# The uv rays in stratosphere break the cfc into chlorine atoms.chlorine reacts with ozone and breaks into oxygen.as oxygen is helpful to man.why it is harmful?

The amount of oxygen produced in this way is small (compared to the 22% of our atmosphere that is oxygen). The problem is we need that layer of ${O}_{3}$ to deal with the incoming UV light. It helps absorb some of that light and makes the suns rays less harmful for us (and plants). Without Ozone layer, too much UV gets through and can cause elevated cancer and reduced crops.