Air Pollutants: Common Toxins In The Air

Air pollution is responsible for millions of premature deaths worldwide every year. Common air pollutants, also known as criteria pollutants, include particulate matter (or particle pollution), ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These pollutants can be emitted from vehicles, combustion engines, industrial processes, and agricultural activities. They have harmful effects on human health, the environment, and property, with particle pollution and ground-level ozone posing the most widespread health threats.

Particulate matter

Sources of particulate matter can be natural or anthropogenic. They include construction sites, unpaved roads, fields, smokestacks, and fires. Most particles form in the atmosphere as a result of complex reactions between chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, cars, and factories.

The health effects of inhaling particulate matter have been widely studied and are well-documented. PM2.5 particles pose the greatest risk to health as they can penetrate deep into the lungs and even enter the bloodstream. This can lead to a range of serious health problems, including respiratory diseases, cardiovascular disease, lung cancer, asthma, and developmental, neurodegenerative, and mental disorders. A 2014 meta-analysis reported that long-term exposure to PM2.5 is linked to a 13% increased risk of heart attacks. Additionally, particulate matter has been associated with premature death, contributing to an estimated 3.22 million deaths globally in 2010.

To protect public health, the EPA has established regulations to reduce emissions of pollutants that form particulate matter. The Air Quality Index (AQI) is a useful tool that provides information on outdoor air quality and associated health risks, helping individuals take appropriate actions to safeguard their health.

Ground-level ozone

Nitrogen oxides, a primary pollutant that contributes to ground-level ozone formation, come predominantly from human activities such as the burning of coal, gasoline, and oil in motor vehicles, homes, industries, and power plants. Volatile organic compounds, the other primary pollutant, arise from human activities such as gasoline combustion, upstream oil and gas production, residential wood combustion, and the evaporation of liquid fuels and solvents. VOCs also have natural sources, including coniferous forests.

To address ground-level ozone pollution, the EPA in the United States has implemented regulations and standards to help states reduce ozone levels in outdoor air. They designate areas as attainment or nonattainment based on air quality standards, with states drafting implementation plans to improve air quality in nonattainment areas. These measures aim to reduce emissions of pollutants that form ground-level ozone, enabling state and local governments to meet national air quality standards.

Carbon monoxide

Indoors, carbon monoxide can be released by a variety of household items, including unvented kerosene and gas space heaters, leaking chimneys and furnaces, and gas stoves. Tobacco smoke is another source of indoor carbon monoxide exposure. Incomplete oxidation during combustion can cause high concentrations of carbon monoxide in indoor air.

Breathing air with a high concentration of CO reduces the amount of oxygen transported in the bloodstream to critical organs like the heart and brain. Very high levels of CO, which are possible indoors or in other enclosed environments, can cause dizziness, confusion, unconsciousness, and even death. While very high levels of CO are not likely to occur outdoors, elevated outdoor CO levels can be dangerous for people with heart disease.

The EPA sets and reviews standards for CO in outdoor air under the Clean Air Act. These standards help state, tribal, and local agencies ensure that CO is maintained at a safe level.

Nitrogen oxides

Nitrogen dioxide, a common nitrogen oxide, has been linked to adverse respiratory effects. Exposure to high concentrations of NO2 can irritate the airways and aggravate respiratory diseases, especially asthma. Prolonged exposure may contribute to the development of asthma and potentially increase susceptibility to respiratory infections. Those living near major roadways are at a higher risk of inhaling elevated levels of NO2, with emissions up to 100% higher than in areas away from roads.

In addition to respiratory impacts, nitrogen oxides have broader environmental consequences. They contribute to nutrient pollution in coastal waters and play a role in forming ground-level ozone, or "bad" ozone, when reacting with volatile organic compounds (VOCs) and sunlight. This type of ozone acts as a barrier, preventing pollution from escaping the higher atmosphere. The presence of NOx also affects visibility, with nitrate particles making the air hazy and difficult to see through.

To address NOx pollution, the EPA has implemented rules to reduce emissions of NO2 and NOx, aiming to improve air quality and protect public health. These regulations are particularly important for sensitive individuals, including children and those with asthma.

Sulphur oxides

The deposition of SOx particles can also damage materials such as stone, as well as culturally significant objects like statues and monuments. Additionally, SO2 and other sulphur oxides contribute to acid rain, which harms trees and plants, inhibits their growth, and damages sensitive ecosystems and waterways.

To address these issues, the EPA has implemented rules to reduce SO2 emissions and other pollutants that form sulphur oxides. These regulations aim to help state and local governments meet national air quality standards. Control measures that reduce SO2 emissions can also lower people's exposure to other gaseous SOx. This can have the added benefit of reducing the formation of particulate sulphur pollutants, thereby improving overall air quality and protecting public health.

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