U.S. Environmental Protection Agency

The U.S. Environmental Protection Agency is perhaps the single best source of information regarding environmental rules, regulations and topics. EPA's mission is to protect human health and the environment. Readers seeking EPA-related information are encouraged to go to EPA's web site:

http://www.epa.gov

All topics covered by EPA are listed alphabetically with links to locate detailed information at:

http://www.epa.gov/ebtpages/alphabet.html

U.S. National Ambient Air Quality Standards

The U.S. Clean Air Act, last amended in 1990, requires the U.S. Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to public health and the environment. The Clean Air Act established two types of national air quality standards. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. The EPA Office of Air Quality Planning and Standards (OAQPS) established National Ambient Air Quality Standards for seven principal pollutants, called "criteria" pollutants. They are listed in the following table. Units of measure for the standards are parts per million (ppm) by volume, milligrams per cubic meter of air (mg/m ³), and micrograms per cubic meter of air ( ?g/m ³).

National Ambient Air Quality Standards