Does Too Much Sun Cause Melanoma?
Two experts debate the issue in the British Medical Journal.
Sam Shuster, a consultant dermatologist at Norfolk and Norwich University Hospital, says that sun exposure is the major cause of the common forms of skin cancer, which are all virtually benign, but not the rarer, truly malignant melanoma.
Shuster says that the common skin cancers develop in pale, sun exposed skin and are less frequent in people who avoid the sun and use protection. In contrast, melanoma is related to ethnicity rather than pigmentation and in 75% of cases occurs on relatively unexposed sites, especially on the feet of Africans. Melanoma occurrence decreases with greater sun exposure and can be increased by sunscreens, while sun bed exposure has a small inconsistent effect. Therefore, he concludes, any causative effect of ultraviolet light on melanoma can only be minimal.
There is good evidence that the reported increase in melanoma incidence is an artefact caused by the incorrect classification of benign naevi as malignant melanomas, this, he argues, explains why melanoma mortality has changed little despite the great increase in alleged incidence.
He recognises that ultraviolet light causes the common, mainly benign skin cancers and, like smoking, wrinkles the skin. But he says, this is not a good enough reason for a blanket ban and we have to strike a balance with the sun's many other effects on health--from psychological and immunological, to the synthesis of vitamin D essential for bones and apparent protection against many major organ cancers.