Chlorofluorocarbon-11 (CFC11) lasts for an average of 74 years in the atmosphere, CFC12 for an average of 111 years, and CFC113 for an average of 90 years. Every CFC molecule destroys thousands of molecules of stratospheric ozone.
Recently, the extent of the Antarctic ozone hole has been recognized. The depletion of stratospheric ozone may lead to increase ultraviolet-B (UV-B) radiation.
UV-B radiation has many damaging effects on human health, such as snow blindness, cataract and skin cancer. UV-B radiation also suppresses the immune defenses against certain infections.
While it is difficult to estimate the numerical effect on the basis of epidemiologic data in the U. S. A., UNEP and WHO estimate that for every 1% decrease in stratospheric ozone, there will be between a 0.3 to 0.6% increase in cataract. They also estimate that for every 1% depletion of ozone, the incidences of basal cell carcinoma, squamous cell carcinoma and malignant melanoma will increase 2.7, 4.6 and 0.6%, respectively. There is also concern that increased UV-B radiation might lead to an increase of the incidence and severity of infectious diseases due to suppression of the immune system.
Since the data on UV-B exposure are extremely limited, it is necessary to confirm the incidence rate of skin cancer in various countries in relation to UV-B exposure.
