News in Science

Study shines new light on damaging UV rays

Invisible danger New evidence suggests that the Sun's UV rays are even more damaging than once thought.

The Sun emits two kinds of UV rays that reach the Earth's surface: UVA and UVB. It has long been thought that these rays don't damage the deeper layers of the skin as much as they damage the top layers.

But new research from King's College London has found that while it's the case for UVB rays, it isn't for UVA.

The study, published in Journal of Investigative Dermatology, has found UVA rays are more carcinogenic than previously realised - a finding scientists say underscores how important it is to limit exposure to the Sun and to tanning studios.

"The damage seemed to increase as it went through the epidermis and we think that is due to a form of backscatter in other words, the damage goes through and is somehow reflected back," says Dr Antony Young, a professor of experimental photobiology at King's College.

That is significant because the deepest layer of the skin, the basal layer, is where cells divide.

"If they carry mutations that has possible consequence in terms of skin cancer. We must try to protect the basal layer," says Young.

Adding concern to this latest finding, is that UVA rays are more prevalent than UVB.

"In sunlight, UVB represents at most 5 or 6 per cent of the UV rays, so the vast majority is UVA," says Young.

He adds, the amount of UVA that reaches the ground isn't dependent on the height of the Sun.

"With UVA, there is much less variation with the height of the sun so the strength of UVA is reasonably constant throughout the day and doesn't change so much with season compared to UVB. So we are exposed to quite a lot of UVA."

Professor Mark Birch-Machin, a skin scientist at University of Newcastle, says it's "a sound piece of science from an excellent team of researchers".

"It confirms something we have known since 2004: that UVA is as much a bad boy of skin cancer as its cousin, UVB."

Lines of defence

Professor Michael Kimlin, the director for the Centre for Research Excellence in Sun and Health at the University of Queensland, says the study also highlights the dangers of sunbeds.

"Depending on which brand and style of solarium, it certainly does alter what type of UV is emitted," says Kimlin. "Typically it's UVA exposure and a little bit of UVB."

He says most sunscreens on Australian shelves are broad-spectrum, which protect against UVB and UVA rays.

"The Australian standard does acknowledge that UVA can be harmful and most of the sunscreens used in the market today are actually what they call broad-spectrum including UVB and UVA protection," he says.

"But I guess the message is that sunscreens shouldn't be the first line of defence."

"This study shows we do need to look at limiting our exposure and trying to stay out of the Sun where possible."