The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty that has guided the gradual phaseout of production of chlorofluorocarbons (CFCs), halons, and other chemicals suspected of thinning the ozone layer. Restoration of the ozone layer is necessary to protect humans, animals, and plants from exposure to dangerous amounts of ultraviolet (UV) radiation. The Montreal Protocol was negotiated in 1987 and went into effect in January 1989. Revisions that have strengthened the Protocol have occurred regularly since 1990 as new scientific, environmental, and technical information has become available.

Each industrialized signatory nation agreed to reduce production of ozone-depleting substances (ODS) during the 1990s except for essential uses for which no substitutes could be found. Developing nations were given a longer timetable and ...