Ultraviolet radiation and health: friend and foe.

While excessive exposure to ultraviolet radiation (UVR) is a significant cause of disease burden in Australia and the Western Pacific region, there are well documented beneficial as well as adverse effects of UVR exposure. Ambient UVR levels do not translate directly to personal UVR dose and thus to biological effect - each person's sun-exposure behaviour and pigmentation also play a role. Exposure in childhood may be more important than exposure in adulthood for both beneficial and adverse effects. Stratospheric ozone depletion increases ambient UVR in the UVB wavelength, possibly the most important wavelength for both beneficial and deleterious health effects. There is ongoing research examining the effects of UVR exposure on immune function, including an examination of the possible role of lack of UVR exposure in the aetiology of multiple sclerosis and type 1 diabetes mellitus.