Brian Barton
The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants known as criteria air pollutants. These pollutants are particulate matter, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. They are called criteria air pollutants because the EPA sets NAAQS for them based on specific criteria: the latest scientific information on their effects on health and welfare. These pollutants are harmful to human health and the environment and can cause property damage.
| Characteristics | Values |
|---|---|
| Number of pollutants | 6 |
| Health impact | Harmful to human health, causing a range of health problems including adverse effects on the nervous system, kidney function, immune system, reproductive and developmental systems, and the cardiovascular and respiratory systems. |
| Environmental impact | Harmful to the environment, causing property damage and damage to trees and plants. |
| Prevalence | Found all over the US |
| Clean Air Act requirements | The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for these pollutants. |
| State/local involvement | States, cities, and towns must maintain levels of these pollutants beneath mandated ceilings or face "nonattainment" fines and penalties. They work together with state, tribal, and local air agencies to attain the standards. |
| Pollutants included | Particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. |
| Regulatory impact | From 1970 to 2022, total emissions of the six major air pollutants dropped by 78% in the US, improving the quality of millions of American lives. |
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What You'll Learn
- The Clean Air Act requires the EPA to regulate these six common pollutants
- They are harmful to human health and the environment, and cause property damage
- They are found all over the US and include particle pollution and ground-level ozone
- Sources of these pollutants include fossil fuels, vehicles, and industrial emissions
- States, cities, and towns must maintain levels below the mandated ceilings or face fines
The Clean Air Act requires the EPA to regulate these six common pollutants
The Clean Air Act requires the Environmental Protection Agency (EPA) to regulate six common pollutants, also known as criteria air pollutants. These pollutants are found all over the United States and can harm human health, the environment, and cause property damage. The six criteria air pollutants include:
- Particle pollution (particulate matter)
- Ground-level ozone (O3)
- Carbon monoxide (CO)
- Sulfur dioxide (SO2)
- Nitrogen dioxide (NO2)
- Lead
The EPA establishes National Ambient Air Quality Standards (NAAQS) for these pollutants, setting permissible levels to protect public health and welfare. The criteria for these pollutants are developed based on human health and environmental considerations, with primary standards focusing on health and secondary standards aimed at preventing environmental and property damage.
The Clean Air Act Amendments of 1990 marked a significant shift by establishing a national permits program, implementing the Montreal Protocol to address ozone layer depletion, and controlling acid rain with a market-based cap-and-trade program for emissions. The EPA's regulatory approach evolved from regulating toxic air pollutants individually to identifying entire categories of industrial sources for nearly 190 toxic air pollutants. This allowed for more effective pollution reduction by mandating appropriate pollution controls and production process changes in relevant industries.
State governments play a crucial role in implementing the Clean Air Act. They are responsible for developing and submitting State Implementation Plans (SIPs) to demonstrate how they will achieve the NAAQS for the six criteria pollutants. The EPA approves these plans and provides support through federal programs, policies, and regulations. The Act also empowers the EPA to take direct regulatory action if states' plans fall short or fail to comply.
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They are harmful to human health and the environment, and cause property damage
The six criteria air pollutants include particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These pollutants are harmful to human health and the environment and cause property damage.
Particle pollution, or particulate matter (PM), is a mixture of tiny particles found in the air, such as dust, dirt, soot, smoke, and liquid droplets. PM can be harmful to human health, particularly the respiratory and cardiovascular systems. Fine particles (PM2.5) and inhalable coarse particles (PM10) are the two types of particulate matter that are most harmful to humans.
Ground-level ozone is formed in the atmosphere by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOCs). Ozone can irritate and harm lungs, making them more susceptible to infection and increasing the frequency of asthma attacks.
Carbon monoxide (CO) is a colorless, odorless gas emitted primarily from combustion processes, such as fossil fuel burning in vehicles and machinery. CO is dangerous as it reduces the oxygen supplied to vital organs like the heart and brain. High levels of CO can lead to dizziness, confusion, unconsciousness, and even death.
Sulfur dioxide (SO2) contributes to particulate matter pollution and can react with other compounds to form small particles that reduce visibility and cause regional haze. At high concentrations, SO2 can harm trees and plants by damaging foliage and reducing growth rates.
Nitrogen dioxide (NO2) is a highly reactive gas and part of the NOx group. It is harmful to the respiratory system and contributes to the formation of other pollutants, including ozone, acid rain, and regional haze, which blocks sunlight and reduces visibility.
Lead is a heavy metal that can adversely affect multiple systems in the human body, including the nervous, reproductive, and developmental systems. Sources of lead emissions include contaminated soil, dust, paint, leaded fuels, coal combustion, and waste incineration.
These criteria pollutants have significant impacts on human health and the environment, leading to property damage and adverse health effects. Regulatory efforts, such as the Clean Air Act, have been successful in reducing emissions and improving air quality.
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They are found all over the US and include particle pollution and ground-level ozone
The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants found all over the United States. These pollutants are known as "criteria pollutants" and include particle pollution and ground-level ozone, as well as carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These criteria pollutants are chosen because they are widespread health and environmental threats, causing harm to human health and the environment, as well as property damage.
Particle pollution, or particulate matter, refers to small particles in the air that can reduce visibility and cause regional haze. These particles may include smoke, dust, dirt, or liquid droplets, and they can be made up of various materials, including acids, chemicals, soil, and metals. Sources of particle pollution can vary but often include vehicle emissions, industrial processes, and natural sources such as wildfires or volcanic activity.
Ground-level ozone, on the other hand, is a harmful air pollutant and the main ingredient in "smog." While ozone in the upper atmosphere protects us from the sun's ultraviolet rays, ground-level ozone is a harmful gas composed of three atoms of oxygen. It is formed when pollutants emitted by vehicles, industrial facilities, and power plants react with sunlight. Ground-level ozone can irritate the respiratory system, causing coughing, throat irritation, and chest tightness. It is particularly harmful to children, the elderly, and people with lung diseases.
To address these issues, the EPA develops human health-based and environmentally based criteria, setting permissible levels of these pollutants. These limits are called primary and secondary standards, respectively. Despite regulatory efforts, millions of people in the United States still live in areas with unhealthy levels of one or more of these criteria pollutants. This highlights the ongoing challenge of improving air quality and protecting public health and the environment.
Furthermore, certain states, including New Hampshire, are part of the Ozone Transport Region (OTR). These states must submit State Implementation Plans (SIPs) for the pollutants that form ozone, regardless of their attainment status regarding ozone standards. This additional measure ensures that actions are taken to improve air quality and protect public health, even in states that have achieved the required standards.
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Sources of these pollutants include fossil fuels, vehicles, and industrial emissions
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 common in the United States and much of the world, and they are generally combustion products released by the burning of fossil fuels.
Vehicles are also a significant source of pollutants, with on-road vehicles being the largest source of carbon monoxide (CO) in the United States. CO is an odourless gas that can come from the incomplete combustion of fossil fuels in boilers and engines, but it is primarily produced by automobiles, trucks, and buses. CO is found in higher concentrations in areas with poor ventilation, such as parking garages, tunnels, or areas with high traffic volumes and congestion. Motor vehicle exhaust and evaporative gasoline emissions are also major sources of benzene, which has adverse effects on human health and the development of animal fetuses.
In addition to fossil fuels and vehicles, industrial emissions contribute to air pollution. Industrial boilers and furnaces burning fossil fuels are sources of NO2 and SO2, respectively. Industrial emissions also contribute to the formation of ground-level ozone, which is a harmful air pollutant and the main ingredient in "smog". Ozone is formed through the reaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Major contributors to ozone formation include motor vehicle exhaust, industrial emissions, gasoline vapours, and chemical solvents.
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States, cities, and towns must maintain levels below the mandated ceilings or face fines
The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six commonly found 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 harmful to human health, the environment, and can cause property damage.
To ensure that air quality meets the standards, the EPA designates areas as either attaining or not attaining the NAAQS. States, cities, and towns that do not meet the standards are required to develop State Implementation Plans (SIPs) to outline a path to achieving and maintaining the NAAQS. These SIPs may include specific control measures and regulations to reduce emissions and bring down pollution levels. Non-attainment areas face the risk of federal sanctions and penalties if they fail to implement the necessary measures to improve air quality and meet the mandated standards.
For example, New Hampshire was designated as non-attainment for the 1971 carbon monoxide standard and has since developed and implemented plans to attain and maintain the NAAQS. Similarly, certain Northeast states, including New Hampshire, are part of the Ozone Transport Region (OTR) and must submit SIPs for ozone-forming pollutants, regardless of their attainment status. This ensures that states take proactive measures to address air quality issues and stay below the mandated ceilings.
The EPA periodically reviews and revises the NAAQS to reflect the latest scientific understanding of the health and environmental impacts of these pollutants. By setting these standards and enforcing them through penalties for non-compliance, the EPA aims to protect public health, improve air quality, and mitigate the harmful effects of criteria air pollutants on the environment and property. States, cities, and towns must, therefore, actively work towards maintaining levels below the mandated ceilings to avoid fines and ensure the well-being of their residents and the environment.
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Frequently asked questions
Criteria air pollutants are common air pollutants that are found all over the United States. They can harm human health, the environment, and cause property damage.
The six criteria air pollutants are particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
Sources of particle pollution include dust, dirt, soot, smoke, and liquid droplets. Ground-level ozone is formed in the atmosphere by a chemical reaction between other directly emitted pollutants, including oxides of nitrogen (NOx) and volatile organic compounds (VOCs). Carbon monoxide is primarily emitted from combustion processes and mobile sources like motor vehicles. Sulfur dioxide is released from the incomplete combustion of fossil fuels. Nitrogen dioxide is formed from NOx emissions, which come from power plants and automobiles. Lead is emitted from lead-contaminated soil, dust, paint, transportation sources using lead in their fuels, and coal combustion.
The Clean Air Act of 1970 empowered the US Environmental Protection Agency (EPA) to establish air quality standards to protect public health and the environment. The six criteria air pollutants were chosen due to their widespread presence and significant health and environmental impacts.
