Air Pollution: Understanding The Main Causes And Contributors

Air pollution is a severe environmental health hazard that affects people of all ages, particularly children and the elderly. It is caused by solid and liquid particles, known as aerosols, and certain gases released into the atmosphere. These pollutants come from various sources, including vehicle emissions, fuel oils, natural gas combustion, manufacturing by-products, power plants, wildfires, and natural processes like volcanic eruptions and decomposing organic matter. The impact of air pollution on human health is significant, with exposure linked to respiratory issues, stunted lung development, cardiovascular problems, and an increased risk of cancer. It is also detrimental to the skin, the body's largest organ, causing redness and potentially contributing to chronic skin conditions. According to the 2020 State of Global Air report, air pollution was responsible for an alarming number of deaths, with 4.5 million linked to outdoor air pollution and 2.2 million to indoor air pollution.

Mobile sources: cars, buses, planes, trucks, and trains

Mobile sources of air pollution include cars, buses, planes, trucks, and trains. These vehicles emit harmful pollutants into the atmosphere, primarily through the burning of fossil fuels such as petrol, diesel, and gasoline. According to the Environmental Protection Agency, mobile sources account for more than half of all air pollution in the United States, with automobiles being the primary contributor.

Cars, trucks, and buses powered by fossil fuels are major contributors to air pollution. They emit pollutants such as carbon dioxide, nitrogen oxides, and particulate matter, which have detrimental effects on human health and the environment. Studies have linked pollutants from vehicle exhaust to adverse impacts on nearly every organ system in the body, including the lungs, heart, and brain. Additionally, carbon monoxide, a poisonous gas emitted by cars and trucks, can cause serious health issues such as lung irritation and increased susceptibility to respiratory infections.

Furthermore, tailpipe emissions from these vehicles contribute to elevated ozone concentrations, leading to the formation of smog. While smog can be intensified by increased heat and ultraviolet radiation, it is also influenced by emissions from cars, trucks, and buses. These vehicles emit volatile organic compounds (VOCs) and nitrogen oxides, which react with each other in the presence of sunlight to form ground-level ozone, a major component of smog.

Transportation, including airplanes, trains, and ships, accounts for a significant portion of heat-trapping gas emissions, contributing to climate change. While public transportation systems like buses, trains, and trams have lower per capita emission rates than private cars, they still produce air pollution throughout their life cycle, including during vehicle operation and fuel production. However, investing in modern, electric, or hybrid public transport fleets can help reduce pollution from these sources.

In addition to combustion sources, non-combustion sources such as tyre and brake wear also contribute to air pollution, especially in urban areas with high traffic density. Heavy-duty vehicles, such as lorries and freight trucks, fall into this category and are major polluters due to their high diesel fuel consumption and subsequent release of nitrogen oxides and particulate matter.

Stationary sources: power plants, oil refineries, factories

Stationary sources of air pollution, such as power plants, oil refineries, and factories, are significant contributors to air pollution and its associated health and environmental impacts. These sources emit large amounts of pollution from a single location, known as point sources of pollution. Power plants, in particular, burn fossil fuels like coal, natural gas, oil, and other fossil fuels, resulting in emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), carbon dioxide (CO2), mercury (Hg), and other pollutants. The health implications of these emissions are severe, with outdoor air pollution causing respiratory issues, strokes, heart disease, lung cancer, and acute and chronic respiratory diseases. According to the World Health Organization (WHO), 4.5 million deaths were linked to outdoor air pollution in 2019, and another 2.2 million to indoor air pollution.

Oil refineries and factories, as part of the broader category of industrial facilities, also contribute to air pollution through various industrial processes. Oil and gas development, for instance, leads to elevated ozone concentrations. Additionally, industrial facilities often involve the combustion of fossil fuels, which are major sources of greenhouse gas emissions. These emissions contribute to the climate crisis, intensifying the effects of air pollution.

The Clean Air Act, enacted in 1970 in the United States, has been crucial in reducing emissions from stationary sources. The Act directs the Environmental Protection Agency (EPA) to develop and implement standards and guidelines to control these emissions. However, despite the progress made, air pollution from stationary sources remains a pressing issue, impacting communities located near and far from these sources.

To address the impacts of stationary sources, such as power plants, on neighbouring communities, the EPA has developed tools like the Power Plants and Neighbouring Community Mapping Tool. This tool helps identify communities that may be exposed to air pollution from power plants, both locally and at a distance, by providing socioeconomic data and characterizing communities based on their proximity to the plants.

Area sources: cities, agricultural areas, wood-burning fireplaces

Cities are a major source of air pollution, with the built environment contributing to nearly 70% of particulate matter. This includes heating buildings, construction, and the traffic associated with it. High-vehicle traffic areas, for instance, have high levels of nitrogen dioxide (NO2), which is detrimental to human health.

In addition to vehicles, wood-burning fireplaces and stoves in cities also contribute to air pollution. Wood smoke adds to outdoor levels of carbon monoxide and increases indoor concentrations. It also emits nitrogen oxides, which contribute to particle pollution, and volatile organic compounds, which include harmful pollutants that contribute to ozone pollution. Some of these gases are carcinogens, including benzene and formaldehyde.

Agricultural areas are another significant source of air pollution. The production of artificial fertilizers, for example, has skyrocketed from about 20 million tons in 1950 to nearly 190 million tons today, with about a third of them being nitrogen-based. When excess fertilizers wash off fields, they can pollute huge watersheds. For instance, each summer, an oxygen-less "dead zone" spreads from the mouth of the Mississippi River, fueled by excess nitrogen from upstream agricultural activities.

Furthermore, agricultural pollution interacts with industrial pollution to create tiny solid particles or aerosols, which are about 1/30th the width of a human hair. These particles can penetrate deep into the lungs, causing heart or pulmonary disease. According to a 2015 study in the journal Nature, these aerosols cause at least 3.3 million deaths each year globally.

Natural sources: wind-blown dust, wildfires, volcanoes

Natural sources of air pollution include wind-blown dust, wildfires, and volcanic activity.

Wind-Blown Dust

Wind-blown dust is a natural source of air pollution that can have significant impacts on human health and safety. Dust storms and "blowing dust" are separate phenomena, but both can cause issues with transportation on land, sea, and air, as well as disrupt renewable energy systems and pose hazards to human health. Dust storms can cause vehicle crashes, while blowing dust can reduce visibility and cause respiratory issues, especially for those with asthma or other respiratory conditions.

Dust commonly originates in semi-arid to arid regions with loose sediments and flat, poorly vegetated land prone to wind erosion, such as global deserts and some agricultural lands. Dust can travel in small puffs over short distances or as huge dust clouds that move across oceans and continents, like the Saharan Air Layer, which transports African dust to the Americas.

Wildfires

Wildfires release smoke and particulate matter into the atmosphere, contributing to air pollution. The impact of wildfires on air quality can be significant, especially in areas where wildfires are frequent or where there are already high levels of air pollution.

Volcanoes

Volcanic activity, such as eruptions, can release large amounts of gases, including sulfur dioxide (SO2), into the atmosphere, causing air pollution. SO2 is a poisonous gas that can irritate the skin and mucous membranes of the eyes, nose, and throat, leading to respiratory distress, especially during physical activity.

The Kilauea Volcano in Hawaii is known for emitting about 2,000 tons of SO2 gas daily during sustained eruption periods. The gas combines with other volcanic emissions and interacts chemically with oxygen, moisture, dust, and sunlight to form "vog," or volcanic smog. Vog is a visible haze composed of gas and a mixture of tiny liquid and solid particles, primarily sulfuric acid and other sulfate compounds. Studies have also found small amounts of toxic metals, including selenium, mercury, arsenic, and iridium, in volcanic air pollution from Kilauea.

Volcanic air pollution can have significant impacts on downwind areas, including reduced visibility, health complaints, and damage to crops.

Fossil fuel combustion: gasoline, oil, diesel, wood

Fossil fuels, such as gasoline, oil, diesel, and wood, are significant contributors to air pollution. Fossil fuels are non-renewable energy sources formed from the remains of prehistoric plants and animals buried in the Earth's crust. The combustion of these fuels releases carbon, contributing to the increase in carbon dioxide (CO2) content in the atmosphere and leading to global warming and climate change.

Gasoline, a derivative of fossil fuels, is a major source of air pollution, particularly when burned as fuel in internal combustion engines. The invention of these engines and their use in automobiles and trucks significantly increased the demand for gasoline. Similarly, diesel fuel, another refined fossil fuel product, is used in engines and contributes to air pollution, with diesel-powered locomotives also transporting coal and crude oil.

Oil, or crude oil, is extracted and refined into various petroleum products, including gasoline and diesel. The process of extracting and refining oil, as well as its combustion, contributes to air pollution. Oil refineries are stationary sources of pollution, emitting large amounts of pollutants from a single location. Additionally, offshore oil drilling poses hazards to aquatic life, and oil shale exploitation has high carbon costs.

Wood, or biomass, has been used for domestic heating and cooking, contributing to household air pollution. While the use of wood as a primary energy source has decreased with the advent of fossil fuels, it still plays a role in energy production today. For example, wood pellets derived from forests are traded globally and used in some industries as a source of bioenergy.

The combustion of fossil fuels, including gasoline, oil, diesel, and wood, releases harmful pollutants into the air, such as particulate matter, carbon monoxide, ozone, nitrogen dioxide, and sulfur dioxide. These pollutants have detrimental effects on human health, causing respiratory and other diseases, and contributing to morbidity and mortality worldwide. Therefore, addressing the combustion of these fossil fuels is crucial in mitigating air pollution and improving public health.

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