In addition to transportation, the burning of fossil fuels also play a role in the high amounts of air pollution in cities. Fossil fuels are burned in generating stations, factories, office buildings, and homes. This particular combustion produces large amounts of ash, soot, and other particulates responsible for much of the smog you see in cities. In addition to the smog, the burning of fossil fuels also produces large amounts of sulfur oxides that can be damaging for anything from plants to buildings.