Question 1 What is air pollution? What are the main sources of air pollution?
Question 2 What is smog? How is smog formed? What are the harmful effects?
Question 3 Name the various constituents of air?
Question 4 How can you reduce air pollution at individual level?
Question 5 Name few sources and harmful effects of Sulphur dioxide?
Question 6 Name few sources and harmful effects of Nitrogen oxide?
Question 7 Name few sources and harmful effects of Carbon monoxide?
Question 8 Name few sources and harmful effects of Chlorofluorocarbons?
Question 9 Name all the major pollutants of air?
The presence of unusually high concentrations of harmful or poisonous substances in the environment (air, water, etc.) is called pollution. Pollution contaminates the air and water with poisonous substances and makes them impure to such an extent that they become harmful to the human beings, other animals, plants as well as to the non-living things.
An unwanted and harmful substance that contaminates the environment (such as air and water) is called a pollutant.
The two main gases present in air are nitrogen and oxygen. Nitrogen makes up about 78% of air whereas oxygen makes up about 21% of air by volume. Air also contains small amounts of carbon dioxide, argon and water vapour.
In addition to the normal constituents, the polluted air may also contain harmful substances such as carbon monoxide, sulphur dioxide, nitrogen oxides, smoke and dust, etc. Many respiratory problems are caused by breathing in polluted air.
Fresh water (usable water) is present in rivers, lakes and ponds. Some fresh water is also present under the ground. Due to increasing water pollution, water-borne diseases are also increasing day by day.
The contamination of air with harmful gases (like sulphur dioxide nitrogen oxides, carbon monoxide), smoke and dust, etc. is called air pollution.
The substance whose presence in air makes it impure or contaminated is called an air pollutant.
A substance becomes an air pollutant when it is present in air in such concentration which is high enough to have a harmful effect on the living or non-living things.
The major pollutants which cause air pollution are : Sulphur dioxide, Nitrogen monoxide, excess of Carbon dioxide, Chlorofluorocarbons, and Suspended particulate matter (such as Dust, Smoke and Fly ash)
Sources of Air Pollution
Most of the air pollution is caused by the burning of fuels such as wood, cow-dung cakes, coal ,kerosene, petrol and diesel in homes, motor vehicles (automobiles), factories and thermal power plants.
The various sources of air pollution are:
(1) Smoke emitted from homes by the burning of fuels like wood, cow-dung cakes, kerosene and coal.
(2) Exhaust gases emitted by motor vehicles (automobiles) due to burning of petrol and diesel.Motor vehicles are the major cause of air pollution in big cities.
(3) Smoke emitted by factories and thermal power plants due to burning of coal.
(4) Oil refineries and industries engaged in the production of metals and manufacture of chemicals.
(5) Stone crushers, cement factories, asbestos factories and lead processing units cause air pollution.
(6) Use of chlorofluorocarbons in refrigeration, air conditioning and aerosol sprays.
(7) Smoking causes air pollution
(8) Forest fires and volcanic eruptions are the two natural sources of air pollution which put smoke and dust into the air.
Harmful Effects of Air Pollution
(1) Sulphur dioxide is produced by the burning of coal in factories and thermal power plants.
(2) Sulphur dioxide is also produced by the burning of petrol and diesel in motor vehicles.
(3) Oil refineries also emit sulphur dioxide gas into air.
(1) Sulphur dioxide gas in the air causes respiratory problems.
(2) If may even cause permanent lung damage.
(3) Sulphur dioxide gas in polluted air produces acid rain. This acid rain damages trees, plants, soil, aquatic animals (like fish) statues, buildings and historical monuments.
(4) Sulphur dioxide also contributes to the formation of a deadly air pollutant called smog.
(1) Nitrogen oxides are produced by the burning of fuels like petrol and diesel in motor vehicles.
(2) They are also produced by the burning of coal in factories and thermal power plants.
The high temperature produced by the burning of fuels like petrol, diesel and coal makes some of the nitrogen and oxygen of air to combine to form nitrogen oxides.
(3) Oil refineries also produce and emit nitrogen oxides into the air.
(1) Nitrogen oxides attack breathing system and lead to lung congestion.
(2) They also attack skin.
(3) Nitrogen oxides present in polluted air produce acid rain.
(4) Nitrogen oxides also contribute to the formation of smog.
Smog is a deadly air pollutant which is formed by the combination of smoke and fog( The minute water particles suspended in air near the surface of earth during cold weather in winter is called fog.)
Smoke contains tiny carbon particles, and harmful gases such as nitrogen oxides and sulphur dioxide. The carbon particles, nitrogen oxides and sulphur dioxide of smoke combine with the condensed water vapour called fog to form smog.
Smog causes cough and aggravates (makes worse) asthma and other lung diseases, especially in children.
(1) Carbon monoxide is produced by the incomplete combustion of fuels like wood, coal, kerosene, petrol and diesel in homes, factories and motor vehicles.
(2) The exhaust gases of motor vehicles (cars, buses and trucks, etc.) contain carbon monoxide which they emit into air.
(3) Cigarette smoke also contains carbon monoxide.
Carbon monoxide is a very poisonous gas.When inhaled carbon monoxide combines with the haemoglobin of our blood and reduces the oxygen-carrying capacity of blood.Due to this, blood is not able to carry sufficient oxygen to our body parts. This lack of oxygen cause respiratory problems (breathing problems). It causes suffocation. If too much carbon monoxide is inhaled, it may even cause death.
Carbon dioxide is produced in excessive amounts by the burning of large quantities of fuels such as wood, coal, kerosene, petrol, diesel, LPG, and CNG in homes, factories and motor vehicles.
Excess of carbon dioxide in air is considered a pollutant (because it produces undesirable changes in the environment). Carbon dioxide is the main greenhouse gas which traps sun’s heat in the earth’s atmosphere by producing greenhouse effect which leads to global warming.
Chlorofluorocarbons are the chemical compounds made of chlorine, fluorine and carbon elements. Chlorofluorocarbons are used in refrigerators, air conditioning and aerosol sprays.
Chlorofluorocarbons are industrially useful gases but they also behave as air pollutants because of their damaging effect on ozone layer.
Chlorofluorocarbons are depleting the useful ozone layer of the upper atmosphere. Chlorofluorocarbons released into the air go up and ultimately reach high into the atmosphere where the protective ozone layer exists. They react with the ozone gas of ozone layer and destroy it gradually. Ozone layer prevents the harmful ultraviolet radiations of the sun from reaching the earth. The destruction of ozone layer by CFCs will allow the extremely harmful ultraviolet radiations of the sun to reach the earth. These ultraviolet radiations can cause skin cancer, cataract, and destruction of plants, including crops. A big hole has already been made by the destruction of ozone gas in the ozone layer over the South Pole of the earth. It is called “ozone hole“.
Suspended particulate matter (SPM)
The finely divided solid or liquid particles suspended in air are called suspended particulate matter.
Some of the examples of suspended particulate matter are : Dust, Smoke and Fly ash.
(a) Dust consists of tiny particles of earth: Dust is produced by blowing wind, heavy traffic on roads, stone crushers and construction activities.
(1) Dust in air spoils our clothes and reduces visibility.
(2) Dust produces allergic reactions in human body and aggravates diseases like bronchitis.
(3) Dust covers the leaves of plants and trees and prevents photosynthesis.
(b) Smoke is mainly tiny particles of carbon in air. Smoke is produced by the burning of fuels like wood, cow-dung, cakes, kerosene, petrol, and diesel in homes, factories, thermal power plants and motor vehicles.
Smoke present in air spoils our clothes and blackens the buildings. Smoke attacks our lungs and causes respiratory diseases.
(c) The minute ash particles formed by the burning of coal and carried into air by the gases produced during burning, is called fly ash.
Fly ash particles present in air cause irritation to the eyes, skin, nose, throat and respiratory tract. Continued breathing in air containing fly ash causes diseases like bronchitis and lung cancer.
The two extremely harmful effects of air pollution on the environment are acid rain and greenhouse effect (or global warming).
Controlling Air Pollution
Some of the ways of controlling air pollution are:
(1) The air pollution can be controlled by using smokeless fuels like LPG, PNG (Piped Natural Gas and Bio-gas for cooking food (instead of wood, cow-dung cakes, or coal). Solar cookers can also be used for cooking food. Solar water heaters should be installed for obtaining hot water.
(2) The air pollution from motor vehicles can be reduced by using CNG (Compressed Natural Gas) as fuel in place of petrol and diesel. CNG is a very clean fuel which does not pollute air
(3) The air pollution from factories, thermal power plants, oil refineries and chemical industries can be controlled by washing down their smoke and waste gases with jets of water. When the smoke and waste gases are sprayed by jets of water before they reach chimney, then soot present in smoke is washed away and most of the poisonous gases like sulphur dioxide and nitrogen oxides get dissolved in water.
(4) The air pollution can be controlled by using non-polluting sources of energy like solar energy, wind energy and hydroenergy for generating electricity. This will reduce the use of fossil fuel like coal which is used for generating electricity at thermal power plants and causes air pollution.
Role in Controlling Air Pollution
Some of the steps which can be taken as individuals (or as a group of individuals) to control air pollution and improve the quality of air around us are as follows :
(1) We should not burn dry leaves, papers and garbage in the open: Leaves should be converted into compost by burying in a pit ; used papers should be sent to paper mills for recycling; and garbage should be deposited in the garbage dumps established by the Municipal Corporation of the city.
(2) We should save electricity: If all of us start saving electricity by avoiding its wastage in homes, schools, shops, offices and factories, the demand for electricity will decrease. This will lead to the burning of less coal to generate electricity. And burning of less coal will reduce air pollution.
(3) We should grow more trees and also take care of the existing trees in our neighbourhood. Trees reduce pollution by absorbing excess carbon dioxide from the air.
(4) We should join “Say No to Crackers” campaign organised by children of many schools during Diwali days to reduce the level of air pollution during the festival season.
(5) We should use bicycle for covering short distances. This will save precious fuel like petrol (which we use in cars, scooters and motorcycles) and also reduce air pollution.
(6) We should use the school bus or public transport bus for going to school.