RADIATION

Exposure to solar and ionizing radiation increases the risk for cancer in humans. Some 5% of solar radiation is within the ultraviolet spect rum and may cause both malignant melanoma and non-melanocytic skin can cer; the latter is regarded as a benign disease and is accordingly not included in our estimation of avoidable cancers. Under the assumption that the rate of occurrence of malignant melanoma of the buttocks of both men and women and of the scalp of women would apply to all parts of the body in people completely unexposed to solar radiation, it was estimated that approximately 95% of all malignant melanomas arising in the Nordic populations around the year 2000 will be due to exposure t o natural ultraviolet radiation, equivalent to an annual number of abo ut 4700 cases, with 2100 in men and 2600 in women, or some 4% of all c ancers notified. Exposure to ionizing radiation in the Nordic countrie s occurs at an average effective dose per capita per year of about 3 m Sv (Iceland, 1.1 mSv) from natural sources, and about 1 mSv from man-m ade sources. While the natural sources are primarily radon in indoor a ir, natural radionuclides in food, cosmic radiation and gamma radiatio n from soil and building materials, the man-made sources are dominated by the diagnostic and therapeutic use of ionizing radiation. On the b asis of measured levels of radon in Nordic dwellings and associated ri sk estimates for lung cancer derived from well-conducted epidemiologic al studies, we estimated that about 180 cases of lung cancer (1% of al l lung cancer cases) per year could be avoided in the Nordic countries around the year 2000 if indoor exposure to radon were eliminated, and that an additional 720 cases (6%) could be avoided annually if either radon or tobacco smoking were eliminated. Similarly, it was estimated that the exposure of the Nordic populations to natural sources of ion izing radiation other than radon and to medical sources will each give rise to an annual total of 2120 cancers at various sites. For all typ es of ionizing radiation, the annual total will be 4420 cancer cases, or 3.9% of all cancers arising in the Nordic populations, with 3.4% in men and 4.4% in women.