London, July 23 : Too much sun exposure has always been linked with the increased risk of melanoma - the less common and deadliest form of skin cancer - but it is still unclear clear if this association is real or not.
Now, two experts, Sam Shuster, a consultant dermatologist at Norfolk and Norwich University Hospital, and Professor Scott Menzies, from the University of Sydney at the Sydney Melanoma Diagnostic Centre, have debated the issue.
According to Shuster, 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.
He said that the common skin cancers develop in pale, sun-exposed skin and are less frequent in people who avoid the sun and use protection.
On contrary, melanoma is related to ethnicity rather than pigmentation and in 75 percent 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 concluded that any causative effect of ultraviolet light on melanoma could only be minimal.
However, Menzies argued that melanoma is far more common on body sites receiving more sun exposure and in people of races who tend to burn rather than tan.
Menzies said that there is considerable evidence that intermittent sun exposure and sunburn are strong independent indicators of the risk of developing melanoma in white populations.
According to him, there is a clear link between increasing cases of melanoma and increasing environmental ultraviolet light.
He claimed that genetic evidence is also supportive, with the major genes causing melanoma showing ultraviolet light "signature" mutations, while people deficient in repairing ultraviolet light genetic damage have a 1000 times greater risk of developing the disease.
"When you examine the geographical, sun exposure and genetic evidence together, sun exposure is clearly a major cause of melanoma," BMJ quoted him, as saying.
The study is published on BMJ.com.