How do CFCs destroy ozone?
CFCs are extremely stable in the lower atmosphere, only a negligible amount are removed by the oceans and soils. However, once CFCs reach the stratosphere, UV light intensities are high enough to break apart the CFC molecule, freeing up the chlorine atoms in them. These free chlorine atoms then react with ozone to form oxygen and chlorine monoxide, thereby destroying the ozone molecule. The chlorine atom in the chlorine monoxide molecule can then react with an oxygen atom to free up the chlorine atom again, which can go on to destroy more ozone in what is referred to as a “catalytic reaction”: Cl + O3 -> ClO + O2 ClO + O -> Cl + O2 Thanks to this catalytic cycle, each CFC molecule can destroy up 100,000 ozone molecules. Bromine atoms can also catalytically destroy ozone, and are about 45 times more effective than chlorine in doing so. For more details on ozone depletion chemistry, see the Usenet Ozone FAQ.
