National Emission Standards for Hazardous Air Pollutants

Emission standards for hazardous air pollutants are set forth in the Section 112 of the Clean Air Act of 1970 and the National Ambient Air Quality Standard . Section 112 directed the Environmental Protection Agency (EPA) to issue a list of hazardous pollutants that were to be regulated. However, the provisions of the 1970 Clean Air Act that were designed to regulate hazardous pollutants proved to be ineffective. Although more than 300 toxic substances are known to be emitted into the air, between 1970 and 1990 emission standards were established for only eight substances: asbestos , benzene , beryllium, coke oven emissions, inorganic arsenic , mercury , radionuclides , and vinyl chloride . Although the EPA had epidemiologic and laboratory data that linked more than sixty other airborne toxins with cancer , birth defects , or neurological disease, they remained unregulated. The regulatory process specified by Section 112 was expensive and conservative. It required the EPA to gather sufficient evidence to demonstrate that an airborne toxin was hazardous before it could act. Frequently, there was a lack of scientific information on the health effects of these toxins. There was also a strong potential for legal challenges by industry.

Records dating from 1987 indicated that between 1987 and 1989, over 2 billion pounds of toxic chemicals were released into the air each year. Furthermore, more toxic chemicals were released into the air than into any other medium (water or soil ) during these three years. Environmentalists and their supporters in Congress argued that the 1970 program had not been successful. The issue of airborne toxins was a major air pollution problem that was not being adequately addressed by Section 112. For this reason, an improved program to regulate airborne toxins became a central component in the efforts to amend the Clean Air Act.

One of the major components in the 1990 Clean Air Act included provisions to regulate hazardous air pollutants. Title III of the law required the thousands of sources of airborne toxins in the country to use the best available technologies to control hazardous air pollutants (HAPs). The act listed 189 chemicals that are considered HAPs. This effectively removed the power to designate hazardous air pollutants from the EPA. However, the legislation did provide a mechanism to designate other HAPs for regulation in the future. Since 2000, all major stationary sources, regardless of age, location, or size, have been required to meet emission standards for every HAP established by the EPA. Major sources of HAPs (those emitting at least 10 tons of one pollutant or 25 tons of a combination of pollutants, per year) are required to apply "maximum achievable control technology" (MACT) and are required to receive emission permits. An incentive-based provision of the 1990 Clean Air Act ensured that sources that voluntarily and permanently achieved HAP reductions of 90% (from 1987 levels) could postpone instillation of MACT for up to six years.

Under the revised law, the EPA was directed to focus on those HAPs and sources that are deemed the most dangerous. Further, the EPA was directed to devise strategies to control all sources of HAPs in urban areas. By the year 2000, the EPA was mandated to identify the 30 HAPs that posed the greatest threat to human health and to identify the sources generating 90% of these emissions. The EPA was also to devise a strategy to reduce HAP-related cancer risk by 75%. It ws estimated that these additional provisions would reduce hazardous air pollutants from industrial sources by 75–90%. The EPA has undertaken programs to comply with these directives. As of 2002, the EPA has not completed any of the mandates.

[L. Fleming Fallon Jr., M.D., Dr.P.H. ]

RESOURCES

BOOKS

Alley, E. R., Cleland, W.L. and Stevens, L.B. Air Quality Control Handbook. New York: McGraw-Hill, 1998.

Davis, Wayne T. Air Pollution Engineering Manual. 2nd ed. New York: John Wiley and Sons, 2000.

Liu, D. H., and B. G. Liptbak. Air Pollution Boca Raton: Lewis Publishers, 1999.

Wirth, John D. Smelter Smoke in North America: The Politics of Transborder Pollution. Lawrence, KS: University Press of Kansas, 1999.

OTHER

American Meteorological Society. Clean Air Act. [July 2002]. <http://www.ametsoc.org/AMS/sloan/cleanair/cleanairlegisl.html>.