U.S. Clean Air Acts

DATE: Enacted 1963, 1970, 1977, and 1990

The Clean Air Act of 1963 and its subsequent amendments have mandated reductions in various atmospheric pollutants, with Congress imposing increasingly stringent standards over time. Some of the provisions of the laws have limited anthropogenic contributions to climate change as well.

Background

Air pollution has long been recognized as a problem in the United States. The passage of the Clean Air Act (CAA) in 1963 provided federal support for efforts to reverse and control air pollution. In 1970, Congress passed the Clean Air Act Extension, amending the CAA to provide for strict national ambient air quality standards (NAAQSs) and their enforcement. The 1970 and later amendments have sought to reduce atmospheric ozone, carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen oxides (NO_x), hydrocarbons, lead, and particulate matter. The 1990 amendments also set provisions for toxic air pollutants. The legislation has been primarily aimed at protecting human health and preventing or reducing acid rain, rather than mitigating climate change.

Summary of Provisions

The CAA of 1963 provided for federal help in dealing with air pollution but indicated few specifics and no standards for enforcement. The 1970 and 1990 CAA amendments have been the most important in establishing specific air pollution policies. Dating from the 1970 amendments, the Environmental Protection Agency (EPA) identified six air pollutants in the United States (and, by extension, worldwide): ozone, sulfur dioxide, nitrogen oxides, carbon monoxide, lead, and particulates. The EPA divided the United States into regions and established acceptable levels for each pollutant in each region in order to reduce pollutant levels nationwide. Some of these pollutants are generated by industries, such as the electric power industry, while others are generated by automobiles. Some of the pollutants, such as SO₂ and NO_x, lead to the production of acid rain, which harms human health, bodies of water into which the rain falls, buildings, and crops. The 1970 and 1977 amendments to the CAA led to reductions in electric power plants’ production of SO₂ and NO_x, as the plants turned to low-sulfur coal or adopted technological fixes, such as scrubbers, that removed these gases from their emissions. Automobile makers modified their engines to burn unleaded gasoline, reducing lead emissions. Decreasing ozone and CO levels proved to be more difficult.

Because of the high cost of reducing emissions, the EPA adopted standards that enabled utilities with low SO₂ emissions to trade some of their polluting capacity to utilities that were unable to meet EPA standards codified in the 1977 amendments. The 1990 CAA went further and allowed utilities to sell some of their excess capacity on the open market. This approach has led to overall reductions in SO₂ in the United States, although levels remain high in some areas.

Congress tightened standards for automobile emissions of the various pollutants with the 1977 and 1990 amendments and directed that the EPA should continue to develop even more stringent standards if ambient air pollution was not reduced. The 1990 amendments to the CAA provided for new enforcement standards for 189 toxic air pollutants such as asbestos, benzene, mercury, or cadmium compounds, as well as providing for the phasing out of stratospheric ozone-depleting substances by 1996. These standards affected various aspects of American life, from oil refineries that emitted numerous toxins to building demolition.

The CAA has been directed toward improving the health of the American people through removing or reducing various air pollutants that have been judged to be harmful to human health and by extension harmful to the environment. It has been a top-down approach that mandated ambient air quality standards and that left it up to industry to achieve the technological means to meet these standards. The record of the CAA has been mixed, but there have been some notable successes, such as the reduction of lead in the atmosphere.

Significance for Climate Change

The CAA in its various iterations has been directed toward improving human health, not dealing with climate change. Nonetheless, some of the standards of the CAA have also had an impact on the climate. In particular two greenhouse gases (GHGs), nitrous oxide (N₂O) and chlorofluorocarbons (CFCs)—which deplete stratospheric ozone—have been regulated by the CAA.

With the 1970 amendments to the CAA, Congress mandated a reduction in NO_x in the atmosphere, which helps reduce nitrous oxide. Automobile exhaust and fertilizer containing nitrogen are major contributors of nitrous oxide to the atmosphere, and coal-burning power plants contribute other nitrogen oxides. Control of NO_x has been more difficult to achieve than control of SO₂. The 1970, 1977, and 1990 CAA amendments provided for progressively tougher standards for the emission of NO_x. The 1990 amendments, for example, provided for cutting nitrogen oxide emissions by an additional 1.8 million metric tons below the 1980 levels. Although N₂O has a lower presence in the atmosphere than do other GHGs such as carbon dioxide or methane, it is estimated to contribute slightly over 6 percent of the worldwide, so reductions are important.

Nitrogen oxide compounds have long been products of industrial society, but production of CFCs has been of more recent vintage. CFCs are composed of chlorine, fluorine, and carbon atoms and are chemically almost inert. Because of this property, they came to be used as refrigerants, as well as propellants for aerosols such as deodorants. CFCs are also long-lived in the atmosphere, so once produced they will remain for a long time. When exposed to ultraviolet radiation in the upper atmosphere, CFC molecules break apart and free up chlorine atoms that, combined with oxygen in the stratosphere, help deplete the ozone layer.

Dating from the late 1970s, one CFC, CFC-11, was banned from use as a propellant. Because of the attractiveness of CFCs as refrigerants and solvents and the difficulty in obtaining substitutes, CFC-11 and two other CFC compounds (CFC-12 and CFC-113) continued in use in refrigerants, air conditioners, and industrial mechanisms. As the severity of the damage to the became recognized, pressure built to ban or curtail the use of all CFCs. The 1990 amendments to the CAA mandated the elimination of new CFCs in the United States and provided for careful handling of CFCs in existing refrigerants and air conditioners so as to limit their escape into the atmosphere. Although some countries continue to make use of CFCs, the position of the United States as a major user made American reduction quite important. Although it will be quite some time before the holes in the Arctic and Antarctic ozone layers no longer exist, the reduction of additional CFC production has decreased further damage to the ozone layer.

In sum, the Clean Air Act and its various amendments have helped in dealing with climate change, although that generally was not their intent. The CAA has regulated two GHGs, limiting their production and use. In addition, the CAA has provided a precedent for congressional action dealing with other GHGs. Despite this advancement, some areas of America continued to experience dangerously high levels of air pollution in the 2020s, such as the San Joaquin Valley. Because the United States is a major producer of GHGs, any reduction in the production of these gases by that nation will have a large impact on climate change globally.

Upon the start of his term in 2021, President Joe Biden attempted to empower the EPA to regulate power plant emissions as part of his administration’s bid to halt global warming. However, the Biden administration encountered a number of roadblocks in its attempts to do so, including a 2024 Supreme Court decision that halted the EPA’s plan to prevent pollution across state lines by cutting the emissions from power plants and factories in Western states that drift into Eastern states. Previously, in 2022, the Supreme Court determined that the EPA did not have the authority under the Clean Air Act to regulate the energy industry after attempting to place limits on carbon emissions created by power plants.

Bibliography

Blatt, Harvey. “America’s Environmental Report Card: Are We Making the Grade?” Environmental Health Perspectives, vol. 113, no. 4, Apr. 2005, doi.org/10.1289/ehp.113-a274a. Accessed 17 Jan. 2023. Provides a summary of the impact of U.S. policy on reducing air pollution and global warming.

“EPA Activities for Cleaner Air.” Environmental Protection Agency, Oct. 2022, www.epa.gov/sanjoaquinvalley/epa-activities-cleaner-air. Accessed 17 Jan. 2023.

Liptak, Adam. "Supreme Court Blocks Biden Plan on Air Pollution." The New York Times, 27 June 2024, www.nytimes.com/2024/06/27/us/politics/supreme-court-biden-air-pollution.html. Accessed 3 July 2024.

Liptak, Adam. "Supreme Court Limits E.P.A.'s Ability to Restrict Power Plant Emissions." The New York Times, 30 June 2022, www.nytimes.com/2022/06/30/us/epa-carbon-emissions-scotus.html. Accessed 3 July 2024.

Rosenbaum, Walter A. Environmental Politics and Policy. 7th ed. Washington, D.C.: CQ Press, 2008. Includes a chapter that places the CAA in the context of command-and-control environmental protection.

Somerville, Richard C. J. The Forgiving Air. Berkeley: University of California Press, 1996. Useful discussion of the impact of the CAA on air pollution and climate change.

United States, Congress, Lattanzio, Richard K. CRSReports, Congressional Research Service (CRS), 13 Sept. 2022. crsreports.congress.gov/product/pdf/RL/RL30853. Accessed 17 Jan. 2023.