Suncream ingredient ‘could damage skin cells when exposed to UV rays’
PUBLISHED: 07:47 EST, 8 May 2012 | UPDATED: 09:10 EST, 8 May 2012
Holidaymakers are advised to slap on plenty of suncream to reduce their risk of skin cancer. But now scientists are saying an ingredient in some bottles could possible harm the skin.
Early research from Missouri University suggests that zinc oxide, when exposed to sunlight, undergoes a chemical reaction that may release unstable molecules known as free radicals.
Free radicals seek to bond with other molecules, but in the process, they can damage cells or the DNA contained within those cells.
The researchers suggest this in turn could potentially increase the risk of skin cancer.
Lead author Dr Yinfa Ma also found that the longer zinc oxide is exposed to sunlight, the greater the potential damage to human cells.
‘Zinc oxide may generate free radicals when exposed to UV (ultraviolet) sunlight, and those free radicals can kill cells,’ Ma said.
However, the authors cautioned people from drawing conclusions about the safety or dangers of sunscreen based on this preliminary research.
For instance Dr Ma said he needed to conduct further tests to see whether zinc oxide truly does generate free radicals as he suspects.
He advised people to continue to take usual precautions in the sun.
‘I still would advise people to wear sunscreen,’ he said.
‘Sunscreen is better than no protection at all.’
Dr Ma and his team studied how human lung cells immersed in a solution containing nano-particles of zinc oxide react when exposed to different types of light over numerous time frames.
Using a control group of cells that were not immersed in the zinc oxide solution, Ma compared the results of light exposure on the various groups of cells.
He found that zinc oxide-exposed cells deteriorated more rapidly than those not immersed in the chemical compound.
Even when exposed to visible light only, the lung cells suspended in zinc oxide deteriorated. But for cells exposed to ultraviolet rays, Ma found that “cell viability decreases dramatically.”
When exposed to ultraviolet long-wave light (ultraviolet A or UVA) for 3 hours, half of the lung cells in the zinc oxide solution died. After 12 hours, 90 percent of the cells in that solution died, Ma found.
Why does zinc oxide, an ingredient used in sunscreen to help block harmful UV rays, cause cells to deteriorate when exposed to sunlight?
According to Ma, when the zinc oxide nano-particles in the solution absorb the UV rays, the reaction releases electrons, which in turn may produce unstable free radical molecules in the zinc oxide solution. Those free radical molecules then bond with other molecules and act as parasites, damaging the other molecules in the process.
Ma is preparing to publish his latest research results in the journal Toxicology and Applied Pharmacology. A publication date has not been determined.
Ma’s research is still in it’s very early stages and far more investigation is needed.
For instance, Ma plans to conduct electron spin resonance tests to see whether zinc oxide truly does generate free radicals.
In addition, clinical trials will be needed before any conclusive evidence may be drawn from his studies.
Besides sunscreen, zinc oxide is used in many commercial products, including plastics, paints, ointments and sealants.
Dr Kat Arney, Cancer Research UK’s science information manager, said: ‘Because the full details of this study are not yet available we can tell little about the safety of zinc oxide from this piece of work.
‘But we do know that getting sunburnt increases the risk of skin cancer – a painful sunburn once every two years can triple the risk of malignant melanoma, the most dangerous form of skin cancer.
‘The best ways to enjoy the sun safely are to cover up with clothing, and spend time in the shade when the sun’s at its strongest – between 11 and 3. We also recommend using sunscreen with at least SPF15.’
For more information on sun safety visit www.sunsmart.org.uk