United Nations Environment Programme

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Facts on Pollutants:



Sulphur Dioxide (SO2)

Sulphur dioxide is a colourless heavy gas with a pungent smell, also known to be an irritant.  


Sources of SO2:
Sulphur dioxide (SO2) comes from the combustion of fossil fuels that contain sulphur. Coal burning accounts for 50% of annual global SO2 emissions, making it the largest source to global emissions, with oil and diesel burning contributing a further 25-30%. Other sources include: metallurgical operations; smelting of non-ferrous ores of copper, lead, nickel, and zinc; manufacturing of sulphuric acid; conversion of wood pulp to paper; and refuse incineration.

Road transport is usually only responsible for a small a small portion (<5%) of total sulphur emissions.

Natural sources of SO2 include volcanic activity.


Human Health Effects of SO2:
Sulphur dioxides have respiratory impacts such as lung irritation, increased breathing rates, and suffocation. The most serious health effect is the aggravation of asthma and chronic bronchitis.
Sulphur dioxides can also irritate the throat and eyes.

Environmental Effects of SO2:

SO2 contributes to the formation of acid rain, which may cause extensive damage to materials and terrestrial ecosystems, aquatic ecosystems, and human populations.

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