Acid rain usually refers to rain with pH value lower than 5 6  It does great harm to human health, ecological environment and construction facilities, and causes direct economic losses of tens of billions of dollars every year  It can be confirmed that sulfur dioxide and nitrogen dioxide in the atmosphere are the main substances forming acid rain  They form water-soluble acids under the action of oxidants in the air
The combustion of coal and oil will release a large amount of sulfur dioxide and nitrogen dioxide into the air.
 Researchers have pointed out that reducing the use of coal and oil is the fundamental policy to prevent acid rain