Tan cannot protect from years in sun's deadly rays

The more time you spend in the sun the higher your risk of contracting skin cancer, even if you are the type who tans rather than burns, say American researchers.

Many studies have linked sun exposure with skin cancer, but the team at the National Cancer Institute say their research is the first to show that the intensity of sunlight a person receives over a lifetime is directly related to his or her risk of contracting melanoma.

An ability to tan did not especially protect a person, said researcher Thomas Fears, who led the study.

Dr Fears said that where people lived as children and as adults were important factors, regardless of their tanning ability.

Their exposure to UVB rays (the sun's ultraviolet rays linked with tanning and burning) in these places was a factor, he said.

The sun's UVA rays were also linked with skin cancer and with the wrinkling that results from sun exposure.

The study team questioned 718 melanoma patients in Philadelphia and San Francisco and compared their answers to those from 945 people who did not have skin cancer.

All was questioned about their ability to tan and tendency to burn and a careful history was developed of their exposure to the sun where they lived, worked and vacationed.

Meters, which measure solar radiation, were then used to estimate how much UVB a person had received. New Orleans, for example, receives 20 per cent more UVB rays each year than Atlanta does.

The researchers used the UVB exposure readings and the patients' ages to determine their average annual intensity of sun exposure.

Writing in the journal Cancer Research, Dr Fears and his colleagues concluded that a 10 per cent increase in the average annual intensity of sun exposure led to a 19 per cent increase in a man's risk for melanoma and a 16 per cent increase for a woman's.

The researchers also found that people spent more time outside in the summer before the age of 20 than after.

They said this might account for the generally accepted idea that childhood exposure to sun was the most important factor in developing skin cancer.

Doctors now say there is no such thing as a safe tan and advice people to reduce their exposure to the sun.

Melanoma is the deadliest form of skin cancer, but is easily treated if caught early. A typical sign is a black, irregularly shaped or bleeding mole.

The American Cancer Society estimates that 53,600 people will be diagnosed with melanoma in the United States this year and 7400 will die of it.

- REUTERS

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