Oregon State University scientists say that sunscreen that includes zinc oxide, a common ingredient, loses much of its effectiveness and becomes toxic after two hours of exposure to ultraviolet radiation. The research, published in the journal ‘Photochemical & Photobiological Sciences’, did a toxicity analysis involving zebrafish, which share a remarkable similarity to humans at the molecular, genetic and cellular levels. They found that zinc oxide degraded the organic mixture and caused a greater than 80% loss in organic filter protection against ultraviolet-A rays, which make up 95% of the UV radiation that reaches the earth. Also, the zinc-oxide-induced photodegradation products caused significant increases in defects to the fish model used to test toxicity. That suggests zinc oxide particles are leading to degradants whose introduction to aquatic ecosystems is environmentally hazardous.
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