How did CFCs get to the poles?
Jet streams flow laterally due to centripetal forces. If CFC gases caused the hole in the ozone layer over the poles, how did those CFCs get there?
CFCs are actually everywhere in the atmosphere and not just over the poles. But over the poles where the CFCs are coldest, you get ice particles, which allow the ozone depleting reactions to occur. So it's not that the CFC concentrations are different, it's just what happens to them. Because Antarctica is completely isolated and surrounded by ocean, you get a whirlpool effect in the atmosphere there which has a concentrating effect. The depleted ozone therefore stays put rather than mixing in with the rest of the atmosphere.