The research, carried out at Missouri University of Science and Technology, looked into what happens to the compounds in sunscreen when they’re exposed to light. In particular, they found that zinc oxide — a staple ingredient in sunscreen — undergoes a chemical reaction when it’s illuminated by bright light that may release unstable molecules known as free radicals.
Those free radicals readily bond with other molecules, but in the process they can damage cells or the DNA contained within those cells, in turn increasing the risk of skin cancer. The tests, which were carried out in the lab using lung cells covered in zinc oxide solution, suggest that it is UV light which causes the reaction to take place most strongly. Which is, you know, precisely the kind you use sunscreen to protect yourself from.
The research, which is to be published in the Journal of Toxicology and Applied Pharmacology, suggests that the harmful effects of the free radicals increases the longer zinc oxide is exposed to sunlight. After three hours of UV exposure, half of the lung cells covered in zinc oxide solution died. After 12 hours, that increased to 90 per cent.
The big question here, of course, if whether people should be concerned. In truth, this is a small study, conducted using lung cells rather than skin cells. While there could well be plenty of truth in the notion that zinc oxide degrades in such a way that increases skin cancer risk, there’s not enough data here to decide if, on balance, sun screen causes more harm than good. In fact, Dr Yinfa Ma, one of the researchers, agrees:
“More extensive study is still needed. This is just the first step. I still would advise people to wear sunscreen; sunscreen is better than no protection at all.”
It will, however, be interesting to see how this strand of research pans out. If further studies — including clinical trials — confirm this effect to be real, the cosmetic industry will have to change the way it produces sunscreen, and quick. [PhysOrg]