Clean Air Act (United States)

The National Ambient Air Quality Standards (NAAQS) govern how much ground-level ozone (O₃), carbon monoxide (CO), particulate matter (PM₁₀, PM_2.5), lead (Pb), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂) are allowed in the outdoor air.[6] 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 health-based standards were called "primary" NAAQS, while standards set to protect public welfare other than health (e.g., agricultural values) were called "secondary" NAAQS. In 1971, EPA promulgated regulations for sulfur oxides, particulate matter, carbon monoxide, photochemical oxidants, hydrocarbons, and nitrogen dioxide (36 FR 22384). Initially, EPA did not list lead as a criteria pollutant, controlling it through mobile source authorities, but it was required to do so after successful litigation by Natural Resources Defense Council (NRDC) in 1976 (43 FR 46258). The 1977 CAA Amendments created a process for regular review of the NAAQS list, and created a permanent independent scientific review committee to provide technical input on the NAAQS to EPA.[7] EPA added regulations for PM2.5 in 1997 (62 FR 38652), and updates the NAAQS from time to time based on emerging environmental and health science.

The National Emissions Standards for Hazardous Air Pollutants (NESHAPs) govern how much of 187 toxic air pollutants are allowed to be emitted from industrial facilities and other sources.[8] Under the CAA, hazardous air pollutants (HAPs, or air toxics) are air pollutants other than those for which NAAQS exist, which threaten human health and welfare. The NESHAPs are the standards used for controlling, reducing, and eliminating HAPs emissions from stationary sources such as industrial facilities. The 1970 CAA required EPA to develop a list of HAPs, and then develop national emissions standards for each of them. The original NESHAPs were health-based standards. The 1990 CAA Amendments (Pub. L.Tooltip Public Law (United States) 101–549 Title III) codified EPA's list, and required creation of technology-based standards according to "maximum achievable control technology" (MACT). Over the years, EPA has issued dozens of NESHAP regulations, which have developed NESHAPs by pollutant, by industry source category, and by industrial process. There are also NESHAPs for mobile sources (transportation), although these are primarily handled under the mobile source authorities.[9] The 1990 amendments (adding CAA § 112(d-f)) also created a process by which EPA was required to review and update its NESHAPs every eight years, and identify any risks remaining after application of MACT, and develop additional rules necessary to protect public health.[10]

The New Source Performance Standards (NSPS) are rules for the equipment required to be installed in new and modified industrial facilities, and the rules for determining whether a facility is "new".[11] The 1970 CAA required EPA to develop standards for newly constructed and modified stationary sources (industrial facilities) using the "best system of emission reduction which (taking into account the cost of achieving such reduction) the [EPA] determines has been adequately demonstrated." EPA issued its first NSPS regulation the next year, covering steam generators, incinerators, Portland cement plants, and nitric and sulfuric acid plants (36 FR 24876). Since then, EPA has issued dozens of NSPS regulations, primarily by source category. The requirements promote industrywide adoption of available pollution control technologies. However, because these standards apply only to new and modified sources, they promote extending the lifetimes of pre-existing facilities. In the 1977 CAA Amendments, Congress required EPA to conduct a "new source review" process (40 CFR 52, subpart I) to determine whether maintenance and other activities rises to the level of modification requiring application of NSPS.[12]

The Acid Rain Program (ARP) is an emissions trading program for power plants to control the pollutants that cause acid rain.[13] The 1990 CAA Amendments created a new title to address the issue of acid rain, and particularly nitrogen oxides (NO_x) and sulfur dioxide (SO₂) emissions from electric power plants powered by fossil fuels, and other industrial sources. The Acid Rain Program was the first emissions trading program in the United States, setting a cap on total emissions that was reduced over time by way of traded emissions credits, rather than direct controls on emissions. The program evolved in two stages: 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. The program has achieved all of its statutory goals.[14]

The CAA ozone program is a technology transition program intended to phase out the use of chemicals that harm the ozone layer.[15] Consistent with the US commitments in the Montreal Protocol, CAA Title VI, added by the 1990 CAA Amendments, mandated regulations regarding the use and production of chemicals that harm Earth's stratospheric ozone layer. Under Title VI, EPA runs programs to phase out ozone-destroying substances, track their import and export, determine exemptions for their continued use, and define practices for destroying them, maintaining and servicing equipment that uses them, identifying new alternatives to those still in use, and licensing technicians to use such chemicals.

Rules for pollutants emitted from internal combustion engines in vehicles.[16] Since 1965, Congress has mandated increasingly stringent controls on vehicle engine technology and reductions in tailpipe emissions. Today, the law requires EPA to establish and regularly update regulations for pollutants that may threaten public health, from a wide variety of classes of motor vehicles, that incorporate technology to achieve the "greatest degree of emission reduction achievable", factoring in availability, cost, energy, and safety (42 U.S.C. § 7521).

EPA sets standards for exhaust gases, evaporative emissions, air toxics, refueling vapor recovery, and vehicle inspection and maintenance for several classes of vehicles that travel on roadways. EPA's "light-duty vehicles" regulations cover passenger cars, minivans, passenger vans, pickup trucks, and SUVs. "Heavy-duty vehicles" regulations cover large trucks and buses. EPA first issued motorcycle emissions regulations in 1977 (42 FR 1122) and updated them in 2004 (69 FR 2397).

Vehicle testing program

The air pollution testing system for motor vehicles was originally developed in 1972 and used driving cycles designed to simulate driving during rush-hour in Los Angeles during that era. Until 1984, EPA reported the exact fuel economy figures calculated from the test. In 1984, EPA began adjusting city (aka Urban Dynamometer Driving Schedule or UDDS) results downward by 10% and highway (aka HighWay Fuel Economy Test or HWFET) results by 22% to compensate for changes in driving conditions since 1972, and to better correlate the EPA test results with real-world driving. In 1996, EPA proposed updating the Federal Testing Procedures[17] to add a new higher-speed test (US06) and an air-conditioner-on test (SC03) to further improve the correlation of fuel economy and emission estimates with real-world reports. In December 2006 the updated testing methodology was finalized to be implemented in model year 2008 vehicles and set the precedent of a 12-year review cycle for the test procedures.[18]

In February 2005, EPA launched a program called "Your MPG" that allows drivers to add real-world fuel economy statistics into a database on EPA's fuel economy website and compare them with others and with the original EPA test results.[19]

EPA conducts fuel economy tests on very few vehicles.[20] Two-thirds of the vehicles the EPA tests themselves are randomly selected and the remaining third is tested for specific reasons.

Although originally created as a reference point for fossil-fueled vehicles, driving cycles have been used for estimating how many miles an electric vehicle will get on a single charge.[21]

The 1970 CAA amendments provided for regulation of aircraft emissions (42 U.S.C. § 7571), and EPA began regulating in 1973. In 2012, EPA finalized its newest restrictions on NOx emissions from gas turbine aircraft engines with rated thrusts above 26.7 kiloNewton (3 short ton-force), meaning primarily commercial jet aircraft engines, intended to match international standards. EPA has been investigating whether to regulate lead in fuels for small aircraft since 2010, but has not yet acted. The 1990 CAA Amendments (Pub. L.Tooltip Public Law (United States) 101–549 § 222) added rules for a "nonroad" engine program (42 U.S.C. § 7547), which expanded EPA regulation to locomotives, heavy equipment and small equipment engines fueled by diesel (compression-ignition), and gas and other fuels (spark-ignition), and marine transport.

EPA has developed a variety of voluntary programs to incentivize and promote reduction in transportation-related air pollution, including elements of the Clean Diesel Campaign, Ports Initiative, SmartWay program, and others.

The federal government has regulated the chemical composition of transportation fuels since 1967, with significant new authority added in 1970 to protect public health.[22] One of EPA's earliest actions was the elimination of lead in U.S. gasoline beginning in 1971 (36 FR 1486, 37 FR 3882, 38 FR 33734), a project that has been described as "one of the great public health achievements of the 20th century."[23] EPA continues to regulate the chemical composition of gasoline, avgas, and diesel fuel in the United States.

The 1990 amendments authorized a national operating permit program, sometimes called the "Title V Program", covering thousands of large industrial and commercial sources. 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.[1]^: 19 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.[24] Most permits are issued by state and local agencies.[25] 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.[24]

One of the most public aspects of the Clean Air Act, EPA is empowered to monitor compliance with the law's many requirements, seek penalties for violations, and compel regulated entities to come into compliance.[26] Enforcement cases are usually settled, with penalties assessed well below maximum statutory limits. Recently, many of the largest Clean Air Act settlements have been reached with automakers accused of circumventing the Act's vehicle and fuel standards (e.g., the 2015 "Dieselgate" scandal).

Much of EPA's regulation of greenhouse gas (GHG) emissions occurs under the programs discussed above. EPA began regulating GHG emissions following the Supreme Court's ruling in Massachusetts v. EPA, the EPA's subsequent endangerment finding, and development of specific regulations for various sources.[27] The EPA's authority to regulate carbon dioxide emissions was questioned by the Supreme Court in West Virginia v. EPA but restored by Congress with the Inflation Reduction Act of 2022, which clarified that carbon dioxide is one of the pollutants covered by the Clean Air Act.[28]

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.[29] In addition, EPA oversees the national greenhouse gas inventory reporting program.[30]

Following the Supreme Court decision in West Virginia v. EPA, which ruled that Congress did not grant EPA to require "outside the fence" options for limiting carbon dioxide at power plants, Congress passed the Inflation Reduction Act of 2022, which in amending the Clean Air Act, specifically defined carbon dioxide, hydrofluorocarbons, methane, nitrous oxide, perfluorocarbons, and sulfur hexafluoride as greenhouse gases to be regulated by the EPA, as well as giving the EPA the ability to regulate the inclusion of renewable sources, notably, through a $27 billion green bank, among other methods.[28][31][32]

Other important but less foundational Clean Air Act regulatory programs tend to build on or cut across the above programs:

• Risk Assessment. Although not a regulatory program per se, many EPA regulatory programs involve risk assessment and management.[33] 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,[34] and many subsequent reports have built on this work.
• 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.[35]
• 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.[36][37] 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.
• 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.[38]

The 1963 act required development of State Implementation Plans (SIPs) as part of a cooperative federalist program for developing pollution control standards and programs.[39] 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.[40]

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.[41]

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.[42]

The Constitution contains no provisions listing environmental standards as an enumerated Federal power, and until 1970 these were essentially handled at the state and local level. However, legislators of the 1960s had been heavily influenced by New Deal-era ideologies of government, allowing considerable expansion of Federal authority, often in excess of what was strictly allowed in the Constitution. 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.[43] This cooperative federal model continues today. The law recognizes that states should lead in carrying out the Clean Air Act, because pollution control problems often require special understanding of local conditions such as geography, industrial activity, transportation and housing patterns. However, states are not allowed to have weaker controls than the national minimum criteria set by EPA. EPA must approve each SIP, and if a SIP is not acceptable, EPA can retain CAA enforcement in that state. For example, California was unable to meet the new standards set by the 1970 amendments, which led to a lawsuit and a federal state implementation plan for the state.[44] The federal government also assists the states by providing scientific research, expert studies, engineering designs, and money to support clean air programs.

The law also 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 are submitted to the EPA for approval under this waiver, with the most recent approval in 2009.[45] The California standard was adopted by twelve other states, and established the de facto standard that automobile manufacturers subsequently accepted, to avoid having to develop different emission systems in their vehicles for different states. However, in September 2019, President Donald Trump attempted to revoke 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, it 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.[46] 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.[47] In March 2022 the Biden administration reversed the Trump-era rule, allowing California to again set stricter auto emissions standards.[48]

The Clean Air Act of 1963 (Pub. L.Tooltip Public Law (United States) 88–206) was the first federal legislation to permit the U.S. federal government to take direct action to control air pollution. It extended the 1955 research program, encouraged cooperative state, local, and federal action to reduce air pollution, appropriated $95 million over three years to support the development of state pollution control programs, and authorized the HEW Secretary to organize conferences and take direct action against interstate air pollution where state action was deemed to be insufficient.[49]

The Motor Vehicle Air Pollution Control Act (Pub. L.Tooltip Public Law (United States) 89–272) amended the 1963 Clean Air Act and set the first federal vehicle emissions standards, beginning with the 1968 models. These standards were reductions from 1963 emissions levels: 72% reduction for hydrocarbons, 56% reduction for carbon monoxide, and 100% reduction for crankcase hydrocarbons.. The law also added a new section to authorize abatement of international air pollution.[51]

President Lyndon B. Johnson signs the 1967 Air Quality Act in the East Room of the White House, November 21, 1967.

The Air Quality Act of 1967 (Pub. L.Tooltip Public Law (United States) 90–148) authorized planning grants to state air pollution control agencies, permitted the creation of interstate air pollution control agencies, and required HEW to define air quality regions and develop technical documentation that would allow states to set ambient air quality and pollution control technology standards, and required states to submit implementation plans for improvement of air quality, and permitted HEW to take direct abatement action in air pollution emergencies. It also authorized expanded studies of air pollutant emission inventories, ambient monitoring techniques, and control techniques.[52][51] This 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.[53] 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.[29]

President Richard Nixon signs the Clean Air Amendments of 1970 at the White House, December 31, 1970.

In the Clean Air Amendments of 1970 (Pub. L.Tooltip Public Law (United States) 91–604), Congress greatly expanded the federal mandate by requiring comprehensive federal and state regulations for both industrial and mobile sources. The law established the National Ambient Air Quality Standards (NAAQS), New Source Performance Standards (NSPS); and National Emissions Standards for Hazardous Air Pollutants (NESHAPs), and significantly strengthened federal enforcement authority, all toward achieving aggressive air pollution reduction goals.

To implement the strict amendments, EPA Administrator William Ruckelshaus spent 60% of his time during his first term 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.[54]

Major amendments were added to the Clean Air Act in 1977 (1977 CAAA) (91 Stat. 685, Pub. L.Tooltip Public Law (United States) 95–95). 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.[53] 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.[29]

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.[55]

President George H. W. Bush signs the Clean Air Act Amendments of 1990 at the White House, November 15, 1990.

Another set of major amendments to the Clean Air Act occurred in 1990 (1990 CAAA) (104 Stat. 2468, Pub. L.Tooltip Public Law (United States) 101–549). 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)[56] 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.[53]

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. 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.[1]^: 16 The NAAQS program was also expanded. Other new provisions covered stratospheric ozone protection, increased enforcement authority and expanded research programs.[57]

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.[58]

The 1990 amendments also included a requirement for the Department of Labor to issue, no later than 12 months from the date of publication of the amendments, and in collaboration with the EPA, a "process safety standard". The text also highlighted the 14 principles on which this should be based. These were implemented in 1992 in OSHA's Process Safety Management regulation (Title 29 CFR Part 1910, Subpart H § 1910.119), as well as in EPA's 1996 Risk Management Program (RMP) rule (Title 40 CFR Part 68).

The Inflation Reduction Act, the budget reconciliation bill signed by President Joe Biden in August 2022, amends the Clean Air Act to allow the EPA to administer $27 billion in grants to green banks nationwide, through a competitive funding mechanism to be called the Greenhouse Gas Reduction Fund. $14 billion will go to a select few nonprofit green banks for a broad variety of direct investments in decarbonization startups, $6 billion will go to investments in low-income and historically disadvantaged communities, and $7 billion will go to distributed solar power in similar communities with no financing alternatives.[59][60][31][61] It is expected to generate high rates of return for the government on private sector investments. It also designates carbon dioxide and other greenhouse gases as substances to be regulated by the EPA, in reaction to the Supreme Court case West Virginia v. EPA, which limited the EPA's authority to institute a program such as the Obama-era Clean Power Plan. The IRA also allows the EPA more leeway to promote renewable energy.[62]