October 6, 2011

expert reaction to new research into UVA and skin cancer, as published in Nature’s Journal of Investigative Dermatology

New research looked at the effect of UVA light and sunbeds on the risk of skin cancer.

Professor Michael Kimlin, Director, NHMRC Centre for Research Excellence in Sun and Health, said:

“This is a well-designed study from a respected team of established researchers. This is really quite exciting. What these researchers are saying is that we may have been looking at the wrong area (or wavelength) of light for years. People have been focusing attention at ultraviolet B (UVB) radiation as we know it contributes to sunburn, a known risk factor for the development of skin cancer.

“This research team is the first to compare the effects of a type of UVA radiation to equivalent doses of UVB radiation. We know that UVA causes premature ageing, but the link between UVA and skin cancer has been tenuous. What these researchers have found out is that UVA might actually contribute to skin cancer and that you don’t have to burn to be at risk (as UVA exposure rarely causes sunburn – it is UVB that causes sunburn).
The outcomes of this work for Australians is two-fold:

1) Solariums typically emit UVA radiation. This study is showing that UVA damages human skin and may contribute to skin cancer and this is something to be concerned about.

2) Environmental Exposure to UVA radiation. In my work, I investigate various sources of UVA exposure to the population. For example, window glass filters all of the incoming UVB radiation, however, they transmit almost 100% of UVA radiation. So, if you are driving in a car with the windows up, you may be indeed receiving UVA exposure and contributing to your risk of skin cancer.

“The highest levels of UVA radiation from the sun are in the early morning and late afternoon, which are the times that people typically spend outside in the heat of summer. From this research it appears that UVA is contributing to skin cancer, then we’re also at high risk at these times of the day and need to consider sun protection at these times.

“Taking onboard these findings, it is important to make skin protection an even greater priority by: covering up with clothing, avoiding the sun where possible, using shade, wearing sunglasses and a hat and using sunscreen as a backup.

“These findings reinforce the high risk of skin cancer in Australia, provide more evidence that we live in a dangerous environment and highlight the importance of our public health campaigns to prevent this highly damaging disease.”

Mr Gavin Greenoak, Managing and Scientific Director of the Australian Photobiology Testing Facility (APTF) affiliated with the University of Sydney, said:

“Sunburn (skin reddening/erythema) is the sign that generalised tissue damage has occurred (including DNA damage) and repair and recovery is underway. The “MED” (Minimal Erythema Dose) is the minimal dose necessary to produce a minimally perceptible reddening of the skin.

“UVA-I (340 – 400nm) causes much less sunburn than UVB (290 – 320nm). The contribution to a sunburn in natural sunlight contributed by UVA-I is approximately 4%.

“In this study the doses of UVA-I were increased until they produced sunburn and it is not surprising that at these high doses DNA lesions were observed. This may be especially relevant to sunbed exposure if similar sunburning doses of UVA-1 are used.

“Human skin is naturally adapted to the continuous sunlight spectrum which is not divided into UVB and UVA, and exposure to it is important for both health and well-being. Too much of it is the problem, and this is likely with all people in Australia who lack the constitutive pigment of the indigenous Aboriginal population.

“Action Spectra used in the study are very useful but characterise biological effects one wavelength at a time, which the skin never sees. We know that wavelength interactions are important, and that UVB and UVA act together in different ways depending on dose. A UVB dose on its own is more damaging to the skin than when UVA in the same proportionality of sunlight is added to it. But the sun does not do this, they are together and continuous, and the distinctions between wavebands are only useful conventions, when we remember that is all they are.

“The study does support a well-established understanding that sun protection modalities should protect from all UV wavelengths emitted by the sun. Ideally, all wavelengths should be protected from equally, so that the quantitative dose is reduced while not changing the proportionality of the sunlight spectrum. Clothing does this very well, and with methods in place and development, Broad Spectrum protection by sunscreens is rapidly becoming a prerequisite rather than an extra.”

Professor Mark Birch-Machin, Skin Scientist at Newcastle University, said:

“This is 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. This work also shows that although UVB causes more types of DNA damage than UVA for the same sun-burn dose (erythema), the effects of UVA go deeper into the skin – suggesting different modes of action.

“In 2006 there was an EU recommendation for UVA protection in suncream to be at least one third of the labelled SPF (the ‘factor’), and most products already conform to this. You can check yours by looking for ‘UVA’ in a circle on the bottle.

“But my advice remains the same: make sure you’re putting enough suncream on. Most people only apply a third to a half of the amount they need – make sure you’re not one of them, especially if we have another autumn heatwave.”

‘UVA1 Induces Cyclobutane Pyrimidine Dimers but Not 6-4 Photoproducts in Human Skin In Vivo’, Journal of Investigative Dermatology, Angela Tewari et al, 6 October 2011; doi:10.1038/jid.2011.283.