The earth’s atmosphere has been keeping a sort of balance between its various constituents over the past billions of years. But the modern human activities such as large scale industrialization, rapid transport systems, changing life styles, and habits like smoking, burning of fossil fuels, and blind deforestation are upsetting the balance of atmosphere.

The major human activities which pollute the atmosphere are as follows:

1. Chemical industries pollute air – The chemical industries releases several poisonous gases into the atmosphere, which pollute air. Similarly industries engaged in the extraction of metals, which produce sulphur dioxide gas by roasting the sulphide ores of metals such as zinc, copper, and iron. This sulphur dioxide goes into the air and causes pollution.
2. Burning of coal, wood, and oil pollutes air – Burning of fuels such as oil, coal, and wood may produces black smoke causing pollutes the air. Smoke contains poisonous gases such as sulphur dioxide and carbon monoxide, which pollutes the atmosphere.
3. Exhaust gases emitted by internal combustion engines – The gas emitted by the engines of automobiles such as trucks, car, buses, and many more contains poisonous gases such as carbon monoxide, hydrocarbons, nitrogen oxides, some lead compounds, and unburnt carbon particles, which pollut the air. Motor vehicles are also main causes of severe pollution in big cities. The railway engines, airplanes, and ships also pollute the air.
4. Dust pollutes air – Dust produced by the heavy traffic and various industrial operations pollutes air.
5. Smoking pollutes air – Smoking produces carbon monoxide and nicotine, which are poisonous chemicals and pollutes air.

When fossil fuels carbon compound, coal, petroleum, and natural gas burnt then they produce carbon dioxide gas, which goes into the atmosphere. The cultivation of soil releases large amount of carbon dioxide. It is estimated that carbon dioxide has already increased around 13 percent in the air. Further carbon monoxide produces by Incomplete combustion of fossil fuels are also goes into the atmosphere.

Deforestation is also human activity, which is dangerous. The green plants absorb excess carbon dioxide from the atmosphere to carry out photosynthesis. New plants should be growth for this purpose. Another part of the atmosphere, which human have durectly affected is the ozone layer, which blocks ultraviolet radiations. The highly useful ozone layer in the upper atmosphere has been threatened by human activities.