What is Air Pollution ?
Air
Air in the atmosphere is a reserve of Oxygen and Carbondioxide without which
survival of plant and animal is not possible. The ozone layer acts as a shield above the earth to prevent harmful ultraviolet radiation of the Sun from reaching the earth surface. The other gases in the atmosphere perform vital functions that maintain living environment in balance. The atmosphere controls the temperature and moisture content during daytime and the nights. It protects the earth surface from constant bombardment of meteors from the space.
AIR POLLUTION
Dust & fume generated through physical movements, mechanical crushing, screening, handling / transfer and chemical / metallurgical process try to become airborne and then spread in the sorrounding atmosphere, if allowed, polluting the ambient conditions.
According to WHO air pollution is defined as limited to situation in which the out-door ambient atmosphere contains materials in concentration which are harmful to man and his surrounding environment. The Air (Prevention and Control of Pollution) Act in general defines air pollutant as any solid, liquid or gaseous substance present in the atmosphere in such concentration as may be or, tend to be injurious to human beings or, other living creatures or, plants or, building structures or environment.
The Pollutants include oxides of Carbon, Nitrogen and Sulphur, Hydrocarbons, inorganic and organic acids, insecticides, bacteria, viruses' etc. Major sources of pollutants are nature or man made (anthropogenic). The chemical composition of particulate air pollutants varies over a wide range. Air pollutants contain twenty-two metals. Most of them are very poisonous. Due to incomplete combustion, some particulate polycyclic organic mater are also produced.
Some gaseous pollutants deserve special mention:
CO (Carbon Monoxide) : It is a chocking gas. The gas acts on haemoglobin and releases oxygen from blood to form a compound known as carboxy-haemoglobin. It causes drowsiness, headache, loss in sense of proportion and even death.
SO2 (Sulphur Dioxide) : It causes burning sensation, pulmonary disease, bronchites, asthma and lung cancer. The gas (also NO2) is oxidised to trioxide and reacting with moisture forms acids, which is washed down to the earth with rain causing acid rain. Acid rain causes extreme damage to buildings, structures, vegetation, and animal world especially aquatic life etc.
The six or seven oxides of Nitrogen are collectively known as Nox.
NO2 (Nitrogen Dioxide) : It is an offensive – smelled (foul odoured ) brown poisonous gas causing different diseases related to our respiration, digestion and nervous system.
H2S (Hydrogen Sulphide) : It is also a foul smelled gas having hazardous effects on human beings.
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