Chlorofluorocarbons may be harming the ozone layer by doing what

Chlorofluorocarbons may be harming the ozonelayer by adding more ozone molecules, blocking ultraviolet light, or by destroying ozone molecules. Chlorofluorocarbons are so hardy, they survive being lofted to the upper atmosphere, where the only thing that can break them down, UV, releases the chlorine from the molecule.

CFCs drift slowly upward to the stratosphere, where they are broken up by ultraviolet radiation, releasing the chlorine that catalytically destroys ozone