Quantitative carcinogenesis in man: solar ultraviolet B dose dependence of skin cancer in Maryland watermen.

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.