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 photochemical smog.
In certain other cities, such as Delhi, smog severity is often
aggravated by stubble burning in neighboring agricultural
areas. The atmospheric pollution levels of Los Angeles,
Beijing, Mexico city and other cities are increased by
inversion that traps pollution close to the ground. It is usually
highly toxic to humans and can cause severe sickness,
shortened life of death. [1]