Clean Air Act

In the United States, the "Clean Air Act" typically refers to the codified statute at 42 U.S.C. ch. 85. That statute is the product of multiple acts of Congress, one of which—the 1963 act—was actually titled the Clean Air Act, and another of which—the 1970 act—is most often referred to as such. In the U.S. Code, the statute itself is divided into subchapters, and the section numbers are not clearly related to the subchapters. However, in the bills that created the law, the major divisions are called "Titles", and the law's sections are numbered according to the title (e.g., Title II begins with Section 201). In practice, EPA, courts, and attorneys often use the latter numbering scheme.

Although many parts of the statute are quite detailed, others set out only the general outlines of the law's regulatory programs, and leave many key terms undefined. Responsible agencies, primarily EPA, have therefore developed administrative regulations to carry out Congress's instructions. EPA's proposed and final regulations are published in the Federal Register, often with lengthy background histories. The existing CAA regulations are codified at 40 C.F.R. Subchapter C, Parts 50–98. These Parts more often correspond to the Clean Air Act's major regulatory programs.

The following are major regulatory programs under the Clean Air Act.

The National Ambient Air Quality Standards (NAAQS) govern how much ground-level ozone (O3), carbon monoxide (CO), particulate matter (PM10, PM2.5), lead (Pb), sulfur dioxide (SO2), and nitrogen dioxide (NO2) are allowed in the outdoor air. The NAAQS set the acceptable levels of certain air pollutants in the ambient air in the United States. Prior to 1965, there was no national program for developing ambient air quality standards, and prior to 1970 the federal government did not have primary responsibility for developing them.

The 1970 CAA amendments required EPA to determine which air pollutants posed the greatest threat to public health and welfare and promulgate NAAQS and air quality criteria for them. …

The 1963 act required development of State Implementation Plans (SIPs) as part of a cooperative federalist program for developing pollution control standards and programs. Rather than create a solely national program, the CAA imposes responsibilities on the U.S. states to create plans to implement the Act's requirements. EPA then reviews, amends, and approves those plans. EPA first promulgated SIP regulations in 1971 and 1972.

The 1970 Amendments imposed eight criteria that an implementation plan must meet. The EPA is required to approve plans that adhere to the Senate's three-year mandate for primary air quality standards even if the Agency feels the plan does not appear feasible. In Union Electric Co. v. Environmental Protection Agency the Supreme Court considered whether the Agency was required to reject plans that were not technologically or economically feasible. The court decided that states could adopt emission standards stricter than national standards and "force" technology (i.e. require installation of more advanced technologies).

The 1977 CAA Amendments added SIP requirements for areas that had not attained the applicable NAAQS ("nonattainment areas"). In these areas, states were required to adopt plans that made "reasonable further progress" toward attainment until all "reasonably available control measures" could be adopted. As progress on attainment was much slower than Congress originally instructed, major amendments to SIP requirements in nonattainment areas were part of the 1990 CAA Amendments.

The 1977 CAA Amendments modified the SIP requirements by adding "Prevention of Significant Deterioration" (PSD) requirements. These requirements protect areas, including particularly wilderness areas and national parks, that already met the NAAQS. The PSD provision requires SIPs to preserve good quality air in addition to cleaning up bad air. The new law also required New Source Review (investigations of proposed construction of new polluting facilities) to examine whether PSD requirements would be met.

The Clean Air Act provided the EPA with enforcement authority and requiring states to develop State Implementation Plans for how they would meet new national ambient air quality standards by 1977. This cooperative federal model continues today. …

Between the Second Industrial Revolution and the 1960s, the United States experienced increasingly severe air pollution. Following the 1948 Donora smog event, the public began to discuss air pollution as a major problem, states began to pass a series of laws to reduce air pollution, and Congress began discussing whether to take further action in response. At the time, the primary federal agencies interested in air pollution were the United States Bureau of Mines, which was interested in "smoke abatement" (reducing smoke from coal burning), and the United States Public Health Service, which handled industrial hygiene and was concerned with the causes of lung health problems.

After several years of proposals and hearings, Congress passed the first federal legislation to address air pollution in 1955. The Air Pollution Control Act of 1955 authorized a research and training program, sending $3 million per year to the U.S. Public Health Service for five years, but did not directly regulate pollution sources. The 1955 Act's research program was extended in 1959, 1960, and 1962 while Congress considered whether to regulate further.

Beginning in 1963, Congress began expanding federal air pollution control law to accelerate the elimination of air pollution throughout the country. The new law's programs were initially administered by the U.S. Secretary of Health, Education, and Welfare, and the Air Pollution Office of the U.S. Public Health Service, until they were transferred to the newly created EPA immediately before major amendments in 1970. EPA has administered the Clean Air Act ever since, and Congress added major regulatory programs in 1977 and 1990. Most recently, the U.S. Supreme Court's ruling in Massachusetts v. EPA resulted in an expansion of EPA's CAA regulatory activities to cover greenhouse gases.

The Clean Air Act of 1963 (Pub. L. 88–206) was the first federal legislation to permit the U.S. federal government to take direct action to control air pollution. …

According to a 2022 review study in the Journal of Economic Literature, there is overwhelming causal evidence that shows that the CAA improved air quality.

According to a 2011 study by EPA, when compared to the baseline of the 1970 and 1977 regulatory programs, by 2020 the updates initiated by the 1990 Clean Air Act Amendments would be costing the United States about $60 billion per year, while benefiting the United States (in monetized health and lives saved) about $2 trillion per year. In 2020, a study prepared for the Natural Resources Defense Council estimated annual benefits at 370,000 avoided premature deaths, 189,000 fewer hospital admissions, and net economic benefits of up to $3.8 trillion (32 times the cost of the regulations). Other studies have reached similar conclusions.

Mobile sources including automobiles, trains, and boat engines have become 99% cleaner for pollutants like hydrocarbons, carbon monoxide, nitrogen oxides, and particle emissions since the 1970s. The allowable emissions of volatile organic chemicals, carbon monoxide, nitrogen oxides, and lead from individual cars have also been reduced by more than 90%, resulting in decreased national emissions of these pollutants despite a more than 400% increase in total miles driven yearly. Since the 1980s, 1/4th of ground level ozone has been cut, mercury emissions have been cut by 80%, and since the change from leaded gas to unleaded gas 90% of atmospheric lead pollution has been reduced. A 2018 study found that the Clean Air Act contributed to the 60% decline in pollution emissions by the manufacturing industry between 1990 and 2008.

Since its inception, the authority given to the EPA by Congress and the EPA's rulemaking within the Clean Air Act has been subject to numerous lawsuits. Some of the major suits where the Clean Air Act has been focal point of litigation include the following: