Meghan Hodges
The Clean Air Act requires the US Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants, or criteria pollutants, that are harmful to public health and the environment. These pollutants are common in outdoor air and come from diverse sources. The EPA works with state, tribal, and local air agencies to attain these standards throughout the country. The Clean Air Act identifies two types of NAAQS: primary standards, which aim to protect public health, including sensitive populations such as asthmatics, children, and the elderly; and secondary standards, which focus on public welfare protection, including safeguarding against decreased visibility and damage to animals, crops, vegetation, and buildings.
| Characteristics | Values |
|---|---|
| Organization | U.S. Environmental Protection Agency (EPA) |
| Air Quality Standards | National Ambient Air Quality Standards (NAAQS) |
| Pollutants | Particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead |
| Number of Pollutants | Six |
| Type of Standards | Primary and secondary |
| Purpose of Primary Standards | Protect public health, including sensitive populations such as asthmatics, children, and the elderly |
| Purpose of Secondary Standards | Protect public welfare, including against decreased visibility, damage to animals, crops, vegetation, buildings, and other materials |
| Units of Measure | Parts per million (ppm), parts per billion (ppb), and micrograms per cubic meter of air (µg/m3) |
| Attainment Status | Federal designation of whether air quality meets NAAQS; states must develop plans to attain and maintain standards |
| Review and Revision | The Administrator may review and revise criteria or promulgate new standards; a committee is appointed to review and recommend new standards every five years |
| State Implementation | State, local, and tribal agencies work with the EPA to develop emission reduction strategies to attain and maintain NAAQS |
What You'll Learn
The Clean Air Act requires the EPA to set primary and secondary NAAQS
The Clean Air Act, last amended in 1990, requires the 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 criteria air pollutants are common in outdoor air and come from numerous and diverse sources. They are:
- Particulate matter
- Ozone
- Carbon monoxide
- Sulfur dioxide
- Nitrogen dioxide
- Lead
The EPA established two types of national air quality standards: primary and secondary standards. The primary standards provide public health protection, including protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. The secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.
The Clean Air Act set a goal of achieving NAAQS in every state by 1975 to address the risks posed by widespread air pollutants. To achieve these standards, the Act directed states to develop State Implementation Plans (SIPs) for appropriate industrial sources. The EPA works together with state, tribal, and local air agencies to attain and maintain the NAAQS throughout the country.
The EPA's Office of Air and Radiation (OAR) develops national programs, policies, and regulations for controlling air pollution and radiation exposure. Under the Clean Air Act, the EPA is also required to establish emission standards for major sources, commonly referred to as "maximum achievable control technology" or "MACT" standards. These standards aim to achieve the maximum degree of reduction in emissions of hazardous air pollutants.
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NAAQS are set for six principal criteria air pollutants
The Clean Air Act requires the United States Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six principal criteria air pollutants. These pollutants are harmful to public health and the environment and are found all over the United States. The six criteria air pollutants are:
- Particulate matter
- Ozone
- Carbon monoxide (CO)
- Sulfur dioxide (SO2)
- Nitrogen dioxide (NO2)
- Lead (Pb)
These pollutants are given the name "criteria" air pollutants because the EPA sets NAAQS for them based on specific criteria: the latest scientific information regarding their effects on health and welfare. They are generally combustion products released by the burning of fossil fuels.
The Clean Air Act identifies two types of NAAQS: primary and secondary standards. Primary standards aim to provide public health protection, including safeguarding the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards, on the other hand, focus on public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.
State, local, and tribal agencies work together with the EPA to develop emission reduction strategies, plans, and programs to ensure they attain and maintain the NAAQS throughout the country. The Menu of Control Measures (MCM) is a document that provides these agencies with existing emission reduction measures and relevant information on their efficiency and cost-effectiveness.
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Primary standards protect public health
The Clean Air Act requires the US Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants, also known as "criteria pollutants". These pollutants are common in outdoor air and are considered 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 identifies two types of national ambient air quality standards: primary and secondary.
The EPA works together with state, tribal, and local air agencies to attain and maintain these standards throughout the country. State, local, and tribal agencies develop emission reduction strategies, plans, and programs to ensure compliance with the NAAQS. For example, New Hampshire has implemented measures such as federal tailpipe standards for new automobiles, traffic flow improvements, and annual emissions inspection programs, resulting in improved air quality and attainment of the NAAQS for carbon monoxide.
Areas that do not meet the NAAQS standards are designated as nonattainment areas and must develop plans to achieve attainment. On the other hand, attainment areas must also develop plans to maintain their status. Failure to attain the NAAQS by the target date can result in penalties, including the withholding of federal highway funds.
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Secondary standards protect public welfare
The Clean Air Act, last amended in 1990, requires the US 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 criteria air pollutants are particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. They are common combustion products released by the burning of fossil fuels.
The Clean Air Act identifies two types of NAAQS: primary and secondary standards. While primary standards focus on protecting public health, secondary standards are designed to protect public welfare.
Secondary standards aim to safeguard public welfare by addressing the adverse non-health effects of air pollution. They include protections against decreased visibility and damage to animals, crops, vegetation, and buildings. For instance, elevated concentrations of sulfur dioxide (SO2) in the atmosphere can react with other compounds to form small particles that contribute to particulate matter pollution, reduce visibility, and cause regional haze. Additionally, high concentrations of gaseous sulfur oxides can harm trees and plants by damaging foliage and impeding growth due to acid rain.
State, local, and tribal agencies play a crucial role in developing emission reduction strategies, plans, and programs to ensure compliance with the NAAQS. The Menu of Control Measures (MCM) provides these agencies with existing emission reduction measures and relevant information on their efficiency and cost-effectiveness.
To ensure that air quality meets the established standards, the EPA designates areas as either attaining (meeting) or not attaining (non-attainment) the NAAQS. When an area is designated as non-attainment, states must develop State Implementation Plans (SIPs) to outline the path to achieving and maintaining the NAAQS. These plans address both local emissions and emissions that drift across state lines, impacting downwind states.
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State, local and tribal agencies work with the EPA to attain NAAQS
The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for six commonly found air pollutants, known as "criteria" air pollutants. These pollutants are harmful to public health and the environment. The six criteria air pollutants are particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
State, local, and tribal agencies work with the EPA to attain NAAQS through the following processes:
Designation of Attainment or Nonattainment Areas
Within two years of setting or revising a NAAQS, the EPA, with input from states and tribes, designates areas as attainment (meeting the standard) or nonattainment (not meeting the standard). These designations are based on air quality data collected from monitors in urban and rural settings.
State Implementation Plans (SIPs)
Within three years of setting or revising a NAAQS, states must submit SIPs demonstrating they have the necessary air quality management components in place to implement the new or revised standard. SIPs are developed by state and local air quality management agencies and submitted to the EPA for approval. For nonattainment areas, SIPs must outline strategies and emissions control measures to improve air quality and meet the NAAQS.
Menu of Control Measures (MCM)
The EPA provides state, local, and tribal air agencies with the Menu of Control Measures (MCM), which includes existing emission reduction measures and relevant information on their efficiency and cost-effectiveness. This helps agencies develop emission reduction strategies, plans, and programs to attain and maintain NAAQS.
Review and Revision of NAAQS
The EPA works with state, tribal, and local air agencies to review and, if necessary, revise the NAAQS to ensure they are based on the latest scientific information regarding the effects of pollutants on health and welfare.
By working together and implementing these processes, state, local, and tribal agencies, and the EPA strive to attain and maintain NAAQS, improving air quality and protecting public health and the environment.
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Frequently asked questions
The Clean Air Act requires the US Environmental Protection Agency (US EPA) to set primary and secondary National Ambient Air Quality Standards (NAAQS) for six principal pollutants.
The six principal pollutants are: particulate matter, ozone, nitrogen oxides, sulfur oxides, carbon monoxide, and lead.
The primary standards are designed to protect public health, including sensitive populations such as asthmatics, children, and the elderly.
The secondary standards are designed to protect public welfare, including against decreased visibility and damage to animals, crops, vegetation, buildings, and other materials.
The NAAQS are reviewed every five years by an independent scientific review committee appointed by the EPA Administrator.
