Clean Air Act

Posted: Apr 14, 2010



The Clean Air Act (CAA) is the core law that establishes a comprehensive national program for reducing emissions from factories, cars, and other sources in order to protect human health and the environment. The law directs the federal Environmental Protection Agency (EPA) to establish national clean air standards, but then gives the states and Indian tribes an opportunity to take a lead role in meeting those standards. The law also gives EPA the responsibility for setting emissions limits for many sources of pollution, including cars and trucks (mobile sources) as well as factories and power plants (stationary sources). Both EPA and the states can go to court to enforce air quality laws; in addition, citizens and businesses can challenge many EPA decisions in court.

In March 2011, commemorating the 40th anniversary of the legislation, EPA released a report estimating the health and economic benefits of the Clean Air Act. According to the EPA's study, the economic benefits of the CAA between 1990-2020 exceed $2 trillion, compared with implementation costs of $65 billion. In 2010 alone, the study says, the reductions in fine particle and ozone
pollution from the 1990 Clean Air Act amendments prevented more than:

  • 160,000 cases of premature mortality
  • 130,000 heart attacks
  • 13 million lost work days
  • 1.7 million asthma attacks

In 2020, the study projects that benefits will be even greater,
preventing more than:

  • 30,000 cases of premature mortality
  • 200,000 heart attacks
  • 17 million lost work days
  • 2.4 million asthma attacks


Key Concepts

National Ambient Air Quality Standards (NAAQS)

The Clean Air Act (CAA) requires the Environmental Protection Agency (EPA) to set national clean air goals for a defined set of air pollutants (NAAQS), but then allows states (and Indian tribes) to take on much of the responsibility for achieving those goals. The first steps in this process require EPA to identify air pollutants that come from many sources and which might endanger public health or the environment. Then EPA assembles experts who develop a document that explains the criteria for why the air pollutant should be regulated (so they are called "criteria pollutants"). So far, EPA has only identified six criteria pollutants, but they are ubiquitous in our society: sulfur dioxide, particulate matter, nitrogen oxide, carbon monoxide, ozone (which is created by the chemical interaction of other pollutants), and lead. EPA sets nationally applicable limits for these pollutants to protect our health. These are called "primary standards." EPA also sets "secondary standards" -- limits on these pollutants to protect visibility and prevent damage to crops, buildings, and so on. 

In January 2010, the EPA issued a draft rule aimed at tightening the standards for ground-level ozone, or smog, proposing to set the health-based "primary" standard for smog within a range of 60 to 70 parts per billion (ppb) when averaged over an 8-hour period. The EPA also proposed a "secondary" standard of 7 to 15 parts per million-hours, aimed at protecting vegetation and ecosystems, including parks, wildlife refuges and wilderness areas. In early September 2011, however, President Obama cited concerns about the potential impacts on the nation's weak economy and requested that the EPA withdraw the NAAQS for ozone and delay new regulation until 2013. Congressional Democrats expressed strong dismay over this decision and vowed their intention to investigate the circumstances surrounding the rule withdrawal. In October 2011, five health and environmental groups filed a lawsuit challenging this decision. (See Washington Post story here.)

For more information on the ozone standard:


Attainment and Nonattainment Areas

Once EPA sets nationally applicable air quality standards, it then examines monitoring data to determine which areas meet those nationally applicable standards, and which do not. Those areas that meet the nationally applicable standards are called "attainment" areas, while those that do not are called "nonattainment" areas (described in EPA's Green Book). 

For example, in November 2009, the EPA released a final rule establishing the initial air quality designations for most areas in the United States, including Indian Country, for the 2006 24-hour fine particle National Ambient Air Quality Standards. States with areas designated nonattainment must undertake certain planning and pollution control activities within these areas in order to attain the standards as quickly as reasonably possible.

Attainment can be more difficult in eastern states, which receive pollution from industrial activities outside their borders. In the summer of 2010, the EPA proposed a new Cross-State Air Pollution Rule, aimed at reducing SO2 emissions by 71 percent and NOx emissions by 52 percent by 2014. (See Legal Planet analysis of the final rule.) Some advocates objected that the standards should be higher, reflecting stricter ozone standards proposed earlier in 2010. Others objected to the fact that the rule included an optional cap-and-trade program. The latter proved an effective objection, and the D.C. Circuit Court of Appeals ordered a temporary halt to the implementation of the new rule at the end of December 2011; in August 2012, the court vacated the rule in its entirety, concluding that (1) the rule impermissibly required upwind states to reduce emissions in excess of their contribution to downwind states' air pollution; and (2) EPA’s decision to implement the rule through a federal implementation plan at the same time it issued upwind state-by-state pollution budgets violated the Clean Air Act by not allowing states adequate time to develop state implementation plans.

For updated information on the EPA's response to this ruling, see the agency's Cross-State Air Pollution Rule website.


State and Tribal Implementation Plans

Once EPA decides that one or more areas of a state have air that is dirtier than what the nationally applicable standards require, then the focus shifts to states and tribes with EPA-approved air quality programs. If a state has an approved program, it must develop a plan for how it will bring the area back into compliance with the air quality standards. The state develops a state implementation plan -- known as a SIP -- to explain how it will reduce emissions, and from what sources. For example, the state could require some factories or other major sources to install reasonably available control technologies (RACT) to reduce emissions and bring the area into compliance with the CAA. 

In 1990, the Congress also authorized tribes to develop air quality programs similar to those adopted by states. By 2005, 20 tribes had received a delegation of CAA authority under EPA's Tribal Authority Rule (TAR). If EPA approves a tribal air program, then the tribe is responsible for developing a tribal implementation plan (TIP). At least two tribes have submitted implementation plans, including the Gila River Indian Community. The Southern Ute Tribe has also recently taken major steps towards regulating their air quality through a tribal administered program. See "Southern Ute tribe's air code on track toward approval," Durango Herald News, 5/11/10.

On April 5, 2010, the EPA provided notice that it is revising its regulations relating to the Clean Air Act requirement that federal actions conform to the appropriate state, tribal, or federal implementation plan for attaining clean air. 

Hazardous Air Pollutants

The CAA deals with hazardous air pollutants, which may pose serious health risks, differently than it deals with other air pollutants such as carbon monoxide that is emitted from cars and trucks, or sulfur dioxide that is emitted from power plants. The CAA identifies almost 200 hazardous air pollutants and the kinds of facilities that emit those pollutants. EPA can add and delete pollutants from that list. In the case of hazardous air pollutants, EPA determines what technology should be installed at each type of facility to achieve the maximum achievable reductions in emissions of these pollutants. Once those technologies are in place for a while, EPA can also assess whether a health risk is still present. If they decide there is a residual health risk, the agency can require even more stringent controls on emissions. 

As part of its toxic air pollutants program, EPA maintains a Toxics Release Inventory (TRI) database. This database includes information for the public about releases of toxic chemicals from manufacturing facilities into the environment through the air, water, and land. You can access the data by typing in your zip code. 

Mobile Sources

U.S. Supreme Court forces EPA into Climate Change Controversy over Motor Vehicles
In an April 2007 decision in Massachusetts v. Environmental Protection Agency, No. 05-1120, (U.S. Apr. 2, 2007) the U.S. Supreme Court decided that:

  • Greenhouse gases are "pollutants"
  • EPA has statutory authority to regulate the emission of such gases from new motor vehicles.
  • EPA could not refuse to regulate the gases without first either forming a reasoned scientific judgment on the link between greenhouse gases and climate change or
  • Providing some reasonable explanation as to why it cannot or will not exercise its discretion to determine whether they do.

Throughout the history of the CAA, Congress has recognized that cars and trucks--referred to as "mobile sources"--are significant contributors to air pollution, but that people and vehicles are highly mobile. For example, a car sold in California could end up being driven in New York state. The CAA therefore establishes nationally applicable rules for the amount of pollution that can be emitted from different kinds of vehicles, and has made those emissions standards more stringent over time. Congress also decided to preclude states from setting emissions requirements for cars, in an effort to achieve national uniformity. As a result, California (which already had a mobile source program in place when Congress first acted) is the only state that can adopt more stringent vehicle emission standards than those set by EPA.

After a seven-year legal battle over whether the state could impose stricter standards than mandated under the Act, the EPA announced on June 30, 2009 that it would give California the waiver it needed to begin regulating greenhouse gas emissions from cars and trucks. The U.S. Chamber of Commerce and the National Automobile Dealers Association filed a petition challenging this waiver, but the D.C. Circuit Court of Appeals upheld the agency's decision in an April 29, 2011 decision. The unanimous decision held that the plaintiffs failed to show that they would be injured by the waiver, and that the challenge is moot because California agreed to synchronize its own rules with the federal fuel economy standards for model year 2012 and beyond.

New Source Review (NSR)

Much of the CAA is focused on ensuring that major new sources of pollution, such as factories, install modern pollution controls at the time of construction. The Congress anticipated that as older stationary sources were enlarged or improved with significant modifications, they too would install pollution controls at that time. In 2003, the EPA issued complex rules that described when a modification at one of these older sources qualifies as "major" and therefore requires the source's owner to install modern pollution controls at the same time. These new rules defined "routine maintenance" as any activity that amounts to less than 20 percent of a plant's value and allowed power plants and other industrial polluters to modernize their plants without installing new pollution technology. In March 2006, a federal appeals court finally blocked the new rule at the request of 14 states that contended that the changes were illegal and could increase the amount of health-threatening pollution in the atmosphere. More recently, Judge Thomas Varlan of the U.S. District Court for the Eastern District of Tennessee found in favor of the Tennessee Valley Authority in a lawsuit in which environmental groups accused the utility of violating the NSR permitting program by not installing new controls when upgrading its facility. Judge Varlan ruled that 1988 upgrades at the TVA's Bull Run plant in Clinton, Tennessee constituted "routine maintenance, repair and replacement" and were therefore exempted from NSR requirements.

Supreme Court Decides NSR issues
In April 2007, the U.S. Supreme Court sided with environmental groups in Environmental Defense v. Duke Energy Corp. The case allows EPA to continue to regulate renovated power plants as "new sources" based on the total amount of pollution they emit, rather than based on the rate at which they emit it. This is important for air quality, as plant renovations often expand the operating time for plants. Increased hours of operation could lead to large increases in pollution if EPA were to use the hourly-rate standard desired by industry to trigger NSR rules and plants were not, consequently, required to reduce their rate of emission when they modify their plants to operate for longer periods of time. 

Another issue related to NSR arises from "fugitive emissions"--such as dust from mining operations or chemicals leaking from pipelines in the course of production. In 2002, the EPA issued an NSR rule that required the inclusion of such fugitive emissions in computing a source's emissions to determine whether NSR rules apply to a proposed facility modification. The EPA changed the rule in December 2008, but the Natural Resources Defense Council petitioned the agency to reconsider the rule change in February 2009. In April 2009, the EPA announced plans to reconsider the Bush-era NSR regulations, and in March 2010, the agency announced that it would delay the rule until October 3, 2011.

In September 2009, the Obama Administration announced plans to scrap the previous administration's guidance on NSR for oil and gas operations, opening the door for environmental challenges to oil and gas fields with multiple sources of emissions. In December 2009, the EPA announced plans to review its new source performance standards for oil and gas operations, in response to a lawsuit filed by environmental groups. In late March 2010 the agency announced that it will accept comments on its proposal but that its "preferred option is to revoke the NSR aggregation amendments." The EPA also proposed to extend the effective date of the aggregation policy to 11/18/10 to give the agency time to complete the reconsideration.

For more information on these court actions as well as other related cases on new source review go to EPA's web page.

A report by the National Research Council on New Source Review for Stationary Sources of Air Pollution may be purchased or viewed on-line. Several 2012 reports by the U.S. Government Accountability Office (GAO) examined implementation of the Clean Air Act's NSR provision: Air Emissions and Electricity Generation at U.S. Power Plants (GAO-12-545R, April 2012); EPA Needs Better Information on New Source Review Permits (GAO-12-590, June 2012).

For additional information on fugitive emissions from oil and natural gas activities, review the Natural Resources Law Center's Intermountain West Oil and Gas BMP Project website.


The CAA requires all major stationary sources of pollution (such as factories, power plants, smelters, refineries) to secure an air quality permit from the state agency (if it has an approved air quality program), a tribal agency, or the EPA. Those permits are open for public examination. In addition, these sources are required to monitor their emissions to assure they are complying with the air quality permits. That information also is available for examination by the public. 

For a time, the EPA had a policy of suspending normal emission standards for large sources holding Clean Air Act Title V permits during periods of "startup, shutdown, and malfunction" (SSM). Environmentalists objected that the SSM exemption was applied inappropriately to periods of normal operation, and the U.S. District Court for the D.C. Circuit agreed in 2008, in the case American Chemistry Council v. Sierra Club. On March 8, 2010, the U.S. Supreme Court declined to review the D.C. Circuit Court's ruling that prohibited the EPA from suspending normal emissions standards for major pollutions sources during SSM periods.

Another controversy involving stationary sources is to what extent the EPA should treat multiple sources in proximity to one another as a single "aggregate" source for permitting. In a closely watched decision, a federal appeals court in August 2012 ruled that the agency improperly aggregated several gas facilities located over a 43-square-mile area in Michigan. (Summit Petroleum Corp. v. U.S. E.P.A., 6th Cir., Aug. 7, 2012).

For more information on air permits, go to EPA's web page

Citizen Suits

If a citizen or a citizen group believes a pollution source is violating its permit, that group or individual can ask a federal court to stop those pollution violations and even to award monetary damages. For example, citizen groups who believe that old coal-fired power plants have modified their facilities without getting a required permit are suing in several parts of the country to force those power plants to install modern emissions controls.   And, early in 2010, environmental groups filed a notice of intent to sue the EPA for failing to meet deadlines to limit pollutants in several western states.

Process Essentials: Protecting Clean Air Areas

In major amendments to the CAA in 1977, the Congress took note of the fact that many areas of the country -- especially in the West -- have clean air. In response, the Congress added several provisions that are designed to keep air quality in these areas from deteriorating, especially in places like national parks. 

Class 1, 2 and 3 Areas

In the 1977 CAA amendments, the Congress decided to classify all those areas that meet or exceed the nationally applicable air quality standards as either class 1, class 2, or class 3. Based on the area's classification, EPA and states can permit certain amounts of increased pollution. The difference between a preexisting level of pollution and a new level is called an "increment." The Congress decided that most national parks and wilderness areas that were already in existence at the time of the 1977 amendments would be designated as class 1 areas, where only a small increase in pollution levels could be permitted. The legislation designated the rest of the clean air areas as class 2, where some additional pollution could occur. In addition, Congress allowed states to designate some areas as class 3, where the most pollution would be allowed, but still not enough to cause a violation of the national air quality standards. However, no states have redesignated a class 2 area as class 3. 

For more information, see the NPS website or the NPS 2006 annual air quality report.

Prevention of Significant Deterioration

When a major new factory or other pollution source is proposed to be constructed, the state air quality agency must assess whether that new source's pollution would cause a degradation of air quality in a class 1 area, or cause the added pollution to exceed the increment allowed for the designated class. If the state agency concludes that a new source would adversely affect air quality related values in a national park or wilderness area, or exceed the allowable "increment," then the agency will require the new source to install more efficient emissions control equipment. 

Visibility Protection

In the 1977 amendments, the Congress also established a program to reduce visibility impairment that was being observed in national parks and wilderness areas like the Grand Canyon. The Congress asked EPA to address both "plumes" that could relatively easily be traced from one or a few sources to a national park or wilderness area as well as the soup of pollutants that came from many, many sources and is transported over long distances (known as regional haze). Using these provisions, EPA was able to leverage a very large coal-fired power plant in Arizona to install pollution controls to help reduce visibility impairment in the Grand Canyon. 

Best Available Retrofit Technology (BART)

If EPA or a citizen group thinks a large source of pollution is directly affecting a class 1 area (a national park or wilderness area that was in existence in August 1977), and can convince the source to voluntarily reduce its emissions, or a federal court to require the source to clean up its emissions, the source likely will be required to install emissions controls that are described as best Available Retrofit Technology, or BART. When applying BART, EPA can consider a number of factors that bear on the feasibility and effectiveness of different pollution control technologies, including costs and environmental impacts of compliance and the remaining useful life of the source. 

Regional Haze

Regional haze can obscure visibility in a national park (e.g., the view from an overlook at Canyonlands), but it is attributable to many, many sources, some of them hundreds of miles away. It is really a "soup" of pollutants. While the 1977 amendments to the CAA directed the EPA to deal with the problem of regional haze, for a number of years the agency did little because it felt the science was inconclusive. In the 1990 amendments to the CAA, the Congress again directed EPA to tackle the issue of regional haze and established a Grand Canyon Visibility Transport Commission to evaluate the regional haze problem in the American Southwest. That commission, which was chaired by governors and tribal leaders and included all stakeholders, recommended a number of control measures, including a cap on emissions of sulfur dioxide from power plants and other sources, as a way to protect air quality in class 1 areas. That program's success is now being used as a model in other parts of the country for dealing with regional haze at national parks and wilderness areas. 

 Crater Lake National Park
ph.cleanair.jpg ph.cleanair2.jpg
 Clear day Hazy day 
 Photos courtesy of the Environmental Protection Agency

A copy of the Grand Canyon Visibility Transport Commission report is available from the Western Governors' Association web site

In a Federal Register notice dated January 9, 2009, the EPA reported that more than three dozen states have failed to submit adequate plans to reduce regional haze affecting national parks and wilderness areas. These plans were supposed to be submitted by December 17, 2007, but the EPA did not take action to enforce the deadline until sued by environmental groups. Five states submitted adequate plans: Arizona, Colorado, Michigan, New Mexico, and Wyoming. See "Missed deadlines in clearing haze over parks," Deseret News, 1/14/11.

In June, 2009, environmental groups petitioned the U.S. Department of the Interior to certify that the nitrogen dioxide emissions from a coal-fired power plant in Washington state is causing haze and impairing visibility in Mt. Ranier and Olympic national parks, a move aimed at forcing tighter pollution controls on the plant.

In March 2010, environmental groups urged the EPA to substantially toughen its smog standards to protect national parks as part of the administration's proposal to tighten its health-based "primary" standard for ozone, or smog, and adopt a new "secondary" standard aimed at protecting vegetation and ecosystems. Sixteen groups wrote EPA a letter on May 20, 2010, asking the agency to establish regional haze plans “that provide the full degree of visibility protection for Class I areas as required by law,” and focusing especially on the 25 states that have not yet submitted plans. They followed with a pair of 60-day notices of intent to sue in January 2011.

In January 2011, environmental groups filed a lawsuit against the Department of the Interior and the Department of Agriculture, calling on the agencies to certify that emissions from several coal-fired power plants are responsible for haze in western national parks and national forests. In June 2011, the parties announced a settlement under which the EPA would approve plans to address haze in Wyoming, Colorado, Montana, and North Dakota. A statement from one of the plaintiffs said that the states' proposals would retire or retrofit at least 18 coal-fired power plants. For an example of one such plan, see "EPA says Montana plants need $90 million in upgrades," Flathead Beacon, 3/25/12.

The latest consent decree between the EPA and environmental groups (approved by a federal judge on March 30, 2012) calls for completion of 34 SIPs over a staggered time period until November 2012. If the states don't meet the deadline, EPA is to prepare Federal Implementation Plans.



Energy Development in the Powder River Basin

In late May 2004, several conservation organizations filed a lawsuit in federal court alleging that the Bureau of Land Management had failed to adequately evaluate the cumulative effect of emissions from coalbed methane wells, coal mines and coal-fired power plants, and other sources on national parks and wilderness areas in the Powder River Basin region. The conservationists allege that these emissions are degrading air quality in those class 1 areas. This lawsuit is the first time critics of oil and gas production in the basin have used air pollution issues as their primary argument in a lawsuit. The conservation organizations contend that the EIS process failed to consider all the coalbed methane wells that are projected for the area as well as emissions from several large surface mines in Wyoming. 

Western Coal at the Crossroads

Power Plant Mercury

In February 2008, the U.S. Court of Appeals for the District of Columbia vacated two key rules issued by the Bush Administration on the regulation of mercury emissions from power plants (State of New Jersey v. EPA). One rule tried to remove coal and oil-fired power plants from strict CAA controls on mercury; the other had set the stage for a controversial cap and trade program for mercury.

As described in Western Coal at the Crossroads, western coal production is an important part of the economies of many western states. In this report, Western Resource Advocates (WRA) argues that the preeminent energy challenge facing the Interior West is to meet growing energy demands in a way that protects the region's natural environment while maintaining a vibrant, productive economy. Coal's large role in the West's energy system has come with a high environmental price tag - consumption of large amounts of water, and emission of vast quantities of air pollution and global warming pollution. WRA's report argues that developing integrated gasification combined cycle power plants using western coal is essential if the region's coal resources are to play a role in meeting the West's electricity needs and continue to provide fuel for coal power plants outside the region.

In July 2010, the Environmental Protection Agency announced new air quality rules for coal-burning power plants, replacing a plan enacted by the Bush administration but thrown out as inadequate in 2008.  The proposed rules will require utilities operating coal-burning plants to install scrubbers and other technology to reduce emissions of sulfur dioxide and nitrous oxides, which react in the atmosphere to form fine particles (soot) and ground-level ozone (smog).

Greenhouse Gas Emissions

President Obama's administration is pursuing a markedly different direction than the prior administration on federal regulation of the gases that contribute to global warming. For example, the EPA reversed position and granted California a waiver to regulate greenhouse gas emissions from automobiles. The U.S. Chamber of Commerce and the National Automobile Dealers Association filed a petition to overturn this decision, and the case is currently pending.

In March, 2009, the EPA set the wheels in motion to reconsider the Bush Administration's decision not to regulate for greenhouse gas emissions. Responding to a deadline established by the Supreme Court in the case Massachusetts v. EPA, on April 24, 2009 the EPA proposed an endangerment finding that links man-made greenhouse gases to threats to public health and welfare. On June 23, 2009, the U.S. Chamber of Commerce petitioned the EPA for an "on the record" hearing to review data that the agency used to support its proposed finding that greenhouse gases threaten human health and welfare. In September 2009, two Senators sent a letter to the EPA asking for a delay in the endangerment finding, and in October a free-enterprise organization petitioned the agency to reopen the public comment period on the proposal, arguing that critical data used to formulate the plan have been destroyed and that the available data are therefore unreliable. The EPA released its endangerment finding on December 7, 2009, prompting a public dispute about whether the finding would trigger national air quality standards for greenhouse gases. A number of states and industry groups filed motions in court to remand the EPA's endangerment finding, based on the same argument about unreliable science. EPA responded in a motion filed in late April 2010, taking issue with the petitioners' argument that the agency is not giving adequate attention to their request for reconsideration, and on August 13, 2010, the EPA issued an order denying the petitions to reconsider the endangerment finding. The U.S. Chamber of Commerce promptly filed a lawsuit challenging the EPA's endangerment finding. On December 10, 2010, the U.S. Court of Appeals for the District of Columbia ruled that the EPA could move forward with its plans to regulate greenhouse gases, and refused the petitioners' requests to stay the rulemaking while legal proceedings address the legality of such regulation under the Clean Air Act (Coalition for Responsible Regulation, et al. v. Environmental Protection Agency).

On April 10, 2009, the EPA proposed a regulation to require reporting of greenhouse gas emissions from all sectors of the economy. Updated information on the final rule as adopted (and subsequently amended) is available at the EPA's Greenhouse Gas Reporting Program website.

In May 2010, the EPA issued a rule aimed at limiting the number of facilities that would be required to obtain New Source Review and Title V operating permits based on their greenhouse gas emissions. EPA’s phased-in approach will start in January 2011, when CAA permitting requirements for greenhouse gas emissions will take effect for large facilities that are already obtaining CAA permits for other pollutants. Those facilities will be required to include greenhouse gas emissions in their permit if they increase these emissions by at least 75,000 tons per year (tpy). In July 2011, CAA permitting requirements will expand to cover all new facilities with greenhouse gas emissions of at least 100,000 tpy and modifications at existing facilities that would increase greenhouse gas emissions by at least 75,000 tpy. See "EPA announces a new rule on polluters," New York Times, 5/13/10. Both industry and environmental groups sued the agency, the industry groups arguing that the rule exceeds the EPA's authority and the Center for Biological Diversity contending that the rule should include a lower threshold for regulation. (The CBD dropped its lawsuit in June 2011.) In November, the EPA issued a guidance document explaining how states and local governments should implement the new permitting program.

On April 1, 2010, the EPA and the National Highway Safety Administration (NHTSA) announced a joint final rule aimed at dramatically reducing greenhouse gas emissions and improve fuel economy for new cars and trucks sold in the United States. The new light-duty vehicle greenhouse gas emissions standard and corporate average fuel economy standards pply to passenger cars, light-duty trucks, and medium-duty passenger vehicles, covering model years 2012 through 2016. They require these vehicles to meet an estimated combined average emissions level of 250 grams of carbon dioxide per mile, equivalent to 35.5 miles per gallon (MPG) if the automobile industry were to meet this carbon dioxide level solely through fuel economy improvements. Together, these standards will cut greenhouse gas emissions by an estimated 960 million metric tons and 1.8 billion barrels of oil over the lifetime of the vehicles sold under the program (model years 2012-2016). In early June 2010, the American Iron and Steel Institute filed a lawsuit against the EPA, asking the U.S. District Court of Appeals for the District of Columbia (Case 10-1134, filed 6/7/10) to review EPA's standard. By mid-July 2010, there were a total of 15 petitions challenging the rule.

After a long delay, in March 2012 the EPA issued reguations concerning
carbon dioxide emissions from new power plants,
following up on a settlement the agency reached in December 2010 after
the Massachusetts v. EPA litigation. The proposed rule would require all
new power plants to meet the same standard of 1,000 lbs of CO2 per
megawatt hour, regardless of the fuel. Compliance with this standard
will be far easier for natural gas plants than for coal-fired power
plants; the latter will likely need to develop and implement carbon
sequestration techonology to comply with the new rule. In April 2013, however, the EPA announced that it was withdrawing the
regulations for power plants, as described in this Legal Planet analysis dated May 24, 2013.

For an analysis of the new EPA regulations effective January 1, 2011, and the political consequences of this approach, see "EPA limit on gases to pose risk to Obama and Congress," New York Times, 12/30/10. For a National Public Radio story (1/3/11) focused on the regulation of power plants, click here. And, for a white paper making the case for this application of the Clean Air Act, see Farber and Sinden, "Six Myths About Climate Change and the Clean Air Act" (Center for Progressive Reform, 2011).

In June 2012, the U.S. Circuit Court of Appeals for the District of Columbia soundly rejected the legal challenges to four actions by the EPA regarding regulation of greenhouse gas emissions under the Clean Air Act. These include: the "timing" rule (which requires that new controls of greenhouse gas emissions from stationary sources be triggered on Jan. 2, 2011, when the new motor vehicle standards went into effect); the "tailoring" rule (which interprets the CAA to apply greenhouse gas emissions limitations only to major polluters); the "endangerment" rule (EPA's initail decision, ruling that greenhouse gas emissions are harmful); and the "tailpipe" rule (adopting new standards for car and light truck emissions). In December 2012, the full D.C. Circuit voted to deny a request to
rehear this argument, but the court's split decision sets the issue up
for possible review by the U.S. Supreme Court, as was requested by industry groups in several petitions filed in the early months of 2013.

For a comprehensive summary of the decision and its aftermath, see these Legal Planet Posts:

See also a special edition of the UCLA Journal of Environmental Law and Policy on using the Clean Air Act to address greenhouse gas emissions, which is summarized in this Legal Planet post of 4/24/12.

In the meantime, in July 2011, a federal district court judge sided with environmental groups and ruled that Section 231 of the Clean Air Act requires the EPA to decide whether airline emissions pose a threat to human health or welfare. The EPA argued that the endangerment ruling was a discretionary act, but Judge Kennedy of the U.S. District Court for District of Columbia wrote that this stance "would defeat the purpose of the act by allowing EPA to shirk its duty to combat air pollution." The case is Center for Biological Diversity v. U.S. EPA, C.V. 10-00985.

Clean Air Act Legislation of the 113th Congress

New information will be added as the Congress takes action.


 Click here to access the full report.


Public Laws

Clean Air Act as amended in 1990 (CAA)
42 U.S.C. sections 7401 to 7671q.


EPA regulations related to the CAA
(40 CFR Part 50 through 97 ) are available from the EPA web site.
GPO Access
The regulations are also available from GPO Access.

Environmental Protection Agency

EPA's air quality home page 
The EPA's web site provides a variety of data, maps and information about air quality and the CAA.
Plain English Guide 
EPA's primer on the CAA

Other Resources
The Save The Clean Air Act web site is a project of -- a collaborative effort of the nation's most influential environmental advocacy organizations harnessing the power of the internet to increase public awareness and activism on today's most important environmental issues. Their web site on clean air includes recent news articles, their own analysis of proposals and current policy, and calls for action.
Grand Canyon Trust
The Grand Canyon Trust is an organization dedicated to protecting and restoring the canyon country of the Colorado Plateau. The organization's web site includes information on the Western Regional Air Partnership and some of the major power plants of the area.

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