An expert said on BMJ.com that the sun causes skin cancers, but not the less common but deadlier form called melanoma. However, other experts disagree.

Sam Shuster, a dermatologist at Norfolk and Norwich University Hospital, said in a news release that most of the cancers associated with the sun are benign. He also said melanoma is related to ethnicity and that 75 percent of cases develop on parts of the body not usually exposed to the sun, such as the feet.

He said that the benign cancers and other effects -- such as wrinkles -- should be balanced against positive effects from the sun, such as spurring vitamin D production. Vitamin D seems to protect against some forms of cancer and strengthen bones.

But Scott Menzies of the University of Sydney said that melanoma is actually more commmon in exposed areas and in people who tend to burn.

He said that intermittent sun exposure and sunburn are strong risk factors for melanoma in white people, for instance and that there is a clear association between getting more ultraviolet light and seeing higher melanoma rates.