To establish the relationship between ultraviolet-B radiation and squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and actinic keratosis (AK), a cross-sectional prevalence survey was performed in a sample of 808 white, male watermen 30 years of age and older residing in the Eastern Shore of Maryland. A measure of personal cumulative ultraviolet-B exposure was determined for each subject from data collected through interviews and field and laboratory measurements. A personal interview elicited skin type, medication history, and other factors. Clinical diagnoses and histologic confirmation were done for current and previously removed skin tumors. The ratio of subjects with SCC to subjects with BCC was approximately 1:1; however, the ratio of BCC to SCC was 1.25:l because BCC cases were more prone to multiple lesions. Watermen with SCC or AK but not BCC had higher average annual ultraviolet-B doses than age-matched controls. This was particularly marked in watermen younger than 60 years of age. Logistic regression showed that an older age, childhood freckling, and blue eyes significantly increased the risk of the development of all three types of skin tumor. Ease of sunburning was associated with BCC and AK, but not with SCC. Watermen in the upper quartile of cumulative ultraviolet-B exposure had a 2.5 times higher risk for the development of SCC when compared with the lower 3 quartiles. This suggests that high levels of ultraviolet-B exposure are important in SCC occurrence. The risk of AK developing was 1.5 times higher for those whose cumulative ultraviolet-B exposure exceeded the median. The relationship of BCC to cumulative ultraviolet-B exposure was not clear and this suggests that different etiologic mechanisms operate for SCC and BCC. Cancer 65:2811-2817,1990. From the

Skin cancer is the most common form of cancer in humans and occurs primarily on sun-exposed areas of the body. In a study of 808 Caucasian Maryland watermen, we examined the prevalence of nonmelanoma skin cancer in relation to age and exposure to solar ultraviolet B (UVB) radiation. For each study subject, the exposure to solar UVB radiation for each year of life after the age of 16 years was calculated. We obtained the data for this analysis by combining a detailed occupational history with laboratory and field measurements. Prevalence of the three major types of nonmelanoma skin neoplasms was analyzed: squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and actinic keratosis (AK). Average annual exposure to UVB radiation was strongly correlated with the prevalence of SCC, but not with the prevalence of BCC or AK. This finding is consistent with dose saturation (plateau in dose-response relationship) for the induction of BCC and AK in humans with high annual exposure to UVB radiation. In addition, two small groups of apparently hypersusceptible individuals were present in the population. One group had SCC despite low annual exposure to UVB radiation, and the other group had multiple skin cancers despite average exposure to UVB radiation.

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