Smog

Smog, term first used in 1905 to describe the combination of smoke and thick fog that hung over London and other cities in Great Britain. London-type fog occurs when moisture in the air condenses on smoke particles produced by burning coal. Sulfur dioxide, the dangerous part of London-type smog, attacks the lungs. Petrochemical smog results from the action of sunlight on hydrocarbons and nitrogen oxides in the air that are formed by burning gasoline and petroleum products. It can irritate the eyes, nose, throat, and lungs. Smog is poisonous in heavy concentrations and can be fatal. It also destroys plant life and deteriorates building materials.

See also: Air pollution.