Kiera Jefferson
Criteria air pollutants are common in New Hampshire, the United States, and much of the world. These pollutants are harmful to human health, the environment, and property. The Clean Air Act requires the US 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. The two dominant sources of criteria pollutants are mobile sources, such as motor vehicles, and machinery that burns fossil fuels.
| Characteristics | Values |
|---|---|
| Number of dominant sources of criteria pollutants | 2 |
| Criteria pollutants | Particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead |
| Dominant sources | Burning of fossil fuels, combustion of coal, oil, or solid waste |
| Other sources of lead emissions | Smelters, mining operations, waste incinerators, battery recycling, production of lead shot and fishing sinkers, lead-based paint, lead pipes |
| Major contributors to ozone | Motor vehicle exhaust, industrial emissions, gasoline vapors, chemical solvents |
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What You'll Learn
- Motor vehicles are a major source of nitrogen oxide and volatile organic compounds, which form ozone
- Fossil fuels: burning them releases combustion products like carbon monoxide
- Industrial emissions: they release nitrogen oxide and volatile organic compounds, which contribute to ozone
- Lead emissions: sources include mining, waste incineration, and burning coal, oil, or solid waste
- Particulate matter: a mixture of dust, dirt, soot, smoke, and liquid droplets in the air
Motor vehicles are a major source of nitrogen oxide and volatile organic compounds, which form ozone
Motor vehicles are a significant contributor to air pollution, particularly in the form of nitrogen oxide and volatile organic compound (VOC) emissions. These pollutants have detrimental effects on both human health and the environment.
Nitrogen oxide emissions from vehicles are primarily reduced through the use of exhaust gas recirculation (EGR) technology. EGR functions similarly to condensing boilers, redirecting exhaust gases back into the engine cylinder. This process reduces the amount of oxygen and lowers the temperature in the cylinder, resulting in fewer harmful emissions. In addition, the implementation of Euro emissions standards and the mandatory inclusion of catalytic converters since 1992 have played a crucial role in decreasing nitrogen oxide emissions. As a result, there has been an 84% reduction in these emissions between 2001 and 2017.
Volatile organic compounds, such as acetone, hexanal, toluene, and p-xylene, are released from vehicles and are major precursors of ozone (O3) and secondary organic aerosols (SOA). These VOCs not only impact air quality but also pose health risks to humans, with certain polycyclic aromatic hydrocarbons (PAHs) being carcinogenic. Studies in Wuhan, China, revealed that vehicle emissions, particularly from diesel engines, significantly contributed to VOC levels, emphasizing the need for stricter emission standards and traffic congestion reduction to mitigate these harmful effects.
The interaction of nitrogen oxides and VOCs in the atmosphere leads to the formation of ozone. While ozone in the upper atmosphere is beneficial, protecting us from harmful ultraviolet (UV) radiation, ground-level ozone is a harmful pollutant. It is a key component of smog, contributing to reduced visibility and adverse health effects, particularly in urban areas with high traffic density.
To address the issue of motor vehicles being a major source of nitrogen oxide and VOCs, several measures can be implemented. These include stricter emission standards, the utilization of advanced emission-reduction technologies, and the promotion of alternative forms of transportation. By enforcing more stringent standards and encouraging the development and adoption of cleaner vehicle technologies, emissions of these harmful pollutants can be significantly reduced, leading to improved air quality and public health outcomes.
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Fossil fuels: burning them releases combustion products like carbon monoxide
Fossil fuels are a dominant source of criteria pollutants, which are common in New Hampshire, the United States, and much of the world. The burning of fossil fuels releases combustion products like carbon monoxide, a colorless, odorless, and toxic gas. Carbon monoxide (CO) is formed when carbon-based fuels are incompletely oxidized during combustion, resulting in the formation of carbon monoxide instead of carbon dioxide. This occurs when there is insufficient oxygen during the combustion process, leading to the incomplete burning of carbon in the fuel. Fossil fuels, such as coal, heavy oils, and conventional hydrocarbon fuels, primarily consist of carbon and hydrogen. While complete combustion of these fuels produces carbon dioxide (CO2) and water (H2O), incomplete combustion yields carbon monoxide along with partially reacted flue gas constituents.
Carbon monoxide is a significant health hazard, as it can reduce the amount of oxygen delivered to vital organs like the heart and brain. Exposure to high levels of carbon monoxide, especially in enclosed spaces, can lead to dizziness, confusion, unconsciousness, and even death. Motor vehicles, including cars, trucks, and construction equipment, are major contributors to carbon monoxide emissions, with vehicle exhaust accounting for about 55% of CO emissions nationwide. Additionally, non-road engines, industrial processes, residential wood burning, and natural sources such as forest fires also produce carbon monoxide.
The combustion of fossil fuels also releases other harmful pollutants, including nitrogen oxides (NOx), sulfur dioxide (SO2), and volatile organic compounds (VOCs). Nitrogen oxides, such as nitrogen dioxide (NO2), are formed during high-temperature combustion processes. Major sources of NOx emissions include motor vehicles, electric utilities, and industrial activities. Sulfur dioxide (SO2) is produced during the combustion of fossil fuels containing sulfur, and it further reacts with other compounds in the atmosphere to form secondary particles that contribute to air pollution. Volatile organic compounds (VOCs), on the other hand, are released from motor vehicle exhaust, industrial emissions, and gasoline vapors, playing a crucial role in the formation of ground-level ozone (O3).
To address the issue of criteria air pollutants, the Clean Air Act was enacted in 1970 to control common pollutants that formed dense smog in cities and industrial centers. The Act requires the EPA to establish National Ambient Air Quality Standards (NAAQS) for six common air pollutants, including carbon monoxide, particulate matter, ozone, sulfur dioxide, nitrogen dioxide, and lead. These standards aim to protect public health and welfare by setting criteria based on the latest scientific information regarding the effects of these pollutants on human health and the environment.
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Industrial emissions: they release nitrogen oxide and volatile organic compounds, which contribute to ozone
The Clean Air Act identifies six common air pollutants, also known as "criteria air pollutants", which are harmful to human health and the environment. These include particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. Ground-level ozone, which is formed by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs), is one of these harmful pollutants.
Industrial emissions are a major contributor to the release of nitrogen oxides and volatile organic compounds, which, in turn, contribute to the formation of ground-level ozone. This occurs when pollutants emitted by industrial boilers, refineries, and chemical plants react in the presence of sunlight. While ground-level ozone is harmful to human health, stratospheric ozone is beneficial as it protects living things from ultraviolet radiation from the sun.
Nitrogen oxides (NOx) are formed primarily through high-temperature combustion, with significant sources including power plants, industrial furnaces, and boilers, as well as motor vehicles. VOCs, on the other hand, are commonly released by chemical plants, gasoline pumps, oil-based paints, auto body shops, and print shops. These emissions react with each other in the atmosphere, leading to the creation of ozone.
The formation of ground-level ozone is not limited to large cities but can occur in smaller cities and rural areas as well. It is most likely to reach unhealthy levels on hot, sunny days in urban environments, but it can also reach high levels during colder months, especially in areas with high local VOC and NOx emissions. The wind can carry ozone over long distances, allowing it to affect ambient air quality in regions far from its source.
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Lead emissions: sources include mining, waste incineration, and burning coal, oil, or solid waste
The Clean Air Act, enacted in 1970, was established to control common pollutants that formed dense, visible smog in many cities and industrial centres across the US. The 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.
Sources of lead emissions include mining, waste incineration, and burning coal, oil, or solid waste. Lead is a heavy metal that can cause adverse health effects through ingestion or inhalation. While sources of lead emissions vary across the US, major sources include lead-contaminated soil, dust, and paint; transportation sources using lead in their fuels; coal combustion; smelters; lead-acid battery manufacturers; and municipal solid waste incinerators.
Waste incineration, particularly medical waste, sludge incineration, and trash incineration, has been identified as a significant source of lead emissions. A study of sediment cores from New York's Central Park Lake spanning 100 years suggests that incineration of solid waste has been the dominant source of atmospheric lead in the New York City metropolitan area during the 20th century. This finding challenges the mainstream assumption that declines in atmospheric lead levels in urban areas during the 1970s and 1980s were primarily due to the introduction of unleaded gasoline.
In addition to waste incineration, mining operations, and burning coal, oil, or solid waste, lead emissions can also come from battery recycling, the production of lead shot and fishing sinkers, and the use of lead-based paint in older homes and buildings. Lead pipes and solder used in plumbing can also contribute to lead exposure.
The EPA's regulatory efforts, including the removal of lead from motor vehicle gasoline, have led to significant reductions in lead levels in the air. Between 1980 and 2014, national levels of lead in the air decreased by 98%. However, lead emissions continue to be a concern, particularly in areas with a history of incinerator construction and operation, such as New York.
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Particulate matter: a mixture of dust, dirt, soot, smoke, and liquid droplets in the air
Particulate matter, also known as particle pollution, is a mixture of solid particles and liquid droplets found in the air. These particles include dust, dirt, soot, smoke, and other tiny solid and liquid particles. Many of these particles are so small that they are invisible to the naked eye, but when their levels are high, they can make the air hazy and thick.
Particulate matter is formed through mechanical and chemical processes. Mechanical processes break down larger particles into smaller ones, and some examples of activities that produce such particles include dust storms, construction, demolition, mining operations, and agriculture. Chemical processes in the atmosphere create most of the fine and ultrafine particles in the air. These chemical processes result in particle pollutants such as elemental black carbon (soot), volatile organic carbon compounds, heavy metals, and ammonia.
The particles vary widely in size, shape, and chemical composition. They may contain inorganic ions, metallic compounds, elemental carbon, organic compounds, and compounds from the earth's crust. The size of these particles is defined by their diameter for air quality regulatory purposes. Particles with a diameter of 10 microns or less (PM10) are inhalable and can induce adverse health effects. Fine particulate matter, or PM2.5, is defined as particles that are 2.5 microns or less in diameter. These particles are so small that they can bypass the body's natural defenses, making their way deep into the lungs and even passing into the bloodstream.
Particulate matter has been shown to have adverse effects on human health, the climate, ecosystems, and materials. Long-term exposure to PM2.5 has been linked to premature death, particularly in people with chronic heart or lung diseases, and reduced lung function growth in children. The International Agency for Research on Cancer (IARC) has also concluded that particulate matter in outdoor air pollution causes lung cancer. In addition, particulate matter can reduce visibility and affect ecosystems through the deposition of particles onto plants, soil, and water. The metal and organic compounds in particulate matter can alter plant growth and yield.
While the air quality in much of the nation has improved, with lower levels of particulate matter than in previous decades, there are still many people living with unhealthy levels of particle pollution. Climate change is also driving increases in dangerous levels of particles from wildfire smoke. It is important for individuals and policymakers to take steps to protect against the harmful effects of particulate matter.
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Frequently asked questions
Criteria pollutants are common combustion products released by the burning of fossil fuels. They are harmful to health and the environment and can cause property damage. The six main criteria pollutants are particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
The dominant sources of criteria pollutants can vary depending on the specific pollutant. However, the burning of fossil fuels and certain industrial activities are significant contributors to the emission of criteria pollutants. Mobile sources, such as motor vehicles, and machinery that burns fossil fuels are major sources of carbon monoxide.
Criteria pollutants can have significant adverse effects on human health. For example, carbon monoxide can reduce the amount of oxygen delivered to vital organs like the heart and brain, leading to dizziness, confusion, unconsciousness, and even death. Lead can affect the nervous system, kidney function, immune system, and reproductive and developmental systems.
In the United States, the Environmental Protection Agency (EPA) plays a crucial role in regulating criteria pollutants through the Clean Air Act. The EPA sets National Ambient Air Quality Standards (NAAQS) for each pollutant based on the latest scientific information regarding their health and environmental impacts. These standards aim to protect public health and welfare by limiting the concentration of pollutants in the air.
