Kiera Jefferson
There are several major atmospheric pollutants that negatively impact human health and the environment. These pollutants are emitted from various sources, including industrial activities, vehicle emissions, and natural processes. One of the most prevalent pollutants is particulate matter (PM), which consists of inhalable particles such as dust, soot, and smoke. PM can be further categorized into PM2.5 and PM10, with diameters of 2.5 micrometres and 10 micrometres, respectively. Another significant pollutant is ground-level ozone (O3), which is a key component of smog and is formed through complex chemical reactions involving nitrogen dioxide and volatile organic compounds. Carbon monoxide (CO), an odourless and colourless gas released from incomplete combustion, is also a major pollutant. Additionally, nitrogen dioxide (NO2), sulfur dioxide (SO2), and lead are considered major atmospheric pollutants, posing risks to both human health and the environment.
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What You'll Learn
Particulate Matter
The smaller particles, with diameters of 2.5 micrometres or less, are known as fine particles or PM2.5. These are the main cause of reduced visibility (haze) and pose the greatest risk to human health. They can be derived from primary sources, such as the combustion of fuels in power generation, industries, or vehicles, and secondary sources, such as chemical reactions between gases. PM2.5 can also be formed from complex reactions of gaseous pollutants, such as nitrogen dioxide and sulfur dioxide, reacting with oxygen and water vapour in the air to form nitrate and sulfate particles.
The health impacts of PM2.5 are significant. Short-term exposures have been linked to the worsening of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD), often leading to hospitalisations. Long-term exposure to PM2.5 has been associated with premature death, particularly in individuals with pre-existing chronic heart or lung diseases. It has also been linked to reduced lung function growth in children.
While air quality has improved over the years due to stricter standards and regulations, many people still live with unhealthy levels of particulate matter. Those living near emission sources, such as power plants, industrial sites, or roadways, are at a higher risk of exposure. Additionally, vulnerable subpopulations, including people of colour, are more susceptible to the adverse health effects of particulate matter pollution.
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Carbon Monoxide
The sources of atmospheric carbon monoxide vary across the world and during different seasons. For example, in Africa, carbon monoxide levels fluctuate with agricultural burning that moves with the seasons north and south of the equator. In contrast, the highest carbon monoxide concentrations in the United States, Europe, and eastern China are typically found around urban areas due to vehicle and industrial emissions. Forest fires can also be a significant source of carbon monoxide pollution, as seen in some years in North America, Russia, the Amazon, and Southeast Asia.
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Nitrogen Oxides
The presence of nitrogen dioxide in the air is indicative of other nitrogen oxides, as it is commonly used as an "'indicator pollutant'" by organisations such as the US EPA. This means that if nitrogen dioxide pollution is detected, other nitrogen oxides are also likely to be present. Nitrogen oxides contribute to particulate pollution, particularly the smallest and most harmful type known as PM2.5, by combining with VOCs, sulfur oxides, ammonia, and other particulates.
Nitrogen oxide emissions have a significant impact on visibility, breathing abilities, water quality, acid rain, and the Earth's temperature. Elevated levels of nitrogen oxides can be found near urban centres due to emissions from cars, trucks, and industrial activities. To address this issue, the EPA works with state, local, and tribal governments to develop plans and implement rules to reduce NOx emissions and improve air quality.
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Polycyclic Aromatic Hydrocarbons
PAHs are a significant atmospheric pollutant, found in particulate form in the air. They are emitted from various sources, including vehicle exhaust fumes, diesel engines, wood-burning stoves, and incinerators. A sampling study in Athens, Greece, found that wood-burning contributed to around a third of PAH urban air pollution, with diesel and oil contributing another third, and gasoline accounting for 29%. The same study also highlighted the seasonal variation in PAH levels, with wintertime concentrations being seven times higher than in other seasons, particularly when atmospheric dispersion is low.
The health effects of PAH exposure have been extensively studied. Short-term exposure can cause eye and respiratory irritation, while long-term exposure has been linked to adverse health outcomes, including lung cancer. Epidemiological research has associated PAH exposure with reduced lung function, exacerbated asthma, and increased rates of obstructive lung and cardiovascular diseases. In addition, PAHs have been linked to poor fetal growth, reduced immune function, and poorer neurological development, including lower IQ.
Due to their carcinogenic and genotoxic properties, PAH concentrations in air, water, and soil are regulated by governmental bodies such as the European Union, the United States Environmental Protection Agency (EPA), and the World Health Organization (WHO). The European Commission has restricted the concentrations of eight carcinogenic PAHs in consumer products that come into contact with the skin or mouth. The EPA has also identified priority PAHs based on their potential health risks.
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Ground-level Ozone
Ozone levels are typically higher during summer due to increased heat and sunlight, which promote ozone formation. Ozone is also more likely to reach unhealthy levels on hot, sunny days in urban environments. However, it can still reach high levels during the colder months. To monitor ozone levels, various techniques are employed, such as LIDAR, ozonesondes, and air quality environmental monitoring networks.
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Frequently asked questions
There are six major atmospheric pollutants, according to the US EPA: particulate matter, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
Particulate matter (PM) refers to inhalable particles composed of sulphate, nitrates, ammonia, sodium chloride, black carbon, mineral dust, or water. PM10 and PM2.5 can affect the lungs and heart and have been linked to premature death in people with heart or lung disease.
Ground-level ozone (O3) is a harmful air pollutant and a major component of smog. It is formed from photochemical reactions with pollutants such as volatile organic compounds, carbon monoxide, and nitrogen oxides emitted from vehicles and industry.
Carbon monoxide (CO) is a colourless, odourless gas produced by the incomplete combustion of carbonaceous fuels such as wood, petrol, coal, natural gas, and kerosene. It is harmful to human health and the environment.
Major sources of lead emissions include lead-contaminated soil, dust, paint, transportation sources using lead in their fuels, coal combustion, smelters, lead-acid battery manufacturers, and municipal solid waste incinerators. Lead exposure can adversely affect the nervous system, kidney function, immune system, and reproductive and developmental systems.
Nitrogen dioxide is an important ozone precursor and a pollutant closely linked to asthma and other respiratory conditions. It contributes to nutrient pollution in coastal waters and is emitted from power plants and automobiles.
