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Clean Air Act (United States)

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.

For other uses, see Clean Air Act (disambiguation).

Long title

An Act to improve, strengthen, and accelerate programs for the prevention and abatement of air pollution, as amended.

CAA

42 U.S.C. ch. 85 (§§ 7401-7671q)

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.

Risk Assessment. Although not a regulatory program per se, many EPA regulatory programs involve risk assessment and management. Over the years, EPA has undertaken to unify and organize its many risk assessment processes. The 1990 CAA Amendments created a Commission on Risk Assessment and Management tasked with making recommendations for a risk assessment framework,[40] and many subsequent reports have built on this work.

[39]

Visibility and Regional Haze. EPA monitors visibility and air clarity (haze) at 156 protected parks and wilderness areas, and requires states to develop plans to improve visibility by reducing pollutants that contribute to haze.

[41]

Interstate pollution control. The Clean Air Act's "good neighbor" provision requires states to control emissions that will significantly contribute to NAAQS nonattainment or maintenance in a downwind state.[43] EPA has struggled to enact regulations that implement this requirement for many years. It developed the "Clean Air Interstate Rule" between 2003 and 2005, but this was overturned by the courts in 2008. EPA then developed the Cross-State Air Pollution Rule between 2009 and 2011, and it continues to be litigated as EPA updates it.

[42]

Startup, Shutdown, & Malfunction. EPA promulgates rules for states to address excess emissions during periods of startup, shutdown, and malfunction, when facility emissions may temporarily be much higher than standard regulatory limits.

[44]

The Clean Air Act and states[edit]

State implementation plans[edit]

The 1963 act required development of State Implementation Plans (SIPs) as part of a cooperative federalist program for developing pollution control standards and programs.[45] 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.[46]


The 1970 Amendments imposed eight criteria that an implementation plan must meet.[47] 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).[48][49]

Current challenges[edit]

As poor air quality is still an issue in the United States, it has been noted that it is 1.5 times more likely for an ethnic minority person to live in an area burdened with air pollution than it is for an ethnic majority person.[94] While the United States is still being affected by the COVID-19 pandemic, research has shown that if someone lives in an area that experiences air pollution, they are 8% more likely to experience long-term COVID effects, potentially with a fatal outcome. This creates a disparity between minority and majority communities of Americans, even though the air pollution that these communities face is often a result of redlining, which places minority communities in areas where industries that heavily pollute the air, as well as high-traffic roadways, reside.[95]


Solutions proposed by the Sierra Club and the Environmental Protection Agency (EPA) include funding clean energy transportation services, lowering acceptable emission levels, and enforcing the Clean Air Act that is already in place more intensely.[96] While the Clean Air Act has been generally effective since it was enacted in 1970, there have been efforts from the fossil fuel industry to override it which have led to worse air pollution in many communities.[97]


An example of an area where the Clean Air Act has not been too effective is the San Joaquin Valley which experiences poor air quality conditions that stem from harmful agricultural practices, heavy traffic on major roadways, and the oil industry.[96] Research shows that the leading air pollutant in the region is known as PM 2.5, or fine particulate matter, and causes health issues in pregnant women exposed to it, such as more severe asthma, decreased FEV1, compromised immunity, and an increased risk of premature birth.[98] Other symptoms that come from exposure to PM 2.5 include chronic bronchitis, reduced lung function in children, and heart and lung-related hospitalizations that can potentially lead to premature death especially if the individual has previous health concerns. In 2004, a mass decrease in PM 2.5 pollution occurred because of a decline in agricultural and biomass burning practices; however, it is still a common occurrence today and PM 2.5 levels have increased. Organizations such as the California Air Resources Board (CARB) have recommended that more sufficient regulations be implemented in the San Joaquin Valley to reduce toxic emissions into the atmosphere.[99] There are now efforts from the EPA, the CARB, and the San Joaquin Valley Air Pollution Control District to enforce regulations from the Clean Air Act and fund further efforts to live in a more sustainable fashion.

Future challenges[edit]

As of 2017, some US cities still do not meet all national ambient air quality standards. It is likely that tens of thousands of premature deaths are still being caused by fine-particle pollution and ground-level ozone pollution.[35]


Climate change poses a challenge to the management of conventional air pollutants in the United States due to warmer, dryer summer conditions that can lead to increased air stagnation episodes. Prolonged droughts that may contribute to wildfires would also result in regionally high levels of air particles.[100]


Transboundary air pollution (both entering and exiting the United States) is not directly regulated by the Clean Air Act, requiring international negotiations and ongoing agreements with other nations, particularly Canada and Mexico.[101]


Environmental justice continues to be an ongoing challenge for the Clean Air Act. By promoting pollution reduction, the Clean Air Act helps reduce heightened exposure to air pollution among minority and low-income communities.[102] But African American populations are "consistently over represented" in areas with the poorest air quality.[103] Dense populations of low-income and minority communities inhabit the most polluted areas across the United States, which is considered to exacerbate health problems among these populations.[104] High levels of exposure to air pollution is linked to several health conditions, including asthma, cancer, premature death, and infant mortality, each of which disproportionately impact minority and low-income communities.[105] The pollution reduction achieved by the Clean Air Act is associated with a decline in each of these conditions and can promote environmental justice for communities that are disproportionately impacted by air pollution and diminished health status.[105]

(2005; amended 2010)

Diesel Emissions Reduction Act

of the United States Code from the LII

As codified in 42 U.S.C. chapter 85

of the United States Code from the US House of Representatives

As codified in 42 U.S.C. chapter 85

as amended (PDF/details) in the GPO Statute Compilations collection

Clean Air Act

from the EPA

Summary of the Clean Air Act

EPA Enforcement and Compliance History Online

. Congressional Research Service report, 2022.

Clean Air Act: A Summary of the Act and Its Major Requirements

EPA Alumni Association Oral History Video "Early Implementation of the Clean Air Act of 1970 in California"