Clean Air Act (United States)

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Clean Air Act
Great Seal of the United States (obverse).svg
Long titleAn Act to improve, strengthen, and accelerate programs for the prevention and abatement of air pollution.
Acronyms (colloquial)CAA
NicknamesClean Air Act of 1963
Enacted bythe 88th United States Congress
EffectiveDecember 17, 1963
Public law 88-206
Statutes at Large 77  Stat.   392
Titles amended 42 U.S.C.: Public Health and Social Welfare
U.S.C. sections amended 42 U.S.C. ch. 85,subch. I § 7401 et seq.
Legislative history
  • Introduced in the Houseas H.R. 6518 by Kenneth A. Roberts (DAL) on July 9, 1963
  • Committee consideration by House Energy and Commerce
  • Passed the House on July 24, 1963 (275-104)
  • Passed the Senate on November 19, 1963 (passed voice vote, in lieu of S. 432)
  • Reported by the joint conference committee on December 5, 1963; agreed to by the House on December 10, 1963 (276-112) and by the Senate on December 10, 1963 (passed voice vote)
  • Signed into law by President Lyndon B. Johnson on December 15, 1963
Major amendments
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 Act Extension 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)
United States Supreme Court cases
Union Elec. Co. v. EPA, 427 U.S. 246 (1976)
Chevron USA v. Natural Resources Defense Council, 467 U.S. 837 (1984)
Whitman v. American Trucking Ass'ns, Inc., 531 U.S. 457 (2001)

The Clean Air Act of 1963 (42 U.S.C. § 7401) is a United States federal law designed to control air pollution on a national level. [1] It is one of the United States' first and most influential modern environmental laws, and one of the most comprehensive air quality laws in the world. [2] [3] As with many other major U.S. federal environmental statutes, it is administered by the U.S. Environmental Protection Agency (EPA), in coordination with state, local, and tribal governments. [4] Its implementing regulations are codified at 40 C.F.R. Sub-chapter C, Parts 50-97.

Title 42 of the United States Code is the United States Code dealing with public health, social welfare, and civil rights.

Air pollution introduction of particulates, biological molecules, or other harmful materials into the Earths atmosphere

Air pollution occurs when harmful or excessive quantities of substances including the gases (CO2, CO, SO2, NO, CH4, CFC, Radon, etc.), particles (both organic and inorganic), and biological molecules are introduced into Earth's atmosphere. It may cause diseases, allergies and even death to humans; it may also cause harm to other living organisms such as animals and food crops, and may damage the natural or built environment. Both human activity and natural processes can generate air pollution.

Environmental law rules of law, promoting the protection of the natural environment

Environmental law, also known as environmental and natural resources law, is a collective address environmental pollution. A related but distinct set of regulatory regimes, now strongly influenced by environmental legal principles, focus on the management of specific natural resources, such as forests, minerals, or fisheries. Other areas, such as environmental impact assessment, may not fit neatly into either category, but are nonetheless important components of environmental law.


The 1955 Air Pollution Control Act was the first U.S. federal legislation that pertained to air pollution; it also provided funds for federal government research of air pollution. [4] The first federal legislation to actually pertain to "controlling" air pollution was the Clean Air Act of 1963. [5] The 1963 act accomplished this by establishing a federal program within the U.S. Public Health Service and authorizing research into techniques for monitoring and controlling air pollution. [6]

Air Pollution Control Act

The Air Pollution Control Act of 1955 was the first Clean Air Act enacted by Congress to address the national environmental problem of air pollution on July 14, 1955. This was "an act to provide research and technical assistance relating to air pollution control". The act "left states principally in charge of prevention and control of air pollution at the source". The act declared that air pollution was a danger to public health and welfare, but preserved the "primary responsibilities and rights of the states and local government in controlling air pollution".

It was first amended in 1965, by the Motor Vehicle Air Pollution Control Act, which authorized the federal government to set required standards for controlling the emission of pollutants from certain automobiles, beginning with the 1968 models. A second amendment, the Air Quality Act of 1967, enabled the federal government to increase its activities to investigate enforcing interstate air pollution transport, and, for the first time, to perform far-reaching ambient monitoring studies and stationary source inspections. The 1967 act also authorized expanded studies of air pollutant emission inventories, ambient monitoring techniques, and control techniques. [7] While only six states had air pollution programs in 1960, all 50 states had air pollution programs by 1970 due to the federal funding and legislation of the 1960s. [8] Amendments approved in 1970 greatly expanded the federal mandate, requiring comprehensive federal and state regulations for both stationary (industrial) pollution sources and mobile sources. It also significantly expanded federal enforcement. Also, EPA was established on December 2, 1970 for the purpose of consolidating pertinent federal research, monitoring, standard-setting and enforcement activities into one agency that ensures environmental protection. [9] [10]

A major stationary source is a source that emits more than a certain amount of a pollutant as defined by the U.S. Environmental Protection Agency (EPA). The amount of pollutants allowed for certain new sources is defined by the EPA's New Source Performance Standards (NSPRS).

Mobile source air pollution

Mobile source air pollution includes any air pollution emitted by motor vehicles, airplanes, locomotives, and other engines and equipment that can be moved from one location to another. Many of these pollutants contribute to environmental degradation and have negative effects on human health. To prevent unnecessary damage to human health and the environment, environmental regulatory agencies such as the U.S. Environmental Protection Agency have established policies to minimize air pollution from mobile sources. Similar agencies exist at the state level. Due to the large number of mobile sources of air pollution, and their ability to move from one location to another, mobile sources are regulated differently from stationary sources, such as power plants. Instead of monitoring individual emitters, such as an individual vehicle, mobile sources are often regulated more broadly through design and fuel standards. Examples of this include corporate average fuel economy standards and laws that ban leaded gasoline in the United States. The increase in the number of motor vehicles driven in the U.S. has made efforts to limit mobile source pollution challenging. As a result, there have been a number of different regulatory instruments implemented to reach the desired emissions goals.

Further amendments were made in 1990 to address the problems of acid rain, ozone depletion, and toxic air pollution, and to establish a national permit program for stationary sources, and increased enforcement authority. The amendments also established new auto gasoline reformulation requirements, set Reid vapor pressure (RVP) standards to control Evaporative emissions from gasoline, and mandated new gasoline formulations sold from May to September in many states. Reviewing his tenure as EPA Administrator under President George H. W. Bush, William K. Reilly characterized passage of the 1990 amendments to the Clean Air Act as his most notable accomplishment. [11]

Acid rain rain that is unusually acidic

Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions. It can have harmful effects on plants, aquatic animals and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. Some governments have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the atmosphere with positive results. Nitrogen oxides can also be produced naturally by lightning strikes, and sulfur dioxide is produced by volcanic eruptions. Acid rain has been shown to have adverse impacts on forests, freshwaters and soils, killing insect and aquatic life-forms, causing paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and statues as well as having impacts on human health.

Ozone depletion Stratospheric phenomena of Earth

Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone around Earth's polar regions. The latter phenomenon is referred to as the ozone hole. There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events.

Reid vapor pressure (RVP) is a common measure of the volatility of gasoline and other petroleum products. It is defined as the absolute vapor pressure exerted by the vapor of the liquid and any dissolved gases/moisture at 37.8 °C (100 °F) as determined by the test method ASTM-D-323, which was first developed in 1930 and has been revised several times. The test method measures the vapor pressure of gasoline, volatile crude oil, jet fuels, naphtha, and other volatile petroleum products but is not applicable for liquefied petroleum gases. ASTM D323-15a requires that the sample be chilled to 0-1 degrees Celsius and then poured into the apparatus; for any material that solidifies at this temperature, this step cannot be performed. RVP is commonly reported in kilopascals or pounds per square inch and represents volatization at atmospheric pressure because ASTM-D-323 measures the gauge pressure of the sample in a non-evacuated chamber.

The Clean Air Act was the first major environmental law in the United States to include a provision for citizen suits. Numerous state and local governments have enacted similar legislation, either implementing federal programs or filling in locally important gaps in federal programs.

In the United States, a citizen suit is a lawsuit by a private citizen to enforce a statute. Citizen suits are particularly common in the field of environmental law.


Counties in the United States with one or more National Ambient Air Quality Standards not met as of June 2017 Counties Designated "Nonattainment" for the National Ambient Air Quality Standards (NAAQS).svg
Counties in the United States with one or more National Ambient Air Quality Standards not met as of June 2017

Title I: Programs and Activities

Graph showing decreases in US air pollution concentrations during 1990 to 2015 National Air Quality Concentration Averages 1990-2015 US EPA.png
Graph showing decreases in US air pollution concentrations during 1990 to 2015

Part A: Air Quality and Emissions Limitations

This section of the act declares that protecting and enhancing the nation's air quality promotes public health. The law encourages to prevent regional air pollution and control programs. It also provides technical and financial assistance for preventing air pollution at both state and local governments. Additional sub chapters cover cooperation, research, investigation, training, and other activities. Grants for air pollution planning and control programs, and interstate air quality agencies and program cost limitations are also included in this section. [12]

Environmental health public health branch focused on environmental impacts on human health

Environmental health is the branch of public health concerned with all aspects of the natural and built environment affecting human health. Environmental health is focused on the natural and built environments for the benefit of human health. The major subdisciplines of environmental health are: environmental science; environmental and occupational medicine, toxicology and epidemiology.

The act mandates air quality control regions, designated as attainment vs non-attainment. Non-attainment areas do not meet national standards for primary or secondary ambient air quality. Attainment areas meet these standards, while unclassified areas cannot be classified based on the available information. [12]

Air quality criteria, national primary and secondary ambient air quality standards, state implementation plans and performance standards for new stationary sources are covered in Part A as well. The list of hazardous air pollutants that the act establishes includes compounds of Acetaldehyde, benzene, chloroform, Phenol, and selenium. The list also includes mineral fiber emissions from manufacturing or processing glass, rock or slag fibers as well as radioactive atoms. The list can periodically be modified. The act lists unregulated radioactive pollutants such as cadmium, arsenic, and poly cyclic organic matter and it mandates listing them if they will cause or contribute to air pollution that endangers public health, under section 7408 or 7412. [12]

The remaining sub-chapters cover smokestack heights, state plan adequacy, and estimating emissions of carbon monoxide, volatile organic compounds, and oxides of nitrogen from area and mobile sources. Measures to prevent unemployment or other economic disruption include using local coal or coal derivatives to comply with implementation requirements. The final sub chapter in this act focuses on land use authority. [12]

Part B: Ozone Protection

Because of advances in the atmospheric chemistry, this section was replaced by Title VI when the law was amended in 1990. [13]

This change in the law reflected significant changes in scientific understanding of ozone formation and depletion. Ozone absorbs UVC light and shorter wave UVB, and lets through UVA, which is largely harmless to people. Ozone exists naturally in the stratosphere, not the troposphere. It is laterally distributed because it is destroyed by strong sunlight, so there is more ozone at the poles. Ozone is created when O2 comes in contact with photons from solar radiation. Therefore, a decrease in the intensity of solar radiation also results in a decrease in the formation of ozone in the stratosphere. This exchange is known as the Chapman mechanism:

O2 + UV photon → 2 O (note that atmospheric oxygen as O is highly unstable)
O + O2 + M → O3 (O3 is Ozone) + M
M represents a third molecule, needed to carry off the excess energy of the collision of O + O2.

Atmospheric freon and chlorofluorocarbons (CFCs) contribute to ozone depletion (Chlorine is a catalytic agent in ozone destruction). Following discovery of the ozone hole in 1985, the 1987 Montreal Protocol successfully implemented a plan to replace CFCs and was viewed by some environmentalists as an example of what is possible for the future of environmental issues, if the political will is present.

Part C - Prevention of Significant Deterioration of Air Quality

The Clean Air Act requires permits to build or add to major stationary sources of air pollution. This permitting process, known as New Source Review (NSR), applies to sources in areas that meet air quality standards as well as areas that are unclassified. [14] Permits in attainment or unclassified areas are referred to as Prevention of Significant Deterioration (PSD) permits, while permits for sources located in nonattainment areas are referred to as non attainment area (NAA) permits. [15]

The fundamental goals of the PSD program are to:

  1. prevent new non-attainment areas by ensuring economic growth in harmony with existing clean air;
  2. protect public health and welfare from any adverse effects;
  3. preserve and enhance the air quality in national parks and other areas of special natural recreational, scenic, or historic value. [15] :3

Part D: Plan Requirements for Non-attainment Areas

Under the Clean Air Act states are required to submit a plan for non-attainment areas to reach attainment status as soon as possible but in no more than five years, based on the severity of the air pollution and the difficulty posed by obtaining cleaner air.

The plan must include:

  • an inventory of all pollutants
  • permits
  • control measures, means and techniques to reach standard qualifications
  • contingency measures

The plan must be approved or revised if required for approval, and specify whether local governments or the state will implement and enforce the various changes. Achieving attainment status makes a request for reevaluation possible. It must include a plan for maintenance of air quality.

Title II: Emission Standards for Moving Sources

Graph showing decreases in US air pollution emissions from transportation sources during 1980-2015, while US population and economic activity increased. Comparison of Growth Areas and Emissions 1980-2015 US EPA.png
Graph showing decreases in US air pollution emissions from transportation sources during 1980-2015, while US population and economic activity increased.

Part A: Motor Vehicle Emission and Fuel Standards

Sub-chapters of Title II cover state standards and grants, prohibited acts and actions to restrain violations, as well as a study of emissions from non road vehicles (other than locomotives) to determine whether they cause or contribute to air pollution. Motorcycles are treated in the same way as automobiles under the emission standards for new motor vehicles or motor vehicle engines. The last few sub chapters deal with high altitude performance adjustments, motor vehicle compliance program fees, prohibition on production of engines requiring leaded gasoline and urban bus standards. [16]

This part of the bill was extremely controversial the time it was passed. The automobile industry argued that it could not meet the new standards. [8] Senators expressed concern about impact on the economy. However the stricter standards led to the creation of the catalytic converter, which was a revolutionary development. (Coincidentally, these converters didn't work well with leaded gas, which contributed to the swift removal of lead from gasoline that was also recognized for having adverse health effects.) [8] Specific new emissions standards for moving sources passed years later.

Part B: Aircraft Emission Standards

Many volatile organic compounds (VOCs) are emitted over airports and affect the air quality in the region. VOCs include benzene, formaldehyde and butadienes which are known to cause health problems such as birth defects, cancer and skin irritation. Hundreds of tons of emissions from aircraft, ground support equipment, heating systems, and shuttles and passenger vehicles are released into the air, causing smog. Therefore, major cities such as Seattle, Denver, and San Francisco require a Climate Action Plan as well as a greenhouse gas inventory. Additionally, federal programs such as the Voluntary Airport Low Emissions Program (VALE) are working to offset costs for programs that reduce emissions. [17]

Title II sets emission standards for airlines and aircraft engines and adopts standards set by the International Civil Aviation Organization (ICAO). However aircraft carbon dioxide emission standards have not been established by either ICAO nor the EPA. [18] It is the responsibility of the Secretary of Transportation, after consultation with the Administrator, to prescribe regulations that comply with 42 U.S. Code § 7571 (Establishment of standards) and ensure the necessary inspections take place. [19]

Part C: Clean Fuel Vehicles

Trucks and automobiles play a large role in deleterious air quality. Harmful chemicals such as nitrogen oxide, hydrocarbons, carbon monoxide and sulfur dioxide are released from motor vehicles. Some of these also react with sunlight to produce Photochemical. [20] These harmful substances change the climate, alter ocean pH and include toxins that may cause cancer, birth defects or respiratory illness. Motor vehicles increased in the 1990s since approximately 58 percent of households owned two or more vehicles. [20] The Clean Fuel Vehicle programs focused on alternative fuel use and petroleum fuels that met low emission vehicle (LEV) levels. Compressed natural gas, ethanol, [21] methanol, [22] liquefied petroleum gas and electricity are examples of cleaner alternative fuel. Programs such as the California Clean Fuels Program and pilot program are increasing demand that for new fuels to be developed to reduce harmful emissions. [20]

The California pilot program incorporated under this section focuses on pollution control in ozone non-attainment areas. The provisions apply to light-duty trucks and light-duty vehicles in California. The state also requires that clean alternative fuels for sale at numerous locations with sufficient geographic distribution for convenience. Production of clean-fuel vehicles isn't mandated except as part of the California pilot program. [12]

Title III: General Provisions

Under the law prior to 1990, EPA was required to construct a list of Hazardous Air Pollutants as well as health-based standards for each one. There were 187 air pollutants listed and the source from which they came. The EPA was given ten years to generate technology-based emission standards. Title III is considered a second phase, allowing the EPA to assess lingering risks after the enactment of the first phase of emission standards. Title III also enacts new standards with regard to the protection of public health. [23]

A citizen may file a lawsuit to obtain compliance with an emission standard issued by the EPA or by a state, unless there is an ongoing enforcement action being pursued by EPA or the appropriate state agency. [24]

Title IV: Noise Pollution

This title pre-dates the Clean Air Act. With the passage of the Clean Air Act, it became codified as Title IV. However, another Title IV was enacted in the 1990 amendments. The second Title IV was then appended to this Title IV as Title IV-A (see below).

This title established the EPA Office of Noise Abatement and Control to reduce noise pollution in urban areas, to minimize noise-related impacts on psychological and physiological effects on humans, effects on wildlife and property (including values), and other noise-related issues. The agency was also assigned to run experiments to study the effects of noise.

Title IV-A: Acid Deposition Control

This title was added as part of the 1990 amendments. It addresses the issue of acid rain, which is caused by nitrogen oxides (NO
) and sulfur dioxide (SO2) emissions from electric power plants powered by fossil fuels, and other industrial sources. The 1990 amendments gave industries more pollution control options including switching to low-sulfur coal and/or adding devices that controlled the harmful emissions. In some cases plants had to be closed down to prevent the dangerous chemicals from entering the atmosphere. [25]

Title IV-A mandated a two-step process to reduce SO2 emissions. The first stage required more than 100 electric generating facilities larger than 100 megawatts to meet a 3.5 million ton SO2 emission reduction by January 1995. The second stage gave facilities larger than 75 megawatts a January 2000 deadline. [26]

Title V: Permits

The 1990 amendments authorized a national operating permit program, covering thousands of large industrial and commercial sources. [27] It required large businesses to address pollutants released into the air, measure their quantity, and have a plan to control and minimize them as well as to periodically report. This consolidated requirements for a facility into a single document. [27]

In non-attainment areas, permits were required for sources that emit as little as 50, 25, or 10 tons per year of VOCs depending on the severity of the region's non-attainment status. [28]

Most permits are issued by state and local agencies. [29] If the state does not adequately monitor requirements, the EPA may take control. The public may request to view the permits by contacting the EPA. The permit is limited to no more than five years and requires a renewal. [28]

Title VI: Stratospheric Ozone Protection

Starting in 1990, Title VI mandated regulations regarding the use and production of chemicals that harm the Earth's stratospheric ozone layer. This ozone layer protects against harmful ultraviolet B sunlight linked to several medical conditions including cataracts and skin cancer. [30]

The ozone-destroying chemicals were classified into two groups, Class I and Class II. Class I consists of substances, including chlorofluorocarbons, that have an ozone depletion potential (ODP) (HL) of 0.2 or higher. Class II lists substances, including hydro chlorofluorocarbons, that are known to or may be detrimental to the stratosphere. Both groups have a timeline for phase-out:

Title VI establishes methods for preventing harmful chemicals from entering the stratosphere in the first place, including recycling or proper disposal of chemicals and finding substitutes that cause less or no damage. [25] The Significant New Alternatives Policy (SNAP) Program is EPA's program to evaluate and regulate substitutes for the ozone-depleting chemicals that are being phased out under the stratospheric ozone protection provisions of the Clean Air Act. [31]

Over 190 countries signed the Montreal Protocol in 1987, agreeing to work to eliminate or limit the use of chemicals with ozone-destroying properties. [30]



Congress passed the first legislation to address air pollution with the 1955 Air Pollution Control Act that provided funds to the U.S. Public Health service, but did not formulate pollution regulation. [32] However, the Clean Air Act in 1963 created a research and regulatory program in the U.S. Public Health Service. [33] The Act authorized development of emission standards for stationary sources, but not mobile sources of air pollution. [34] :211 The 1967 Air Quality Act mandated enforcement of interstate air pollution standards and authorized ambient monitoring studies and stationary source inspections. [35]

In the Clean Air Act Extension of 1970, Congress greatly expanded the federal mandate by requiring comprehensive federal and state regulations for both industrial and mobile sources. [36] The law established four new regulatory programs:

The 1970 law is sometimes called the "Muskie Act" because of the central role Maine Senator Edmund Muskie played in drafting the bill. [38]

To implement the strict new Clean Air Act of 1970, during his first term as EPA Administrator William Ruckelshaus spent 60% of his time on the automobile industry, whose emissions were to be reduced 90% under the new law. Senators had been frustrated at the industry's failure to cut emissions under previous, weaker air laws. [39]

The Clean Air Act Amendments of 1977 required Prevention of Significant Deterioration (PSD) of air quality for areas attaining the NAAQS and added requirements for non-attainment areas. [40]

The 1990 Clean Air Act added regulatory programs for control of acid deposition (acid rain) and stationary source operating permits. The provisions aimed at reducing sulfur dioxide emissions included a cap-and-trade program, which gave power companies more flexibility in meeting the law's goals compared to earlier iterations of the Clean Air Act. [41] The amendments moved considerably beyond the original criteria pollutants, expanding the NESHAP program with a list of 189 hazardous air pollutants to be controlled within hundreds of source categories, according to a specific schedule. [42] The NAAQS program was also expanded. Other new provisions covered stratospheric ozone protection, increased enforcement authority and expanded research programs. [43]

History of the Clean Air Act


President Lyndon B. Johnson signing the 1967 Air Quality Act in the East Room of the White House, November 21, 1967. Clean Air Act Signing.jpg
President Lyndon B. Johnson signing the 1967 Air Quality Act in the East Room of the White House, November 21, 1967.

The legal authority for federal programs regarding air pollution control is based on the 1990 Clean Air Act Amendments (1990 CAAA). These are the latest in a series of amendments made to the Clean Air Act (CAA), often referred to as "the Act." This legislation modified and extended federal legal authority provided by the earlier Clean Air Acts of 1963 and 1970. [7]

The 1955 Air Pollution Control Act was the first federal legislation involving air pollution; it authorized $3 million per year to the U.S. Public Health Service for five years to fund federal level air pollution research, air pollution control research, and technical and training assistance to the states. Subsequently, the act was extended for four years in 1959 with funding levels at $5 million per year. The act was then amended in 1960 and 1962. Although the 1955 act brought the air pollution issue to the federal level, no federal regulations were formulated. Control and prevention of air pollution was instead delegated to state and local agencies. [32]

The Clean Air Act of 1963 was the first federal legislation regarding air pollution control. It established a federal program within the U.S. Public Health Service and authorized research into techniques for monitoring and controlling air pollution. In 1967, the Air Quality Act was enacted in order to expand federal government activities. In accordance with this law, enforcement proceedings were initiated in areas subject to interstate air pollution transport. As part of these proceedings, the federal government for the first time conducted extensive ambient monitoring studies and stationary source inspections.

The Air Quality Act of 1967 also authorized expanded studies of air pollutant emission inventories, ambient monitoring techniques, and control techniques. [7]

Clean Air Act of 1970

The Clean Air Act of 1970 (1970 CAA) authorized the development of comprehensive federal and state regulations to limit emissions from both stationary (industrial) sources and mobile sources. Four major regulatory programs affecting stationary sources were initiated:

  • the National Ambient Air Quality Standards [NAAQS (pronounced "knacks")],
  • State Implementation Plans (SIPs),
  • New Source Performance Standards (NSPS),
  • and National Emission Standards for Hazardous Air Pollutants (NESHAPs).

Enforcement authority was substantially expanded. This very important legislation was adopted at approximately the same time as the National Environmental Policy Act . [7] [10]

Clean Air Act Amendments of 1977

Major amendments were added to the Clean Air Act in 1977 (1977 CAAA). The 1977 Amendments primarily concerned provisions for the Prevention of Significant Deterioration (PSD) of air quality in areas attaining the NAAQS. The 1977 CAAA also contained requirements pertaining to sources in non-attainment areas for NAAQS. A non-attainment area is a geographic area that does not meet one or more of the federal air quality standards. Both of these 1977 CAAA established major permit review requirements to ensure attainment and maintenance of the NAAQS. [7] These amendments also included the adoption of an offset trading policy originally applied to Los Angeles in 1974 that enables new sources to offset their emissions by purchasing extra reductions from existing sources. [8]

Clean Air Act Amendments of 1990

Another set of major amendments to the Clean Air Act occurred in 1990 (1990 CAAA). The 1990 CAAA substantially increased the authority and responsibility of the federal government. New regulatory programs were authorized for control of acid deposition (acid rain) [44] and for the issuance of stationary source operating permits. The NESHAPs were incorporated into a greatly expanded program for controlling toxic air pollutants. The provisions for attainment and maintenance of NAAQS were substantially modified and expanded. Other revisions included provisions regarding stratospheric ozone protection, increased enforcement authority, and expanded research programs. [7]


Some of the principal milestones in the evolution of the Clean Air Act are as follows: [7]

The Air Pollution Control Act of 1955

  • First federal air pollution legislation
  • Funded research on scope and sources of air pollution

Clean Air Act of 1963

  • Authorized a national program to address air pollution
  • Authorized research into techniques to minimize air pollution

Air Quality Act of 1967

  • Authorized enforcement procedures involving interstate transport of pollutants
  • Expanded research activities

Clean Air Act of 1970

  • Established National Ambient Air Quality Standards
  • Established requirements for State Implementation Plans to achieve them
  • Establishment of New Source Performance Standards for new and modified stationary sources
  • Establishment of National Emission Standards for Hazardous Air Pollutants
  • Increased enforcement authority
  • Authorized control of motor vehicle emissions

1977 Amendments to the Clean Air Act of 1970

  • Authorized provisions related to prevention of significant deterioration
  • Authorized provisions relating to non-attainment areas

1990 Amendments to the Clean Air Act of 1970

  • Authorized programs for acid deposition control
  • Authorized controls for 189 toxic pollutants, including those previously regulated by the national emission standards for hazardous air pollutants
  • Established permit program requirements
  • Expanded and modified provisions concerning National Ambient Air Quality Standards
  • Expanded and modified enforcement authority


Since the initial establishment of six mandated criteria pollutants (ozone, particulate matter, carbon monoxide, nitrogen oxides, sulfur dioxide, and lead), advancements in testing and monitoring have led to the discovery of many other significant air pollutants. [45]

However, with the act in place and its many improvements, the U.S. has seen many pollutant levels and associated cases of health complications drop. According to the EPA, the 1990 Clean Air Act Amendments has prevented or will prevent:

Year 2010
(cases prevented)
Year 2020
(cases prevented)
Adult Mortality - particles160,000230,000
Infant Mortality - particles230280
Mortality - ozone4,30071,000
Chronic Bronchitis54,00075,000
Heart Disease - Acute Myocardial Infarction130,000200,000
Asthma Exacerbation1,700,0002,400,000
Emergency Room Visits86,000120,000
School Loss Days3,200,0005,400,000
Lost Work Days13,000,00017,000,000

This chart shows the health benefits of the Clean Air Act programs that reduce levels of fine particles and ozone. [46]

In 1997 EPA tightened the NAAQS regarding permissible levels of the ground-level ozone that make up smog and the fine airborne particulate matter that makes up soot. [47] [48] The decision came after months of public review of the proposed new standards, as well as long and fierce internal discussion within the Clinton administration, leading to the most divisive environmental debate of that decade. [49] The new regulations were challenged in the courts by industry groups as a violation of the U.S. Constitution's nondelegation principle and eventually landed in the Supreme Court of the United States, [48] whose 2001 unanimous ruling in Whitman v. American Trucking Ass'ns, Inc. largely upheld EPA's actions. [50]

The Clean Air Act (CAA or Act) directs the EPA to establish national ambient air quality standards (NAAQS) for pollutants at levels that will protect public health. The EPA and the American Lung Association promoted the 2011 Cross State Air Pollution Rule (CSAPR) as a means of controlling ozone and fine particle emissions. It was claimed that this prevented up 400,000 asthma cases and saved two millions workdays and schooldays that otherwise would have been lost to respiratory illnesses. Cities and power companies sued the EPA over the law in EPA v. EME Homer City Generation, but the case was eventually decided in favor of the EPA. [51]

Roles of the federal government and states

The 1970 Clean Air Act required states to develop State Implementation Plans for how they would meet new national ambient air quality standards by 1977. [52] Although the 1990 Clean Air Act is a federal law covering the entire country, the states do much of the work to carry out the Act. The EPA has allowed the individual states to elect responsibility for compliance with and regulation of the CAA within their own borders in exchange for funding. For example, a state air pollution agency holds a hearing on a permit application by a power or chemical plant or fines a company for violating air pollution limits. However, election is not mandatory and in some cases states have chosen to not accept responsibility for enforcement of the act and force the EPA to assume those duties.

In order to take over compliance with the CAA the states must write and submit a state implementation plan (SIP) to the EPA for approval. A state implementation plan is a collection of the regulations a state will use to clean up polluted areas. The states are obligated to notify the public of these plans, through hearings that offer opportunities to comment, in the development of each state implementation plan. The SIP becomes the state's legal guide for local enforcement of the CAA. For example, Rhode Island law requires compliance with the Federal CAA through the SIP. [53] The SIP delegates permitting and enforcement responsibility to the state Department of Environmental Management (RI-DEM).

The federal law recognizes that states should lead in carrying out the Clean Air Act, because pollution control problems often require special understanding of local industries, geography, housing patterns, etc. However, states are not allowed to have weaker pollution controls than the national minimum criteria set by EPA. EPA must approve each SIP, and if a SIP isn't acceptable, EPA can take over CAA enforcement in that state. For example, California was unable to meet the new standards set by the Clean Air Act of 1970, which led to a lawsuit and a federal state implementation plan for the state. [54]

The United States government, through the EPA, assists the states by providing scientific research, expert studies, engineering designs, and money to support clean air programs.

Metropolitan planning organizations must approve all federally funded transportation projects in a given urban area. If the MPO's plans do not, Federal Highway Administration and the Federal Transit Administration have the authority to withhold funds if the plans do not conform with federal requirements, including air quality standards. [55] In 2010, the EPA directly fined the San Joaquin Valley Air Pollution Control District $29 million for failure to meet ozone standards, resulting in fees for county drivers and businesses. This was the results of a federal appeals court case that required the EPA to continue enforce older, stronger standards, [56] and spurred debate in Congress over amending the Act. [57]

Most notably, the law prevents states from setting standards that are more strict than the federal standards, but carves out a special exemption for California due to its past issues with smog pollution in the metropolitan areas. In practice, when California's environmental agencies decide on new vehicle emission standards, they submit these to the EPA for approval under this waiver, with the most recent approval in 2009. [58] The California standard was adopted by twelve other states, and it based on the de facto standard that automobile manufactures have subsequently built towards, as to avoid having to develop multiple lines of emission systems in their vehicles for different states. However, in September 2019, President Donald Trump revoked this waiver, arguing that the stricter emissions have made cars too expensive, and by removing them, will make vehicles safer. EPA's Andrew Wheeler also stated that while the agency respects federalism, they could not allow one state to dictate standards for the entire nation. California's governor Gavin Newsom considered the move part of Trump's "political vendetta" against California and stated his intent to sue the federal government. [59] Twenty-three states, along with the District of Columbia and the cities of New York City and Los Angeles joined California in a federal lawsuit challenging the administration's decision. [60]

State programs

Many states, or concerned citizens of the state, have established their own programs to help promote pollution clean-up strategies.

For example, (in alphabetical order by state)

Interstate air pollution

Air pollution often travels from its source in one state to another state. In many metropolitan areas, people live in one state and work or shop in another; air pollution from cars and trucks may spread throughout the interstate area. The 1990 Clean Air Act provides for interstate commissions on air pollution control, which are to develop regional strategies for cleaning up air pollution. The 1990 amendments include other provisions to reduce interstate air pollution.

The Acid Rain Program, created under Title IV of the Act, authorizes emissions trading to reduce the overall cost of controlling emissions of sulfur dioxide.

Leak detection and repair

The Act requires industrial facilities to implement a Leak Detection and Repair (LDAR) program to monitor and audit a facility's fugitive emissions of volatile organic compounds (VOC). The program is intended to identify and repair components such as valves, pumps, compressors, flanges, connectors and other components that may be leaking. These components are the main source of the fugitive VOC emissions.

Testing is done manually using a portable vapor analyzer that read in parts per million (ppm). Monitoring frequency, and the leak threshold, is determined by various factors such as the type of component being tested and the chemical running through the line. Moving components such as pumps and agitators are monitored more frequently than non-moving components such as flanges and screwed connectors. The regulations require that when a leak is detected the component be repaired within a set number of days. Most facilities get 5 days for an initial repair attempt with no more than 15 days for a complete repair. Allowances for delaying the repairs beyond the allowed time are made for some components where repairing the component requires shutting process equipment down.

Application to greenhouse gas emissions

EPA began regulating greenhouse gases (GHGs) from mobile and stationary sources of air pollution under the Clean Air Act for the first time on January 2, 2011, after having established its first auto emissions standards in 2010. [63] Standards for mobile sources have been established pursuant to Section 202 of the CAA, and GHGs from stationary sources are controlled under the authority of Part C of Title I of the Act. The EPA's auto emission standards for greenhouse gas emissions issued in 2010 and 2012 are intended to cut emissions from targeted vehicles by half, double fuel economy of passenger cars and light-duty trucks by 2025 and save over $4 billion barrels of oil and $1.7 trillion for consumers. The agency has also proposed a two-phase program to reduce greenhouse gas emissions for medium and heavy duty trucks and buses. [8]

Below is a table for the sources of greenhouse gases, taken from data in 2008. [64] Of all greenhouse gases, about 76 percent of the sources are manageable under the CAA, marked with an asterisk (*). All others are regulated independently, if at all.

Electric Generation*34%
Large Non-Agricultural Methane Sources*5%
Light-, Medium-, and Heavy-Duty Vehicles*22%
Other Transport7%
Commercial and Residential Heating7%

Clean Air Act and environmental justice

By promoting pollution reduction, the Clean Air Act can help reduce heightened exposure to air pollution among communities of color and low-income communities. [65] Environmental researcher Dr. Marie Lynn Miranda notes that African American populations are “consistently over represented” in areas with the poorest air quality. [66] 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. [67] 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 communities of color and low-income communities. [68] 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. [68]

Clean Air Act violations

The EPA analyzes violators of the Clean Air Act and addresses the violators accordingly. For companies or parties that do not comply with the act monetary penalties can be cited. Per day the EPA could fine civil administrators $37,500 per day, with a maximum of about 8 days; unless otherwise mandated by the EPA. For a field citation which is against federal facilities which are not abiding by EPA standards can get fines up to $7,500 per day. [69]

Major cases of Clean Air Act violations include:


A 2017 study found that the Clean Air Act of 1970 led to an over 10 percent reduction in pollution ("ambient TSP levels") in counties that exceeded the pollution thresholds set by the Act in the three years after the regulation went into effect. The study found that this regulation-induced reduction in air pollution has caused affected workers to work more and earned one percent more in annual earnings. The authors estimate that cumulative lifetime income gain for each affected individual is approximately $4,300 in present value terms. [72]

In addition, because air quality across the United States improved; it is estimated 205,000 premature deaths and millions of other respiratory complications were prevented which resulted in an economic savings of $50 trillion versus the $523 billion invested to meet the Clean Air Act standard. [73]

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. [8]

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. [74]

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. [75] [76]

Future challenges

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. [77]

As of 2017, some US cities still don't 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. [8]

Air pollution is not bound to a nation. Often, air coming into the U.S. contains pollution from upwind countries, making it harder to meet air quality standards. In turn, air that travels downwind of the U.S. likely has pollutants in it already. Addressing this may require international negotiations of reductions of pollutants in the originating countries. [8] This also relates to the challenge of climate change.


Diane Katz, a research fellow for the Heritage Foundation, criticized the validity of the Clean Air Act by stating, "The largest proportion of economic benefit is based on the value of avoiding premature mortality. Yet the valuation of this benefit ranks among the most significant uncertainties in the study, according to the researchers. Alternative estimates they cite would lower the benefit calculation by up to 22 percent." [78] The Clean Air Act is a constant battle between current economic benefits versus future cost benefits of both health of the nation, and economy.[ citation needed ]

See also

Related Research Articles

Pollutant substance or energy source damaging to the environment

A pollutant is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. A pollutant may cause long- or short-term damage by changing the growth rate of plant or animal species, or by interfering with human amenities, comfort, health, or property values. Some pollutants are biodegradable and therefore will not persist in the environment in the long term. However, the degradation products of some pollutants are themselves polluting such as the products DDE and DDD produced from the degradation of DDT.

Industrial waste is the waste produced by industrial activity which includes any material that is rendered useless during a manufacturing process such as that of factories, industries, mills, and mining operations. Types of industrial waste include dirt and gravel, masonry and concrete, scrap metal, oil, solvents, chemicals, scrap lumber, even vegetable matter from restaurants. Industrial waste may be solid, liquid or gaseous. It may be hazardous or non-hazardous waste. Hazardous waste may be toxic, ignitable, corrosive, reactive, or radioactive. Industrial waste may pollute the air, the soil, or nearby water sources, eventually ending up in the sea. Industrial waste is often mixed into municipal waste, making accurate assessments difficult. An estimate for the US goes as high as 7.6 billion tons of industrial waste produced every year. Most countries have enacted legislation to deal with the problem of industrial waste, but strictness and compliance regimes vary. Enforcement is always an issue.

Clean Water Act Primary federal law in the United States governing water pollution

The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the responsibilities of the states in addressing pollution and providing assistance to states to do so, including funding for publicly owned treatment works for the improvement of wastewater treatment; and maintaining the integrity of wetlands. It is one of the United States' first and most influential modern environmental laws. As with many other major U.S. federal environmental statutes, it is administered by the U.S. Environmental Protection Agency (EPA), in coordination with state governments. Its implementing regulations are codified at 40 C.F.R. Subchapters D, N, and O.

The National Emissions Standards Act, officially known as the Motor Vehicle Air Pollution Control Act, is a 1965 amendment to the U.S. Clean Air Act of 1963. The amendment set the first federal vehicle emissions standards, beginning with the 1968 models. These standards were reductions from the 1963 emissions: 72% reduction for hydrocarbons, 56% reduction for carbon monoxide, and 100% reduction for crankcase hydrocarbons. The impact the regulatory standards will have on air quality in the future, as well as the potential characteristics of the vehicle fleet can be analyzed with the use of roadway air dispersion models.

The National Emission Standards for Hazardous Air Pollutants, also using the acronym NESHAP, are emission standards set by the United States Environmental Protection Agency—EPA. The standards are for air pollutants not covered by National Ambient Air Quality Standards—NAAQS, that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness.

National Ambient Air Quality Standards

The U.S. National Ambient Air Quality Standards are standards for harmful pollutants. Established by the United States Environmental Protection Agency (EPA) under authority of the Clean Air Act, NAAQS is applied for outdoor air throughout the country.

A State Implementation Plan (SIP) is a United States state plan for complying with the federal Clean Air Act, administered by the Environmental Protection Agency (EPA). The SIP, developed by a state agency and approved by EPA, consists of narrative, rules, technical documentation, and agreements that an individual state will use to control and clean up polluted areas.

New Source Performance Standards (NSPS) are pollution control standards issued by the United States Environmental Protection Agency (EPA). The term is used in the Clean Air Act Extension of 1970 (CAA) to refer to air pollution emission standards, and in the Clean Water Act (CWA) referring to standards for water pollution discharges of industrial wastewater to surface waters.

Design for the Environment (DfE) is a design approach to reduce the overall human health and environmental impact of a product, process or service, where impacts are considered across its life cycle. Different software tools have been developed to assist designers in finding optimized products or processes/services. DfE is also the original name of a United States Environmental Protection Agency (EPA) program, created in 1992, that works to prevent pollution, and the risk pollution presents to humans and the environment. The program provides information regarding safer chemical formulations for cleaning and other products. EPA renamed its program "Safer Choice" in 2015.

The South Coast Air Quality Management District, also using the acronym South Coast (AQMD), formed in 1976, is the air pollution agency responsible for regulating stationary sources of air pollution in the South Coast Air Basin, in Southern California. The separate California Air Resources Board is responsible for regulating mobile sources in the air basin.

Criteria air Pollutants (CAP), or criteria pollutants, are a set of air pollutants that cause smog, acid rain, and other health hazards. CAPs are typically emitted from many sources in industry, mining, transportation, electricity generation and agriculture. In many cases they are the products of the combustion of fossil fuels or industrial processes.

Title 40 is a part of the United States Code of Federal Regulations. Title 40 arranges mainly environmental regulations that were promulgated by the US Environmental Protection Agency (EPA), based on the provisions of United States laws. Parts of the regulation may be updated annually on July 1.

To protect the environment from the adverse effects of pollution, many nations worldwide have enacted legislation to regulate various types of pollution as well as to mitigate the adverse effects of pollution.

Air quality law

Air quality laws govern the emission of air pollutants into the atmosphere. A specialized subset of air quality laws regulate the quality of air inside buildings. Air quality laws are often designed specifically to protect human health by limiting or eliminating airborne pollutant concentrations. Other initiatives are designed to address broader ecological problems, such as limitations on chemicals that affect the ozone layer, and emissions trading programs to address acid rain or climate change. Regulatory efforts include identifying and categorizing air pollutants, setting limits on acceptable emissions levels, and dictating necessary or appropriate mitigation technologies.

The United States Environmental Protection Agency (EPA) began regulating greenhouse gases (GHGs) under the Clean Air Act from mobile and stationary sources of air pollution for the first time on January 2, 2011. Standards for mobile sources have been established pursuant to Section 202 of the CAA, and GHGs from stationary sources are currently controlled under the authority of Part C of Title I of the Act. The basis for regulations was upheld in the United States Court of Appeals for the District of Columbia in June 2012.

United States regulation of point source water pollution

Point source water pollution comes from discrete conveyances and alters the chemical, biological, and physical characteristics of water. In the United States, it is largely regulated by the Clean Water Act (CWA). Among other things, the Act requires dischargers to obtain a National Pollutant Discharge Elimination System (NPDES) permit to legally discharge pollutants into a water body. However, point source pollution remains an issue in some water bodies, due to some limitations of the Act. Consequently, other regulatory approaches have emerged, such as water quality trading and voluntary community-level efforts.

The Ventura County Air Pollution Control District (VCAPCD), formed in 1968, is the air pollution agency responsible mainly for regulating stationary sources of air pollution for Ventura County. The District was formed by the Board of Supervisors in response to the county's first air pollution study which identified Ventura County as having a severe air quality problem.

Environmental Defense v. Duke Energy Corporation, 549 U.S. 561 (2007), is a United States Supreme Court case in which the Court held that while a term may be used more than once in a statute, an agency has the discretion to interpret each use of the term in a different way based on the context. In a unanimous decision, the Court held in favor of the plaintiff's argument.


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Further reading