What Human Activities Affect the Stratospheric Ozone Layer?
Initially, theories about the cause of ozone-layer depletion abounded. Many factors were suggested, from the sun to air motions to human activity. In the 1970s and 1980s, the scientific evidence showed conclusively that human-produced chemicals are responsible for the observed depletions of the ozone layer. The ozone-depleting compounds contain various combinations of carbon with the chemical elements chlorine, fluorine, bromine, and hydrogen (the halogen family in the periodic table of the elements). These are often described by the general term halocarbons. The compounds include chlorofluorocarbons (CFCs which are used as refrigerants, foam-blowing agents, electronics cleaners, and industrial solvents) as well as halons (which are used in fire extinguishers). The compounds are useful and benign in the troposphere, but when they eventually reach the stratosphere, they are broken apart by the sun’s ultraviolet radiation. The chlorine and bromine atoms released from these compounds are
