How did chlorofluorocarbons contribute to ozone depletion over Antarctica?

Chlorofluorocarbons (CFCs) contribute to ozone depletion by releasing chlorine into the stratosphere. Once these compounds reach the upper atmosphere, ultraviolet radiation causes them to dissociate, freeing chlorine atoms that catalyze the destruction of ozone molecules.2

Over Antarctica, this process is intensified by the circumpolar vortex, which isolates air and creates extremely cold temperatures. These conditions lead to the formation of polar stratospheric clouds (PSCs). Chemical reactions on the surface of PSC particles convert stable, less-reactive chlorine compounds into highly reactive forms, such as molecular chlorine, which accumulate during the polar night.1

When sunlight returns in the spring, it breaks these molecules into single chlorine atoms. These atoms then aggressively react with and destroy ozone, leading to the significant thinning known as the Antarctic ozone hole. This cycle demonstrates the critical importance of global efforts, such as the Montreal Protocol, in regulating ozone-depleting substances to protect the environment and human health.12