UV-B radiation: a health risk in the Arctic?

Seasonal stratospheric ozone depletion in the Arctic has raised the questio n of whether the associated increases in ultraviolet-B (290-320 nm) constit ute a significant health risk in Arctic populations. Increases in skin canc er in Europe and the USA from excess UV-B resulting from ozone depletion ha ve been predicted. Skin cancer is, however, rare in Inuit populations. UV-B also causes a selective down regulation of the immune system which may be a natural regulatory mechanism evolved to prevent autoimmune attack on sunlight-altered skin. The action spectrum for UV-B immunosuppression impli cated a unique skin photoreceptor molecule, urocanic acid (UCA), which isom erizes from the trans to the cis isomer on exposure to UV-B, the cis isomer being immunosuppressive. This form of immunosuppression is important in sk in cancer and possibly in infectious diseases. The epidemiology of non-Hodgkin's lymphoma shows a relationship with UV exp osure, postulated to be via the immunosuppressive effects of UV-B. Cancers which show an excess in Inuit populations include nasopharyngeal and saliva ry gland cancer. Genetic factors appear to be involved, but these are thoug ht to be virally related cancers possibly associated with the high viral lo ad in these populations. In several studies on non-Arctic populations, sali vary gland cancer has been linked to ultraviolet exposure. A potential role for UV-B exposure in these cancers in the Arctic needs to be explored. In view of the high levels of POPs in some Arctic regions, potential intera ctions between the immunosuppression caused by some of these pollutants and the effects of UV-B need to be investigated.