The U.S. Clean Air Act
The Clean Air Act (CAA) of 1970 gave the U.S. Environmental Protection Agency (EPA) authority to regulate air pollutants. The EPA then listed and regulated six "criteria pollutants": carbon monoxide, particulate matter, volatile organic compounds (VOCs, a precursor of smog), nitrogen oxides (NOx, also a precursor of smog), lead, and sulfur dioxide (a component of acid rain). In 1990, Congress amended the CAA and added a list of 189 toxic air pollutants selected on the basis of their potential health and/or environmental hazards. The 1990 Amendments also allow the EPA to add new chemicals to the list as necessary. New sections addressing Air Operating Permits and protection of stratospheric ozone were also added.
To regulate air pollutants, EPA defined specific categories of sources that release air pollutants. Categories include municipal waste incinerators, oil refineries, coal-burning power plants, chemical plants, and more. Emission sources are identified as either major (large) or sector (smaller) sources. In some cases, EPA specified exactly how to reduce pollutant releases but wherever possible companies still have flexibility to choose how they meet requirements. Many sources are required to use Maximum Available Control Technology (MACT) to reduce pollutant releases.
Washington State Clean Air Act
The Washington State legislature adopted Washington's Clean Air Act (70.94 RCW) in 1967. This Act is the basis for state and local air pollution rules in Washington. Regulations at the state level must be as protective or more protective of human health and the environment than those of the U.S. Clean Air Act.
Seven local clean air agencies enforce air pollution rules in Washington, including the Puget Sound Clean Air Authority (PSCAA). The Washington State Department of Ecology handles air pollution matters in areas of the state where a local agency has not been established.
Washington State Department of Ecology Air page: http://www.ecy.wa.gov/air.html.
The Puget Sound Clean Air Agency (PSCAA): http://www.pscleanair.org/Pages/default.aspx