The Clean Air Act s the law that defines EPA's responsibilities for protecting and improving the nation's air quality and the stratospheric ozone layer. The last major change in the law, the Clean Air Act Amendments of 1990, was enacted by Congress in 1990. 

Air pollution control and clean air quality preservation are vital to reducing dangers to public health and welfare, injury to agricultural crops and livestock, hazards to air and ground transportation, and atmospheric deterioration. (Source: EPA / Photo: Shutterstock)