Airborne Toxins: What Makes Pollutants Harmful?

Air pollution is the release of various gases, finely divided solids, or finely dispersed liquid aerosols into the atmosphere at rates that exceed the natural capacity of the environment to dilute or absorb them. These airborne substances are considered air pollutants when they reach concentrations in the air that negatively impact human health, the economy, or the environment. There are six major air pollutants, known as criteria pollutants, which include ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These criteria pollutants are of particular concern due to their widespread presence and adverse effects on human health, the environment, and property.

Particle pollution

Overall, particle pollution is a serious issue that requires ongoing efforts to improve air quality and protect the health and well-being of people, especially those who are more vulnerable to its effects.

Ground-level ozone

Air pollution is the release of various gases, finely divided solids, or finely dispersed liquid aerosols into the atmosphere at rates that exceed the environment's capacity to dissipate, dilute, or absorb them. Air pollution can have undesirable health, economic, and aesthetic effects.

To address ground-level ozone pollution, the U.S. Environmental Protection Agency (EPA) designates areas as attainment or nonattainment based on national ambient air quality standards. States with nonattainment areas must develop implementation plans to improve air quality and meet the standards. The EPA also works to reduce emissions of pollutants that form ground-level ozone through national and regional rules, helping state and local governments improve air quality.

Carbon monoxide

Air pollution refers to the release of various gases, finely divided solids, or finely dispersed liquid aerosols into the atmosphere at rates that exceed the environment's capacity to dilute or absorb them. These substances can accumulate in the air, causing undesirable health, economic, or aesthetic consequences.

The presence of carbon monoxide in the air can have detrimental health effects. CO reduces the delivery of oxygen to the body's organs and tissues, particularly affecting the heart and brain. Exposure to CO can cause chest pain, diminished exercise capacity, and other cardiovascular issues, especially for individuals with pre-existing heart conditions. Even healthy individuals can experience adverse effects, including vision problems, reduced cognitive abilities, and difficulty performing complex tasks.

To mitigate the impact of CO pollution, organizations like the U.S. Environmental Protection Agency (EPA) establish standards and collaborate with state, tribal, and local agencies to ensure that CO levels are maintained within safe limits. These efforts are guided by legislation such as the Clean Air Act, which mandates the creation of National Ambient Air Quality Standards (NAAQS) for criteria air pollutants like carbon monoxide.

Sulfur dioxide

Air pollution is defined as the release of various gases, finely divided solids, or finely dispersed liquid aerosols into the atmosphere at rates that exceed the natural capacity of the environment to dissipate, dilute, or absorb them. These substances may reach concentrations in the air that cause undesirable health, economic, or aesthetic effects.

The presence of sulfur dioxide in the atmosphere can have several detrimental effects. Firstly, SO2 and other sulfur oxides can contribute to the formation of acid rain, which can harm sensitive ecosystems. Secondly, these gases can react with other compounds in the atmosphere to form small particles that contribute to particulate matter (PM) pollution. These particles may penetrate deeply into the lungs and, in sufficient quantities, can cause health problems. Additionally, high concentrations of gaseous sulfur oxides can harm trees and plants by damaging foliage and decreasing growth. The deposition of sulfur particles can also stain and damage stone and other materials, including culturally important objects such as statues and monuments.

To mitigate the negative impacts of sulfur dioxide, the Environmental Protection Agency (EPA) has established national ambient air quality standards for SO2. These standards aim to protect against exposure to sulfur oxides as a group, and reducing SO2 emissions can also lower exposures to other gaseous SOx. The EPA works with state, local, and tribal governments to identify areas where air quality does not meet the standards and to develop plans for reducing SO2 levels.

Nitrogen dioxide

Air pollution is the release of various gases, finely divided solids, or finely dispersed liquid aerosols into the atmosphere at rates that exceed the natural capacity of the environment to dissipate and dilute or absorb them. These substances may reach concentrations in the air that cause undesirable health, economic, or aesthetic effects.

Outdoor NO2 concentrations are highest in dense urban areas, on or near heavily travelled roadways, and in large urban regions such as the Northeast corridor, Chicago, and Los Angeles. The principal outdoor source of nitrogen dioxide is road traffic. Indoor sources of NO2 include tobacco smoke and gas-, wood-, oil-, kerosene-, and coal-burning appliances, such as stoves, ovens, space and water heaters, and fireplaces, particularly those that are unflued or poorly maintained. The average nitrogen dioxide concentration over several days may exceed 150 μg/m3 when unvented gas stoves are used.

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