Air pollution is mainly the result of a combination of various chemicals released into the atmosphere. For instance, petrol and diesel burn in an automobile engine and produce pollutants. The exhaust gases of internal combustion engines such as those in cars, aeroplanes etc. contain a large amount of carbon monoxide. Carbon monoxide is formed due to the incomplete combustion of fuel. Petrol is a mixture of hydrocarbons and when petrol is burnt inside an engine carbon dioxide and water are formed if combustion is complete. If combustion is incomplete as it often is, carbon monoxide and carbon particles are also formed. Carbon monoxide is highly poisonous. It reacts with haemoglobin of man to form carboxy-haemoglobin. Due to this, haemoglobin will not be able to carry oxygen which can cause suffocation and untimely death.
Automobiles have been playing a very important role in making life comfortable for man. Cars being built today are more powerful than older models. The manufacturers, therefore, have to increase the compression ratio of their engines. Thus combustion takes place at higher pressure causing an increase in temperature. At a higher temperature, atmospheric nitrogen combines with oxygen to form oxides of nitrogen that are harmful to the human respiratory system. They are injurious to plant life too.
Due to the increased number of automobiles in the cities, excessive carbon dioxide is discharged into the atmosphere. Carbon dioxide along with other gases, may cause rise in the average atmospheric temperature. These gases allow sunlight to reach the ground but they prevent the sunâ€™s heat from escaping out of the atmosphere into the space. This is known as green house effect. Therefore heat is trapped on the surface of the earth that causes global warming.
Another pollutant present in the exhaust gases of automobiles is lead bromide. Tetra ethyl lead is added to petrol to improve the anti-knocking property of petrol. Leaded gasoline on combustion produces lead bromide, which is highly poisonous.