Our doctors tell us to slather on sunscreen to prevent skin cancer – but what can we do if our sunblock of choice actually increases the risk of cancer? A team of researchers believes that zinc oxide, a common ingredient in sun care products, could react with sunlight and create a chemical reaction that releases free radicals – molecules that are often attributed to causing cancer. The study will be published soon in the journal .

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Dr. Yinfa Ma and Qingbo Yang at the Missouri University of Science and Technology conducted toxicology studies that suggest the longer that zinc oxide is exposed to sunlight, the greater the possible damage to human cells. Ma immersed human lung cells in a solution that contained nano-particles of zinc oxide and then exposed them to light. He discovered that the cells exposed to zinc oxide and then light deteriorated at a faster rate than those not submerged within the zinc oxide compound. He also found that all cells exposed to zinc oxide slowly broke down, but that when they were subjected to ultraviolet (UV) rays, the rate at which they died increased dramatically. Half of the cells exposed to zinc oxide and UV light died after three hours; 90 percent within 12 hours.

Ma believes that when zinc oxide particles absorb UV rays, the ensuing reaction releases electrons that in turn create the unstable cancer-causing free radicals. Those free radicals then bond with other molecules and behave like parasites that damage the other molecules. So should we ditch those tubes of sunscreen just in time for summer?

The research is still in the early stages, so Ma warns people about making any conclusions over whether sunscreen containing zinc oxide is safe or not. He acknowledges that additional research is needed, such as electron spin resonance testing to determine whether zinc oxide actually creates free radicals. What is Ma’s advice in the meantime? Continue to use use sunscreen and limit your exposure under the sun.

+ Missouri University of Science and Technology

Via Gizmodo, PHYSORG