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Environmental Law: The Clean Air Act

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Air Pollution Prevention and Control under the Clean Air Act

In late October 1948, a heavy cloud of smog and airborne particles settled over a valley in Donora, Pennsylvania.  The valley was heavily populated by industrial mills, punctuated with billowing smokestacks and reeking with an eye-watering stench.  The thick, poisonous cloud caused at least twenty deaths in the five days it lingered stagnantly over the small town.  Just four years later, a similar event in London claimed thousands of lives and caused innumerable illnesses. [1]  By the mid-twentieth century, rapid industrialization had given rise to a global public health and environmental crisis that the world had never experienced before: the ravages of air pollution. 

In 1963, Congress passed the Clean Air Act, the first federal law that regulated whether and how certain pollutants may be released into the atmosphere.  Congress designed the statute “to protect and enhance the quality of the Nation’s air resources” by means of cooperative efforts at the federal, state, and local level.[2]  The original statute was conservative; it merely provided federal funds for air pollution research and created a federal public health program. [3]  However, Congress has expanded the scope of the Clean Air Act several times since it was passed.  The modern form of the Act requires private actors, state governments, and federal agencies to work together to develop and enforce key technology-based standards designed to combat some of our nation’s most serious air pollution problems. 

The Clean Air Act is a federal law, meaning that it was passed by Congress and applies to all state and local jurisdictions under the constitutional doctrines of federal supremacy and preemption.  However, state governments have some latitude in the administration of the law.  For example, states may elect to administer and enforce Clean Air Act permits within their borders, or they may defer to the federal Environmental Protection Agency.  When not serving as the main enforcement authority, U.S. Environmental Protection Agency monitors state air pollution programs and intervenes if necessary to ensure that state agencies are following the letter of the law.  Some states have gone so far as to create their own, more stringent, air pollution protection programs, as the Clean Air Act sets only the mandatory minimum standards.  While they are not required by the Act, states are encouraged to take the lead in Clean Air Act enforcement due to their superior knowledge of local industries, geology, residential settlement, and other data relevant to curbing air pollution.  [4]

The State Implementation Plan (“SIP”) requirement is one aspect of the Clean Air Act under which state governments have very little flexibility.  The Act requires the EPA to set specific standards for six common pollutants, known as the “criteria pollutants,” proven to damage property and harm human health and the environment: Carbon Monoxide, Lead, Nitrogen Dioxide, Ozone, Particulate Matter, and Sulfur Dioxide. [5]  These limits, known as the National Ambient Air Quality Standards or “NAAQS” (pronounced “Knacks”), create hardline standards for the six criteria pollutants: Carbon Monoxide may not exceed 9 parts per million over 8 hours or 35 parts per million over 1 hour, Lead is limited to 0.15 micrograms per cubic meter, Nitrogen Dioxide can be only 53 parts per billion over 1 year, Ozone must be 0.07 parts per million or less over 8 hours, Particulate Matter can be no more than 35 micrograms per cubic meter over 24 hours, and Sulfur Dioxide limits are set at 75 parts per billion over 1 hour.[6]  The EPA sets the NAAQS using the best information available at the time and revises the standards as necessary.[7]  Once the NAAQS are in place, the Clean Air Act requires each state to develop a State Implementation Plan, which is a set of policies that the state has designed to meet the EPA’s standards.  SIP requirements are very stringent and must include plans to curb emissions of the six criteria pollutants both within the state’s own borders and in neighboring downwind states.[8] 

Regardless of type or source, anyone emitting air pollutants regulated by the Clean Air Act must apply for and receive a permit.  Standards for award of a permit vary based upon the type of pollutant and the type of source emitting the pollutant.  In order to receive a permit under the Act, new “stationary sources” of air pollution – such as factories, chemical refineries, and power plants – in regions of low air quality are held to the most stringent standard.  To secure a permit, these polluters must demonstrate that they emit at the Lowest Achievable Emissions Rate (LAER), meaning that the facility can demonstrate that the pollution created by the new building will be completely offset by pollution reductions in other facilities in the area.  This requirement can add substantial cost to a proposed project and is designed to deter development of polluting industries in areas already impacted by air pollution.  For new or substantially modified sources of air pollution in areas with good air quality, facility owners must use the Best Available Control Technology (BACT) for the criteria pollutants.  The EPA determines which technologies qualify as “BACT” based upon the control technology’s cost and effectiveness.  Once the EPA has identified a certain technology as meeting the BACT standard, it becomes mandatory for all new sources of air pollution in areas of acceptable air quality.  Any existing stationary source of air pollution is required to use Reasonably Available Control Technology (RACT) to limit their air pollutant emissions, which is the minimum pollution-control standard under the Clean Air Act.[9] 

The Clean Air Act regulates many contaminants beyond the six criteria pollutants under the NAAQS program.  In a major amendment to the Act, Congress required the EPA to begin regulating hazardous or “toxic” air pollutants known to cause serious health effects such as cancer, reproductive impacts, or birth defects.  Congress took a very strong position with the new National Emissions Standards of Hazardous Air Pollutants; rather than waiting for the Environmental Protection Agency to come up with a list of toxic air pollutants, Congress identified 190 separate hazardous air toxins and required the EPA to set standards for these pollutants appropriate for the protection of public health and welfare.  Any facility that emits a listed hazardous air pollutant must secure a permit and install equipment that the EPA has identified as the Maximum Achievable Control Technology (MACT).  The MACT standard requires all emitters of air toxins to achieve the standard created by the cleanest facility in their industry.  In other words, the MACT benchmark shifts as emissions control technologies continue to develop, but all similar facilities are held to the standard of their highest-achieving competitor.[10]

Congress has also directed the EPA to issue standards for “mobile sources,” which includes any on-road and off-road vehicle, motorized lawn and garden equipment, locomotive, motor boat, or aircraft, as well as the fuels these items use to operate.  The EPA enforces its mobile source standards through mandatory testing and certification of new technologies.  Manufacturers of mobile sources have strong incentives to perform well in this initial testing and avoid additional government oversight.  However, the Act mandates harsh penalties for polluters who do not meet its requirements.  Knowing and intentional violations of a Clean Air Act permit or State Implementation Plan is a federal crime, carrying with it a penalty of hefty fines and up to two years in prison.  Violations of the Clean Air Act that do not rise to the criminal standard are subject to civil penalties of $37,500 per violation, per day.  Further, in a deviation from typical law enforcement policies, the Act enables private citizens to bring civil actions on their own initiative against alleged violators of the Clean Air Act. [11] 

The prospect of civil enforcement and steep fines encourage compliance with the Clean Air Act among even the most evasive polluters.  However, the motivation to cut costs by avoiding environmental regulation is a driving force in the regulated community.  In a recent headline-grabbing scandal, German auto manufacturer Volkswagen was discovered to have installed certain technologies designed to cheat the environmental testing the Clean Air Act mandates for new mobile sources.  The technology, designed to make vehicles appear compliant with the Act even when emitting up to 40 times more air pollution than what is allowed by law, exposed the popular auto maker to several billion dollars in civil liability.[12]  In a settlement reached as part of a plea agreement, Volkswagen committed over $2.9 billion to the development of new Nitrogen Dioxide control technologies, $4 billion for investment in zero emission vehicle technologies, and $1.45 billion in direct civil penalties.  These fines, together with other penalties levied against the company for violation of consumer protection laws, are estimated to amount to a staggering $10 billion loss for Volkswagen.[13]  

Although the prospect of being forced to pay billions of dollars in Clean Air Act fines, penalties, and compensation is an obvious deterrent to violations as egregious as intentional cheating, Fiat Chrysler Automobiles is presently facing a civil enforcement action based on facts nearly identical to the Volkswagen emissions scandal.   In January 2017, the EPA served Fiat with a notice of violation of the Clean Air Act alleging that the company also used emission cheating software to misrepresent air pollution emissions for over 100,000 of their Dodge and Jeep vehicles.[14]  While the degree of the company’s culpability is yet to be determined, the fact remains that financial incentives to cheat environmental controls are very strong.

The Clean Air Act, as amended, creates a comprehensive system of regulations and policies designed to address several different air pollution problems.  The Act distinguishes itself from other environmental statutes by relying on precise technology-based standards rather than the hardline prohibitions or qualitative standards typical in statutes like the Endangered Species Act and Clean Water Act.  Rather than articulate general standards and allow the regulated community latitude in achieving goals, the Clean Air Act requires polluters to install specific control technologies.  However, the financial burden of installing and maintaining mandatory air pollution control technology creates strong incentives for polluters to break the law.   As a result, federal, state, and local leaders must cooperate in enforcement and administration of the Act in order to ensure that human health, property, and the environment are protected from the damages of air pollution.


[1] American Meteorological Society. (1999). Environmental Events. Retrieved from https://www.ametsoc.org/sloan/cleanair.

[2] Clean Air Act Section 101, 42 USC § 7401 (1990).

[3] U.S. Environmental Protection Agency. (2017, January 3). Evolution of the Clean Air Act. Retrieved from Clean Air Act Overview: https://www.epa.gov/clean-air-act-overview/evolution-clean-air-act.

[4] U.S. Environmental Protection Agency. (2017, January 10). Government Partnerships to Reduce Air Pollution. Retrieved from Clean Air Act Overview: https://www.epa.gov/clean-air-act-overview/government-partnerships-reduce-air-pollution

[5] U.S. Environmental Protection Agency. (2017, January 10). Criteria Air Pollutants. Retrieved from Clean Air Act Overview: https://www.epa.gov/criteria-air-pollutants (citing Clean Air Act Section 109, 42 USC § 7409 (1990)).

[6] U.S. Environmental Protection Agency. (2017, December 20). Criteria Air Pollutants: NAAQS Table. Retrieved from Clean Air Act Overview: https://www.epa.gov/criteria-air-pollutants/naaqs-table#1.

[7] Clean Air Act Section 109, 42 USC § 7409 (1990).

[8] U.S. Environmental Protection Agency. (2017, January 10). Government Partnerships to Reduce Air Pollution. Retrieved from Clean Air Act Overview: https://www.epa.gov/clean-air-act-overview/government-partnerships-reduce-air-pollution

[9] U.S. Environmental Protection Agency. (2013, March 22). Clean Air Act in a Nutshell: How it Works. Retrieved from: https://www.epa.gov/sites/production/files/2015-05/documents/caa_nutshell.pdf.

[10] U.S. Environmental Protection Agency. (2013, March 22). Clean Air Act in a Nutshell: How it Works. Retrieved from: https://www.epa.gov/sites/production/files/2015-05/documents/caa_nutshell.pdf.

[11] Clean Air Act Section 113, 42 USC § 7413.

[12] U.S. Environmental Protection Agency. (2017, January 12). Learn About Volkswagen Violations. Retrieved from Volkswagen Violations: https://www.epa.gov/vw/learn-about-volkswagen-violations#timeline.

[13] U.S. Environmental Protection Agency. (2017, January 12). Volkswagen Clean Air Act Civil Settlement. Retrieved from Enforcement: https://www.epa.gov/enforcement/volkswagen-clean-air-act-civil-settlement#civil.

[14] U.S. Environmental Protection Agency. (2017, January 12). Notice of Violation for Model Yar 2014-2016 diesel light-duty vehicles (Dodge Ram and Jeep Grand Cherokee). Retrieved from https://www.epa.gov/sites/production/files/2017-01/documents/fca-caa-nov-2017-01-12.pdf.