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Lifeguards brandish their white-streaked noses like badges of honor, but the same sunscreen ingredient designed to protect us from skin cancer could in fact be leaving us more vulnerable than before, according to a new study from the Missouri University of Science and Technology. Cell-toxicity studies by Yinfa Ma, a professor of chemistry, and graduate student Qingbo Yang suggest that zinc oxide—or at least its nano-sized counterpart—undergoes a chemical reaction in the presence of sunlight. The result? Unstable molecules known as free radicals that can ravage other cells and any embedded genetic material within.

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Ma immersed human lung cells in a solution containing nanoparticles of zinc oxide, exposing them to different types of light over several time frames. After comparing the results with a control group, they discovered that zinc-oxide-exposed cells deteriorated more rapidly than those not immersed in the chemical compound. Cells suspended in zinc oxide deteriorated even when exposed to visible light only. For cells exposed to ultraviolet rays, however, Ma found that “cell viability decreases dramatically.”

Ma cautions that the research is still in its early stages and should not be used to draw conclusions about sunscreen safety.

As alarming as the findings may be, Ma cautions that the research is still in its early stages and should not be used to draw conclusions about the safety—or dangers—of sunscreen just yet. “More extensive study is still needed,” he adds. “This is just the first step.”

Further tests are needed to determine if zinc oxide—in nano form or otherwise—truly does generate free radicals, for instance. Plus, clinical trials are necessary before any conclusive declarations can be made. Ma’s advice to sunbathers in the meantime? Continue to slather on that sunscreen and limit your exposure to the sun.”I still would advise people to wear sunscreen,” he says. “Sunscreen is better than no protection at all.”

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+ Missouri University of Science and Technology

[Via ScienceDaily]