Outdoor Air Pollution and Your Health.

www.thoracic.org C LI P A N D C O P Y Where Does Outdoor Air Pollution Come From? Air pollution is the name for the mixture of harmful particles and gases in the air around us that we breathe. Air pollution is produced by both human activity and naturally occurring events. Burning of fossil fuels by motor vehicles (including cars, buses and trucks) and power plants (including coal-fired and natural gas plants) releases a mixture of pollutants, such as tiny particles (particulate matter, PM), nitrogen oxides (NOx) and volatile organic compounds (VOCs). Chemical reactions in the atmosphere between NOx and VOCs produce ground-level ozone, a component of smog. Naturally-occurring sources of pollutants include forest fires, volcanoes, and dust storms. Forest fires release a range of pollutants, from particulate matter and acrolein (a respiratory irritant) to carcinogens (causing cancer) such as formaldehyde and benzene. Dust particles from roads or desert environments also pollute the air. Tiny airborne particles from power plant emissions or forest burning can travel thousands of miles and affect the air quality in distant places. In general, pollution levels are highest closest to the source of emission.