Question

what causes smog in cities

Answer 1

smoke of vehicle engine
smoke of industries

Answer 2

Unfortunately, fires occur routinely in the city. Most fires in the city occur in buildings and homes but fires can start from many other sources such as rubbish, automobiles, and brush. The smoke that is created is an air pollutant and can lower the quality of the air we breathe. This fact sheet provides information on potential health effects and ways to limit exposure to smoke.
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