Air pollution : Science NCERT /CBSE Revision Notes
Air pollution is caused when the presence of pollutants in the air harm both living and non-living things and also produce harmful environmental effects. Substances that cause harmful changes in the air are called pollutants. Air pollution is caused due to the presence of pollutants in the air.
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Air pollution is caused by burning fossil fuels, like coal and petroleum, in industries, power plants and vehicles, and by burning of firewood and dung cakes. Pollutants are also released into the air by natural events like a dust storm, forest fire or volcanic eruption.
There are different types of air pollutants.
- Automobile emissions produce high levels of carbon monoxide, carbon dioxide, nitrogen dioxide and smoke. Respiratory problems are a result of this type of pollution.
- Incomplete burning of fossil fuels, like petrol and diesel, results in the production of colourless, odourless and toxic carbon monoxide gas.
Smog is a mix in the air of smoke and chemicals with fog. The chemical components of smog can include ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide. Smog can trigger breathing difficulties like asthma and coughing.
Pollutants like sulphur dioxide and nitrogen dioxide are released in large quantities by petroleum refineries. These emissions can cause respiratory problems and also permanent lung damage.
CFCs or chlorofluorocarbons are synthetic products that contain carbon, chlorine and fluorine. They were formerly used as a refrigerant and as a propellant in aerosol or air sprays. CFCs contribute to the depletion of the ozone layer that protects us from the harmful ultraviolet rays of the sun.
Soot is released when automobiles burn fossil fuels, like petrol and diesel. Particles of soot remain in the air for long periods and are a major cause of reduced visibility. They are harmful to health, and when inhaled, can cause respiratory diseases. Power plants, steel and mining industries also release harmful particle pollutants.
Pollutants like sulphur dioxide and nitrogen dioxide, which are produced by industries like rubber processing, automobile chemicals and the Mathura oil refinery near Agra are responsible for the decolourisation of the Taj Mahal. These gases react with water vapour in the atmosphere and form sulphuric acid and nitric acid. Precipitation carries these acids back to the earth as acid rain.
The corrosion of the Taj Mahal due to acid rain is called ‘marble cancer.’ Global warming has already started melting the polar ice caps, which has resulted in a rise in the global sea level. Gases, like methane, nitrous oxide and water vapour, also contribute to the greenhouse effect, and, along with carbon dioxide, are collectively called the greenhouse gases.
Steps to prevent air pollution:
- Use of fuels like CNG and unleaded petrol in automobiles.
- Switching to alternative fuels, like solar energy, hydropower and wind energy.
- Planting trees.
- Travelling to school on a bicycle or on public transport or car pooling.
- Avoiding the burning of leaves, trash and vegetable matter.
- Restricting cigarette smoking.