In the last few years, scientists have found evidence that a chemical in sunscreen can harm coral reefs. It is common to find “reef-safe” sunscreens in stores that are made without the coral-harming chemical, oxybenzone.

Despite governments banning sunscreens containing oxybenzone – which normally protects cells from harmful ultraviolet light – nobody actually knew the biology of how or why it was killing corals. Djordje Vuckovic and Bill Mitch are civil and environmental engineers who study chemical pollutants. They asked an obvious but important question: If nobody knows exactly why normal sunscreens are harming reefs, how could anyone know “reef-safe” sunscreens are actually safe for reefs?

Working with a team of biologists, they designed a clever experiment to understand how oxybenzone harms corals. Using sea anemones, acrylic UV sunglasses and a lot of chemical analysis, they found that a common cellular process actually converts oxybenzone into a sunlight-activated toxin that can kill corals and anemones.

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Daniel Merino

Assistant Science Editor & Co-Host of The Conversation Weekly Podcast

Many places have banned sunscreens with certain chemicals in an attempt to help protect coral reefs. Westend61 via Getty Images

Corals and sea anemones turn sunscreen into toxins – understanding how could help save coral reefs

Djordje Vuckovic, Stanford University; Bill Mitch, Stanford University

Researchers have long suspected that an ingredient in sunscreen called oxybenzone was harming corals, but no one knew how. A new study shows how corals turn oxybenzone into a sunlight-activated toxin.

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