Analysis of the risk of skin cancer from sunlight and solaria in subjects living in northern Europe.

The risk of non-melanoma skin cancer in northern Europeans who indulge in sunbathing or use a UVA solarium was estimated using a mathematical model of skin cancer incidence that makes allowance for childhood, occupational and recreational sun exposure. This model demonstrates that the cumulative incidence of skin cancer in indoor workers is about 2-3% by the age of 70, yet this risk can increase 5-fold if they indulge in a two-week sunbathing vacation each summer. The use of a UVA solarium is also shown to increase the risk of skin cancer. Because risk increases with the approximate square of annual solarium exposure, it is not possible to define a 'safe' level of exposure. Instead, it is shown that weekly use of a UVA solarium from age 20 until middle age (40-50) gives a relative cumulative incidence of 1.3 compared with non-users of sun beds and sun canopies. The risk begins to increase rapidly for more frequent use, particularly when solaria are used in combination with sunbathing.