Air Pollution: Sources And Origins

Air pollution is caused by solid and liquid particles and certain gases that are suspended in the air. These particles and gases can come from car and truck exhaust, factories, dust, pollen, mould spores, volcanoes, and wildfires. The burning of fossil fuels, such as coal, gasoline, or natural gas, is a major source of air pollution, as are vehicle emissions, industrial emissions, and solid fuel combustion. Natural sources such as volcanic eruptions, bushfires, and dust storms can also contribute to air pollution, sometimes in combination with human activities that worsen their effects.

Vehicle emissions

Carbon monoxide is a significant concern, with vehicle emissions being the largest source of this toxic gas in the United States. Carbon monoxide is a harmful gas that can have detrimental effects on human health, especially for those living near busy roads or with prolonged exposure during commutes. Nitrogen oxides (NOx) are another critical pollutant, formed when internal combustion engines burn nitrogen in the air. Diesel vehicles are major contributors to NOx emissions, with California's transportation sector responsible for nearly 80% of nitrogen oxide pollution.

Sulfur dioxide (SO2) is produced by burning sulfur-containing fuels, particularly diesel and coal. It poses health risks, especially to children and asthmatics, as it can form fine particles in the atmosphere. Volatile organic compounds (VOCs) react with nitrogen oxides in the presence of sunlight to form ground-level ozone, a primary component of smog. While ozone in the upper atmosphere is beneficial for blocking harmful radiation from the sun, ground-level ozone irritates the respiratory system.

Particulate matter (PM) is another pollutant from vehicle emissions, including the soot seen in exhaust. Fine particles, smaller than the diameter of a human hair, can penetrate deep into the lungs and pose serious health risks. Additionally, vehicles emit pollutants that contribute to global climate change, such as carbon dioxide (CO2), the principal greenhouse gas. While CO2 is essential for life on Earth, burning fossil fuels releases excessive amounts, overwhelming the planet's natural absorption systems.

Heavy-duty vehicles, such as trucks and buses, play a significant role in global warming emissions. They comprise only 10% of all vehicles but contribute more than 25% of global warming emissions and substantial amounts of air pollution. The growing popularity of SUVs and pickup trucks, which often deliver poor mileage, also offsets the progress made by more fuel-efficient modern vehicles. However, there is a growing market for zero-emission heavy-duty vehicles, which can help reduce heat-trapping emissions and improve air quality.

Industrial emissions

In the United States, industrial air pollution disproportionately affects communities of color and low-income areas. This is due to historical racist zoning policies and discriminatory lending practices, resulting in polluting industries being located near these communities. As a result, residents are exposed to hazardous air pollutants, leading to increased health risks and economic burdens.

To address industrial emissions, the European Union (EU) has implemented the Industrial Emissions Directive, which aims to prevent and reduce pollution from over 50,000 large industrial plants, including power plants, refineries, waste treatment facilities, and intensive livestock rearing. The directive sets emission limit values based on the Best Available Techniques (BAT) and requires EU countries to organise site inspections regularly.

The Clean Air Council in the US also works to reduce industrial air pollution by advocating for policy changes, educating the public, and taking legal action against highly polluting industries. Similarly, the Southern Environmental Law Center (SELC) is committed to improving air quality in Southern communities by holding polluting industries accountable and strengthening permits and emission limits.

By regulating industrial emissions and enforcing pollution controls, these organisations aim to protect ecosystems and human health from the detrimental effects of air pollution caused by industrial activities.

Natural sources

Sandstorms, which are becoming more common as more areas experience desertification, send sand and dust into the air. Radon gas is another example of a pollutant that comes mostly from natural sources.

Particulate matter (PM), or particle pollution, includes all airborne substances that are not gases. The main natural sources of PM are sea spray, wildfires, volcanoes, and dust storms. In comparison to human-caused PM, natural PM tends to be coarser.

While methane is emitted by both natural and industrial sources, it is released in large amounts during oil and gas drilling. Methane is also a major emission from coal mines and agricultural processes.

Fossil fuels

Particulate matter, specifically PM2.5, refers to airborne particles with a diameter of up to 2.5 microns, or about one-thirtieth the width of a human hair. These tiny particles can remain suspended in the air, making them easily inhalable and capable of penetrating deep into the lungs and entering the bloodstream. This can lead to adverse health effects, including respiratory issues, cardiovascular problems, and damage to multiple organs.

Ground-level ozone, or smog, is formed when emissions from burning fossil fuels react with sunlight. While ozone in the upper atmosphere protects us from harmful solar radiation, ground-level ozone is a significant health hazard. It can irritate the eyes, throat, and lungs, particularly in children, the elderly, and those with asthma or allergies.

The combustion of fossil fuels in industries, power generation, and transportation contributes significantly to air pollution. According to a global modelling study, air pollution from fossil fuels is responsible for approximately 5 million premature deaths each year, with 61% of the total 8.3 million deaths linked to fossil fuel emissions. This highlights the urgent need for a transition to clean, renewable energy sources.

Additionally, the burning of fossil fuels releases greenhouse gases, such as carbon dioxide and methane, which contribute to climate change. These gases trap heat in the Earth's atmosphere, leading to rising temperatures, sea levels, and more extreme weather events. The consequences of burning fossil fuels are evident in melting glaciers, rising sea levels, and increasing global temperatures.

Addressing air pollution from fossil fuels is crucial not only for mitigating climate change but also for improving public health, particularly in low-income communities and communities of color that are often disproportionately affected by air pollution.

Commercial and domestic sources

Residential wood burning is a significant contributor to fine particle emissions, accounting for 55% of Minnesota's direct fine particle emissions. Cars, trucks, trains, construction and agricultural equipment, boats, and snowmobiles also fall into this category, and while each may not pollute much on their own, together they emit almost half of Minnesota's air pollution. Older diesel vehicles and equipment are of particular concern, as they can produce significantly more harmful air pollution than newer models. Federal regulations have played a crucial role in reducing vehicle emissions by implementing standards for car manufacturing, fuel production, and fuel composition.

Household combustion devices, such as those used for cooking and heating, are another major source of indoor and outdoor air pollution. The combustion of fossil fuels, such as coal, gasoline, and natural gas, releases pollutants that contribute to smog and soot. Smog, or ground-level ozone, forms when emissions from these fuels react with sunlight. Soot, a type of particulate matter, consists of tiny particles of chemicals, soil, smoke, dust, or allergens that are carried in the air. Both smog and soot can have detrimental effects on respiratory health, especially for children, the elderly, and individuals with asthma or allergies.

In addition to transportation and residential sources, local businesses and industrial facilities contribute to commercial air pollution. Industrial processes, such as iron, steel, and rubber product manufacturing, power generation, and oil and gas drilling, release pollutants into the air. Volatile organic compounds (VOCs), found in paints, cleaning supplies, pesticides, and even craft materials, vaporize at or near room temperature and are released during combustion. Polycyclic aromatic hydrocarbons (PAHs), another type of organic compound, are produced as by-products in various industrial processes and are also found in particulate matter.

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