Industrial smog is comprised of toxic emissions and is caused by burning fossil fuels, such as coal. The emissions rise into the air and collect as thick clouds of dust and other particles.
Toxic substances, such as sulfur dioxide and other pollutants, are carried into the air when fossil fuels are burned in factories. The formation of smog is aided by cold or humid temperatures, which help trap the pollutants in lower altitudes due to the high water content in the air. Smog gathers in the affected area, reducing visibility and air quality. The pollutants from smog may dissolve into condensation and fall to the surface as acid rain, which is harmful to the environment.