National Ambient Air Quality Standards (NAAQS)
The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards 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) has set national Ambient Air Quality Standards for six principal pollutants, which are called "criteria" pollutants. Reproduced below is the criteria pollutant NAAQS table found on the EPA website. Units of measure for the standards are parts per million (ppm) by volume, parts per billion (ppb - 1 part in 1,000,000,000) by volume, milligrams per cubic meter of air (mg/m3), and micrograms per cubic meter of air (µg/m3).
As of January, 2017
Content Last Updated January 23, 2017