Air Pollution: Understanding Its Formation And Causes

Air pollution is a major threat to global health and prosperity, causing more than 6.5 million deaths each year worldwide. It is caused by a combination of human-made and natural sources, including vehicle emissions, fuel oils, natural gases, manufacturing by-products, and fumes from chemical production. Natural sources of air pollution include wildfires, volcanic eruptions, and gases emitted from decomposing organic matter. These sources release solid and liquid particles, called aerosols, and certain gases into the air, which can have harmful effects on both the planet and human health.

Burning fossil fuels

Nitrogen oxides, for example, contribute to the formation of smog and acid rain. Smog is a type of air pollution commonly found in cities, appearing as a brown haze or smoky fog that reduces visibility. It forms when ground-level ozone, a harmful gas created by chemical reactions between pollutants and sunlight, combines with other particles in the air. Acid rain, on the other hand, is caused by the deposition of nitrogen compounds and sulfur oxides in the atmosphere, which then fall back to the land and water bodies, negatively impacting aquatic life and ecosystems.

Additionally, the burning of fossil fuels releases fine particulate matter (PM 2.5), which is of particular concern due to its ability to be inhaled deeply into lung tissue, causing serious health problems. Studies have linked exposure to air pollution from fossil fuel combustion to an increased risk of preterm birth, low birth weight, and various neurodevelopmental disorders in children. The combustion of fossil fuels also contributes to climate change, intensifying the production of allergens, such as mold and pollen, and setting the stage for dangerous wildfires, which further exacerbate air pollution.

Furthermore, the extraction and drilling processes associated with fossil fuels can also lead to air pollution. For instance, fracking, a controversial method of extracting oil and gas, has been linked to toxic air pollution, exposing millions of people to harmful substances. Similarly, mining operations, particularly strip mining, can release large amounts of stored carbon into the atmosphere, adding to the overall pollution levels.

The impact of burning fossil fuels on air pollution is far-reaching and poses a significant threat to global health and the environment. It is essential to recognize the urgency of transitioning to cleaner and more sustainable energy sources to mitigate the harmful effects of air pollution caused by fossil fuel combustion.

Vehicle emissions

In the 1940s, an unusual form of air pollution, known as "LA smog," affected Los Angeles, California. This pollution was characterised by its daytime formation and nighttime dissipation, eye irritation, high oxidant levels, and plant damage. While various sources contributed to the issue, vehicle emissions, specifically from the production, refining, marketing, and automotive use of petroleum products, were identified as a significant factor.

Motor vehicles, including cars, trucks, and buses, are major sources of air pollutants in urban settings. In typical urban areas, these vehicles produce at least half of the hydrocarbons and nitrogen oxides present in the air. The individual emissions from each car may be small, but the large number of vehicles on the roads and traffic congestion contribute significantly to air pollution. Additionally, older vehicles tend to emit more pollution and use more gasoline due to the deterioration of emission control technology over time.

It is important to note that the impact of vehicle emissions on air pollution is not limited to a specific location or time. For example, the agricultural burning of crop remnants, while practised in rural areas, can have negative effects on the respiratory health of children in nearby communities. Additionally, discriminatory policies and practices have resulted in communities of colour being disproportionately exposed to air pollution, including vehicle emissions, leading to health issues and economic consequences.

Industrial processes

The burning of fossil fuels, such as coal, natural gas, and oil, is a significant contributor to industrial air pollution. This practice began during the Industrial Revolution in the mid-1700s, when coal was widely used to heat homes and power factories and engines. Today, the combustion of fossil fuels continues to be a major source of pollution, with vehicles, airplanes, power plants, and factories relying on these fuels. The release of methane, a potent greenhouse gas, during oil and gas drilling, further exacerbates the problem.

Manufacturing and construction industries also play a significant role in air pollution. Inefficient industrial processes and a lack of energy efficiency contribute to higher emissions. Technological upgrades and improved process control can help mitigate this issue by reducing combustion inefficiencies and optimizing fuel use. Additionally, the use of direct fossil fuels and combined heat and power systems can enhance energy efficiency in the industrial sector.

Certain industries, such as petrochemical plants, steelmaking facilities, and hazardous waste sites, pose significant threats to air quality. The extraction and processing of natural gas and oil lead to the release of pollutants, while the production of plastics contributes to air pollution. The Clean Air Council, for instance, has expressed concern over the abundance of ethane, a byproduct of fracking, being used in petrochemicals and plastics.

To address industrial air pollution, a combination of collective and individual efforts is necessary. Transitioning to cleaner fuels, improving industrial processes, maximizing energy efficiency, and adopting renewable energy sources are crucial steps. Regulatory measures, such as cap-and-trade programs, provide incentives for companies to reduce emissions, while organizations like the Clean Air Council advocate for policies that address immediate health and environmental concerns.

Wildfires

The fine particulate matter, PM2.5, is of particular concern as it can travel deep into the lungs and may even enter the bloodstream. These fine particles comprise approximately 90% of the total particle mass in wildfire smoke. Coarse particles, or PM10-2.5, are also present in wildfire smoke, albeit in smaller amounts. These particles are generally larger than 2.5 micrometres and can be generated from mechanical operations such as construction and agriculture.

The gases emitted by wildfires, such as carbon dioxide and carbon monoxide, contribute to air pollution and climate change. Carbon dioxide is a greenhouse gas that traps heat in the atmosphere, leading to global warming. Carbon monoxide is a poisonous gas that can be harmful to human health, even leading to death in high concentrations. Wildfire smoke can also contain volatile organic compounds, which have both short-term and long-term health effects.

The impact of wildfires on air pollution is expected to worsen as the world warms due to climate change. Increased drought conditions, strong winds, and higher temperatures create hotter and longer fire seasons, making forests more vulnerable to fires. This trend is already being observed, with global wildfires and vegetation fires in 2024 generating around 1,940 megatonnes of carbon monoxide. The number of wildfires is projected to increase by almost 15% by 2030 and 30% by 2050, according to a UNEP-backed report.

The relationship between wildfires, air pollution, and climate change forms a vicious cycle. Wildfires release black carbon, a super pollutant that intensifies heatwaves, alters weather patterns, and accelerates the melting of ice and snow, further exacerbating climate change. At the same time, climate change increases the likelihood of wildfires, creating a self-perpetuating loop.

Volcanic activity

Volcanic ash or dust released into the atmosphere during an eruption can shade sunlight and cause temporary cooling. Larger particles of ash fall out of the air quickly, but the smallest particles of dust can get into the stratosphere and travel vast distances, often worldwide. These tiny particles are so light that they can stay in the stratosphere for months, blocking sunlight and causing cooling over large areas of the Earth.

Volcanic gases, such as sulfur dioxide, carbon dioxide, and hydrogen fluoride, can also cause air pollution. Sulfur dioxide, in particular, can move into the stratosphere and combine with water to form sulfuric acid aerosols, which reflect incoming solar radiation, causing a cooling effect on the Earth's surface. While the carbon dioxide expelled from human activity is a major contributor to atmospheric greenhouse gases, volcanism also expels carbon dioxide, and a single volcanic eruption can release as much carbon dioxide in one day as 250 years of anthropogenic activity.

The health effects of volcanic air pollution can be significant, affecting large populations thousands of kilometers away from the source for days, decades, or even centuries. Volcanic gases and ash can cause respiratory issues, irritate the skin and eyes, and lead to other health problems such as gastroenteritis, dental fluorosis, and cardiovascular issues. Volcanic ash can also be hazardous to grazing livestock and can damage or force the shutdown of drinking water and wastewater treatment facilities.

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