California Air Resources Board

A number of air pollutants, emitted from a variety of sources, impact the health of Californians everyday. Air monitoring data show that over 90 percent of Californians breathe unhealthy levels of one or more air pollutants during some part of the year. The U.S. Environmental Protection Agency (U.S. EPA) and the California Air Resources Board (CARB) establish health-based ambient air quality standards to identify outdoor pollutant levels that are considered safe for the public - including those individuals most sensitive to the effects of air pollution, such as children and the elderly.

U.S. EPA has set National Ambient Air Quality Standards (NAAQS) for six pollutants, including ozone and particulate matter. These are referred to as the “criteria” pollutants. CARB has set California Ambient Air Quality Standards (CAAQS) for the same six pollutants, as well as for four additional pollutants.

CARB also identifies other air pollutants as toxic air contaminants (TACs) - pollutants that may cause serious, long-term effects, such as cancer, even at low levels. Most air toxics have no known safe levels, and some may accumulate in the body from repeated exposures. The Board has identified about 200 pollutants as air toxics, and measures continue to be adopted to reduce emissions of air toxics. Both criteria pollutants and toxic air contaminants are measured statewide to assess the adequacy of programs for cleaning the air. CARB works with local air pollution control districts to reduce air pollution from all sources.

The table below briefly summarizes the most common health and environmental effects for each of the air pollutants for which there is a national and/or California ambient air quality standard, as well as for toxic air pollutants. Follow the links for more detailed information specific to each pollutant.