* The atmosphere is a complex dynamic natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth 's ecosystems.
Natural sources * Dust from natural sources, usually large areas of land with little or no vegetation. * Methane, emitted by the digestion of food by animals, for example cattle. * Radon gas from radioactive decay within the Earth 's crust. Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health hazard. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after cigarette smoking. * Smoke and carbon monoxide from wildfires. * Volcanic activity, which produce sulfur, chlorine, and ash particulates.
Sources of air pollution refer to the various locations, activities or factors which are responsible for the releasing of pollutants in the atmosphere. These sources can be classified into two major categories which are:
Anthropogenic sources (human activity) mostly related to burning different kinds of fuel * "Stationary Sources" include smoke stacks of power plants, manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices * "Mobile Sources" include motor vehicles, marine vessels, aircraft and the effect of sound etc. * Chemicals, dust and controlled burn practices in agriculture and forestry management. Controlled or prescribed burning is a technique sometimes used in forest