The U.S. Clean Air Act (CAA) is a federal law that attempts to improve air quality by regulating air pollution. The CAA was first enacted in 1970 but underwent major amendments in 1977 and 1990. These amendments added measures to prevent depletion of the stratospheric ozone layer and to control emissions related to acid rain. The act frames the responsibilities of the Environmental Protection Agency (EPA) for establishing national air quality standards and sets deadlines for compliance. Although the CAA seeks to protect the environment from damage caused by air pollutants, the primary goal of the law is to safeguard public health. Many of the programs associated with the CAA are often regarded as successful; however, controversy surrounds the EPA's use of scientific evidence, its ...