Lecture Notes - Environmental Pollution - Causes, effects and control of air - Class 9 PDF Download

 Page 1


1 
 
Lecture 7. Environmental pollution: Causes, effects and control of air 
 
 
India today is one of the first ten industrialized countries of the world. Today we have a good 
industrial infrastructure in core industries like metals, chemicals, fertilizers, petroleum, food etc. what 
has come out of these? Pesticides, detergents, plastics, solvents, fuels, paints, dyes, food additives etc. 
are some examples. Due to progress in atomic energy, there has also been an increase in radioactivity in 
the biosphere. Besides these, there are a number of industrial effluents and emissions particularly 
poisonous gases in the atmosphere. Mining activities also added to this problem particularly as solid 
waste. 
 Thus, pollution is a necessary evil of all development. Due to lack of development of a culture of 
pollution control, there had resulted a heavy backlog of gaseous, liquid and solid pollution in our 
country. It is to be cleaned. Thus pollution control in our country is a recent environmental concern. 
 What is pollution ? Pollution is an undesirable change in the physical, chemical or biological 
characteristics of air, water and soil that may harmfully affect the life or create a potential health hazard 
of any living organism. Pollution is thus direct or indirect changes in any component of the biosphere 
that is harmful to the living component(s), and in particular undesirable for man, affecting adversely the 
industrial progress, cultural and natural assets or general environment. 
 What are pollutants? Any substance which causes pollution is called a pollutant. A pollutant 
may thus include any chemical or geochemical (dust, sediment, grit etc.) substance, biotic component or 
its product, or physical factor (heat) that is released intentionally by man into the environment in such a 
concentration that may have adverse harmful or unpleasant effects. 
Environmental Pollutants 
 The various principal pollutants which pollute our air, water, land are as follows : 
(1) Deposited matter – soot, smoke, tar, dust, grit etc. 
(2) Gases – Oxides of nitrogen (NO, NO
2
), sulphur (SO
2
), carbon monoxide, halogens, (chlorine, 
bromine, iodine), 
(3) Acids droplets – sulphruric, acid nitric acid etc. 
(4) Fluorides 
(5) Metals – Mercury, lead, iron, zinc, nickel, tin, cadmium, chromium etc. 
Page 2


1 
 
Lecture 7. Environmental pollution: Causes, effects and control of air 
 
 
India today is one of the first ten industrialized countries of the world. Today we have a good 
industrial infrastructure in core industries like metals, chemicals, fertilizers, petroleum, food etc. what 
has come out of these? Pesticides, detergents, plastics, solvents, fuels, paints, dyes, food additives etc. 
are some examples. Due to progress in atomic energy, there has also been an increase in radioactivity in 
the biosphere. Besides these, there are a number of industrial effluents and emissions particularly 
poisonous gases in the atmosphere. Mining activities also added to this problem particularly as solid 
waste. 
 Thus, pollution is a necessary evil of all development. Due to lack of development of a culture of 
pollution control, there had resulted a heavy backlog of gaseous, liquid and solid pollution in our 
country. It is to be cleaned. Thus pollution control in our country is a recent environmental concern. 
 What is pollution ? Pollution is an undesirable change in the physical, chemical or biological 
characteristics of air, water and soil that may harmfully affect the life or create a potential health hazard 
of any living organism. Pollution is thus direct or indirect changes in any component of the biosphere 
that is harmful to the living component(s), and in particular undesirable for man, affecting adversely the 
industrial progress, cultural and natural assets or general environment. 
 What are pollutants? Any substance which causes pollution is called a pollutant. A pollutant 
may thus include any chemical or geochemical (dust, sediment, grit etc.) substance, biotic component or 
its product, or physical factor (heat) that is released intentionally by man into the environment in such a 
concentration that may have adverse harmful or unpleasant effects. 
Environmental Pollutants 
 The various principal pollutants which pollute our air, water, land are as follows : 
(1) Deposited matter – soot, smoke, tar, dust, grit etc. 
(2) Gases – Oxides of nitrogen (NO, NO
2
), sulphur (SO
2
), carbon monoxide, halogens, (chlorine, 
bromine, iodine), 
(3) Acids droplets – sulphruric, acid nitric acid etc. 
(4) Fluorides 
(5) Metals – Mercury, lead, iron, zinc, nickel, tin, cadmium, chromium etc. 
2 
 
(6) Agrochemicals – Biocides (pesticides, herbicides, fungicides, nematicides, bactericides, 
weedicides etc), and fertilizers. 
(7) Complex organic substances – Benzene, ether, acetic acid, benzopyrenes etc. 
(8) Photochemical oxidants – Photochemical smog, ozone, peroxyacetyl nitrate (PAN), 
peroxybenzoil nitrate (PBzN), nitrogen oxides, aldehydes, ethylene etc. 
(9) Solid wastes 
(10) Radioactive waste 
(11) Noise  
 
 
Kinds of Pollution 
 Various types of pollutions are classified in different ways. On the basis of the type of 
environment being polluted, we may recognize air pollution, water pollution, land soil pollution, marine 
pollution etc. on the basis of the kind of pollutant involved, we may have sulphur dioxide pollution, 
fluoride pollution, carbon monoxide pollution, smoke pollution, lead pollution, mercury pollution, solid 
waste pollution, radioactive pollution, noise pollution etc. Of the variety of pollutants, we recognize the 
following two basic types of pollutants: non degradable and biodegradable. 
(1) Nondegradable pollutants 
 These are the materials and poisonous substances like aluminium cans, mercuric salts, long-
chain phenolics, DDT etc. that either do not degrade or degrade only very slowly in nature. They are not 
cycled in ecosystem naturally but by subsequent movement in food chains and biogeochemical cycles. 
(2) Biodegradable pollutants  
Page 3


1 
 
Lecture 7. Environmental pollution: Causes, effects and control of air 
 
 
India today is one of the first ten industrialized countries of the world. Today we have a good 
industrial infrastructure in core industries like metals, chemicals, fertilizers, petroleum, food etc. what 
has come out of these? Pesticides, detergents, plastics, solvents, fuels, paints, dyes, food additives etc. 
are some examples. Due to progress in atomic energy, there has also been an increase in radioactivity in 
the biosphere. Besides these, there are a number of industrial effluents and emissions particularly 
poisonous gases in the atmosphere. Mining activities also added to this problem particularly as solid 
waste. 
 Thus, pollution is a necessary evil of all development. Due to lack of development of a culture of 
pollution control, there had resulted a heavy backlog of gaseous, liquid and solid pollution in our 
country. It is to be cleaned. Thus pollution control in our country is a recent environmental concern. 
 What is pollution ? Pollution is an undesirable change in the physical, chemical or biological 
characteristics of air, water and soil that may harmfully affect the life or create a potential health hazard 
of any living organism. Pollution is thus direct or indirect changes in any component of the biosphere 
that is harmful to the living component(s), and in particular undesirable for man, affecting adversely the 
industrial progress, cultural and natural assets or general environment. 
 What are pollutants? Any substance which causes pollution is called a pollutant. A pollutant 
may thus include any chemical or geochemical (dust, sediment, grit etc.) substance, biotic component or 
its product, or physical factor (heat) that is released intentionally by man into the environment in such a 
concentration that may have adverse harmful or unpleasant effects. 
Environmental Pollutants 
 The various principal pollutants which pollute our air, water, land are as follows : 
(1) Deposited matter – soot, smoke, tar, dust, grit etc. 
(2) Gases – Oxides of nitrogen (NO, NO
2
), sulphur (SO
2
), carbon monoxide, halogens, (chlorine, 
bromine, iodine), 
(3) Acids droplets – sulphruric, acid nitric acid etc. 
(4) Fluorides 
(5) Metals – Mercury, lead, iron, zinc, nickel, tin, cadmium, chromium etc. 
2 
 
(6) Agrochemicals – Biocides (pesticides, herbicides, fungicides, nematicides, bactericides, 
weedicides etc), and fertilizers. 
(7) Complex organic substances – Benzene, ether, acetic acid, benzopyrenes etc. 
(8) Photochemical oxidants – Photochemical smog, ozone, peroxyacetyl nitrate (PAN), 
peroxybenzoil nitrate (PBzN), nitrogen oxides, aldehydes, ethylene etc. 
(9) Solid wastes 
(10) Radioactive waste 
(11) Noise  
 
 
Kinds of Pollution 
 Various types of pollutions are classified in different ways. On the basis of the type of 
environment being polluted, we may recognize air pollution, water pollution, land soil pollution, marine 
pollution etc. on the basis of the kind of pollutant involved, we may have sulphur dioxide pollution, 
fluoride pollution, carbon monoxide pollution, smoke pollution, lead pollution, mercury pollution, solid 
waste pollution, radioactive pollution, noise pollution etc. Of the variety of pollutants, we recognize the 
following two basic types of pollutants: non degradable and biodegradable. 
(1) Nondegradable pollutants 
 These are the materials and poisonous substances like aluminium cans, mercuric salts, long-
chain phenolics, DDT etc. that either do not degrade or degrade only very slowly in nature. They are not 
cycled in ecosystem naturally but by subsequent movement in food chains and biogeochemical cycles. 
(2) Biodegradable pollutants  
3 
 
 They are the domestic wastes that can be rapidly decomposed under natural condition. They 
may create problems when they accumulate (i.e. their input into the environment exceeds their 
decomposition). 
Atmosphere 
The earth’s vertically extended atmosphere, an envelope of gases is divided into the following 
layers : (i) troposphere (up to 5 km) – the lowest atmosphere in which temperature decreases with 
height bounded by land or sea surface below and by tropopause above, (ii) stratosphere (5 to 45 km) -  
the region above the troposphere, in which temperature increases up to 90
0
C with height. This is limited 
by stratopause, (iii) mesosphere (45 to 80 km) – the part between stratosphere and thermosphere 
(ionosphere). Temperature again decreases up to – 80
0
C. (iv) thermosphere (ionosphere) – above 80 km, 
the upper part in which temperature increases with height. There is no boundary between the 
atmosphere and void of outer space. About 75% of the earth’s atmosphere lies within 16 km. of the 
surface and 99% of the atmosphere lies below an altitude of 30 km. 
 The atmosphere is an insulating blanket around the earth. It is source of essential gases, 
maintains a narrow difference of day and night temperatures and provides a medium for long-distance 
radio communication. It also acts as shield around the earth against lethal UV radiations and meteors. 
Without atmosphere, there will be no lightening, no wind, no clouds, no rains, no snow and no fire.  
 Normal composition of clean air at or near sea (1990) is as follows: 
 Gases Percent (by Volume) 
 Nitrogen 78.084 
 Oxygen 20.9476 
 Argon 0.934 
 Carbon dioxide 0.0314 
 Methane 0.0002 
 Hydrogen 0.00005 
 Other gases minute 
  
Page 4


1 
 
Lecture 7. Environmental pollution: Causes, effects and control of air 
 
 
India today is one of the first ten industrialized countries of the world. Today we have a good 
industrial infrastructure in core industries like metals, chemicals, fertilizers, petroleum, food etc. what 
has come out of these? Pesticides, detergents, plastics, solvents, fuels, paints, dyes, food additives etc. 
are some examples. Due to progress in atomic energy, there has also been an increase in radioactivity in 
the biosphere. Besides these, there are a number of industrial effluents and emissions particularly 
poisonous gases in the atmosphere. Mining activities also added to this problem particularly as solid 
waste. 
 Thus, pollution is a necessary evil of all development. Due to lack of development of a culture of 
pollution control, there had resulted a heavy backlog of gaseous, liquid and solid pollution in our 
country. It is to be cleaned. Thus pollution control in our country is a recent environmental concern. 
 What is pollution ? Pollution is an undesirable change in the physical, chemical or biological 
characteristics of air, water and soil that may harmfully affect the life or create a potential health hazard 
of any living organism. Pollution is thus direct or indirect changes in any component of the biosphere 
that is harmful to the living component(s), and in particular undesirable for man, affecting adversely the 
industrial progress, cultural and natural assets or general environment. 
 What are pollutants? Any substance which causes pollution is called a pollutant. A pollutant 
may thus include any chemical or geochemical (dust, sediment, grit etc.) substance, biotic component or 
its product, or physical factor (heat) that is released intentionally by man into the environment in such a 
concentration that may have adverse harmful or unpleasant effects. 
Environmental Pollutants 
 The various principal pollutants which pollute our air, water, land are as follows : 
(1) Deposited matter – soot, smoke, tar, dust, grit etc. 
(2) Gases – Oxides of nitrogen (NO, NO
2
), sulphur (SO
2
), carbon monoxide, halogens, (chlorine, 
bromine, iodine), 
(3) Acids droplets – sulphruric, acid nitric acid etc. 
(4) Fluorides 
(5) Metals – Mercury, lead, iron, zinc, nickel, tin, cadmium, chromium etc. 
2 
 
(6) Agrochemicals – Biocides (pesticides, herbicides, fungicides, nematicides, bactericides, 
weedicides etc), and fertilizers. 
(7) Complex organic substances – Benzene, ether, acetic acid, benzopyrenes etc. 
(8) Photochemical oxidants – Photochemical smog, ozone, peroxyacetyl nitrate (PAN), 
peroxybenzoil nitrate (PBzN), nitrogen oxides, aldehydes, ethylene etc. 
(9) Solid wastes 
(10) Radioactive waste 
(11) Noise  
 
 
Kinds of Pollution 
 Various types of pollutions are classified in different ways. On the basis of the type of 
environment being polluted, we may recognize air pollution, water pollution, land soil pollution, marine 
pollution etc. on the basis of the kind of pollutant involved, we may have sulphur dioxide pollution, 
fluoride pollution, carbon monoxide pollution, smoke pollution, lead pollution, mercury pollution, solid 
waste pollution, radioactive pollution, noise pollution etc. Of the variety of pollutants, we recognize the 
following two basic types of pollutants: non degradable and biodegradable. 
(1) Nondegradable pollutants 
 These are the materials and poisonous substances like aluminium cans, mercuric salts, long-
chain phenolics, DDT etc. that either do not degrade or degrade only very slowly in nature. They are not 
cycled in ecosystem naturally but by subsequent movement in food chains and biogeochemical cycles. 
(2) Biodegradable pollutants  
3 
 
 They are the domestic wastes that can be rapidly decomposed under natural condition. They 
may create problems when they accumulate (i.e. their input into the environment exceeds their 
decomposition). 
Atmosphere 
The earth’s vertically extended atmosphere, an envelope of gases is divided into the following 
layers : (i) troposphere (up to 5 km) – the lowest atmosphere in which temperature decreases with 
height bounded by land or sea surface below and by tropopause above, (ii) stratosphere (5 to 45 km) -  
the region above the troposphere, in which temperature increases up to 90
0
C with height. This is limited 
by stratopause, (iii) mesosphere (45 to 80 km) – the part between stratosphere and thermosphere 
(ionosphere). Temperature again decreases up to – 80
0
C. (iv) thermosphere (ionosphere) – above 80 km, 
the upper part in which temperature increases with height. There is no boundary between the 
atmosphere and void of outer space. About 75% of the earth’s atmosphere lies within 16 km. of the 
surface and 99% of the atmosphere lies below an altitude of 30 km. 
 The atmosphere is an insulating blanket around the earth. It is source of essential gases, 
maintains a narrow difference of day and night temperatures and provides a medium for long-distance 
radio communication. It also acts as shield around the earth against lethal UV radiations and meteors. 
Without atmosphere, there will be no lightening, no wind, no clouds, no rains, no snow and no fire.  
 Normal composition of clean air at or near sea (1990) is as follows: 
 Gases Percent (by Volume) 
 Nitrogen 78.084 
 Oxygen 20.9476 
 Argon 0.934 
 Carbon dioxide 0.0314 
 Methane 0.0002 
 Hydrogen 0.00005 
 Other gases minute 
  
4 
 
Air is necessary for the survival of all higher forms of life on Earth.  On an average, a person 
needs at least 30 lb of air every day to live, but only about 3 lb of water and 1.5 lb of food.  A person can 
live about 5 weeks without food and about 5 days without water, but only 5 minutes without air.  
Naturally, every one likes to breathe fresh, clean air.  But the atmosphere, that invisible yet essential 
Ocean of different gases called air, is as susceptible to pollution from human activities as are water and 
land environments.  
Air Pollution 
It is defined as the excessive concentration of foreign material in the atmosphere , which affects the 
health of individuals and also causes damage to the property. 
Air pollution episodes 
• London smog : SO
2
 ? H
2
SO
3
 vapours in the atmosphere. When automobile exhausts are trapped by 
this smog and exposed to sunlight, it produces photochemical smog. 
• Bhopal gas tragedy : The poisonous gas, methyl isocyanate (MTC) leakage in the pesticide 
manufacturing plant of Union Carbide of India Ltd., (UCIL), Bhopal, Madhya Pradesh on December 3, 
1984. 46 tons of MIC was released spreading to 40 km. Effects : About 65,000 people suffered from 
various disorders in eyes, lungs, stomach, heart, etc. The immediate symptom is bronchospasm 
which causes coughing, chest pain and abdominal pain. Nearly 3000 people died within a short span 
of time,  1600 domestic animals died and  crop yields were reduced . 
• Darkening effect of Taj Mahal  
 Taj Mahal is a white marble stone mausoleum.  Recently it was observed that the walls of Taj 
Mahal has become darkened and disfigured due to air pollution from nearby Mathura Oil refinery. 
  H
2
O + SO
2
 ? H
2
SO
3 ,    
SO
2
 + O
2
 ? SO
3
; SO
3
 + H
2
O ? H
2
SO
4
.   
The acid rain reacts with marble stone (CaCO
3
) to produce calcium sulphate, causing darkening and 
disfigurement. 
Types, sources and effects of air pollution 
 Air pollution may be simply defined as the presence of certain substances in the air in high 
enough concentrations and for long enough duration to cause undesirable effects.  “Certain substances” 
may be any gas, liquid or solid, although certain specific substances are considered significant pollutants 
because of very large emission rates are harmful and unwanted effects.  “Long enough durations” can 
Page 5


1 
 
Lecture 7. Environmental pollution: Causes, effects and control of air 
 
 
India today is one of the first ten industrialized countries of the world. Today we have a good 
industrial infrastructure in core industries like metals, chemicals, fertilizers, petroleum, food etc. what 
has come out of these? Pesticides, detergents, plastics, solvents, fuels, paints, dyes, food additives etc. 
are some examples. Due to progress in atomic energy, there has also been an increase in radioactivity in 
the biosphere. Besides these, there are a number of industrial effluents and emissions particularly 
poisonous gases in the atmosphere. Mining activities also added to this problem particularly as solid 
waste. 
 Thus, pollution is a necessary evil of all development. Due to lack of development of a culture of 
pollution control, there had resulted a heavy backlog of gaseous, liquid and solid pollution in our 
country. It is to be cleaned. Thus pollution control in our country is a recent environmental concern. 
 What is pollution ? Pollution is an undesirable change in the physical, chemical or biological 
characteristics of air, water and soil that may harmfully affect the life or create a potential health hazard 
of any living organism. Pollution is thus direct or indirect changes in any component of the biosphere 
that is harmful to the living component(s), and in particular undesirable for man, affecting adversely the 
industrial progress, cultural and natural assets or general environment. 
 What are pollutants? Any substance which causes pollution is called a pollutant. A pollutant 
may thus include any chemical or geochemical (dust, sediment, grit etc.) substance, biotic component or 
its product, or physical factor (heat) that is released intentionally by man into the environment in such a 
concentration that may have adverse harmful or unpleasant effects. 
Environmental Pollutants 
 The various principal pollutants which pollute our air, water, land are as follows : 
(1) Deposited matter – soot, smoke, tar, dust, grit etc. 
(2) Gases – Oxides of nitrogen (NO, NO
2
), sulphur (SO
2
), carbon monoxide, halogens, (chlorine, 
bromine, iodine), 
(3) Acids droplets – sulphruric, acid nitric acid etc. 
(4) Fluorides 
(5) Metals – Mercury, lead, iron, zinc, nickel, tin, cadmium, chromium etc. 
2 
 
(6) Agrochemicals – Biocides (pesticides, herbicides, fungicides, nematicides, bactericides, 
weedicides etc), and fertilizers. 
(7) Complex organic substances – Benzene, ether, acetic acid, benzopyrenes etc. 
(8) Photochemical oxidants – Photochemical smog, ozone, peroxyacetyl nitrate (PAN), 
peroxybenzoil nitrate (PBzN), nitrogen oxides, aldehydes, ethylene etc. 
(9) Solid wastes 
(10) Radioactive waste 
(11) Noise  
 
 
Kinds of Pollution 
 Various types of pollutions are classified in different ways. On the basis of the type of 
environment being polluted, we may recognize air pollution, water pollution, land soil pollution, marine 
pollution etc. on the basis of the kind of pollutant involved, we may have sulphur dioxide pollution, 
fluoride pollution, carbon monoxide pollution, smoke pollution, lead pollution, mercury pollution, solid 
waste pollution, radioactive pollution, noise pollution etc. Of the variety of pollutants, we recognize the 
following two basic types of pollutants: non degradable and biodegradable. 
(1) Nondegradable pollutants 
 These are the materials and poisonous substances like aluminium cans, mercuric salts, long-
chain phenolics, DDT etc. that either do not degrade or degrade only very slowly in nature. They are not 
cycled in ecosystem naturally but by subsequent movement in food chains and biogeochemical cycles. 
(2) Biodegradable pollutants  
3 
 
 They are the domestic wastes that can be rapidly decomposed under natural condition. They 
may create problems when they accumulate (i.e. their input into the environment exceeds their 
decomposition). 
Atmosphere 
The earth’s vertically extended atmosphere, an envelope of gases is divided into the following 
layers : (i) troposphere (up to 5 km) – the lowest atmosphere in which temperature decreases with 
height bounded by land or sea surface below and by tropopause above, (ii) stratosphere (5 to 45 km) -  
the region above the troposphere, in which temperature increases up to 90
0
C with height. This is limited 
by stratopause, (iii) mesosphere (45 to 80 km) – the part between stratosphere and thermosphere 
(ionosphere). Temperature again decreases up to – 80
0
C. (iv) thermosphere (ionosphere) – above 80 km, 
the upper part in which temperature increases with height. There is no boundary between the 
atmosphere and void of outer space. About 75% of the earth’s atmosphere lies within 16 km. of the 
surface and 99% of the atmosphere lies below an altitude of 30 km. 
 The atmosphere is an insulating blanket around the earth. It is source of essential gases, 
maintains a narrow difference of day and night temperatures and provides a medium for long-distance 
radio communication. It also acts as shield around the earth against lethal UV radiations and meteors. 
Without atmosphere, there will be no lightening, no wind, no clouds, no rains, no snow and no fire.  
 Normal composition of clean air at or near sea (1990) is as follows: 
 Gases Percent (by Volume) 
 Nitrogen 78.084 
 Oxygen 20.9476 
 Argon 0.934 
 Carbon dioxide 0.0314 
 Methane 0.0002 
 Hydrogen 0.00005 
 Other gases minute 
  
4 
 
Air is necessary for the survival of all higher forms of life on Earth.  On an average, a person 
needs at least 30 lb of air every day to live, but only about 3 lb of water and 1.5 lb of food.  A person can 
live about 5 weeks without food and about 5 days without water, but only 5 minutes without air.  
Naturally, every one likes to breathe fresh, clean air.  But the atmosphere, that invisible yet essential 
Ocean of different gases called air, is as susceptible to pollution from human activities as are water and 
land environments.  
Air Pollution 
It is defined as the excessive concentration of foreign material in the atmosphere , which affects the 
health of individuals and also causes damage to the property. 
Air pollution episodes 
• London smog : SO
2
 ? H
2
SO
3
 vapours in the atmosphere. When automobile exhausts are trapped by 
this smog and exposed to sunlight, it produces photochemical smog. 
• Bhopal gas tragedy : The poisonous gas, methyl isocyanate (MTC) leakage in the pesticide 
manufacturing plant of Union Carbide of India Ltd., (UCIL), Bhopal, Madhya Pradesh on December 3, 
1984. 46 tons of MIC was released spreading to 40 km. Effects : About 65,000 people suffered from 
various disorders in eyes, lungs, stomach, heart, etc. The immediate symptom is bronchospasm 
which causes coughing, chest pain and abdominal pain. Nearly 3000 people died within a short span 
of time,  1600 domestic animals died and  crop yields were reduced . 
• Darkening effect of Taj Mahal  
 Taj Mahal is a white marble stone mausoleum.  Recently it was observed that the walls of Taj 
Mahal has become darkened and disfigured due to air pollution from nearby Mathura Oil refinery. 
  H
2
O + SO
2
 ? H
2
SO
3 ,    
SO
2
 + O
2
 ? SO
3
; SO
3
 + H
2
O ? H
2
SO
4
.   
The acid rain reacts with marble stone (CaCO
3
) to produce calcium sulphate, causing darkening and 
disfigurement. 
Types, sources and effects of air pollution 
 Air pollution may be simply defined as the presence of certain substances in the air in high 
enough concentrations and for long enough duration to cause undesirable effects.  “Certain substances” 
may be any gas, liquid or solid, although certain specific substances are considered significant pollutants 
because of very large emission rates are harmful and unwanted effects.  “Long enough durations” can 
5 
 
be anywhere from a few hours to several days or weeks; on a global scale, durations of months and 
years are of concern.  
Sources 
Air pollution results from gaseous emission from mainly industry, thermal power stations, 
automobiles, domestic combustion etc. 
1. Industrial chimney wastes: There are a number of industries which are source of air pollution. 
Petroleum refineries are the major source of gaseous pollutants. The chief gases are SO
2
 and 
NO
x
. Cement factories emit plenty of dust, which is potential health hazard. Stone crushers and 
hot mix plants also create a menace. Food and fertilizers industries which emit gaseous 
pollutants. Chemical manufacturing industries which emit acid vapours in air.  
2. Thermal power stations:  There are a number of thermal power stations and super thermal 
power stations in the country. The National thermal  power corporation (NTPC) is setting up four 
mammoth coal-powered power stations to augment the energy generation. These are at 
Singrauli in U.P., Korba in M.P., Ramagundam in Andhra Pradesh and Farakka in W. Bengal. The 
coal consumption of thermal plants is several million tones. The chief pollutants are fly ash, SO 
2
 
and other gases and hydrocarbons. 
3. Automobiles: The toxic vehicular exhausts are a source of considerable air pollution, next only 
to thermal power plants. The ever increasing vehicular traffic density posed continued threat to 
the ambient air quality. Chief sources of emission in automobiles are (i) exhaust system, (ii) fuel 
tank and carburettor and (iii) crankcase. The exhaust produces many air pollutants including 
unburnt  hydrocarbons, CO, NO
x
 and lead oxides. There are also traces of aldehydes, esters, 
ethers, peroxides and ketones which are chemically active and combine to form smog in 
presence of light. Evaporation from fuel tank goes on constantly due to volatile nature of petrol, 
causing emission of hydrocarbons. The evaporation through carburettor occurs when engine is 
stopped and heat builds up, and as much as 12 to 40 ml of fuel is lost during each long stop 
causing emission of hydrocarbons. 
Criteria Air Pollutants 
The five primary criteria pollutants include the gases- Carbon Monoxide (CO), nitrogen oxides 
(NO
x
) , sulfur dioxide (SO
2
), and solid or liquid particulates (smaller than 10 µm), and particulate lead.  
a) Carbon Monoxide