प्रदूषण तथ्य

Though some particulates arise from natural sources such as dust, sea salt, and wildfires (we remove these types from our AQLI analyses), most PM2.5 pollution is produced by humans.

The fact that burning coal pollutes the air has been known for a long time. Around 1300, King Edward I of England decided that the punishment for anyone who burned coal in his kingdom would be death. Today, fossil fuel combustion is the leading global source of anthropogenic PM2.5[10] acting through three distinct pathways[11] :

First, because coal contains sulfur, coal-fired power plants and industrial facilities generate sulfur dioxide gas. Once in the air, the gas may react with oxygen and then ammonia in the atmosphere to form sulfate particulates.

Second, combustion that occurs at high temperatures, such as in vehicle engines and power plants, releases nitrogen dioxide, which undergoes similar chemical reactions in the air to form nitrate particulates.

Finally, diesel engines, coal-fired power plants, and burning of coal for household fuel all involve incomplete combustion. In this type of combustion, not enough oxygen is present to generate the maximum amount of energy possible given the amount of fuel. Part of the excess carbon from the fuel becomes black carbon, a component of PM2.5 that is a significant contributor to climate change.

Finally, diesel engines, coal-fired power plants, and burning of coal for household fuel all involve incomplete combustion. In this type of combustion, not enough oxygen is present to generate the maximum amount of energy possible given the amount of fuel. Part of the excess carbon from the fuel becomes black carbon, a component of PM2.5 that is a significant contributor to climate change.

In addition to fossil fuel combustion, humans generate PM2.5 through the combustion of biofuels such as wood and crop residue for household cooking and heating. Biofuel burning emits black carbon and organic particulates. In many parts of the world, biofuel combustion’s contribution to particulate pollution is comparable to that of fossil fuels. The burning of biomass—forests, savannah, and crop residue on fields—to clear land for agriculture is also a significant source of anthropogenic particulate pollution.[12]