Fact sheets

The ozone layer is threatened by a number of industrial chemicals, including CFCs (chlorofluorocarbons), which are used as coolants in refrigerators and air conditioners; halons, which are found in fire extinguishers; methyl bromide, a pesticide; and HCFCs (hydrogenated CFCs), which are used as a CFC substitute, since they are much less damaging to the ozone layer than CFCs.

These industrial chemicals all share two characteristics —they are very stable at ground level, and they contain chlorine or bromine. Once released into the atmosphere these chemicals rise slowly upward through the ozone layer, where they break apart in the harsh ultraviolet sunlight and release highly reactive chlorine (from CFCs and HCFCs) or bromine (from halons and methyl bromide). Chlorine atoms have a voracious appetite for ozone. A single chlorine atom is capable of destroying thousands of molecules of ozone, and bromine is even more destructive.