National Ambient Air Quality Standards (NAAQS)

To control ambient air quality, the Clean Air Act requires the Environmental Protection Agency (EPA) to set national ambient air quality standards for pollutants considered harmful to public health and the environment. Last amended in 1990, the Clean Air Act established two types of standards for ambient air quality. Primary standards concern the minimum level of air quality necessary to keep people from becoming ill and are aimed at protecting public health. These primary standards are intended to provide an adequate margin of safety for the public, which has been defined to include a representative sample of the so-called sensitive populations such as the elderly, children, and asthmatics. The secondary standards are aimed at promoting public welfare. This includes protection against visibility impairment and damage ...