How Air is Polluted?

As we just breafly explained in the previous article Pure Air, air is the most important for our survival. However, air can be easily polluted  by the changes in atmosphere due to human occupation. For example, 1. changes due to respiration op people and animals – these are chiefly carbon dioxide, water vapors and organic matter and oxygen diminishes. It also raises the temperature; 2. changes due to combustion (of coal gas, oil, etc.) – mainly air pollution derived from coal in the process of combustion by the oxidation of carbon of the air is carbon dioxide. Carbon monoxide may also be formed by combustion; 3. decomposition (of organic – animal and vegetable matter)  there are released poisonous gases such as carbon dioxide, hydrogen sulphide, ammonia, carbon disulphide etc. Bacteria and fungi also grow rapidly in such air; 4. trade, traffic and manufacturing processes which give off dust, fumes, vapors, gases (due to dust etc.) – the inorganic particles of dust are chiefly composed of silica, aluminium silicate, carbonate, carbon magnesium and sodium chloride, etc. These are found in the air of houses  due to debris arising from the wear and tear of articles in domestic use, such as dust, soot and ashes. Mineral particles arise from the factories; 5. burning of refuse, agricultural activities (e.g. crop spraying, pest control) and nuclear energy programme also contribute to pollution.

Many micro-organism are found in the air. They are emitted by coughing or speaking and after floating in the air. Air is polluted by pathogenic micro-organism in close proximity to patients whose expired air is charged with bacteria as in the case of persons suffering from tuberculosis, influenza etc., House dust is more harmful than the street dust.

The effects of air pollution  are either immediate and delayed.
– Immediate effects- Epidemiological studies have shown that a sudden increase in air pollution has been associated with immediate increase in the mortality and morbidity. The symptoms are usually referable to the respiratory system.
– Delayed effects –
1. Chronic bronchitis.
2. Primary lung cancer – It is generally agreed that atmospheric pollution is a factor of importance in the causation of lung cancer. City dwellers have up to 3 times more cancer than the rural inhabitants.
3. Effects on plants, animals, spotting and burning of leaves, destruction of crops and retarded growth of the plants subjected to air pollution have been observed. Fluorides present in the fumes are toxic to the animals. Cattle suffer by eating foliage contaminated with fluorides.
4. Social and economic effects -These are indirectly due to impairment of human, plant and animal health. The effects are – 1) – corrosion of metals and building materials, cost of cleaning and repairing. (2) Unpleasant odors.

The control or prevention of air pollution is ultimately an engineering problem. It includes education of the population about the harmful effects of smoke, dust etc. and the ways of controlling it; the value and importance of clean air should be inculcated in them.

The public should be encouraged about the methods of reducing and preventing air pollution. The following procedures are recommended (by WHO) for the prevention and control of air pollution :

(1) Containment – That is, prevention of escape of toxic substance into the ambient air. The major contribution in this field is the development of ‘arrestors’ for the removal of contaminants.

(2) Careful planning and selecting sites for the factories and dwellings. The factories should be made in the outskirts of the town.

(3) Increased use of electricity & natural gas, in factories to use of smokeless fuels and to introduce modern and efficient furnaces.

(4) Establishment of green belts between industrial areas and residential areas.

(5) Improvement in the vehicles & the traffic management to reduce pollution from the automobile vehicles, reduction of smoke and fumes by efficient maintenance of engine. In this atomic age, atmospheric pollution by dispersal of radiation in air is assuming a great importance and as its effect is cumulative, no concentration can be ignored.

Air pollution by industrial smoke can be considerably prevented by adopting these methods :

-Use of smokeless fuels, e.g. coke in boiler and furnaces,

-Use of mechanical stokers or employment of skilled labors for careful stoking of furnaces,

-Provision of efficient furnace plans with accurately maintained draughts,

-Enforcement of laws relating to smoke nuisance, etc.


  1. muhamed ali

    what is this i used it for lesson and it is good materila ilike

  2. muhamed ali

    your companie is very good i use it for our science

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