Air Pollution: 3 Types And Their Harmful Effects

Air pollution is responsible for millions of premature deaths worldwide annually. It is caused by a variety of different pollutants, which can be found both outdoors and indoors. Three of the most common types of air pollution are particulate matter (PM), ground-level ozone, and carbon monoxide. PM is made up of tiny particles of solids or liquids in the air, which can be inhaled and cause irritation to the eyes, nose, and throat. Ground-level ozone is a major component of smog, which can cause eye irritation and respiratory issues. Carbon monoxide is a harmful gas that can have serious health effects, including reproductive problems and birth defects. These pollutants are regulated by organizations such as the EPA and WHO, which work to improve air quality and protect public health.

Particulate matter (PM)

PM2.5 particles are associated with the most significant adverse health effects related to air pollution. Short-term exposure to PM2.5 has been linked to respiratory issues, including asthma and chronic obstructive pulmonary disease (COPD). Long-term exposure can have more severe consequences, including premature death, particularly in individuals with pre-existing heart or lung conditions. Additionally, PM2.5 has been identified as a contributing factor to reduced visibility, known as haze, in certain regions of the United States.

PM10 particles, while larger, can still be inhaled into the lungs and cause adverse health effects. Studies have suggested a potential link between long-term exposure to PM10 and respiratory mortality. However, the specific health impacts of PM10 are less well-defined compared to PM2.5.

The sources of PM2.5 and PM10 particles differ. Coarse particles (PM10) typically originate from pollen, sea spray, and wind-blown dust from natural sources like erosion and agricultural activities, as well as human activities such as construction, unpaved roads, and mining operations. On the other hand, fine particles (PM2.5) can be derived from primary sources like the combustion of fuels in power generation, industrial processes, or vehicles. They can also have secondary sources, forming in the atmosphere through chemical reactions between gases such as sulfur dioxide and nitrogen oxides.

To protect public health, organisations like the US Environmental Protection Agency (EPA) have established regulations and standards for particulate matter pollution. The EPA's rules aim to reduce emissions of pollutants that contribute to PM, assisting state and local governments in meeting national air quality standards. Additionally, tools like the Air Quality Index (AQI) provide daily information to help individuals understand the level of air pollution in their area and take appropriate actions to safeguard their health when necessary.

Carbon monoxide (CO)

CO is a significant air pollutant, particularly in outdoor air, where it is emitted by a wide range of combustion sources, including motor vehicles, trucks, power plants, and other machinery that burn fossil fuels. The greatest sources of outdoor CO emissions are typically cars and other vehicles with fossil fuel-powered engines. These emissions are especially high in urban areas and places with heavy traffic congestion.

Indoor sources of CO include gas stoves, malfunctioning or improperly vented gas appliances (such as water heaters, furnaces, and clothes dryers), wood stoves, space heaters, fireplaces, tobacco smoke, and unvented kerosene heaters. The highest levels of indoor CO usually occur during colder months when inversion conditions are more frequent, trapping air pollution near the ground.

The health effects of CO are primarily due to its ability to reduce oxygen delivery in the bloodstream to critical organs like the heart and brain. Exposure to CO can cause dizziness, confusion, unconsciousness, and even death at very high levels. People with heart disease are particularly vulnerable to the effects of CO, even at lower levels, which can cause chest pain and reduced exercise capacity. Repeated exposure may contribute to further cardiovascular issues. High levels of CO can also affect healthy individuals, potentially causing vision problems and impairing cognitive functions such as the ability to work, learn, and perform complex tasks.

To control CO pollution and protect public health, organisations like the US Environmental Protection Agency (EPA) set and review standards for acceptable CO levels in outdoor air. These standards help state, tribal, and local agencies ensure that CO is maintained at safe levels.

Nitrogen dioxide (NO2)

NO2 is formed when nitric oxide reacts with available oxidants such as oxygen, ozone, and VOCs in the air. Road traffic is the primary outdoor source of this pollutant, while tobacco smoke and the burning of fuels like gas, wood, oil, kerosene, and coal are significant indoor sources. The use of unvented gas stoves can cause the average nitrogen dioxide concentration to exceed 150 μg/m3.

Short-term exposure to high concentrations of NO2 (above 200 µg/m3) can cause inflammation of the airways and increase susceptibility to respiratory infections. It can also exacerbate symptoms in individuals with pre-existing lung or heart conditions.

In the environment, NO2 deposition can lead to long-term harm to sensitive habitats by increasing nitrogen concentrations in soil or water, which can significantly alter plant community structures and affect associated animal species. Additionally, NO2 is a precursor pollutant in the formation of ozone.

Nitrogen dioxide levels have been decreasing over time, with the annual mean concentration in rural areas of the UK decreasing by 71% from 1997 to 5.2 μg/m3 in 2023. This decrease is attributed to the reduction in emissions of nitrogen oxides, particularly from road transport sources.

Sulphur dioxide (SO2)

SO2 emissions that lead to high concentrations of SO2 in the air can also lead to the formation of other sulfur oxides (SOx). These sulfur oxides 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 contribute to respiratory illness and other health problems, especially in children, the elderly, and those with pre-existing conditions. Longer exposures can aggravate existing heart and lung conditions.

SO2 and other sulfur oxides can contribute to acid rain, which can harm trees and plants, inhibit plant growth, and damage sensitive ecosystems and waterways. They can also react with other compounds in the atmosphere to form fine particles that reduce visibility (haze) in parts of the United States, including national parks and wilderness areas. The deposition of these particles can also stain and damage stone and other materials, including culturally important objects such as statues and monuments.

To address the issue of SO2 pollution, the US Environmental Protection Agency (EPA) has established national ambient air quality standards for SO2. These standards are designed to protect against exposure to sulfur oxides and reduce people's exposures to gaseous SOx. The EPA also works with state, local, and tribal governments to identify areas where air quality does not meet SO2 standards and develop plans to reduce SO2 levels.

Ground-level ozone (O3)

Ground-level ozone is a "secondary" pollutant, formed when two primary pollutants, nitrogen oxides (NOx) and volatile organic compounds (VOCs), react in sunlight and stagnant air. These primary pollutants are emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources. About 95% of NOx from human activity comes from burning coal, gasoline, and oil, while VOCs primarily come from gasoline combustion, upstream oil and gas production, and residential wood combustion.

Ozone levels are typically higher on hot, sunny days in urban areas, but they can also reach high levels during the colder months. Wind can carry ozone over long distances, allowing even rural areas to experience elevated ozone levels.

To address ground-level ozone pollution, the EPA works with states, tribes, and air quality monitors to designate 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 EPA's standards. These regulations are crucial for protecting public health and the environment from the adverse effects of ground-level ozone.

Ground-level ozone pollution is a serious issue, with the World Health Organization (WHO) recognizing ozone (O3) as one of six common air pollutants that contribute to premature deaths and adverse health outcomes globally. It is essential to monitor and reduce ground-level ozone levels to safeguard human health and well-being, as well as protect the environment.

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