Greta Jimenez
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 particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. They are harmful to human health and the environment, and can cause property damage. The EPA develops human health-based and/or environmentally based criteria (science-based guidelines) for setting permissible levels of these pollutants.
| Characteristics | Values |
|---|---|
| Number of pollutants | Six |
| Pollutants | Particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead |
| Health impact | Harmful to human health, particularly for people with asthma, children, older adults, and people who are active outdoors |
| Environmental impact | Harmful to the environment, including trees, plants, wildlife, and water bodies |
| Property damage | Can cause property damage and transportation hazards |
| Primary standards | Based on human health, set to protect public health |
| Secondary standards | Intended to prevent environmental and property damage |
| EPA tracking | EPA tracks air concentrations through measurements at selected monitoring sites and emissions through engineering estimates |
| Progress | Despite progress, millions still live in counties with unhealthy air due to these pollutants |
Particle pollution
Smaller particles, called PM2.5, pose a greater risk as they can penetrate deep into the lungs and even enter the bloodstream. Particle pollution can affect anyone, but certain individuals are more susceptible. For example, those with asthma may experience worsened symptoms during periods of high pollution levels.
Outdoor air quality has seen improvements, but challenges persist. Particle pollution, along with ground-level ozone, are the most widespread health threats among the criteria air pollutants. The EPA continuously monitors air concentrations and emissions to track the presence and impact of these pollutants across the country.
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Ground-level ozone
Ozone is a gas composed of three oxygen atoms. While ground-level ozone is harmful, stratospheric ozone is beneficial as it forms a protective layer that shields the Earth from the sun's harmful ultraviolet rays. This "good" ozone occurs naturally in the upper atmosphere.
The harmful effects of ground-level ozone on human health are significant. It can cause coughing and shortness of breath, and can lead to more severe conditions such as damaged airways, chronic bronchitis, asthma, and emphysema. People with pre-existing lung diseases are particularly vulnerable. Even after symptoms disappear, ozone can continue to damage the lungs.
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Carbon monoxide
As a criteria air pollutant, carbon monoxide is one of the six common air pollutants that contribute to smog, acid rain, and other environmental problems, as well as pose risks to human health. These pollutants are found all over the United States and can have detrimental effects on both the environment and human well-being. The Clean Air Act requires the US Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for these pollutants, in collaboration with state, tribal, and local air agencies.
Additionally, certain atmospheric conditions can exacerbate the issue. During cold winter weather, an inversion layer can form in the atmosphere, trapping pollution, including carbon monoxide, near the ground and preventing it from mixing with cleaner air above. This further contributes to the health risks associated with carbon monoxide exposure.
To protect human health and the environment, regulatory bodies like the EPA work to implement and maintain standards that aim to reduce the presence of criteria air pollutants like carbon monoxide. These efforts include setting standards, monitoring areas that meet the standards, and collaborating with local agencies to ensure compliance. By addressing carbon monoxide pollution, these measures help mitigate its harmful impacts on the environment, human welfare, and overall air quality.
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Sulfur dioxide
Criteria air pollutants are a set of six pollutants that are considered harmful to public health and the environment. The Clean Air Act requires the US Environmental Protection Agency (EPA) to set national ambient air quality standards (NAAQS) for these pollutants. Sulfur dioxide (SO2) is one of the six criteria air pollutants.
When sulfur dioxide is released into the atmosphere, it can react with other air pollutants, leading to the formation of harmful fine particulate matter (PM2.5) and acid rain. These secondary pollutants can have detrimental impacts on the environment, including damage to crops, vegetation, and ecosystems, as well as causing corrosion to buildings and infrastructure.
In terms of human health, exposure to sulfur dioxide can irritate the respiratory system, causing coughing and making it difficult for people, especially those with asthma, to breathe properly. It can also worsen existing heart and lung conditions, and prolonged exposure may contribute to the development of respiratory and cardiovascular diseases.
To protect public health and the environment, regulatory bodies, such as the EPA, have established standards and regulations to limit sulfur dioxide emissions and maintain acceptable air quality levels. These standards aim to reduce the presence of SO2 in the atmosphere, thereby mitigating its harmful effects on human health and the environment.
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Nitrogen dioxide
NO2 can irritate airways and aggravate asthma, leading to increased susceptibility to respiratory infections. The nitrate particles resulting from NOx reactions reduce visibility and cause regional haze. Furthermore, NOx in the atmosphere contributes to nutrient pollution in coastal waters. While emission controls have been implemented in power plants and vehicles, these efforts have been offset by increasing energy demands and vehicle usage.
To address these issues, the EPA establishes National Ambient Air Quality Standards (NAAQS) and designates areas as meeting (attainment) or not meeting (nonattainment) these standards. States with areas designated as nonattainment must develop State Implementation Plans (SIPs) to outline the steps necessary to achieve and maintain the NAAQS. These plans aim to protect public health and welfare, including sensitive populations and the environment.
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Frequently asked questions
Criteria air pollutants are a group of six common air pollutants that are found all over the United States. These pollutants include particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
Criteria air pollutants are generally combustion products released by the burning of fossil fuels. Sources of these pollutants include power plants, motor vehicles, industrial boilers, waste incinerators, natural events such as wildfires, and certain industrial processes.
Criteria air pollutants can have significant adverse effects on both human health and the environment. For example, carbon monoxide is a poisonous gas that is dangerous to human health and can even be deadly at high concentrations. Nitrogen dioxide can irritate airways, aggravate asthma, and increase susceptibility to respiratory infections. Sulfur dioxide can harm the human respiratory system and also damage trees and plants through the formation of acid rain. Particle pollution can penetrate deeply into the lungs and cause health issues. Overall, these pollutants can cause property damage and negatively impact soils, water, crops, wildlife, and climate.
The Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for criteria air pollutants. The EPA develops human health-based and/or environmentally based criteria (science-based guidelines) for setting permissible levels of these pollutants. The limits based on human health are called primary standards, while those intended to prevent environmental and property damage are called secondary standards.
