ozone shield, the layer of ozone that hangs in the atmosphere from 20 to 40 miles above the surface of the earth and protects the earth from excessive ultraviolet radiation. Some experts claim that the manufacture of various chemicals, such as chlorofluorocarbons used as propellants in aerosol sprays, and the effects of high-flying jet aircraft are destroying this protective layer and allowing excessive amounts of ultraviolet radiation to penetrate the earth’s atmosphere, thus subjecting humans to increased dangers of skin cancer and other health problems. Some chemistry experts and federal health officials also claim that an additional threat comes from nitrous oxide in nitrogenous fertilizers rising into the atmosphere and reacting unfavorably with the ozone shield. The ozone shield is implicated in certain health problems that affect some air travelers. See also ozone sickness.
