Air pollution is the contamination of the air by harmful substances. These substances , called pollutants, can occur naturally or they can be produced by human activities. Natural pollutants include dust, pollen, salt particles, smoke from forest fires, and gases from organic waste. Most pollution caused by human activities is directly or indirectly the result of burning of fuels in furnaces or engines.

Air pollution has a detrimental effect on human health. It can contribute to respiratory disease like bronchitis, emphysema, asthma, lung cancer. Air pollution also harms or destroy plants and animal life, and damages property.

Types of Air Pollutants

• Carbon oxides - is the largest single group of pollutants.
• Carbon monoxide - a colorless and odorless poison, it is a gas produced when fuel incompletely burned in engines, furnaces and space heaters. A major source of this is the Vehicles.
• Carbon Dioxide - a produced by normal combustion (burning). Although it is not a serious pollutant, it is believed that the continuous build up of this gas in the atmosphere could cause what they call a " green house effect" by reducing the flow of heat from the earth back into the space, thus causing a possible warming of the earth.

• Sulfur dioxide - one of the most dangerous of all air pollutants. The major sources of this pollutants are Factories and electric power plants that use sulfur-containing coal or oil as fuel. In the air, some sulfur dioxide is converted to sulfuric acid, which is then deposited on the earth's surface, usually by rain. This acid rain has caused damage to the environment in many parts of the world.
• Nitrogen oxide - are mildly poisonous brown gas. These are produced in automobile engines and other devices where combustion takes place. Gas ranges are a major source of nitrogen oxides.
• Hydrocarbon pollutant - produced by unburned fuel and are emitted mostly by motor vehicles. This also contribute to smog.
• Particulate matter - a tiny liquid or solid particles in the air. Particulate matter includes smoke, dust, and soot, which may contain toxic substances like asbestos, fluorides, lead, and mercury. Tobacco smoke is one of the major source of particulate matter.

• Chlorofluorocarbons (CFC's) - are synthetic substances that have has a variety of industrial uses. It is believed that CFC's can also contribute to a "greenhouse effect" resulting in a warming of the earth. Some scientist also believe that CFC's are destroying ozone that absorbs potencially harmful ultraviolet radiation from the sun.
• Radon - is a naturally occurring radioactive gas formed in varying concentrations in the ground. The waste products of radon enters building from the ground, in place where there is a high concentration of radon, dangerous level of this gas may accumulate in building where there is poor ventilation.

Ozone - a form of oxygen , used to purify and deodorize the air and to sterilize the water.

Ozone layer - a layer of the upper atmosphere , containing a high concentration of ozone that absorbs sun ultraviolet radiation.

Smog - fog that has been mixed and polluted by smoke.