How do CFCs destroy the ozone layer?
Emissions of CFCs to date have accounted for roughly 80% of total stratospheric depletion. Whilst chlorine is a natural threat to ozone, CFCs which contain chlorine are a man-made problem. Although CFC molecules are several times heavier than air, winds mix the atmosphere to altitudes far above the top of the stratosphere much faster than molecules can settle according to their weight. CFCs are insoluble in water and relatively unreactive in the lower atmosphere but are quickly mixed and reach the stratosphere regardless of their weight. When UV radiation hits a CFC molecule it causes one chlorine atom to break away. The chlorine atom then hits an ozone molecule consisting of three oxygen atoms and takes one of the oxygen molecules, destroying the ozone molecule and turning it into oxygen. When an oxygen molecule hits the molecule of chlorine monoxide, the two oxygen atoms join and form an oxygen molecule. When this happens, the chlorine atom is free and can continue to destroy ozone.
