It’s a simple, two-step formula that’s been engrained in our minds since we were kids: You go to the beach. You slap on sunscreen. Dealing with melanoma isn’t on anyone’s to-do list.
But when you coat your skin in lotion to avoid becoming a ball of fire, you might unknowingly be poisoning the ocean. According to a study published in the Environmental Science & Technology journal last month, the metallic components found in most sunscreens react to the sun’s rays and create hydrogen peroxide, a chemical compound that is poisonous to algae.
Researcher and co-author of the study David Sánchez-Quiles says it’s hard to predict when the hydrogen peroxide concentration will start to have a major impact on ocean ecosystems. But, he adds, scientists should start looking for solutions now.
“Now is the time to face the problem; it is not a good idea to look the other way,” he said in an email.
Sánchez-Quiles and fellow researcher Antonio Tovar-Sánchez, of the Department of Global Change Research at Spain’s Instituto Mediterráneo de Estudios Avanzados, tested the hydrogen peroxide concentration in the water at the Mediterranean getaway of Majorca Island’s Palmira Beach.
They found that titanium dioxide and zinc oxide nanoparticles, which are found in most sunscreens, react with ultraviolet light from the sun to form “significant amounts” of hydrogen peroxide—the same chemical used to lighten hair for dying. It’s toxic to phytoplankton, microscopic algae that’s a food source for a wide range of sea creatures, from shrimp to jellyfish to whales.
Hydrogen peroxide levels in Palmira’s waters spiked in the summer and were highest around noon every day. And summer, of course, is when thousands of tourists flock to the island on vacation; the researchers estimate that roughly four kilograms of titanium dioxide is released into the ocean via sunscreen every day.
Recognizing the problem is one thing, but solving it will likely be more of a challenge.
“Nowadays, the use of sunscreens has proven the most effective method to prevent a great number of skin diseases, so not using sunscreen is not a solution to the problem,” Sánchez-Quiles said. “I don’t know what the solution is, but scientific and cosmetic companies must work together to get a compromise between human and environmental health.”