Why do we need these air quality regulations?

Under the Clean Air Act, the Environmental Protection Agency establishes primary and secondary national standards for air quality. The National Ambient Air Quality Standards (NAAQS) primary standards set limits to protect public health, including the health of sensitive populations such as asthmatics, children, and the elderly. The NAAQS secondary standards set limits to protect public welfare, including protection against decreased visibility (haze), damage to animals, crops, vegetation, and buildings.