Discuss pollution caused by CO.
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What are different sources of CO pollution? What are the effects of continuous exposure to CO on human beings?

Carbon monoxide is a colourless and tasteless gas and is not soluble in water. It is formed in a number of ways:
(i) By the incomplete combustion of fuels and substances containing carbon.

(ii) By the reaction between CO₂ and carbon at high temperature particularly in a blast furnace.

(iii) By the dissociation of carbon dioxide at high temperature.

(iv) Some natural processes like volcanic activity, natural gas emission, seed germination, electrical discharge during storm etc release some amount of CO into the atmosphere.
(v) Carbon monoxide is also released by the combustion of diesel, petrol etc. in the engines of automobiles and as a result of certain industrial processes.

Harmful effects:
(i) Effect of CO on human health: Carbon monoxide when inhaled passes through the lungs into the blood where it reacts with haemoglobin (Hb) of the red blood corpuscles (RBC) to form a stable compound known as carboxy haemoglobin (Hb – CO).

The latter is not in a position to transport the inhaled oxygen to various parts of the body. This will cause suffocation and ultimately lead to death. 
(ii) Effect of CO on plants: A high concentration of carbon monoxide will harmfully affect the plants causing leaf drop, a decrease in leaf size and premature ageing of the plants.