Human-Caused Air Pollution: Major Sources And Their Impact

Man-made sources of air pollution, also known as anthropogenic sources, are responsible for most of the world's air pollution. The burning of fossil fuels such as coal, gasoline, and diesel for transportation, electricity, and industrial processes is the largest source of air pollutants. Vehicles like cars, trucks, buses, trains, and ships emit pollutants such as carbon monoxide, nitrogen oxides, particulate matter, sulfur dioxide, and volatile organic compounds. Industrial activities, including factories, power plants, and refineries, emit pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter. Other sources of air pollution include agricultural activities, waste disposal, and the use of chemicals such as chlorofluorocarbons and hydrochlorofluorocarbons. These human activities contribute to global climate change and have negative impacts on human health and the environment.

Fossil fuels and vehicles

Vehicles are a significant source of nitrogen dioxide pollution in the atmosphere. Vehicle exhaust is a major contributor to nitrogen dioxide emissions, which cause the reddish-brown colour of smog and react with sunlight to produce harmful ozone. In addition to nitrogen dioxide, vehicle emissions also include carbon monoxide, a colourless, odourless, and poisonous gas formed by the combustion of fossil fuels. When inhaled, carbon monoxide blocks oxygen from reaching vital organs in the body.

Transportation is a major source of air pollution, particularly from vehicles with internal combustion engines. These vehicles release carbon monoxide, nitrogen oxides, and volatile organic compounds, contributing to urban air quality issues and climate change. Heavy traffic in cities results in pollution from motor vehicle exhaust, with pollutants such as greenhouse gases contributing to global warming.

To address air pollution from vehicles, cities are transitioning to electric buses and trucks, which produce zero tailpipe emissions and have lower global warming emissions. Additionally, individuals can minimise driving and opt for carpooling or public transportation to reduce vehicle emissions.

Industrial activities

Power plants, refineries, and factories are major sources of sulfuric air pollutants, with the United States and industrialized nations contributing significantly to global air pollution. The burning of fossil fuels in these industries leads to the formation of smog, acid rain, and an increase in greenhouse gas emissions, contributing to climate change.

Nitrogen dioxide, a characteristic component of smog, is produced by vehicles, factories, and power plants. It reacts with sunlight to form harmful ozone, which is a secondary air pollutant. Additionally, nitrogen oxides are emitted from industries where nitric acid is produced or used, as well as from automobile exhausts, low-heat burners, and furnaces.

Hydrogen sulfide is another pollutant emitted from certain industries, with major sources being the Kraft pulp and petroleum refinery industries. Hydrogen fluoride, which is highly harmful to humans and animals even at low concentrations, is released by manufacturers of phosphatic fertilizers, brick plants, pottery, the aluminium industry, and ferro-enamel works.

Chlorine and its compounds are also significant industrial air pollutants, with sources including chemical industries, water purification processes, sewage plants, and swimming pools. Furthermore, methane emissions from livestock waste disposal and agricultural activities contribute to climate change, with Europe's agricultural sector being responsible for approximately 90% of ammonia emissions and 80% of methane emissions.

Power plants

Coal-burning power plants are a major contributor to air pollution, releasing mercury, a potent neurotoxin that accumulates in waterways and fish, posing risks to human health, particularly in children. These plants also emit acid gases that transform into deadly particle pollution, worsening asthma, triggering heart attacks, causing lung cancer, and reducing life expectancy.

Nitrogen oxides, a product of power plants, automobiles, and industrial processes, are the second-highest contaminant in major cities. In the presence of sunlight, nitrogen dioxide, a component of smog, reacts with other gases to form ozone, a widespread air pollutant that spreads across vast distances.

Oil and gas development, including exploration, drilling, storage, and transportation, contribute to air pollution. Leaks from pipelines and storage facilities, as well as diesel locomotive emissions, further exacerbate the issue. Additionally, the extraction and production of fuels carry risks for workers and nearby communities, with coal miners facing increased risks of lung conditions such as pneumoconiosis.

The transition to clean, renewable, and non-combustion sources of electricity, such as solar, wind, geothermal, and tidal power, is crucial for improving lung health and mitigating climate change. By adopting zero-emission power sources, we can dramatically reduce health risks and premature deaths associated with air pollution from power plants.

Chlorofluorocarbons (CFCs)

CFCs were first synthesized in 1928 by Thomas Midgley, Jr. of General Motors, as safer chemicals for refrigerators used in large commercial applications. Frigidaire was issued the first patent for the formula for CFCs on December 31, 1928. In 1930, General Motors and DuPont formed the Kinetic Chemical Company to produce Freon, and by 1935, over 8 million refrigerators utilizing R-12 were sold by Frigidaire and its competitors. In 1932, the Carrier Engineering Corporation used Freon-11 (CFC-11) in the world's first self-contained home air-conditioning unit, called the "Atmospheric Cabinet".

Because of their safety record for nontoxicity, Freon became the preferred coolant in large air-conditioning systems. Public health codes in cities were revised to designate chlorofluorocarbons as the only gases that could be used as refrigerants in public buildings. Growth in CFCs continued over the following decades, leading to peak annual sales of over 1 billion USD, with greater than 1 million metric tons being produced annually.

However, in 1974, it was discovered by two University of California chemists, Professor F. Sherwood Rowland and Dr. Mario Molina, that the use of chlorofluorocarbons was causing a significant depletion in atmospheric ozone concentrations. This initiated the environmental effort that eventually resulted in the enactment of the Montreal Protocol. As a result of CFCs contributing to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs).

While CFCs themselves are nontoxic, overexposure at concentrations of 11% or more may cause dizziness, loss of concentration, central nervous system depression, or cardiac arrhythmia. Vapors displace air and can cause asphyxiation in confined spaces. The combustion products of CFCs include hydrofluoric acid and related species.

Nitrogen oxides

There are seven oxides of nitrogen that can be found in the air, but nitric oxide (NO) and nitrogen dioxide (NO2) are the two primary nitrogen oxides associated with combustion sources. Nitric oxide is rapidly oxidized in the air to form nitrogen dioxide, which is a highly reactive gas. This gas causes the reddish-brown colour of smog and reacts with sunlight to produce harmful ozone. It also contributes to the formation of acid rain.

Motor vehicles are the leading source of nitrogen dioxide pollution, with vehicle exhaust being responsible for high emissions in urban areas. In addition to transportation, factories and power plants also contribute to NOx emissions. Industrial activities, such as the production or use of nitric acid, emit significant amounts of nitrogen oxides. Power stations alone account for about one-quarter of NOx emissions in some countries.

Other sources of nitrogen oxides include indoor combustion appliances, such as stoves, ovens, and heaters, particularly those that are unflued or poorly maintained. Tobacco smoke and the burning of certain fuels, such as wood, oil, kerosene, and coal, can also produce nitrogen dioxide. Additionally, agricultural fertilization and the use of nitrogen-fixing plants contribute to atmospheric NOx levels by promoting nitrogen fixation by microorganisms.

While NOx emissions have decreased in some sectors due to cleaner fuels and more modern power stations, overall emissions remain a challenge. This is due to the increasing number of road vehicles and the slow implementation of emission control strategies for stationary and mobile sources. As a result, NOx continues to be a significant contributor to air pollution, particularly in densely populated urban areas.

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