Stationary Sources

• A wood-burning oven produces huge amounts of sulphur dioxide and carbon monoxide.Jupiterimages/Photos.com/Getty Images
  
  Stationary sources of air pollutants are furnaces, waste incinerators, ores, manufacturing facilities, power plants and all types of fuel-burning heating devices. According to EPA's National Emission Inventory (NEI) database records, these are the largest sources of sulphur dioxide, with 73 percent of it coming from fossil fuel combustion at power plants and 20 percent coming from industrial facilities. Extraction of metal from ores also generates small amounts of sulphur dioxide and huge amounts of lead particles into the air. Both sulfur dioxide and lead are responsible for several respiratory problems. EPA has been setting standards for sulphur dioxide since 1971 to protect the general public from adverse effects of breathing in this deadly gas.
  
  

Mobile Sources

• Automobiles contribute 50 percent of carbon monoxide to atmospheric air.John Harrelson/Getty Images Sport/Getty Images
  
  These include motor vehicles, aircraft and marine vehicles, among others. Naturally, most of the carbon monoxide, nitrogen oxide and volatile organic compound emissions to ambient air come from mobile sources in urban areas.The reactions between oxides of nitrogen and volatile organic compounds in the presence of sunlight produce another pollutant known as ground-level ozone. Despite several major attempts to make automobile engines more fuel efficient, emissions from automobiles in the United States increased in the latter part of the 20th century due to increased in the use of cars as well as production of bigger cars and trucks with massive engines.
  
  

Forest Fires

• Forest fires generate fogs rich in fine particles.Stockbyte/Stockbyte/Getty Images
  
  Apart from chemical reactions, the other major source of particulate matter is burning fire. As far as agriculture and management of forests are concerned, controlled fire is very useful in farming and greenhouse gas abatement because it renews the forest by stimulating the growth of some desirable forest trees. The particulate matter emitted from the fire, if inhaled in the form of fine particles present in the smoke and smog, can be dangerous; they have been linked with aggravated asthma, decreased lung function, difficulties in breathing. Forest fire is also a potential source of carbon monoxide gas and ground-level ozone present in urban smog. The presence of particulate matter in air is closely monitored by the EPA under the Clean Air Act, governed by the final report of December 2008 on "Air Quality Criteria for Particulate Matter."
  
  

Waste Deposition

• The digestion of organic wastes dumped at the landfills by anaerobic bacteria leads to production of methane gas and some pollutants rich in compounds of lead. Methane gas is nontoxic, but it is highly inflammable and very asphyxiant. Military activities like manufacture and use of nuclear weapons; uses of toxic gases and germ warfare during wars; and adventures into rocketry are all potential sources of air pollutants. Minimizing the emission of air pollutants should involve long-term planning, conservation and a sincere commitment to preserving the environment and the natural world.