3. Chlorofluorocarbons (CFCs)
Chlorofluorocarbons (CFCs) were once widely used as refrigerants, solvents, and propellants in aerosol products due to their stability and non-flammability. However, in the mid-1970s, scientists discovered that CFCs released into the atmosphere were depleting the ozone layer, which protects Earth from harmful ultraviolet radiation. This led to the 1987 Montreal Protocol, an international treaty aimed at phasing out the production and use of ozone-depleting substances, including CFCs. The protocol has been successful in reducing CFC emissions, contributing to the gradual recovery of the ozone layer (britannica.com).
