Doses of solar ultraviolet radiation correlate with skin cancer rates in Japan.

We analyzed trends in the disease rate of skin cancers in the 1976-80 and 1986-90 intervals in the 27 university hospitals in Japan. We also measured doses of solar ultraviolet (UV) radiation at Sapporo, Kobe and Miyazaki to evaluate the relationship between the two in Japan. The rates of basal cell carcinoma (BCC) and actinic keratosis (AK) were higher in 1986-90 than in 1976-80, whereas the rate of squamous cell carcinoma (SCC) was lower in 1986-90 than in the earlier period. The rates of SCC, BCC and AK in the southern part of Japan were about five times higher than those in the north, and the average daily UV dose measured with a Robertson-Berger meter in 1995 was about 1.8 times higher in Miyazaki than in Kobe. That measured by MS-210D UV dosimeter in Sapporo was about 0.53 times lower than in Kobe. These results demonstrate that solar UV dose is higher in the southern part of Japan than that in the northern part, explaining the higher rate of non-melanoma skin cancer in southern part of Japan. A significant increase of AK and BCC may reflect the trend of UV increase in Japan.