Table of Contents
Air pollution is the entry of chemicals, particles or air into the atmosphere, biological substances that cause human discomfort, disease or death, harm others, damage to living animals such as food crops, or the natural environment or created environment. A substance present in the air that is known to be harmful to humans and the environment is called air pollutant or contaminant. What Are The Main Causes of Air Pollution – the answer can be these contaminants.
Air pollutants can be in the form of solid particles, liquid droplets or gases. Again they can be natural or man-made. Contaminants can also be classified as primary or as Secondary. Typically, primary pollutants are produced directly from a process such as ash from a volcanic eruption, carbon monoxide gas from a motor vehicle exhaust, or Sulfur dioxide is emitted from the factory. However, unlike primary pollutants, secondary pollutants are not emitted directly. Rather, the primary pollutants react with each other to form secondary pollutants in the air. An example of a secondary contaminant is ground ozone which produces photochemical fumes. Furthermore, some contaminants can be both primary and secondary. That is, they both emit directly or can be formed from the other primary contaminant.
Main causes of air pollution
The main causes of air pollution can be divided into two categories.
- Man-made causes of air pollution
- Natural causes of air pollution
That means, the contaminants in the air can come from both natural and man-made sources. Natural sources include air pollutant dust from fires and volcanic eruptions and volatile biochemicals emitted by some plants. Volcanic eruptions and chemicals released from some natural forest fires can temporarily reach harmful levels where they occur.
Human inputs from outside air pollutants occur mostly in industrial and urban areas where people, cars and factories are concentrated. Most of these pollutants come from burning fossil fuels in power and industrial plants (stationary sources) and motor vehicles (mobile sources).
Man-made causes of air pollution
- Stationary source: These include power plants, different manufacturing factories, many types of reactors, fuel heating machines, various waste incinerators etc. These generate large amounts of smoke, which is one of the main causes of air pollution in developing and poor countries. Burning of wood, plant and animal wastes also cause a lot of air pollution.
- Mobile source: Mobile sources include motor vehicles, ships, aircraft etc. These cause both air pollution and sound pollution. These vehicles emit carbon monoxide (CO) which is a colorless, odorless and toxic gas. Other sources such as incomplete combustion of natural gas, coal or wood also produces CO and cause air pollution.
- Gases emitted from paints, hair sprays, aerosol sprays, varnishes and other such solvents cause air pollution.
- Not having adequate waste disposal systems lead to piles of waste around settlements. These piles of wastes produce methane gas (CH4). CH4 is a toxic and highly flammable gas that can form explosive mixtures with air. Incomplete combustion of CH4 also generates carbon monoxide said earlier.
- Military source: Toxic substances are released during war and gases from military warfare, nuclear weapons, rockets, etc. used in the war or during military training or expedition are released into the air and cause air pollution.
- Using lead (Pb) pipes, lead solder, leaded paint in houses and apartments, lead in computer & TV monitors, candles containing lead cores causes emission of lead into the air and pollute the air.
- Burning of coal and oil causes photochemical reaction in the atmosphere in presence of oxygen and produce industrial smog.
- Burning of wastes such as polythene, paper, plastic causes the production of CO and pollute air.
- Acid rain: Automobile engines, refining of oil, combustion of sulfur containing coal in the electric power cause emission of NOx and Sox which are responsible for acid deposition in the air such as sulfuric acid (H2SO4) and nitric acid (HNO3). These acid substances can remain in the air for 2-14 days and descend to the earth’s surface with rain called acid rain.
- Cutting trees also affect the air.
Natural causes of air pollution
- Forest fires are a major natural cause of air pollution.
- Radon gas from radioactive decay in the Earth’s crust is another natural cause of air pollution. This radioactive gas is generated from the decay of radium metal. Ra is a colorless, odorless, naturally occurring radioactive gas which is very dangerous for human health. This gas can accumulate in the buildings, especially in confined areas such as basements or undergrounds. It is considered to be the second leading cause of lung cancer.
- On hot days, plants such as black gum, poplar, oak and willow release significant amounts of environmentally significant VOCs in some areas. These VOCs react with primary pollutants such as NOx, SOx to form secondary pollutants which cause air pollution. This is also a natural causes of air pollution.
- Animal digestion (specially domestic animals such as cattle) is another cause of natural air pollution. This produces methane, which is responsible for greenhouse gases.
- Natural volcanic activity produces sulfur, chlorine and ash particulate that cause air pollution.
- Dust from a large area or land without vegetation (for example desert) is another major cause of air pollution.
Major Outdoor Air Pollutants
Carbon monoxide (CO) is one of the major outdoor air pollutants. It is a colorless, odorless, and highly toxic gas that forms during the incomplete combustion of carbon-containing materials.
Major source: Major sources are motor vehicle exhaust, burning of forests and grasslands, tobacco smoke, and open fires and inefficient stoves used for cooking.
Health effects: CO reacts with hemoglobin in red blood cells and reduces the ability of blood to transport oxygen to body cells and tissues. Chronic exposure to CO can trigger heart attacks and aggravate lung diseases such as asthma and emphysema. CO can also cause headache, nausea, drowsiness, mental impairment, collapse, coma, and death.
CO2 is also a colorless and odorless gas. About 93% of the CO2 in the atmosphere is the result of the natural carbon cycle and the rest comes from human activities.
Source: Comes mostly from burning fossil fuels and clearing CO2-absorbing forests and grasslands. Industrial revolution is another major source.
Effects: Increasing levels of CO2 from human activities are contributing to global warming and climate change. High levels of CO2 in the air causes respiration problem.
Nitrogen oxides and nitric acid:
Nitric oxide (NO) is a colorless gas that is produced by the reaction of nitrogen and oxygen gas in air at the high-combustion temperatures in automobile engines and coal-burning plants. NO is also generated from the Nitrogen cycle by the combination of lightning and certain soil bacteria. NO reacts with oxygen in the air to form nitrogen dioxide (NO2) which is a reddish-brown gas. NO and NO2 are collectively called nitrogen oxides (NOx). Some of the NO2 reacts with water vapor (H2O) in the air to form nitric acid (HNO3) and nitrate salts (NO3). These gases play a role in the formation of photochemical smog, greenhouse gas.
Effects: Nitrogen oxides will irritate the eyes, nose, and throat; irritate respiratory organ ailments like respiratory illness and bronchitis; and increase status to metabolism infections by impairing the system. they’ll conjointly suppress plant growth and cut back visibility once they are converted to acid and nitrate salts.
Sulfur dioxide and sulfuric acid:
Like CO2 and NO, Sulfur dioxide (SO2) could be a colorless gas with an irritating odor. Concerning third of the SO2 within the atmosphere comes from natural sources as a part of the sulfur cycle. The rest simple fraction comes from human sources, principally combustion of sulfur-containing coal in power and industrial plants and oil refinement and smelting of compound ores. within the atmosphere, SO2 is converted to aerosols, that are microscopic suspended droplets of sulfuric acid (H2SO4) and suspended particles of salt (SO42-) that come back to the earth as an element of acid deposition.
Effects: pollutant, acid droplets, and salt particles decrease visibility and irritate respiration issues. SO2 and H2SO4 will injure crops, trees, soils, and aquatic life in lakes. They additionally corrode metals and damage paint, paper, leather, and stone on buildings and statues.
Suspended particulate matter (SPM) consists of a spread of solid particles and liquid droplets small and light enough to stay suspended within the air for long periods. Almost sixty two percent (62%) of the SPM in outside air comes from natural sources like mud, wild fires, and ocean salt. The remaining thirty eighth comes from human sources like coal-burning power and industrial plants, motorized vehicles, plowed fields, building, unpaved roads, and tobacco smoke. The most harmful types of SPM are fine particles (PM-10, with a median diameter of less than 10 micrometers) and ultrafine particles (PM-2.5, with a median diameter of less than 2.5 micrometers).
Effects: These particles will irritate the nose and throat, harm the lungs, irritate bronchial asthma and respiratory disorder, and shorten life. poisonous particulates, like lead, cadmium, and polychlorinated biphenyls will cause mutations, fruitful issues, and cancer. Particulates additionally reduce visibility, corrode metals, and discolor garments and paints.
O3 is a colorless and extremely reactive gas that could be a major part of photochemical smog.
Effects: It will cause coughing and respiration problems, worsen respiratory organ and heart diseases, reduce resistance to colds and respiratory illness (pneumonia), and irritate the eyes, nose, and throat. It conjointly damages plants, rubber in tires, fabrics, and paints.
Ozone within the layer close to ground level is commonly observed as “bad” ozone, whereas the ozone in the stratosphere layer is considered as “good” ozone that protects us from harmful ultraviolet light radiation. However, human activities are reducing the amount of good ozone within the layer and increasing the number of harmful unhealthy gas (bad ozone) within the layer close to ground level—especially in some urban areas.
Volatile organic compounds (VOCs):
Organic compounds that exist as gases within the atmosphere are referred to as volatile organic compounds (VOCs). Most are hydrocarbons, like isoprene (C3H8) and terpenes like C10H15 emitted by the leaves of many plants, and alkane series methane (CH4), a greenhouse gas. Almost a third of the world’s CH4 emissions come from natural sources, largely plants, wetlands, and termites. The remainder comes from human sources, primarily rice paddies, landfills, oil and fossil fuel wells, and cows (mostly from their belching). Benzene (C6H6) is found in automobile and power plant emissions and tobacco smoke.
Effects: long-run exposure to benzene will cause leukemia, varied blood disorders, and immune system injury. Short exposure to high levels will cause dizziness, state of mind, and death.
Formation of Major Outdoor Air Pollutants:
|Carbon monoxide (CO)||2C + O2 = 2CO|
|Carbon dioxide (CO2)||C + O2 = CO2|
|Nitric oxide (NO)||N2 + O2 = 2NO|
|Nitrogen dioxide (NO2)||2NO + O2 = 2NO2|
|Sulfur dioxide (SO2)||S + O2 = SO2|
Major indoor air pollutants
|Chloroform||Chlorine treated water in hot showers||Cause cancer|
|1,1,1-Trichloroethane||Aerosol sprays||Dizziness, irregular breathing|
|Nitrogen oxides||Kitchen gas stoves and kerosene heaters, woodstoves||Irritated lungs, children’s colds, headaches|
|Particulates||Pollen, pet dander, dust mites, cooking smoke particles||Irritated lungs, asthma attacks, itchy eyes, runny nose, lung disease|
|Asbestos||Insulation of pipes, vinyl ceiling and floor tiles||Lung disease, lung cancer|
|Carbon monoxide||Faulty furnaces, unvented gas stoves and kerosene heaters, woodstoves||Headaches, drowsiness, irregular heartbeat, death|
|Methylene chloride||Paint strippers and thinners||Nerve disorders, diabetes|
|Tobacco smoke||Cigarettes||Lung cancer, respiratory ailments, heart disease|
|Radon-222||Radioactive soil and rock surrounding foundation, water supply||Lung cancer|
|Benzo-α-pyrene||Tobacco smoke, woodstoves||Lung cancer|
|Styrene||Carpets and plastic products||Kidney and liver damage|
|Formaldehyde||Stuffing of furniture, paneling, particleboard, foam insulation||Irritation of eyes, throat, skin, and lungs; nausea; dizziness|
|Tetrachloroethylene||Dry cleaning fluid fumes of clothes||Nerve disorders, damage to liver and kidneys, possible cancer|
|Para-dichlorobenzene||Air fresheners, mothball crystals||Cancer|
With their high concentrations of cars and factories, urban areas usually have higher outside pollution levels than rural areas have. However prevailing winds will unfold long-lived primary and secondary air pollutants from urban and industrial areas to the countryside and to different urban areas.
Air pollution was once a regional issue restricted largely to cities. Currently it’s a global problem, for the most part because of the sheer volume of pollutants produced. Pollutants getting into the atmosphere in Asian country such as India and China currently notice their method across the Pacific where they have an effect on the West Coast of North America. There’s no place on the earth that has not been suffering from air pollution.