Sources of Air Pollution

1. Natural Sources: The atmosphere is polluted due to various natural processes, some of which are wind-blown dust, smoke, fly ash, gass from forest fires, gases, and odors from swamps and marshes, pollen, fungi spores from the ocean. Fog in humid low-lying areas, anaerobic decomposition of organic matter, atmospheric reactions, and natural terpene hazes from pine trees in a mountainous region.

Volcanic eruptions release great amounts of sulphur dioxides. Anaerobic decomposition of organic matter generates methane gas which upon oxidation in the air gives out carbon monoxide. Organic substances decay to produce stinking gases like H2S too. Photooxidation of marine organic substances and biological oxidation by oceanic organisms generates carbon monoxide on the ocean surface which diffuses in the air.

2. Anthropogenic or Man-made Sources: Along with natural pollutants, there are pollutants of anthropogenic origin too. The bulk of the air pollution sources is linked to anthropogenic activities. It is an endowment of the modern lifestyle. The multiple uses of fossils for transportation in vehicles, for industrial uses, for conservation of energy, heating and for cooling as well as the treatment of industrial and municipal wastes, all add to air pollution.

The major anthropogenic sources of air pollution can also be grouped as:

  • Domestic: Coal combustion generates an enormous amount of smoke, soot, dust, CO, SO2, NOx. However, burning LPG releases fewer amounts of pollutants comparatively.
  • Automobiles: Motor vehicles play an important role in air pollution. Automobile emissions have been identified as the major source of air pollution in the Kolkata metropolitan region. It is contributing nearly 60-70 percent of air pollution. India is the fifth leading car producer in the world in 2011.

    It is also the leading producer of three-wheelers. The number of government-registered vehicles on roads in India is 142 million vehicles in the year 2011-12. The country’s vehicle population has grown in alarming proportions during the last decade.

3. Industries:

i. Fertilizer plants: They generate sulfur oxides, nitrogen oxides, hydrocarbons, PM, and fluorine.

ii. Thermal plants: Fly ash, soot, SO2, CO, NO.

iii. Textile Industries: Cotton fibres and dust, NO4, chlorine gas, naphtha vapours, smoke and SO2, etc.

iv. Steel plants and metallurgical operations: Carbon monoxide, carbon dioxide, sulphur dioxide, phenol, fluorine, cyanide, particulate matter, copper, lead, zinc, etc.

v. Petroleum: Fossil fuels include petroleum and coal. Emissions are mainly sulphur dioxide. Additionally, carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides, hydrocarbons, particulate matter, and traces of metals are produced.

vi. Paper and pulp: PM, SO2, H2S, methyl mercaptan.

vii. Food processing: It often releases dimethyl sulphide and various types of odor.

4. Agriculture: It mainly pesticides and herbicides like chlorinated hydrocarbons, phosphates, nitrates, etc.