Study suggests zinc oxide may be harmful

Rolla, Mo. - New research proposes that zinc oxide, a common ingredient in sunscreens, may not be as effective as previously thought and may actually cause damage to cells.

Cell toxicity studies done by researchers at Missouri University of Science and Technology suggest that zinc oxide, when exposed to sunlight, may release free radicals, potentially increasing the risk of skin cancer, Newswise reports. The studies noted greater potential cell damage was related to longer exposure of zinc oxide to sunlight.

According to the study, which is being prepared to be published in Toxicology and Applied Pharmacology, scientists immersed human lung cells in a solution containing very small amounts of zinc oxide and studied the reactions to different types of light exposure over varying amounts of time. The researchers found that zinc oxide-exposed cells deteriorated more rapidly than a control group, with a dramatic decrease in cell viability upon exposure to ultraviolet (UV) rays.

Exposure to three hours of UVA resulted in the death of half of the lung cells in the zinc oxide solution. After 12 hours, only about 10 percent of the cells were alive, Newswise reports.

According to the study authors, the zinc oxide absorbs UV rays, which may produce free radicals. These molecules proceed to bond with and damage other molecules. The study expands on earlier research published in the January 2009 edition of the Journal of Nanoparticle Research.

The authors noted that research on zinc oxide’s possible effects on other cells is still in the preliminary stages, and advised people not to draw conclusions about the safety or dangers of sunscreen based on this early research.

“More extensive study is still needed. This is just the first step,” said Yinfa Ma, Ph.D., a professor at Missouri S&T and one of the study’s lead authors. “I still would advise people to wear sunscreen. Sunscreen is better than no protection at all.”

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