Clean Air Act (United States)

Clean Air Act
Long title	An Act to improve, strengthen, and accelerate programs for the prevention and abatement of air pollution, as amended.
Acronyms (colloquial)	CAA
Enacted by	the 88th United States Congress
Effective	December 17, 1963
Codification
U.S.C. sections created	42 U.S.C. ch. 85 (§§ 7401-7671q)
Legislative history
	Passed the House on July 24, 1963 (273–102); Signed into law by President Lyndon B. Johnson on December 17, 1963;
Major amendments
	Clean Air Act of 1963 (77 Stat. 392, Pub. L. 88–206); Motor Vehicle Air Pollution Control Act of 1965 (79 Stat. 992, Pub. L. 89–272); Air Quality Act of 1967 (81 Stat. 485, Pub. L. 90–148); Clean Air Amendments of 1970 (84 Stat. 1676, Pub. L. 91–604); Clean Air Act Amendments of 1977 (91 Stat. 685, Pub. L. 95–95); Clean Air Act Amendments of 1990 (104 Stat. 2468, Pub. L. 101–549); Inflation Reduction Act (136 Stat. 2063, Pub. L. 117–169 (text) (PDF))
United States Supreme Court cases
	Union Elec. Co. v. EPA, 427 U.S. 246 (1976); Chevron v. NRDC, 467 U.S. 837 (1984); Whitman v. Am. Trucking Ass'ns, 531 U.S. 457 (2001); Alaska Department of Environmental Conservation v. EPA, 540 U.S. 461 (2004); Engineer Manufacturers Association v. South Coast Air Quality Management District, 541 U.S. 246 (2004); Department of Transportation v. Public Citizen, 541 U.S. 752 (2004); Massachusetts v. EPA, 549 U.S. 497 (2007); Environmental Defense v. Duke Energy Corp., 549 U.S. 561 (2007); American Electric Power Co. v. Connecticut, 564 U.S. 410 (2011); EPA v. EME Homer City Generation, L. P., 572 U.S. 489 (2014); Utility Air Regulatory Group v. Environmental Protection Agency, 573 U.S. 302 (2014); Michigan v. EPA, No. 14-46, 576 U.S. ___ (2015); HollyFrontier Cheyenne Refining, LLC v. Renewable Fuels Assn., No. 20-472, 594 U.S. ___ (2021); West Virginia v. EPA, No. 20-1530, 597 U.S. ___ (2022); Ohio v. EPA, No. 23A349, 603 U.S. ___ (2024); Oklahoma v. EPA, No. 23-1067, 605 U.S. ___ (2025); EPA v. Calumet Shreveport Refining, No. 23-1229, 605 U.S. ___ (2025);

The Clean Air Act (CAA) is the United States' primary federal air quality law, intended to reduce and control air pollution nationwide. Initially enacted in 1963 and amended many times since, it is one of the United States' first and most influential modern environmental laws.

As with many other major U.S. federal environmental statutes, the Clean Air Act is administered by the U.S. Environmental Protection Agency (EPA), in coordination with state, local, and tribal governments.^[1]^: 2–3 EPA develops extensive administrative regulations to carry out the law's mandates. Associated regulatory programs, which are often technical and complex, implement these regulations. Among the most important, the National Ambient Air Quality Standards program sets standards for concentrations of certain pollutants in outdoor air, and the National Emissions Standards for Hazardous Air Pollutants program which sets standards for emissions of particular hazardous pollutants from specific sources. Other programs create requirements for vehicle fuels, industrial facilities, and other technologies and activities that impact air quality. Newer programs tackle specific problems, including acid rain, ozone layer protection, and climate change.

The CAA has been challenged in court many times, both by environmental groups seeking more stringent enforcement and by states and utilities seeking greater leeway in regulation.

Although its exact benefits depend on what is counted, the Clean Air Act has substantially reduced air pollution and improved US air quality—benefits which EPA credits with saving trillions of dollars and many thousands of lives each year.

^ "The Plain English Guide to the Clean Air Act" (PDF). Washington, DC: US Environmental Protection Agency (EPA). April 2007. p. 19. EPA 456/K-07-001.

[EPA_Plain_English_Guide-1] "The Plain English Guide to the Clean Air Act" (PDF). Washington, DC: US Environmental Protection Agency (EPA). April 2007. p. 19. EPA 456/K-07-001.

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