The combustion of coal and hydrocarbons produce a mixture of carbon dioxide, carbon monoxide, sulphur dioxide, oxides of nitrogen and unburnt hydrocarbons. Though combustion of fuels is helping us in many ways, yet combustion of fuels is one of the major causes of pollution in atmosphere in our cities and towns. Most of air pollution is due to the products of combustion of fuels in homes, transport and industry. The main pollutants in air are carbon monoxide, carbon dioxide, oxides of sulphur and nitrogen. As our energy need is increasing, we are burning more and more fuels. The increased use of fuels is causing more and more problems of fuels. The contamination of air with dust, smoke and harmful gases is called air pollution.

The fossil fuels cause air pollution in the following ways:

The combustion of fossil fuels produces carbon dioxide which is released in the atmosphere. Though carbon dioxide gas is non-toxic (non-poisonous) but excess of carbon dioxide in atmosphere is not desirable. The increased concentration of CO2 in air may lead to undesirable changes in the climate. Carbon dioxide has a tendency to absorb infra-red radiations emitted by the sun and, therefore, it will result into excessive heating of the earth's atmosphere which affects all the lives on the earth. This effect produced by carbon dioxide is known as green house effect.

It is speculated that if the concentration of carbon dioxide continued increasing, the average temperature of the earth will increase. According to the estimate, the temperature of the earth is increasing by about 0.05'C every year. The warming up of the earth would ultimately melt all the glaciers on poles and snow on different mountains. This would increase the water level of the sea and as a result the cities located on the coastal areas likely to be flooded.

Combustion of coal, gasoline or other fossil fuels in the presence of insufficient supply of air liberates carbon monoxide. Carbon monoxide is very dangerous for life. It may combine with haemoglobin in the blood and forms a compound known as carboxy haemoglobin. Due to the formation of this compound, the blood becomes incapable of transporting oxygen to our body parts. This leads to respiratory troubles, headache, dizziness, unconsciousness, etc.

Fossil fuels also contain compounds of sulphur and nitrogen. These compounds on combustion gives oxides of sulphur and nitrogen which are corrosive and poisonous. Sulphur dioxide is very irritating and affects our lungs. During rains, the gases mix with water falling down and forms acids which fall to the earth with rain. This polluted rain is called acid rain. This is very corrosive and harmful for both living and non-living things. It destroys living bodies, eats up lime stone and marble of buildings and corrodes metals.

Combustion also releases some unburnt hydrocarbons. Some of these are health hazards. The burning of petrol in automobiles also produces pollutants such as carbon monoxide, unburnt carbon particles and lead compounds. Scientists are working with full strength to device methods to control pollutions.