What causes thinning of ozone layer?

i need something short and sweet but mainly describes it in a nutshellWhat causes thinning of ozone layer?
The overall cause of ozone depletion is the presence of chlorine-containing source gases, like CFCs. In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction. This mechanism takes place everywhere, where there is sunlight. The overal effect is a gradual depletion (a few percent per year) of the ozone layer.





The effect is enhanced at the poles, because of the formation of polar stratospheric clouds which act as catalyzers.