Pollution has been defined by Odum (1971) as “the undesirable change in the physical, chemical or biological characteristics of air, land and water that may affect the human life. The pollutants cause undesirable physical and biological changes.

Man is searching for food and better living conditions. It has destroyed the environment. Man has added a lot of dust, smoke, poisonous gases and radiations in the atmosphere. He has created problem of soil erosion, waterlogging and salinity. He has added injurious chemicals to the soil, river and sea due to the pesticide and fertilizers. He is throwing poisonous liquid, solid and gaseous waste in the surroundings. He has developed weapons and produced dangerous chemicals to kill other humans. Thus he is increasing pollution in the environment.


Odum defines pollutant as “residues of things we make, use and thraw away are called pollutants. The pollutants may be:

  1.   The pollutant may be gases like CO, SO2 etc.
  1. These may be metals like lead, zinc, chromium etc.
  2. There may be industrial pollutants like cyanide compounds, acetic acid acids.
  3. Agriculture pollutants are pesticides, herbicides, fungicides and fertilizers.
  4. Photochemical pollutants are ozone oxides, CFC (Chloroflouro carbon).
  5. Radiations from radioactive substance also act as pollutants

There are two types of pollutants:

I. Nondegradable pollutants: The pollutants which are not degraded or degraded at very slov, rate are called Nondegradable pollutants. These are mostly inorganic compounds like metallic oxides. DDT etc.

2. Biodegradable pollutants: The pollutants which are degraded by microorganism are called biodegradable pollutants. These include domestic sewage.

There are different types of pollutions, air, water, soil etc.


The WHO (World Health Organization) defines air pollution in following words. The presence of substances in the atmosphere produced directly or indirectly by man which affect his health and properties is called air pollution.

Burning of the fuel, fossil fuel and waste of different kinds release poisonous gases. These gases are sulphur dioxide, carbon monoxide, hydrogen sulphide, fluorine, chlorine, ammonia, bromine, iodine, nitrogen oxide, ozone etc. Ethylene, acetylene, benzopyrene, propylene and many other hydrocarbons are also released as pollutant. Ethylene is released from automobiles, combustion of natural gas, coal or wood. Millions of tons of poisonous gases are released every year in industrial countries. These gases are produced by factories, electricity power, stations and automobiles.

Types of air pollutants

There are two types of air pollutants:

(a) Primary air pollutants

The substances which are emitted directly from some sources are called primary air pollutants. These include:

  1. Sulphur compounds like SO2, H2S. These gases are produced by the oxidation of fuel.
  1. Carbon compounds like CO, CO, and hydrocarbons. These compounds are produced by incomplete combustion of gasoline.
  2. Nitrogen compounds are NO, NO, and NH3.
  3. Halogen compounds are HF, MCI. These are produced by the industrial processes.
  4. Particles of different sizes suspended in air also act pollutant

(b) Secondary pollutants

The pollutants which are produced by the reactions of primary pollutants in the atmosphere are called secondary pollutants. These reactions may be:

I. Photochemical reactions: These reactions occur between nitrogen

oxide, oxygen and waste carbons in the presence of light. It forms peroxyacetly nitrate (PAN) and ozone 01. Similarly, Chloroflouro carbon (CFC) reacts with ozone layer. It is also a photochemical # reaction. The chlorine of CFC react with 03 and release 0, and atomic oxygen. It causes ozone depletion or ozone hole.

2. Acid rain: In this case, sulphur dioxide (SO2) reacts with rain water to form sulphuric acid sulphuric acid fall on soil with rain. It is called acid rain.

3. Smog: The fog with smokes and chemical fumes forming dark and thick covering called smog. Smog is very common in all industrial countries.

Effects of air pollutants

  1. Effect on plants: Air pollutants have very dangerous effects on plants. Thick smog kills million of trees each year. An air pollutant causes tissue collapse and necrosis. They causes deplasmolysis of the cells. Some pollutants cause chlorosis in the leaves. Thus pale green or yellow patches appear in the leaves. Some pollutants cause shunted growth in plants. Acid rain also destroys different parts of the plants.
  2. Effects on animals and humans: There are certain direct effects of pollutants in animals. They affect on respiratory tract and lungs. They cause pulmonary edema, chronic bronchitis and lung cancer. SO2, NO, and NH3 gases causes irritation in eyes and nose. These are suffocating gases. Carbon mono oxide (CO) is the most dangerous gas It is produced by incomplete combustion of fossil fuel. It reacts with haemoglobin and form a stable compound caroxyhaemoglobin. It decreases the carrying capacity of haemoglobin for oxygen.Industries release many metals in the air like lead and chromium. These metals are carcinogenic. Similarly, some radioactive substance enters into the atmosphere. They also cause cancer.
  1. Green house effect: CO2 is released by the burning of fuel in industries. It forms a layer in the atmosphere. This layer allows the solar radiations to pass. But it does not allow the thermal radiation of earth to pass out. Thus temperature of the earth is continuously rising. It is changing the climatic pattern of the earth. Glaciers are melting rapidly and more evaporation take place form ocean. It causes sever flooding.
  2. Ozone depletion: The photochemical reaction of CFC with Ozone produce ozone hole. Ozone filters most of the ultraviolet radiations. Now these radiations fall on the earth directly. These radiations have very lethal effects on human. They can cause skin cancer and other skin and eye diseases.

Control of air pollution

Following measures can reduce air pollution




  1. High quality lead free petrol should be used It has low sulphur
  2. Use of CNG (Compressed Natural Gas) also reduces the air pollution. It is environment friendly gas.
  3. Two stroke engines should be replaced by four stroke engines. Four stroke engine do not produce CO.
  4. All the industrialists should be bound to install treatment cells in the chimneys of their industries.
  5. CFC gases should be replaced by green gas in refrigerators and air conditioners.


Life is impossible without water. Water is used in different activities like drinking, bathing, disposal of sewage, irrigation and for generating electricity. Undesirable pollutants are added in water. It causes pollution in water.

Sources and effects of water pollution

I. Domestic sewage: It includes household wastes. These wastes have food wastes, detergents and human feces. These wastes are drained into streams and rivers without treatment. Domestic sewage adds nitrogen and phosphate in water. Thus thick bloom of blue green algae is produced on water. It consume:: oxygen at night. Therefore, most of the fishes die due to deficiency of oxygen. There is rapid decomposition of filament of algae. It pr.-duces unpleasant smell. The increased productivity of lake cause• due to enrichment of nutrients is called eutrophication.

  1. Industrial effluents: Industrial waste is called effluents. These are also discharged into the rivers. These wastes come from textile, sugar and fertilizer factories etc. Most of the industrial effluents are toxic. It kills the decomposing bacteria of pond, lake and river. Thus these water bodies become highly contaminated.

The industrial effluents also contain some metals like iron, chromium, mercury, copper and cadmium. These metals cause harmful effects in humans. Mercury produces nervous disorder.

  1. Fertilizers: Artificial fertilizers are used to improve the fertility of soil. Excess fertilizers seep into the ground water or it is carried into the drinking water. Fertilizers are very dangerous for human health. Nitrates of the fertilizers enter into the intestine of man. The intestinal bacteria change them into nitrites. The nitrites enter into the blood. They react with haemoglobin. Therefore, infants face the shortage of oxygen. This disease is galled methohemoglobinemia.
  2. Pesticides and herbicides: Pesticides ,are widely used to kill pests These pesticides are carried away by running wafer into ponds an. rivers. They finally reach the oceans. Some pesticides incorporate into the bodies of plants. The herbivores eat these plants. These pesticides go into their body. Finally herbivores are eaten tiy. human. These pesticides go into human body. The amount of pesticides n increased at each trophie level. It is called biological magnification. Pesticides and herbicides kill many phytoplanktons ant zooplanktons. These also kill many fishes. DDT may cause cance, and nervous disorder in humans.
  3. Mineral oils: Sometimes. oil is discharged into the oceans from oi ships. This oil is not dissolved in water. It is very dangerous for the ocean life.
    Control of water pollution

    1.  Sewage should be treated properly before draining it into canals rivers. Sewage treatment plants should be installed in all the cities.
    1. Similarly, the effluents of the industries should be properly treated Laws should be enacted to bind the industrialists to install treatmen plants.
    2. Fertilizers should be used in measured quantities.
    3. Biological control should be preferred over pesticides.


    Population is increasing day by day. Therefore, large area of land becoming contaminated. There are different causes of contamination K land. There are folloss Mg sources of land Pollution:

    1.  Industrial wastes: Inc industries dispose off 165 million tone mil waste each year. The major sources of land pollution are cemen glass, fiber glass, paper industries. The solid wastes of the. industries are deposited on the land. They make the land unlit 11. cultivation. The solid wastes or cement and textile industries  cause lung diseases.
    1. Agricultural pollution: The solid v‘astes of cement and papt. industries deposits on soil. They damage the plants.
    2. Domestic pollution: Domestic pc-210*am includes broken appliance. polythene bags, broken plastic. household garbage. animal waste and glass wares. These pollutants destroy the natural beauty.


    Any unwanted sound is called noise. The dumping of unwantec

    sound into atmosphere is called noise pollution. Our county is facing the problem of urbanization mid industrialization. Number of industries has been established in cites. These industries and vehicle produce a lot noise. Most the houses, schools and hospitals are located near noise pollutecrareas. Noise affects them badly.

    Effects of noise pollution

    Constant noise destroys man mentally and physically. It contracts the blood vessels. The skin becomes pale. Adrenaline is released as a result of noise pollution. It raises blood pressure. It also causes hypertension. High intensity sounds cause deafness. It causes headache, fatigue and nausea. It also affects the pregnant woman.

    Control of noise pollution

    1. Green belts should be established in open spaces in the cities. Plants are efficient absorber of noise. Thus they will absorb most Of the noise.
    1. Noise producing machinery should he installed in sound proof rooms.
    2. No factories or building be constructed in the 10 mile radius of airport.

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