Modern smog, as found for example in Los Angeles, is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.his kind of smog is caused by the burning of large amounts of coal within a city; this smog contains soot particulates from smoke, sulphur dioxide and other components.