Meghan Hodges
The National Ambient Air Quality Standards (NAAQS) are limits on atmospheric concentration set by the United States Environmental Protection Agency (EPA) for six principal pollutants (criteria air pollutants) that can be harmful to public health and the environment. These pollutants are typically emitted from many sources in industry, mining, transportation, electricity generation, and agriculture. The Clean Air Act, which was last amended in 1990, requires the EPA to establish these standards for the six common air pollutants: particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. The Air Quality Index (AQI) is used as a yardstick to measure the level of air pollution and the associated health concerns, with higher AQI values indicating more significant pollution and health risks.
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What You'll Learn
National Ambient Air Quality Standards (NAAQS)
A pollutant standard is a definition of the maximum amount of a pollutant averaged over a specified period that can be present in outdoor air without harming public health. The Clean Air Act Amendments of 1970 instruct the U.S. Environmental Protection Agency (U.S. EPA) to set primary and secondary National Ambient Air Quality Standards (NAAQS) to protect public health and the environment.
The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants, or "criteria pollutants," that are common in outdoor air, harmful to public health and the environment, and that come from numerous and diverse sources. These pollutants include particulate matter, ozone, nitrogen oxides, sulfur oxides, carbon monoxide, and lead. The Clean Air Act identifies two types of NAAQS: primary and secondary standards.
Primary Standards
Primary standards provide public health protection, including protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. These standards define clean air by setting a maximum amount of pollutant that can be present in the air without causing harm to public health.
Secondary Standards
Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings. These standards protect the public welfare from adverse effects related to impacts on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility, and climate, as well as damage to property, transportation hazards, economic values, and personal comfort and well-being.
NAAQS Review and Revision
The Clean Air Act requires the EPA to review and revise, if necessary, each of the NAAQS at five-year intervals. This review process involves a comprehensive review of the relevant scientific literature, risk and exposure assessments, and policy assessments. The resulting documents are released for public comment and peer review by the Clean Air Scientific Advisory Committee (CASAC). After considering public comments and peer review feedback, the EPA Administrator selects a proposed NAAQS, which is released for further public comment. The Administrator then considers the comments received and publishes the final NAAQS in the Federal Register. This review schedule ensures that NAAQS are based on the most recent scientific findings.
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Criteria Air Pollutants (CAP)
A pollutant standard is a level of air quality that is set to protect public health. The Environmental Protection Agency (EPA) establishes a national air quality standard for five major air pollutants regulated by the Clean Air Act. The Air Quality Index (AQI) is a scale from 0 to 500, with higher values indicating greater levels of air pollution and health concerns. An AQI value of 50 or below is considered good air quality, while a value over 300 indicates hazardous air quality.
Now, focusing on Criteria Air Pollutants (CAP):
The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for six commonly found and harmful air pollutants known as criteria air pollutants. These pollutants include particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. They are called criteria air pollutants because the EPA develops human health-based and environmentally based criteria for setting permissible levels.
The six criteria air pollutants are found all over the United States and can harm human health, the environment, and cause property damage. Particle pollution and ground-level ozone are the most widespread health threats among these pollutants. To protect public health, primary standards are set, including safeguarding the health of sensitive populations such as asthmatics, children, and the elderly. Secondary standards are also established to provide public welfare protection, preventing damage to animals, crops, vegetation, and buildings.
The EPA tracks two types of air pollution trends for each pollutant: air concentrations based on actual measurements at monitoring sites and emissions based on engineering estimates of total pollutant release. Despite improvements over the years, millions still reside in areas with unhealthy air quality due to one or more of these six criteria air pollutants. The ECATT Air Monitoring Stations help capture data on criteria air pollutants through a network of ambient air monitoring stations across the country. This data is vital for understanding and addressing air pollution levels and their impacts on human health and the environment.
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![Rapid techniques for calculating the pollutant standards index (PSI) by Lance A. Wallace and Wayne R. Ott. 1979 [Leather Bound]](https://m.media-amazon.com/images/I/61IX47b4r9L._AC_UY218_.jpg)
Air Quality Index (AQI)
The Air Quality Index (AQI) is a tool used by the EPA in the United States to communicate about outdoor air quality and health. The AQI runs from 0 to 500, with higher values indicating greater levels of air pollution and health concerns. For instance, an AQI value of 50 or below signifies good air quality, whereas a value over 300 represents hazardous air quality. Each of the six categories of the AQI is colour-coded and corresponds to a specific level of health concern.
The AQI is established for five major air pollutants regulated by the Clean Air Act. These pollutants include ozone and particle pollution, which are monitored through interactive maps and air sensors. The Clean Air Act identifies two types of national ambient air quality standards: primary standards and secondary standards. Primary standards aim to protect public health, especially for sensitive populations such as asthmatics, children, and the elderly. On the other hand, secondary standards focus on public welfare protection, including safeguarding against reduced visibility and harm to animals, crops, vegetation, and buildings.
The AQI values play a crucial role in determining the level of health risk associated with air pollution. When the AQI is at or below 100, the air quality is generally considered satisfactory. However, as the AQI rises above 100, the air quality deteriorates and becomes unhealthy first for sensitive groups and then for everyone as the values continue to climb.
The AQI serves as a valuable resource for individuals and communities to quickly assess the air quality in their local areas, states, or even at a national level. By referring to the AQI, people can take appropriate measures to protect their health when air pollution levels become a concern. Additionally, the AQI provides a basis for implementing measures to improve air quality and mitigate potential health risks for the public.
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Primary and Secondary Standards
The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants ("criteria" air pollutants) that are harmful to public health and the environment. These pollutants are common in outdoor air and come from numerous and diverse sources. The six criteria air pollutants are particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
The Clean Air Act identifies two types of national ambient air quality standards: primary and secondary standards. The primary standards provide public health protection, including safeguarding the health of "sensitive" populations such as asthmatics, children, and the elderly. These standards aim to protect public health with an adequate margin of safety.
The secondary standards, on the other hand, focus on public welfare protection. They address adverse effects on soils, water, crops, vegetation, animals, wildlife, weather, visibility, climate, property damage, transportation hazards, economic values, and personal comfort and well-being. These standards aim to maintain and improve the overall quality of the environment and people's comfort and security.
The Air Quality Index (AQI) is a useful tool for understanding air quality. It is a yardstick that runs from 0 to 500, with higher values indicating higher levels of air pollution and greater health concerns. AQI values below 50 represent good air quality, while those over 300 indicate hazardous air quality. This index helps people quickly assess the air quality in their communities and take appropriate actions to protect their health when necessary.
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Clean Air Act
The Clean Air Act (CAA) is a comprehensive federal law that regulates air emissions from stationary and mobile sources in the United States. It was established in 1970 under President Richard Nixon, with the bipartisan legislation passing unanimously in the Senate and 374-to-1 in the House of Representatives. The Act recognises the right to healthy air quality for all Americans, regardless of where they live.
The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants ("criteria" air pollutants) that can be harmful to public health and the environment. These six major pollutants are ozone, particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. The EPA establishes an Air Quality Index (AQI) for each of these pollutants, with higher AQI values indicating greater levels of air pollution and health concerns.
The Clean Air Act Amendments of 1977 expanded the scope of the original Act by including provisions to protect areas with clean air and tightening rules around automobile emissions. The 1990 Amendments marked a significant shift in how the EPA regulated toxic air pollutants, moving away from a one-chemical-at-a-time approach. These amendments also introduced cost-effective approaches to reducing air pollution, such as a national permits programme for large industries and a market-based cap-and-trade programme for emissions to control acid rain.
Section 112 of the Clean Air Act specifically addresses emissions of hazardous air pollutants. It requires the EPA to establish maximum achievable control technology (MACT) standards for major sources and certain area sources. Major sources are defined as stationary sources emitting or capable of emitting 10 tons or more of a hazardous air pollutant per year. The EPA must review and revise these standards as necessary to address any residual risks.
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