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Causes of Air Pollution

The incorporation of unwanted impurities in the atmosphere which could alter the composition of the atmosphere is known as pollution. 
These unwanted impurities are called pollutants. The deterioration of environment; air, water and soil cause pollution in these bodies.
There are several chemical substances which contribute to air pollution. 
There are several chemicals which are harmful for the composition of air such as Nitrogen Oxides, Carbon Monoxides, and other organic compounds. 
These sources usually originates from natural and human sources. But out of these sources;only anthropogenic activities contribute to the air pollution problem. 

Some natural resources of air pollution are forest fires, eruption in volcano, erosion in wind, dispersal of pollen grain and evaporation of organic compounds. 
These natural factors do not contribute much in air pollution as there are several ecological cycles which can control the positive or negative effects of these resources. Therefore, anthropogenic effects are main issue for air pollution.

 We know that the atmosphere is a layer around our earth which can divide in to five layers. 
Out of these five layers; troposphere is the lowest layer which is close to earth surface and next layer is known as Stratosphere which contains high concentration of ozone gas. 

This ozone gas acts as protective layer for living bodies as ozone molecules have tendency to absorb the ultra-violet radiations which are very harmful for human beings.  
But due to the human activities a whole lot of air pollutants and especially CFC (chlorofluorocarbon) get released in the air which reacts with Ozone gas and destroys it gradually. 
The depletion of Ozone gas in stratosphere layer increases the effect of Ultra-Violet rays on Earth surface. 

The Troposphere layer is mainly effected due to the Oxides of Nitrogen, Sulphur and Carbon which are continually added into the atmosphere due to human activities such as excess use of automobiles, industrial smoke etc. 

The presence of oxides of sulphur and nitrogen in the atmosphere causes acid rain which mainly contains sulphuric acid and nitric acid with water. It is extremely harmful for living and non-living bodies. 

The deterioration of Taj Mahal is best example of effect of acid rain.  The main resource of oxides of sulphur is burning of fossil fuel which is added excess of sulphur in air in the form of SO2 gas. 

The Sulphur di-Oxide gas is harmful for animals and human beings as it can further react with atmospheric oxygen to form sulphur tri Oxide gas. 
The reaction of SO3 gas with water results the formation of poisonous sulphuric acid.  
We know that there is 79% of N2 in atmosphere which is not harmful for living or non-living system as it is a non-reactive molecule due to the presence of triple bond between two nitrogen atoms. 

Therefore N2 gas cannot react with any of the other compound under normal conditions. 
But in the presence of lighting and low pressure it reacts with O2 to for various oxides such as NO, NO2, N2O3 etc. which could further react to form several poisonous compounds like HNO3 (nitric acid).  

Another major source of Oxides of Nitrogen in automobile engines in which due to the presence of high temperature, nitrogen reacts with O2 to form oxides. 
These oxides of nitrogen and sulphur are quite harmful for human beings as they cause irritation in lungs and create breathing problems. 

They also reduce the rate of photosynthesis in plant and can cause an acute respiratory disease in human beings. 
The heavy industrialization and population explosion are major causes of air pollution as it increases the demands of automobiles and our everyday needs. 
Oxides of Carbon such as Carbon Monoxide, Carbon di-Oxide are mainly produced due to incomplete combustion of Carbon. 

Out of these two oxides; CO is more harmful as it has tendency to bind with haemoglobin in blood and block the availability of Hb for O2 binding.