Air Pollution: Sources, Effects, Prevention, and Control

Air pollution has multiple sources, including natural as well as man-made sources. Keep reading to learn more about the different types of air pollution, their effects, and possible ways to control them.

Air Pollution is an undesirable change in the physical, chemical or biological characteristics of air.

Air Pollutants are the substances which pollute the air.

The pollution of air can be caused by natural processes or by human activities.

Natural Sources

Natural sources of air pollution include dust storms, forest fires, ash from smoking volcanoes, the decay of organic matters and pollen grains floating in the air.

Manmade Sources

Population explosion, deforestation, urbanisation and industrialisation are all human causes of air pollution. Their effects can be explained as follows:

• The burning of fuels like wood, cow dung cakes, coal and kerosene in homes pollute the air.
• Exhaust gases emitted by motor vehicles that pollute the air are the major source of pollution in big cities.
• Industries pollute the air by releasing various types of substances such as sulphur dioxide, oxides of carbon, nitrogen oxide, chlorine, asbestos dust and cement dust.
• Thermal power plants pollute the air by emitting sulphur dioxide and fly-ash.
• Nuclear power plants pollute the air by releasing radioactive rays.
• The use of fertilisers and pesticides in agriculture pollute the air.
• Mining activities release particulate matter into the air and pollutes it.
• The indiscriminate cutting of trees and clearing of forests increases the amount of carbon dioxide in the atmosphere and thereby pollutes it.
• The use of chlorofluorocarbons in refrigeration, fire extinguishers and aerosol sprayers pollutes the air by depleting the ozone layer.
• Smoking pollutes the air by emitting carbon monoxide and nicotine.

Environmental Impacts

• It causes depletion of the ozone layer, due to which ultraviolet radiation can reach the earth and cause skin cancer and damage to the eyes and immune system.
• It causes acid rain, which damages crop plants, trees, buildings, monuments, statues and metal structures and also makes the soil acidic.
• It causes the greenhouse effect and global warming, which leads to excessive heating of the earth's atmosphere, further leading to weather variability and a rising in sea level. The increased temperature may cause the melting of ice caps and glaciers, resulting in floods.

Human Health Impacts

• Air pollution affects the respiratory system, causing breathing difficulties and diseases such as bronchitis, asthma, lung cancer, tuberculosis and pneumonia.
• It affects the central nervous system causing carbon monoxide poisoning. CO has more affinity for haemoglobin than oxygen and thus forms a stable compound carboxy haemoglobin (COHb), which is poisonous and causes suffocation and death.

• Pollution of the air from certain metals, pesticides and fungicides causes serious ailments.
• Lead pollution causes anaemia, brain damage, convulsions and death.
• Certain metals cause problems in the kidneys, liver, circulatory system and nervous system.
• Fungicide pollution can cause nerve damage and death.
• Pesticides like DDT (dichloro diphenyl trichloroethane), which are toxic, enter into our food chain and get accumulated in the body. This can cause kidney disorders and problems of the brain and circulatory system.

Different techniques are used for controlling air pollution depending on whether they are caused by gaseous pollutants or by particulate pollutants.

Methods of Controlling Gaseous Pollutants

The pollution caused by gaseous pollutants like hydrocarbons, sulphur dioxide, ammonia, carbon monoxide, etc. can be controlled by using three different methods: combustion, absorption and adsorption.

Combustion: This technique is applied when the pollutants are organic gases or vapours. The organic air pollutants are subjected to 'flame combustion or catalytic combustion' when they are converted to a less harmful product, carbon dioxide, and a harmless product, water.

Absorption: In this method, the polluted air containing gaseous pollutants is passed through a scrubber containing a suitable liquid absorbent. The liquid absorbs the harmful gaseous pollutants present in the air.

Adsorption: In this method, the polluted air is passed through porous solid adsorbents kept in suitable containers. The gaseous pollutants are adsorbed at the surface of the porous solid, and clean air passes through.

Methods of Controlling Particulate Emissions

The air pollution caused by particulate matter like dust, soot, ash, etc. can be controlled by using fabric filters, wet scrubbers, electrostatic precipitators and certain mechanical devices.

Mechanical devices work in the following ways:

• Gravity: In this process, the particulates settle down by the action of gravitational force and get removed.
• Sudden change in the direction of airflow: This brings about the separation of particles due to greater momentum.

Fabric filters work by passing the particulate matter through a porous medium made of woven or filled fabrics. The particulates present in the polluted air are filtered and get collected in the fabric filters, while the gases are discharged. The process of controlling air pollution by using fabric filters is called 'bag filtration'.

Wet scrubbers are used to trap SO₂, NH₃ and metal fumes by passing the fumes through water.

Electrostatic precipitators induce an electric charge on particles when polluted air containing particulate pollutants is passed through them. Then the aerosol particles (such as smoke) are attracted to oppositely charged electrodes, and they get precipitated from the air.

Other Methods of Controlling Air Pollution

• Tall chimneys should be installed in factories.
• Efficiently designed equipment and smokeless fuels should be used in homes and industries.
• Renewable and non-polluting sources of energy like solar energy, wind energy, etc. should be used.
• Automobiles should be properly maintained and adhere to emission control standards.
• More trees should be planted along roadsides and houses.

Air is essential to the wellbeing of the earth, humans and other living beings. We must take responsibility, both collectively and individually, to control the harmful effects of pollution.