Air Quality Alert: 6 Common Pollutants To Watch Out For

Air pollution is a serious issue that poses a threat to human health and the environment. Six common air pollutants, known as criteria air pollutants, are regulated by the Environmental Protection Agency (EPA) in the United States. These pollutants include particle pollution (or particulate matter), ground-level ozone, carbon monoxide, lead, nitrogen oxides, and sulfur oxides. These pollutants are found all over the United States and are primarily caused by human activities, such as the burning of fossil fuels and industrial processes. The Clean Air Act, established in 1970, set National Ambient Air Quality Standards to protect public health and the environment, and since then, significant progress has been made in reducing emissions and improving air quality. However, challenges remain, and more than half of all Americans still live in areas with unsafe levels of air pollution.

Ground-level ozone

Ozone is a gas composed of three atoms of oxygen. It occurs naturally in the upper atmosphere, where it forms a protective layer that acts as a shield against the sun's harmful ultraviolet rays. This is known as stratospheric ozone, and it is considered "good" ozone. Ground-level ozone, on the other hand, is a harmful air pollutant and the main ingredient in smog. It is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. This type of ozone is a concern due to its negative impact on human health and the environment.

The major sources of ground-level ozone formation are motor vehicle exhaust, industrial emissions, and chemical solvents. Cars, power plants, industrial boilers, refineries, and chemical plants are among the primary contributors to the emissions of pollutants that lead to the creation of ground-level ozone. The Clean Air Act identifies ground-level ozone as one of the six common air pollutants, and the Environmental Protection Agency (EPA) has established regulations to help states reduce ozone levels in outdoor air.

To monitor ground-level ozone, various techniques are employed, such as LIDAR (a ground-based remote sensing method using lasers) and ozonesondes (instruments attached to meteorological balloons that directly measure ozone concentration at different altitudes). These measurements help in understanding and managing the impact of ground-level ozone on air quality and human health. The EPA works with states and tribes to improve air quality in areas that do not meet the national standards, designated as "nonattainment areas."

Particle pollution

It is formed through two main processes: mechanical and chemical. Mechanical processes involve breaking down larger particles into smaller ones, while chemical processes create fine and ultrafine particles through reactions between various gases and compounds in the atmosphere. Elemental black carbon (soot), volatile organic carbon compounds, heavy metals, and ammonia are some of the pollutants released through these chemical reactions.

Certain individuals are more vulnerable to the effects of particle pollution, including people with heart and lung diseases, pregnant women, older adults, children, and babies. Particle pollution levels tend to be higher near busy roads, in urban areas (especially during rush hour), and in industrial zones. Weather conditions, such as calm or stagnant air, can also contribute to higher particle concentrations.

Carbon monoxide

Indoor sources of carbon monoxide include gas stoves, leaking chimneys, furnaces, unvented kerosene or gas space heaters, wood stoves, and cigarette smoke. The highest levels of indoor CO typically occur during colder months when air pollution is trapped near the ground due to inversion conditions. Exposure to carbon monoxide can have serious health consequences, as it reduces the amount of oxygen delivered to the body's organs and tissues. Even healthy individuals can experience negative effects from high levels of CO exposure, including vision problems, reduced manual dexterity, and difficulty performing complex tasks.

Lead

Sources of lead emissions vary from one place to another. At a national level, major sources of lead in the air include ore and metals processing, and piston-engine aircraft operating on leaded aviation fuel. Other sources include waste incinerators, utilities, and lead-acid battery manufacturers. The highest air concentrations of lead are usually found near lead smelters.

Historically, motor vehicles and industrial sources were significant contributors to lead emissions. While motor vehicle emissions have decreased due to the phasing out of leaded gasoline, lead is still used in general-aviation gasoline for piston-engine aircraft. The U.S. Environmental Protection Agency (EPA) notes that regulatory efforts, including the removal of lead from motor vehicle gasoline, led to a 98% decrease in lead levels in the air between 1980 and 2014.

Human exposure to lead can occur through inhalation of lead particles in the air or ingestion of lead that has settled onto soil, dust, or other surfaces. Once in the body, lead distributes throughout the bloodstream and accumulates in the bones. Lead exposure can have detrimental effects on various physiological systems, including the nervous system, kidney function, immune system, reproductive and developmental systems, and the cardiovascular system. It can also impair the blood's oxygen-carrying capacity. Children are particularly vulnerable to the neurological effects of lead exposure, which may include behavioural problems, learning deficits, and lowered IQ.

Nitrogen dioxide

Breathing in air with high concentrations of NO2 can irritate the airways in the human respiratory system. Short-term exposure can aggravate respiratory diseases, especially asthma, leading to coughing, wheezing, or difficulty breathing. It can also cause hospital admissions and emergency room visits. Longer exposure to high concentrations of NO2 may contribute to the development of asthma and increase susceptibility to respiratory infections. Scientific evidence suggests that exposure to NO2 could also cause asthma in children.

The highest concentrations of outdoor NO2 are found in large urban regions, with levels being higher on or near heavily travelled roadways. The EPA has identified areas where the air quality does not meet national NO2 standards, and state and local governments are working to develop plans to reduce the amount of NO2 in the air.

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