Cancer risk: A leading dermatologist yesterday warned Irish people to make sure they use sun screen which protects against UVA as well as UVB rays after further research highlighted the cancer causing potential of UVA rays.
Dr Gillian Murphy, consultant dermatologist at the Mater and Beaumont Hospitals, said one tenth of sunburn comes from UVA rays and it was important to protect against them.
She warned against some products, such as once-a-day application sunscreens, which she said did not provide sufficient protection against UVA rays.
"People should look at the labels carefully and they should not go lower than a factor 10. If you pick up a sunscreen with a protection factor of 10 or more, it will be pretty good for UVA protection as well. A product with a high protection factor of 30 to 50 will not have got such a high SPF without it having high UVA protection," she said.
Dr Murphy added that all this was nonsense unless the person using the sunscreen put on the same amount as was used in laboratory tests to achieve the SPF on the bottle. "The average person in Ireland puts on about one third of what they should so they get one third of the SPF," she said.
Yesterday new research from Australia published in the journal Proceedings of the National Academy of Sciences indicated UVA rays are potentially far more damaging to skin cell DNA than previously thought. UVA rays were found by University of Sydney researchers, who examined 16 tumours, to penetrate deeper into the skin than the shorter wavelength UVB rays which cause most sunburn.
Because UVA rays are less strongly absorbed by DNA than UVB, they had been considered less of a cancer risk. But the new research shows this belief is mistaken. Changes in the tumours, bearing the hallmark of UVA damage, were found in the deep basal keratinocyte cell layer. The basal skin layer harboured more UVA than UVB mutation "fingerprints". The vast majority of UVB mutations were in the outer layers of the skin.
The researchers led by Dr Gary Halliday wrote: "The importance of protecting the population not just from UVB but also from UVA irradiation has profound implications on public health worldwide."
They also said the widespread use of UVB-blocking sunscreens in Australia may have led to increased exposure to UVA. Dr Murphy said it was already known that UVA rays caused cancer but she said Australians had gone for mainly UVB sunscreen as they were cheaper.