Kiera Jefferson
The Clean Air Act, enacted in 1970, contains provisions to control six common pollutants that formed dense, visible smog in many US cities and industrial centres. The Act requires the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) for these six criteria air pollutants, which include particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These pollutants are harmful to human health and the environment, and the EPA sets standards to regulate their emissions and protect public health and welfare. The EPA designates areas as meeting (attainment) or not meeting (nonattainment) the standards, and states must develop plans to attain and maintain the NAAQS.
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What You'll Learn
The Clean Air Act
The 1990 Clean Air Act Amendments were revised to curb four major threats to the environment and the health of millions of Americans: acid rain, urban air pollution, toxic air emissions, and stratospheric ozone depletion. The 1990 Amendments also created a new title to address the issue of acid rain, particularly targeting nitrogen oxide and sulfur dioxide emissions from electric power plants powered by fossil fuels.
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National Ambient Air Quality Standards (NAAQS)
The Clean Air Act requires the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) for six common air pollutants, also known as "criteria" air pollutants. These pollutants are common in outdoor air and are harmful to public health and the environment. The six criteria pollutants are:
- Particulate matter
- Ozone
- Carbon monoxide
- Sulfur dioxide
- Nitrogen dioxide
- Lead
The Clean Air Act Amendments of 1970 instruct the EPA to set primary NAAQS to protect public health and secondary NAAQS to protect plants, forests, crops, and materials from damage. The primary standards aim to safeguard the health of sensitive populations, including asthmatics, children, and the elderly. On the other hand, the secondary standards focus on protecting public welfare, including preventing decreased visibility and damage to animals, crops, vegetation, and buildings.
The EPA sets NAAQS based on the latest scientific information regarding the health and welfare effects of these pollutants. The process of establishing NAAQS involves a comprehensive review of scientific literature, risk and exposure assessments, and policy assessments. These assessments are summarised in documents that undergo public peer review by the Clean Air Scientific Advisory Committee (CASAC). After considering public comments and making necessary changes, the final NAAQS are published in the Federal Register.
To ensure that NAAQS remains up-to-date, the Clean Air Act requires the EPA to review and revise the standards periodically, typically at five-year intervals. This review process helps to ensure that the standards are based on the most recent scientific findings and advancements. Additionally, states play a crucial role in implementing NAAQS by developing State Implementation Plans (SIPs) to attain and maintain the standards. Nonattainment areas, or areas that do not meet the standards, must develop plans to achieve NAAQS, while attainment areas work to maintain their status.
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Primary and secondary standards
The Clean Air Act, enacted in 1970, contains key provisions to control common pollutants that formed dense, visible smog in many cities and industrial centres across the United States. The Act requires the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) for six common air pollutants, also known as "criteria" air pollutants. These pollutants are particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
The Clean Air Act also requires the EPA to set both primary and secondary NAAQS for criteria pollutants. Primary standards aim to protect public health, including sensitive populations such as asthmatics, children, and the elderly. These standards ensure that individuals, especially those with pre-existing health conditions, are safeguarded from the harmful effects of air pollution.
On the other hand, secondary standards focus on public welfare protection. These standards address issues like decreased visibility and damage to animals, crops, vegetation, and buildings. By enforcing these standards, the EPA aims to mitigate the negative impacts of air pollution on the environment and infrastructure.
When an area is designated as "nonattainment," meaning it does not meet the NAAQS, states are required to develop State Implementation Plans (SIPs). These plans outline the specific steps and strategies that will be implemented to achieve and maintain compliance with the NAAQS. SIPs are crucial for ensuring that air quality standards are met and that the health and welfare of the public are protected.
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Particulate matter
The Clean Air Act, enacted in 1970, contains key provisions to control common pollutants, which at the time of the law's enactment formed dense, visible smog in many US cities and industrial centres. The Act requires the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) for six common air pollutants, also known as "criteria" air pollutants. These pollutants are particulate matter, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
- PM10: inhalable particles, with diameters generally 10 µm and smaller. PM10 can irritate the eyes, nose, and throat. Dust from roads, farms, dry riverbeds, construction sites, and mines are types of PM10.
- PM2.5: fine inhalable particles, with diameters generally 2.5 µm and smaller. PM2.5 can get into the deep parts of the lungs and even into the bloodstream. It is associated with the greatest proportion of adverse health effects related to air pollution, both in the United States and worldwide. Short-term exposures to PM2.5 have been linked to worsening respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Long-term exposure to PM2.5 has been linked to premature death, particularly in people with chronic heart or lung diseases, and reduced lung function growth in children.
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Hazardous pollutants
Hazardous air pollutants, also known as air toxics, are substances that cause or are suspected of causing cancer, birth defects, or other serious health issues. They can be gases, such as hydrogen chloride, benzene, and toluene, or compounds and metals such as asbestos, cadmium, mercury, and chromium. The Clean Air Act requires the EPA to regulate these hazardous air pollutants from categories of industrial facilities in two phases.
The EPA has classified 188 pollutants as hazardous. These pollutants are known to have a wide range of health and environmental impacts. They can be released into the air through chemical releases and accidents at industrial facilities, as well as during the transportation of hazardous materials. Major sources of outdoor toxic air pollutants include emissions from coal-fired power plants, industries, refineries, and vehicles like cars, trucks, and buses. Certain industries also produce specific toxins, such as ethylene oxide leaks from medical equipment sterilization facilities.
Indoor air can also contain hazardous pollutants from sources like tobacco smoke, asbestos-containing building materials, and consumer products such as cleaning supplies and air fresheners. People can be exposed to these pollutants by inhaling the air where they live, but also through other pathways. For example, these pollutants can settle into waterways, streams, rivers, and lakes, leading to potential ingestion through drinking water or consumption of fish from these waters.
To address the issue of hazardous air pollutants, the EPA uses emissions and ambient monitoring data to develop regulatory programs aimed at limiting emissions from stationary sources. Additionally, states develop State Implementation Plans (SIPs) to outline their strategies for implementing, maintaining, and enforcing the National Ambient Air Quality Standards (NAAQS). These plans address both primary standards, which focus on protecting public health, and secondary standards, which aim to safeguard public welfare.
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Frequently asked questions
No legislation has identified seven major criteria pollutants. However, the Clean Air Act, enacted in 1970, identifies six major criteria air pollutants: particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
Criteria air pollutants are specific contaminants that serve as key indicators for air quality. They are regulated by agencies and are used to set standards for good air quality.
Criteria air pollutants can harm human health and the environment and cause property damage. For example, carbon monoxide can reduce the amount of oxygen delivered to the body's organs, and lead is a probable human carcinogen that can cause developmental effects in children.
