A single chlorine atom can destroy 100,000 ozone molecules.

Chlorofluorocarbons (CFCs) were widely used in refrigerants and aerosol propellants until the late 20th century. When these stable compounds reach the stratosphere, intense ultraviolet radiation breaks them down, releasing highly reactive chlorine atoms. This discovery was famously detailed by researchers Mario Molina and F. Sherwood Rowland in 1974, a feat that later earned them the Nobel Prize in Chemistry in 1995.The destruction of ozone occurs through a catalytic cycle where a chlorine atom reacts with an ozone molecule (O3) to form chlorine monoxide (ClO) and an oxygen molecule (O2). The chlorine monoxide then reacts with a free oxygen atom to release the original chlorine atom back into the environment. This means the chlorine is not consumed in the reaction and can repeat the process over and over again.According to the Environmental Protection Agency (EPA), a single chlorine atom can keep this cycle going for up to two years, destroying approximately 100,000 ozone molecules during its lifespan. This massive imbalance led to the thinning of the ozone layer, particularly over Antarctica. In response, the 1987 Montreal Protocol was established to phase out CFC production globally, which has since allowed the ozone layer to begin a slow recovery process.