The CAA was passed by Congress in 1970 and signed into law by President Nixon. This Act is the basic Federal law for controlling toxic air pollution. It requires EPA to keep an up-to-date list of industrial pollutants that are hazardous to human health, and set an emission standard for each “with an ample margin of safety.” Under the law, EPA prepares minimum pollution standards, and States prepare implementation plans showing how these standards will be attained. States issue permits for the release of listed pollutants into the atmosphere, and take samples to evaluate the State’s air quality. Of the 320 toxic air pollutants named in the act, EPA has to date completed regulations governing only 7, in large part because industry protests have resulted in legal precedents requiring costly and lengthy scientific studies to show that a pollutant has harmful effects at a certain level.

The CAA was expanded, with its central public health approach reaffirmed, under Presidents Carter and Bush. The CAA requires EPA to review public health standards for six major air pollutants every 5 years. Under the law, the standards must be set to “protect public health with an adequate margin of safety” and be based only upon a consideration of public health, with cost factors coming into account only during the implementation phase. EPA recently completed the scientific review for five of the six pollutants and has set new, updated standards for only two of these—ozone and particulate matter.