewed July 2, 2013


Ambient air quality standards (AAQS) define clean air, and are established to protect even the most sensitive individuals in our communities. An air quality standard defines the maximum amount of a pollutant that can be present in outdoor air without harm to the public's health. Both the Air Resources Board (ARB) and the U.S. Environmental Protection Agency (U.S. EPA) are authorized to set ambient air quality standards.

California Ambient Air Quality Standards

This site describes California ambient air quality standards and the current review of these standards mandated by the Children's Environmental Health Protection Act (CEHPA, Senate Bill 25, Escutia, 1999).

Federal Standards and Other Resources

This site provides links to Federal activities related to Ambient Air Quality Standards.

Ozone Standard Review

Ozone, a major component of smog, is a reactive gas capable of damaging the tissues of the lungs and respiratory tract. ARB staff reviewed the scientific literature and recommended revisions to the ozone standard based on that review. The revised standard became effective on May 17, 2006.

Nitrogen Dioxide Standards Review

Nitrogen Dioxide is a reactive gas capable of damaging the cells lining the respiratory tract. ARB staff reviewed the scientific literature and recommended revisions to the NO2 standards based on that review. On February 19, 2007, the Board adopted staff's recommendations; the revised standards became effective on March 20, 2008.

Particulate Matter Standards Review

Particulate Matter (PM) consists of tiny particles that are easily inhaled deep into the lungs and may cause a variety of harmful health effects. In an evaluation of current California air quality standards mandated by the Children's Environmental Health Protection Act, PM standards were identified as a top priority for review. ARB staff reviewed the scientific literature and recommended revisions to the PM standards based on that review. On June 20, 2002, the Board adopted staff's recommendations and the revised standards became effective on July 5, 2003.
  • Methodology for Quantifying PM-Associated Mortality 
    On August 31, 2010 the ARB released a report describing updated methodology, based on the U.S. Environmental Protection Agency's recent assessment, for estimating the number of premature deaths associated with PM2.5 exposure. Further details can be found at this link.

Air Quality Monitoring

The Air Quality Monitoring Program measures real-time pollutant concentrations at more than 200 locations throughout California, including approximately 40 ARB sites.

Area Designation Maps

Each year, the ARB reviews air quality data to determine if different geographical areas of California meet current State and Federal air quality standards.

Ambient Air Quality Standards List Serve

Please join our listserve message server to receive email notifications of additions to this page and other information concerning Ambient Air Quality Standards.

A Bit of History

Historical Archive of ARB Comments on the 1996 U.S. EPA Revisions to the PM and Ozone Standard  Revisions

For more information on Ambient Air Quality Standards please contact Dr. Linda Smith or at (916) 327-8225.