Kiera Jefferson
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 pollutants are particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. Criteria pollutants are common in New Hampshire, the United States, and much of the world, and are generally combustion products released by the burning of fossil fuels. While the EPA has made significant strides in improving air quality and enforcing standards, the presence of these pollutants remains a concern, with areas designated as nonattainment requiring specific plans to attain and maintain the required standards.
| Characteristics | Values |
|---|---|
| Number of pollutants | Six |
| Type of pollutants | Particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead |
| Purpose of NAAQS | To protect public health and the environment |
| NAAQS types | Primary standards (protect public health) and secondary standards (protect public welfare) |
| Review process | The EPA is required to review the NAAQS periodically based on the latest scientific information |
| Nonattainment | Areas that do not meet the NAAQS standards |
| SIPs | State Implementation Plans developed by states to attain and maintain NAAQS standards |
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What You'll Learn
Particulate matter
The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for six major pollutants, also known as "criteria" air pollutants. These pollutants are harmful to public health and the environment. The six criteria air pollutants are:
- Particulate matter
- Ozone (O3)
- Carbon monoxide (CO)
- Sulfur oxides (SOx) or sulfur dioxide (SO2)
- Nitrogen oxides (NOx) or nitrogen dioxide (NO2)
- Lead (Pb)
The EPA has established standards for particulate matter in the NAAQS to protect public health and welfare. The standards set limits on the concentration of particulate matter in the air, with the primary standards aimed at protecting public health and the secondary standards aimed at protecting public welfare, such as reducing visibility issues and damage to crops, vegetation, and buildings.
The NAAQS for particulate matter have been periodically reviewed and revised to ensure that they are based on the latest scientific information and health effects data. For example, in 2012, the annual PM2.5 standard was lowered to better protect public health. Additionally, states are required to develop implementation plans, known as State Implementation Plans (SIPs), to achieve and maintain the NAAQS for particulate matter and other criteria pollutants.
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Ozone
Tropospheric ozone, in particular, has multiple negative impacts. It is a major short-lived climate pollutant, with its levels having increased by between 2-12% per decade since 1995, depending on the region of the world. The largest increases in tropospheric ozone have been observed over developing regions, including East Asia, the Persian Gulf, India, northern South America, the Gulf of Guinea, and Malaysia/Indonesia.
To address ozone pollution, rules have been implemented to require emissions reductions from power plants, vehicles, and other industries. However, the impacts of climate change, such as hotter summers and wildfires, can raise ozone levels, making it a continuous concern for air quality regulators.
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Carbon monoxide
The Clean Air Act, enacted in 1970 and last amended in 1990, was established to control common pollutants that formed dense, visible smog in many cities and industrial centres across the United States. The Act 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. On the other hand, secondary standards focus on public welfare protection, safeguarding against decreased visibility and damage to animals, crops, vegetation, and buildings.
To ensure the protection of public health and the environment, the EPA periodically reviews the NAAQS for carbon monoxide and the other criteria pollutants. In 2011, the EPA decided to retain the existing NAAQS for CO after conducting a review of the air quality criteria. This decision underscores the ongoing efforts to maintain and improve air quality standards across the country.
It is worth noting that some states, including New Hampshire, have made significant progress in attaining and maintaining the NAAQS for carbon monoxide. New Hampshire, for instance, has had no violations of the CO standards since the early 1980s, demonstrating a commitment to improving air quality and public health. Overall, the regulation of carbon monoxide as a criteria pollutant under the Clean Air Act plays a crucial role in safeguarding the well-being of individuals and the environment from the harmful effects of this toxic gas.
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Nitrogen dioxide
The EPA has established both primary and secondary NAAQS for nitrogen dioxide. The primary standards aim to protect public health, especially sensitive populations, while the secondary standards focus on public welfare, including the prevention of decreased visibility and damage to animals, crops, vegetation, and buildings.
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Lead
The Clean Air Act requires the Environmental Protection Agency (EPA) to set 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.
Once released into the air, lead can be inhaled or ingested through contact with contaminated soils, dust, or other surfaces. Ingestion of lead that has settled onto surfaces is the main route of human exposure. Lead distributes throughout the body via the bloodstream and accumulates in the bones. High levels of exposure can adversely affect multiple systems in the body, including the nervous, kidney, immune, reproductive, developmental, and cardiovascular systems. Lead exposure also reduces the blood's ability to carry oxygen. In children, lead exposure can cause neurological issues, while adults may experience cardiovascular problems such as high blood pressure and heart disease.
To address lead pollution, the EPA has implemented standards and regulations. For example, in October 2008, the EPA lowered the acceptable level of lead in the air from 1.5 micrograms per cubic meter to 0.15 micrograms per cubic meter. Areas that do not meet the NAAQS for lead are designated as nonattainment areas, and states are required to develop State Implementation Plans (SIPs) to achieve and maintain compliance with the standards.
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Frequently asked questions
Criteria pollutants are common in outdoor air and are considered harmful to public health and the environment.
The six criteria pollutants are ozone, particulate matter, lead, carbon monoxide, nitrogen dioxide, and sulfur dioxide.
Sources of particulate matter can be human-made, such as charbroiling, construction equipment, trains, and vehicle exhausts. Natural sources include pollen, wildfires, dust, sea salt, and volcano eruptions.
Primary standards aim to protect public health, including sensitive populations such as asthmatics, children, and the elderly. Secondary standards focus on public welfare protection, safeguarding against decreased visibility, damage to property, transportation hazards, and adverse effects on soils, water, crops, and animals.
The Clean Air Act, first enacted in 1970 and last amended in 1990, requires the EPA to set National Ambient Air Quality Standards (NAAQS) for six principal criteria pollutants. The Act also establishes health-based standards to protect public health and the environment.
