Tiny sunscreen particles may pose risk
Tiny particles of a substance commonly found in sunscreens could be toxic if swallowed, researchers say, though the amount ingested would have to be large and consumed on an ongoing basis.
Nanoparticles, or particles smaller than 100 nanometres, of zinc oxide, which is a common ingredient in sunscreens, can be harmful if ingested, according to scientists at the University of Utah.
They conducted lab tests in which colon cells were exposed to zinc nanoparticles, which are less than 1/50,000th the width of a human hair.
The researchers found that when the cells came in direct contact with the particles — the equivalent of eating two grams of sunscreen or about one-10th of an ounce — they died. And zinc nanoparticles were twice as toxic as the larger particles found in conventional zinc powder.
"Unintended exposure to nano-sized zinc oxide from children accidentally eating sunscreen products is a typical public concern, motivating the study of the effects of nanomaterials in the colon," the scientists said in a release.
Not major concern
However, Prof. Philip Moos with the Department of Pharmacology and Toxicology at the University of Utah, told CBC News that in the grand scheme of things, the consumption of zinc oxide is not a major concern.
"The general public is very unlikely to consume enough of it to be toxic. We think that zinc oxide would be unlikely to make it though the GI system because of stomach acid," he said, as it would be broken down in a person's body and excreted.
The researchers concede that the study did not address how passage through the digestive tract would affect the particles — they were studied in isolation — and that further research is needed.
Moos said that zinc oxide is safer than the organic particles in other sunscreens, contained in avobenzone or oxybenzone, as it is not absorbed through the skin. "I think they [zinc oxide sunscreens] are actually safer in the long run."
The study was published online in February in the American Chemical Society journal Chemical Research in Toxicology.