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TL;DR: The Clean Air Act has been the cornerstone of air pollution regulation in the United States since 1970, empowering the EPA to protect public health and the environment. Sparked by deadly smog events and public advocacy, the Act has significantly reduced emissions from both stationary and mobile sources, including a 78% drop in key pollutants. Its provisions have improved vehicle emissions, phased out leaded gasoline, and addressed challenges like acid rain and ozone depletion. The Clean Air Act has brought both major public health and economic benefits — emphasizing the importance of continued support for the EPA from the federal government.
According to the World Health Organization, air pollution is a major environmental health problem that results in roughly 6.7 million premature deaths annually and contributes to global warming. Legislation and regulation are primary strategies for mitigating these harmful effects. Over the last century, countries such as the United States have implemented legislation to curb air pollution, with the Clean Air Act standing out as a catalyst in the fight against the harmful impacts of air pollution.
The history behind the Clean Air Act
The history of the Clean Air Act of 1970 begins with the Donora Smog of 1948. Near the end of October 1948, the towns of Donora and Webster in Pennsylvania experienced an intense smog caused by a combination of factory emissions and a temperature inversion weather phenomenon, trapped by Donora’s unique geography.
This smog lasted less than a week but killed at least 20 people, inflicted serious illness on 1,440 people, and gave an additional 4,470 people mild to moderate symptoms. Nearly half of the total working-class population of Donora was affected, with higher rates of cancer deaths occurring even over the next decade. This tragedy, along with several other factors, including London’s Great Smog, and the publication of Silent Spring by Rachel Carson, led to the galvanization of the public and the passing of air quality legislation.
The United States passed its first legislation addressing air pollution in 1955 in the form of the Air Pollution Control Act. This act provided funds for federal research into air pollution. In 1963, the United States followed up with the first act aimed at directly controlling air pollution. Yet, the biggest impact was made by the Clean Air Act of 1970, which enabled the federal government to take on a much larger role in controlling air pollution.
At roughly the same time as the Clean Air Act of 1970, the National Environmental Policy Act was passed, establishing the U.S. Environmental Protection Agency (EPA). The EPA is responsible for implementing the various requirements of the Clean Air Act.
Later on, in 1990, Congress dramatically revised and expanded the Clean Air Act of 1970 to give the EPA greater authority to implement and enforce air quality standards. This included the EPA’s acid rain program, as well as revisions to tackle categories of industrial sources (for 187 toxic air pollutants) rather than merely addressing one pollutant at a time, which is less efficient. The EPA also began issuing permits for select emission sources. In 1997, the EPA published limits for Particulate Matter 2.5 (particles that are 2.5 μm or smaller in diameter).
What is the Clean Air Act?
The Clean Air Act (CAA) is a comprehensive federal law that regulates air emissions from stationary and mobile sources. It enables the EPA to enact a variety of programs and initiatives aimed at reducing air pollution.
For instance, the act gives the EPA authority to limit air pollution emissions from chemical plants, diesel engines, utilities, and steel mills. In 1998, the EPA also began limiting volatile organic compound (VOC) emissions from consumer products and architectural coatings (such as paints), because they can contribute to ground-level ozone air pollution by requiring formula changes.
The Clean Air Act enables the Environmental Protection Agency to tackle mobile transportation from multiple angles. The EPA has set regulations that have forced manufacturers to make cleaner engines, refiners to produce cleaner fuels, and areas with higher pollution to implement maintenance programs and passenger vehicle inspections. Also, the CAA requires the EPA to oversee new transportation projects, such as highway construction, to prevent more air pollution.
Some other provisions of the Clean Air Act include granting the EPA additional powers to help prevent transboundary air pollution across state borders and regional haze that impairs visibility. Through a combination of monetary penalties, incentives, and limited allowances, the EPA has addressed acid rain by forcing electric power plants to reduce their sulfur dioxide (SO2) emissions. The 1990 provisions of the Clean Air Act helped establish the Chemical Safety Board to investigate accidental releases of toxic chemicals from industrial facilities. Moreover, the act has allowed the EPA to set up initiatives to phase out stratospheric ozone-depleting chemicals in order to help heal the Earth’s protective ozone layer.
Although tribal, state, and local governments are largely responsible for meeting the Act’s requirements, the Environmental Protection Agency plays a vital role in assisting, funding, conducting research for, and enforcing the Clean Air Act. They make sure that local governments meet these regulations. Congress and the EPA are responsible for providing billions of dollars to local agencies and tribal nations in service of the Clean Air Act.
One of the primary facets of the CAA was that it authorized the United States Environmental Protection Agency to put in place National Ambient Air Quality Standards (NAAQS).
The National Ambient Air Quality Standards
The National Ambient Air Quality Standards exist for six harmful criteria air pollutants. These pollutants are carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), ozone (O3), particulate matter (PM), and sulfur dioxide (SO2). For each criteria pollutant, the NAAQS includes two standards: a primary standard and a secondary standard. The former aims to protect public health (including particularly vulnerable populations), whereas the latter aims to protect public welfare (such as managing visibility as well as safeguarding animals, crops, vegetation, and buildings).
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The Clean Air Act requires periodic scientific reviews of the NAAQS to occur every five years. These reviews are lengthy and meticulous. They lay the groundwork for possible revision or upholding of the current ambient air quality standards. These reviews ensure that the NAAQS best protects public health and welfare in the current moment.
Within two years of setting new or revised NAAQS, the EPA designates areas as either attainment areas, meaning that they are meeting the standards, or nonattainment areas, meaning they have not met the standards. The EPA uses air quality monitoring and modeling data as well as input from the states and tribes of the regions in question to determine the status of each area.
After another year, all states must submit state implementation plans (often called infrastructure SIPs) to show how they can consistently meet the new standards. Nonattainment areas are given 18-24 months (depending on which pollutants are overabundant) to submit SIPs, and must adhere to specified control requirements. The EPA may approve parts of the SIPs or replace them with their own federal implementation plan (FIP) before the plans become law, enforceable in a federal court.
The impacts of the Clean Air Act
The Clean Air Act has led to incredible progress toward cleaner air for Americans. Between 1970 and 2020, the combined emissions of six common pollutants (particulate matter, sulfur dioxide, nitrogen oxides, volatile organic compounds, carbon monoxide, and lead) have been reduced by 78%.
Under the Clean Air Act, the EPA has dramatically changed the nature of transportation. Compared to 1970 vehicle models, new cars, pickup trucks, and SUVs are about 99% cleaner for common air pollutants such as hydrocarbons, nitrogen oxides, carbon monoxide, and particulate matter emissions. New heavy-duty trucks and buses are similarly about 99% cleaner than 1970 models. The EPA has also reduced the amount of the toxic chemical benzene found in gasoline. New commercial marine vessels are about 90% cleaner for particulate matter emissions than in 1970. Since 2010, the EPA has even begun taking action to reduce aircraft emissions.
One of the most incredible benefits of the Clean Air Act has been the phasing out of lead in gasoline in the United States. This is one of the great public health achievements of the 20th century. Even small amounts of lead can have adverse health effects, especially in children. Yet, due to the efforts of the EPA, there was a 98% reduction in the percentage of U.S. children (between 1 and 5 years of age) with elevated levels of lead in their blood (>10 μg/dL) from the period of 1976–1980 to the period of 1999–2002. Today, children and adults are much safer from lead in the United States than they were in the past.
Stationary sources have also seen significant emission reductions. New coal-fired power plants now usually install control devices that capture up to 98% of the sulfur dioxide and frequently up to 90% of the nitrogen oxide emissions when compared to uncontrolled levels. Today, stationary sources release roughly 1.5 million tons less toxic air pollutants per year than in 1990.
The EPA’s efforts have contributed to a decrease in acid rain within the United States. Wet sulfate deposition, a common indicator of acid rain, dropped by over 70% between 1989–1991 and 2020–2022. This has further reduced the acidity of surface waters.
The EPA’s work has also led to mercury emissions falling about 80% between 1990 and 2014, and it is estimated that the EPA’s efforts to heal the ozone layer will save millions of lives from skin cancer. These are just some of the benefits that the Clean Air Act, and by extension the United States Environmental Protection Agency, is responsible for.
There is a common myth that environmental protection must come at the cost of the economy and industry. However, the EPA’s regulations have proven that the Clean Air Act has been a good economic investment for the United States. Cleaner air leads to fewer pollution-related health issues, medical bills, and absenteeism days from work. In 2020, the central benefits of the CAA outweighed costs by a factor of more than 30 to 1.
Looking forward
These many benefits demonstrate the importance of both the Clean Air Act and the Environmental Protection Agency in protecting public health and the environment. In order to secure and further these impacts, the EPA must be given the support it deserves.
Air quality monitoring is essential to many of the Clean Air Act’s initiatives. To learn more about how Clarity Movement’s ambient air quality sensors can help, find out how to build a solution with us.