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.”
By: Paul Gillette
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