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Why were chlorofluorocarbons restricted in refrigerators and air conditioners?

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A labeled diagram of the periodic table entry for fluorine, showing its atomic number 9, symbol F, atomic weight 18.998, electron configuration, and indicating it is a halogen and a gas at room temperature. — fluorine Properties of fluorine.

Chlorofluorocarbons (CFCs) were restricted in refrigerators and air conditioners because they were discovered to be a significant environmental threat to the ozone layer.1

Although CFCs were initially valued as nontoxic and nonflammable refrigerants, research demonstrated that when these compounds are released into the atmosphere, they accumulate in the stratosphere. Once there, ultraviolet radiation causes the CFC molecules to dissociate, releasing chlorine atoms. These chlorine atoms react with and destroy ozone molecules, a process that depletes the stratospheric ozone layer that shields Earth from harmful radiation. The depletion of this layer is linked to increased risks of skin cancer and other genetic damage in organisms.1

Due to these dangers, international efforts such as the Montreal Protocol were established to phase out the production of CFCs and other ozone-depleting substances.1