The incidence-sun exposure relationship for all three cancers is well described by the power law. SCC is dependent on total UV exposures, while BCC, and even more CM, is dependent also on exposure patterns, with intermittent exposures being most carcinogenic.

No abstract

Latitudinal dependencies of UVA and UVB were studied together with relevant epidemiological data for squamous cell carcinoma (SCC) and cutaneous malignant melanoma (CMM) in Norway and Sweden. Our data support the hypothesis that solar UVA radiation may play a role for CMM induction. The etiologies of SCC and CMM are different according to a latitudinal dependency and differences in age curves. Sun exposure patterns, age-related decay rates of repair of UV damage and sex hormones may play different roles for the two skin cancers. Also, UVB induction of vitamin D may be involved. CMM incidence rates among young people have decreased or been constant since about 1990 in Norway and Sweden. All reasons for UVA contributing to CMM will be discussed.

Solar ultraviolet (UV) radiation is the main source of vitamin D production and is also the most important environmental risk factor for cutaneous malignant melanoma (CMM) development. In the present study the relationships between daily or seasonal UV radiation doses and vitamin D status, dietary vitamin D intake and CMM incidence rates at different geographical latitudes were investigated. North-South gradients of 25-hydroxyvitamin D (25(OH)D) generation and CMM induction were calculated, based on known action spectra, and compared with measured vitamin D levels and incidence rates of CMM. The relative roles of UVA and UVB in CMM induction are discussed. Latitudinal dependencies of serum 25(OH)D levels and CMM incidence rates can only partly be explained by ambient UV doses. The UV sensitivity is different among populations with different skin color. This is well known for CMM, but seems also to be true for vitamin D status. The fact that UV-induced vitamin D may reduce the risk of CMM complicates the discussion. To some extent high dietary vitamin D intake seems to compensate low UV doses.