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Air Pollution Prevention Under the Clean Air Act - Module 2 of 5

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Module 2: Air Pollution Prevention Under the Clean Air Act


The atmosphere is a critical common resource protected by an extensive set of laws and regulations to prevent air pollution. This module begins with air pollution law and the policies created by the federal Clean Air Act. Next, the module discusses how state and federal agencies work together to achieve important goals in environmental policy. We will then close with recent developments in U.S. air pollution prevention law.


History of Federal Air Pollution Control


In 1955, Congress passed America’s first federal law directly addressing air pollution , called the Air Pollution Control Act, which established a framework for researching and protecting air quality nationwide.[1] This initial law left most of the responsibility for pollution control to the individual states, but cross-boundary issues created by air pollution created conflicts. Congress then passed the Clean Air Act to establish a national framework for the protection of the atmosphere.[2]


The 1963 Clean Air Act had several important amendments that are still relied on. Congress passed the Motor Vehicle Air Pollution Control Act in 1965, which set standards for controlling automobile pollution emissions.[3] The next major amendment was the Air Quality Act of 1967, which expanded federal authority to regulate air pollution between states.[4]  


The Clean Air Act established the major regulatory programs that limit air pollution from stationary sources, such as factories and buildings, and mobile sources, including automobiles, farm equipment, and ships. The Act includes the National Ambient Air Quality Standards Program, State Implementation Plan requirement, New Source Performance Standards and the National Emission Standards for Hazardous Air Pollutants programs, all of which remain in force and effect today. The Clean Air Act of 1970 has been overhauled by Congress twice: once in 1977 and again in 1990. The 1977 Amendments prevented air quality deterioration in areas that have achieved their goals. The last major amendment of the Clean Air Act in 1990 addressed the challenges of acid rain, ozone depletion, and toxic air pollution. The amendment created a permitting program for buildings and increased the EPA’s enforcement authority.


Air Pollution Prevention Under the Clean Air Act


Poor air quality has been proven to negatively impact several aspects of human health, including causing respiratory issues, asthma, cancer, economic challenges and even death. Historically disadvantaged and low-income communities suffer the most from pollution, and the Clean Air Act works to protect the health and welfare of affected communities. [5]  


The Clean Air Act is our nation’s foremost law addressing air pollution and its effects on the public health, created to protect and enhance the quality of the air.[6] This act is a federal law that regulates air pollution on a national level.[7] The law is administered by the Environmental Protection Agency, created in 1970 to assist Congress and work alongside state, local, and tribal governments to enforce the new wave of environmental laws. The EPA is responsible for monitoring several environmental laws, and under the Clean Air Act, the agency plays a major role in protecting public health and improving the nation’s air quality.


The Supreme Court has rejected the idea that air pollution standards under the law can be adjusted in consideration of the economic benefits provided by a polluter. Harm-based pollution standards created under the Clean Air Act’s programs consider only human and environmental health, not economic costs.[8] In that case, Whitman v. American Trucking Association, the Court ruled that the administrator of the EPA (in that case, Christine Todd Whitman, representing the George W. Bush administration) could not consider cost of implementation in setting air quality standards because the Act itself hadn’t provided for such consideration.


The Clean Air Act primarily focuses around a handful of key policies. First, the law creates a system for cleaning up the most commonly found pollutants, called “criteria air pollutants.” Next, policies are enforced to reduce transboundary pollution, or air pollution that travels across state or international borders. A science-based program also has been designed to reduce the occurrence of acid rain and toxic air pollutants, and aims to protect the stratospheric layer, including Earth’s ozone layer.  Finally, the Clean Air Act explicitly gave the EPA the authority to regulate greenhouse gas emissions in order to prevent climate change.[9]


The Clean Air Act requires EPA to set the National Ambient Air Quality Standards, or the NAAQS (pronounced “knacks”)[10] for the criteria of air pollutants, which are considered harmful to the public’s health and the health of our ecosystems. Under the Clean Air Act, any air pollutant that the EPA considers as having adverse effects on the public health fits the definition of a criteria air pollutant.[11] Currently, these pollutants are carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter and sulfur dioxide.[12]


These pollutants are not, however, the most dangerous substances regulated by the Clean Air Act. Section 112 of the law lists the pollutants that Congress specifically identified as hazardous. The EPA Administrator is responsible for periodically reviewing the list and revising it when appropriate. Section 112 also sets emission limits by requiring the maximum degree of hazardous air pollution emissions.[13]


In 1990, Congress amended the Clean Air Act to address the harmful effects of acid rain. Congress created economic incentives for the reduction of the pollutants that cause acid rain, called a cap-and-trade program. Industries could sell emission credits by limiting their emissions and selling their allowances, providing an incentive to reduce pollution levels, and this market-based approach has proven very effective at reducing the negative impact of acid rain nationwide.[14]


Mobile and Stationary Sources of Air Pollution


The Clean Air Act is also structured to regulate mobile sources of air pollution, such as cars and farming equipment.[15] Motor vehicles are major sources of air pollution, and the EPA has developed a suite of policies that regulate vehicle emissions. The EPA maintains fuel exhaust emission standards, pollution restrictions on heavy-duty highway vehicles, gasoline quality standards, and a list of rules that apply to off-road mobile sources of air pollution including airplanes, boats, and recreational vehicles.[16]


Because the Clean Air Act was passed strictly to protect human health and the environment, the EPA can enforce air pollution restrictions that can be costly to automobile producers. Some automobile manufacturers have tried to avoid the costs of compliance with the EPA’s strict standards by creating schemes to evade the law, but many of these plans have backfired, resulting in record-breaking fines. A 2018 scandal surfaced involving Volkswagen’s U.S. companies and the emissions from certain models from their diesel cars. The EPA discovered that Volkswagen had been intentionally installing technology in certain vehicles designed to cheat air pollution tests required by the Clean Air Act. The company-wide conspiracy continued for several years, affecting nearly 600,000 vehicles sold between 2009 and 2016. Volkswagen’s actions amounted to a criminal violation of the Clean Air Act, and the company eventually pled guilty to three felonies. To ensure this wouldn’t happen again, the EPA slammed Volkswagen with $4.3 billion in penalties and damages.[17]


Under Section 111 of the Clean Air Act, the EPA must set air quality standards for stationary sources of air pollution separately from mobile source standards. New stationary sources of air pollution are also regulated differently than previously existing ones. New Stationary Source Standards are established by evaluating the amount of air pollution a stationary source may emit based on potential endangerment of the public health and welfare. Unlike other sections of the Clean Air Act, the EPA may consider the cost of achieving reduced emissions balanced against health and environmental impacts when making technology-based air pollution decisions. [18] Existing stationary sources of air pollution, on the other hand, are held to looser standards.


An existing source may be considered a new source (subjecting it to the tougher regulations) if it is modified in a significant way. A federal appellate court has defined the change from an existing to new source as any improvement that affects more than 20% of the value of the stationary source to a more tightly-regulated air pollution source.[19] Courts determine these upgrades on a case-by-case basis. One major case brought by an environmental nonprofit against national electricity producer Duke Energy Corporation argued that alterations made to several of the company’s power plants qualified as modifications that made the plants subject to stricter regulation. The question went all the way to the Supreme Court, which decided that so long as the EPA’s view of the modifications are reasonable, Duke Energy Corporation had to abide by them.[20]


The Clean Air Act may be complicated, but it’s been very effective at reducing air pollution around the country. From the time the modern Clean Air Act was passed in 1970 until 2017, emissions for all the criteria air pollutants decreased by 73 percent.[21] Studies have shown that the Clean Air Act has resulted in a 25 percent drop in ground-level ozone, a component of smog. The law has also reduced the amount of mercury in the environment by 45 percent, sulfur dioxide by 71 percent, nitrogen dioxide by 46 percent, and a whopping 92 percent reduction of lead contamination in the air.[22] It’s hard to imagine the state of America’s air quality without this important law.


Federal, State and Local Cooperation in the Prevention of Air Pollution


The EPA administers and enforces the Clean Air Act and has the authority to punish violators with monetary penalties. However, the law also places responsibility on federal, state, local and tribal governments to control air pollution within their borders, requiring these governments to create and enforce plans to maintain air quality standards. The Clean Air Act also requires these public organizations to control pollution emissions that travel across state or international borders.[23]


The EPA and local governments work together to prevent and remediate air pollution, but they each have their roles. For each criteria of air pollutants, the EPA sets, reviews, and revises standards, and determines whether the areas have met the appropriate standards.[24] Once the standards are set and published by the federal agency, state and local governments must step in to act.


The EPA’s standards for criteria pollutants are used by states to develop their own State Implementation Plans, drafted by individual states and sent to EPA Administrators for review and authorization. The EPA administrator may endorse a state implementation plan that’s compliant with federal law. However, if it’s not approved within two years, the administrator must propose a federal implementation plan for the state to meet the appropriate standards.[25]


Modern Developments


The Clean Air Act has been subject to legal challenges and judicial inquiry in recent years. A landmark case under the Clean Air Act was Massachusetts v. EPA, in which the Supreme Court concluded that carbon and other emissions that may contribute to global warming are, in fact, air pollutants covered by the Clean Air Act.[26] Because of the EPA’s authority under the Act, the EPA could continue to regulate emissions in the hopes of climate change prevention.[27]   


Following this decision, in 2009 the EPA issued the opinion that greenhouse gas emissions were endangering the public health and welfare and it sought to limit emissions from cars and trucks. The EPA required that all new or modified stationary sources of greenhouse gas pollution obtain permits and emission controls before being constructed.


Around the same time that the Supreme Court was reviewing the Massachusetts v. EPA case, Congress was working on the 2010 Clean Air Act Amendments. The amendments’ objectives were to eliminate chlorofluorocarbons to protect the ozone layer. This was a huge success, although some opine that the 2010 amendment was necessary to comply with the U.S. ratification of the Montreal Protocol, an international treaty designed to protect the ozone layer. [28]


The Clean Power Plan of 2015 was a policy created to set emission guidelines for coal-fired powerplants. The guidelines limited the amount of carbon dioxide emissions power plants could emit. Supporters defended the policy change because it was designed to slow the pace of climate change and encourage older coal plants to shift toward efficiency improvements, but as of late 2018, the Trump administration was proposing to roll back the Clean Power Plan’s environmental regulations. Many critics are concerned that this policy will reduce environmental benefits created by the plan without resulting in economic benefits to the coal industry promised by the current administration. [29] As a result, the future of the Clean Power Plan is unknown.





The Clean Air Act has played a critical role in improving and maintaining air quality nationwide. The law focuses on technological solutions to air pollution, resulting in new levels of innovation while still addressing the challenges that arise as more people live and work in the United States. The next module analyzes America’s system of surface water protection, focusing on the policies created by the Clean Water Act and the Safe Drinking Water Act.





[1]  Air Pollution Control Act, Pub.L. 84–159, ch. 360, 69 Stat. 322 (1955).

[2]  42 U.S.C. § 7401 et seq.

[3] Motor Vehicle Air Pollution Control Act, Pub.L. 89–272, 79 Stat. 992, (1965).

[4] Air Quality Act, Pub.L. 90–148, 81 Stat. 485 (1967).

[5] EPA, Clean Air Act Overview, Air Pollution: Current and Future Challenges, https://www.epa.gov/clean-air-act-overview/air-pollution-current-and-future-challenges (Last Viewed September 17, 2018).

[6] See e.g. Nat. Res. Def. Council, Inc. v. U.S.E.P.A., 507 F.2d 905, 908 (9th Cir. 1974).

[9] EPA, Clean Air Act Overview, Clean Air Act Text, https://www.epa.gov/clean-air-act-overview/clean-air-act-text

 (Last Viewed September 17, 2018).

[11] 42 U.S.C. § 7408(a)(2)(B).

[12] EPA, Clean Air Act Overview, NAAQS Table, https://www.epa.gov/criteria-air-pollutants/naaqs-table (Last Viewed September 17, 2018).

[14] EPA, Acid Rain Program, Overview, https://www.epa.gov/airmarkets/acid-rain-program (last viewed September 27, 2018).

[16] EPA, Emissions Standards Reference Guide, All EPA Emissions Standards, https://www.epa.gov/emission-standards-reference-guide/all-epa-emission-standards (Last Viewed October 2, 2018).

[17] EPA, Volkswagen Violations, Learn About Volkswagen Violations, https://www.epa.gov/vw/learn-about-volkswagen-violations (Last Viewed October 2, 2018).

[19] New York v. E.P.A., 443 F.3d 880 (D.C. Cir. 2006).

[21] EPA, Clean Air Act Overview, The Clean Air Act in a Nutshell: How It Works, https://www.epa.gov/clean-air-act-overview/clean-air-act-nutshell-how-it-works (Last Viewed September 17, 2018).

[22] Union of Concerned Scientists, Clean Air Act, https://www.ucsusa.org/global-warming/solutions/reduce-emissions/the-clean-air-act.html#.W6KWaWRKgy5 (Last Viewed September 16, 2018).

[23] Firestone, David B., Reed, Frank C., Stanton, Caitlin R., Environmental Law for Non-Lawyers, Fifth Edition, p. 105, SoRo Press, 2014; 42 U.S.C. § 7408-§12.

[24] EPA, Clean Air Act Overview, Process of Reviewing the National Ambient Air Quality Standards, https://www.epa.gov/criteria-air-pollutants/process-reviewing-national-ambient-air-quality-standards (Last Viewed September 17, 2018).

[25] 42 U.S.C.A. § 7410.

[27] Firestone, David B., Reed, Frank C., Stanton, Caitlin R., Environmental Law for Non-Lawyers, Fifth Edition, p. 33, SoRo Press, 2014.

[28] Center for Biological Diversity, The Clean Air Act, https://www.biologicaldiversity.org/programs/climate_law_institute/global_warming_litigation/clean_air_act/index.html (Last Viewed September 16, 2018).