Decreased concentration of stratospheric ozone allows increased levels of UV-B rays to reach the earth's surface. Stratospheric ozone depletion is caused when chlorine reacts with ozone. Chlorine found in nature is water soluble. Therefore, most is removed in the lower atmosphere by rain, snow and ice and does not reach the stratosphere.
Some compounds are more harmful to the ozone layer than others.
The ODP of each compound is established relative to CFC-11. Each year, approximately 300,000 appliances and car air conditioners containing about 340 tons of CFCs and HCFCs are disposed of. Regulations are in place to help prevent the release of CFCs into the environment. In addition to the CFC production ban, servicers and disposers of appliances and motor vehicle air conditioners are required to obtain technician certification, proper refrigerant recovery or recycling equipment, and keep records. For more information on ozone depletion, how it occurs, common myths and health effects, visit the EPA's Ozone Web site.