The decrease of strastospheric ozone was first reported in 1974 and its decrease was linked to the presence of manmade compounds in the atmosphere – the most damaging of which is the class of compounds know as Chloroflurocarbons or CFCs.

CFCs are the major category of man-made halocarbons. Halocarbons are formed when halogen gases such as fluorine, chlorine and bromine become attached to carbon. The smaller halocarbons turn into a gas quite easily and are the prime suspects in ozone depletion.

CFCs are used in industry in a variety of ways. They were discovered in the 1930s by American chemist Thomas Midgley, and came to be used in refrigerators, home insulation, plastic foam, and throwaway food containers.

The non-reactivity of CFC's, so desirable to industry, allows them to drift for years in the environment until they eventually reach the stratosphere. High in the stratosphere, intense UV solar radiation splits the chlorine molecules off the CFC's. These then attract one of the three oxygen atoms in the ozone molecule (O3) – destroying the ozone by turning it into oxygen. A single chlorine atom can destroy over 100 000 molecules of ozone in this way.

CFCs vary widely in their stability and in how effective they are at destroying ozone. Unfortunately, most of them will persist in the atmosphere for many years (from 50 to over 200 years). Although many countries have moved to reduce the use of CFCs, this long life of CFCs means that the impact of chlorofluorocarbons currently in the atmosphere will continue well into the next century.