Clean Air Act (1963, 1970, 1977, 1990)


The 1970 Clean Air Act and major amendments to the act in 1977 and 1990 serve as the backbone of federal efforts to control air pollution in the United States. This law and its amendments established one of the most complex regulatory programs in the country.


In 1963, the first Clean Air Act was passed. The act provided permanent federal aid for research, support for the development of state pollution control agencies, and federal involvement in cross-boundary air pollution cases. An amendment to the act in 1965 directed the Department of Health, Education and Welfare (HEW) to establish federal emission standards for motor vehicles. (In 1965, HEW administered air pollution laws. The Environmental Protection Agency [EPA] was not created until 1970.) The 1967 Air Quality Act provided additional funding to the states, required them to establish Air Quality Control Regions, and directed HEW to obtain and make available information on the health effects of air pollutants and to identify pollution control techniques.


The Clean Air Act of 1970 marked a dramatic change in U.S. air pollution policy. Following enactment of this law, the federal government, not the states, would be the focal point for air pollution policy. This act established the framework that continued as of 2012 to be the foundation for air pollution control policy. The impetus for this change was the belief that the state-based approach was not working and increased pressure from a developing environmental consciousness across the country. Public sentiment was growing so significantly that environmental issues demanded the attention of high-ranking officials. In fact, the leading policy shapers on the issue were President Richard Nixon and Senator Edmund Muskie of Maine.


The regulatory framework of the Clean Air Act featured four key components. First, National Ambient Air Quality Standards (NAAQSs) were established for six major pollutants: carbon monoxide, lead (in 1977), nitrogen dioxide, ground-level ozone (a key component of smog), particulate matter, and sulfur dioxide. For each of these pollutants, sometimes referred to as criteria pollutants, primary and secondary standards were set. The primary standards were designed to protect human health; the secondary standards were based on protecting crops, forests, and buildings if the primary standards were not capable of doing so. The act stipulated that these standards must apply to the entire country and be set by the EPA, based on the best available scientific information. The costs of attaining these standards were not among the factors considered. The EPA was also directed to set standards for less common toxic air pollutants.

Third, mobile source emission standards were established to control automobile emissions. These standards were specified in the statute (rather than left to the EPA), and schedules for meeting them were also written into the law. It was thought that such an approach was crucial to ensure success with the powerful auto industry. The pollutants regulated were carbon monoxide, hydrocarbons, and nitrogen oxides, with goals of reducing the first two pollutants by 90% and nitrogen oxides by 82% by 1975.

The final component of the air protection act dealt with the implementation of the new air quality standards. Each state would be encouraged to devise a state implementation plan (SIP), specifying how the state would meet the national standards. These plans had to be approved by the EPA; if a state did not have an approved SIP, the EPA would administer the Clean Air Act in that state. However, since the federal government was in charge of establishing pollution standards for new mobile and stationary sources, even the states with an SIP had limited flexibility. The states focused on the control of existing stationary sources and, if necessary, mobile sources. The states had to set limits in their SIPs that allowed them to achieve the NAAQSs by a statutorily determined deadline. One problem with this approach was the construction of tall smokestacks, which helped move pollution out of a particular airshed but did not reduce overall pollution levels. The states were also charged with monitoring and enforcing the Clean Air Act.


Efforts to control air pollution in the United States date back to 1881, when Chicago and Cincinnati passed laws to control industrial smoke and soot. Other municipalities followed, and the momentum continued to build. In 1952, Oregon became the first state to adopt a significant program to control air pollution, and three years later, the federal government became involved for the first time, when the Air Pollution Control Act was passed. This law provided funds to assist the states in their air pollution control activities.


The 1977 amendments to the Clean Air Act dealt with three main issues: nonattainment, auto emissions, and the prevention of air quality deterioration in areas where the air was already relatively clean. The first two issues were resolved primarily by delaying deadlines and increasing penalties. Largely in response to a Supreme Court decision in favor of environmentalists (Sierra Club v. Ruckelshaus, 1972), the 1977 amendments included a program for the prevention of significant deterioration (PSD) of air that was already clean. This program would prevent polluting the air up to the national levels in areas where the air was cleaner than the standards. In Class I areas, areas with near pristine air quality, no new significant air pollution would be allowed. Class I areas are airsheds over large national parks and wilderness areas. In Class II areas, a moderate degree of air quality deterioration would be allowed. In Class III areas, air deterioration up to the national secondary standards would be allowed. Most of the country that had air cleaner than the NAAQSs was classified as Class II. Related to the prevention of significant deterioration was a provision to protect and enhance visibility in national parks and wilderness areas even if the air pollution was not a threat to human health. The impetus for this section of the bill was the growing visibility problem in parks, especially in the Southwest.

Throughout the 1980s, efforts to further amend the Clean Air Act were stymied. President Ronald Reagan opposed any strengthening of the act, which he argued would hurt the economy. In Congress, the controversy over acid rain between members from the Midwest and the Northeast further contributed to the stalemate. Gridlock on the issue broke with the election of George H. W. Bush, who supported amendments to the act, and the rise of Senator George Mitchell of Maine to Senate Majority Leader. Over the next two years, the issues were hammered out between environmentalists and industry and between different regions of the country. Major players in Congress were Representatives John Dingell of Michigan and Henry Waxman of California and Senator Robert Byrd of West Virginia and Senator Mitchell.

Due to the failure of the toxic air pollutant provisions of the 1970 Clean Air Act, more stringent provisions were adopted requiring regulations for all major sources of 189 varieties of toxic air pollution within ten years. Areas of the country still in nonattainment for criteria pollutants were given from three to 20 years to meet these standards. These areas were also required to impose tighter controls to meet the standards. To help these areas and other parts of the country, the act required stiffer motor vehicle emissions standards and cleaner gasoline. Finally, three chemical families that contribute to the destruction of the stratospheric ozone layer (chlorofluorocarbons [CFCs], hydrochloroflurocarbons [HCFCs], and methyl chloroform) were to be phased out of production and use.

In 1997, the EPA issued revised NAAQSs, setting stricter standards for ozone and particulate matter. The American Trucking Association and other state and industry groups challenged the legality of the new standards on the grounds that the EPA did not have the authority under the act to make such changes. On February 27, 2001, the U.S. Supreme Court unanimously upheld the constitutionality of the Clean Air Act as interpreted by the EPA, and all remaining legal challenges to other aspects of the standards change were rejected by a Washington, DC, district court ruling in early 2002.

Research and general acceptance

The Clean Air Act met with mixed success. The national average pollutant levels for the criteria pollutants decreased. Nevertheless, many localities did not achieve these standards and were in perpetual nonattainment. Not surprisingly, major urban areas were those most frequently in nonattainment. The pollutant for which standards are most often exceeded is ozone, or smog. This is due in part to increases in nitrogen oxides (NOx), which disperse ozone. NOx emissions increased by approximately 20% between 1970 and 2000. As a result, some parts of the country have had worsening ozone levels. According to the EPA, the average ozone levels in 29 national parks increased by over 4% between 1990 and 2000.

The greatest successes of air pollution control came with lead, which between 1981 and 2000 was reduced by 92% (largely due to the phasing-out of leaded gasoline), and particulates, which were reduced by 47% in the same period. Overall particulate emissions were down 88% since 1970. Carbon monoxide dropped by 46% and volatile organic compounds and sulfur dioxides declined by over 40% each between 1970 and 2000. However, air quality analysis is complex, and it is important to note that some changes may be due to shifts in the economy, changes in weather patterns, or other such variables rather than directly attributable to the Clean Air Act.

In February 2002, President George W. Bush introduced the Clear Skies Act of 2003, an initiative that would have made significant changes to the Clean Air Act. Among them would have been a weakening or elimination of new source review regulations and BART rules and a new cap-and-trade plan that would allow power plants that produced excessive toxic emissions to buy credits from other plants who had levels under the standards. The Bush administration hailed the initiative as a less expensive way to accelerate air pollution clean-up and a more economy-friendly alternative to the Kyoto Protocol for greenhouse gas reductions, while environmental groups and other critics called it a roll-back of the Clean Air Act progress. This legislation was never enacted because it never moved beyond the Senate Environment and Public Works committee.

In 2007, the Supreme Court ruled in Massachusetts v. EPA that the EPA has the power to regulated carbon dioxide (CO2) and other greenhouse gas emissions under the Clean Air Act. The High Court stated that the Clean Air Act terms require the EPA to administer greenhouse gas regulation, unless the EPA could prove that greenhouse gases do not contribute to climate change or could offer a reasonable explanation as to why the EPA should not regulate greenhouse gases. In April 2009, the EPA declared that CO2 and other greenhouse gases were a threat to the public's health and welfare. President Obama urged Congress and the Senate to pass comprehensive climate legislation that included regulation of greenhouse gas emissions. In 2009 and 2010, proposed legislation failed to garner enough support. The Obama administration announced that the EPA would move to enact regulations in the absence of congressional action.

See also Acid rain ; Air pollution ; Climate change ; Lead ; Ozone ; Smog .



Collin, Robert W. The Environmental Protection Agency: Cleaning Up America's Act. Westport, CT: Greenwood Press, 2005.

DuPuis, E. Melanie. Smoke and Mirrors: The Politics and Culture of Air Pollution. New York: New York University Press, 2004.

Ellerman, A. Denny. Markets for Clean Air: The U.S. Acid Rain Program. New York: Cambridge University Press, 2005.

Wooley, David, and Elizabeth Morss. Clean Air Act Handbook. Deerfield, IL: Clark Boardman Callaghan, 2009.


U.S. Department of Energy. “Clean Air Act Amendments of 1990.” (accessed September 22, 2012).

U.S. Environmental Protection Agency (EPA). “Summary of the Clean Air Act.” August 23, 2012. (accessed September 22, 2012).

Christopher McGrory Klyza
Paula Anne Ford-Martin

  This information is not a tool for self-diagnosis or a substitute for professional care.