In 1987, 24 countries signed an historic treaty under the United Nations Environmental Plan. This treaty was called the Montreal Protocol on Substances that Deplete the Stratospheric Ozone Layer. The Montreal Protocol was the first cooperative effort by nations from around the world to protect the environment and call for reduction and eventual elimination of a class of compounds. It called for periodic scientific, technical, and economical options assessments to determine if further revisions were required.
The original protocol called for a 50% reduction in chlorofluorocarbon (CFC) chemical production by 1998. However, the use, elimination, and phaseout of CFCs — and hydrochlorofluorocarbons (HCFCs) — was discussed in many different languages throughout most of the 90s.