If you knew the slightest thing about the problem with ozone destroying chemicals, of which the
chlorinated freons were prime culprits, you would know that they were a problem because they were supremely stable in the lower atmosphere (pure chlorine not so at all), and were able to transport chlorine to the ozone layer (unlike natural chlorine compounds), whereupon UV light broke them down, released the chlorine, starting a
chain reaction destroying the ozone.