SKIN-CANCER

It is estimated that 92,000 new cases of melanoma and 2,750,000 cases of nonmelanocytic skin cancer occur worldwide each year. Incidence of these cancers varies more than 100-fold from low rates in Asian popula tions to very high rates in the white population of Australia. Inciden ce of melanoma has been increasing in white populations by some 3% to 7% per year over the past 30 years; recent very sharp increases in som e populations are probably due to early and increasing detection of ca ncers that were already there. Incidence of nonmelanocytic skin cancer s probably is also increasing. Sun exposure is the main cause of skin cancer, accounting for at least 65% of melanomas worldwide and a much higher proportion in white populations. Pattern as well as amount of s un exposure is important in determining the risk of melanoma and proba bly also of basal cell carcinoma, with an intermittent pattern being a ssociated with the greatest risk. There is increasing evidence that no nsolar sources of ultraviolet radiation, in particular sunlamps and su nbeds, increase the risk of melanoma, and PUVA therapy and exposure to ionizing radiation are established causes of nonmelanocytic skin canc er.