A common sunscreen ingredient may be contributing to the deaths of coral reefs around the world, according to a new study.
Sunscreen that sloughs off beachgoers and swimmers or travels in wastewater from nearby sinks and showers is toxic to coral, and inhibits the growth of new coral that keeps reefs going, says a group of scientists from several institutions.
Global coral reef loss is happening all over the world. The study's lead researcher, Craig Downs, told CNBC that the Caribbean has lost 80 percent of its coral reefs in the last 50 years. The loss of the reefs threatens local ecosystems, but also fishing and tourism industries, which are crucial to the economies of islands and coastal regions.
Warming ocean temperatures, especially during El Niño, are often linked to the "bleaching" of coral reefs, a worsening global phenomenon where the living reefs go completely white and die. But Downs and his colleagues say chemicals in the water are playing a role, too.
"Climate change plays a big role, but it does not explain totally what is happening," Downs told CNBC. "It is our opinion that pollution plays a large role. The problem is that we lose a percentage of coral reefs every year, and very rarely do we see a recovery."
The researchers focused on oxybenzone, an ingredient that blocks UV rays and is in thousands of sunscreen and personal care products. It's also in body fragrances, hair styling products, lip balm, dish soap, bath oil, some types of makeup and insect repellent.
The team decided to study oxybenzone after doing underwater investigations in the Caribbean. While on the Caribbean island of St. John, they were tipped off to the idea of studying the impact of sunscreen pollution by a local resident.
"We were talking about it in town on St. John and a local guy overheard us and said, 'You have to go out at 4 or 5 p.m. and see the oil on top of the water.' And we did, we saw this oily sheen on the surface of the ocean by the beach," Downs said.
They harvested samples of coral planula — young, free-floating coral larvae — from the ocean and exposed them to the toxin.
They found oxybenzone is toxic to coral even at extremely low concentrations of 65 parts per trillion, roughly equal to the ratio of a single drop to 6.5 Olympic-size swimming pools, Downs said. The young coral were deformed and died off before being able to mature and replenish the reefs. They also found that it damages coral DNA, and may make coral more vulnerable to bleaching.
The researchers noted concentrations of oxybenzone several times above the threshold in several areas — the highest concentration was 1,400,000 parts per trillion in Trunk Bay, a popular area in the U.S. Virgin Islands National Park. Concentrations in Hawaii ranged from 800 parts per trillion to 19,000 parts per trillion.
Darrell Rigel, a dermatologist and clinical professor of dermatology at New York University, said that while he is not a coral biologist, he questions whether the results the team achieved in the experiment could be extrapolated into a natural environment, such as an actual coral reef.
"There need to be more studies in this area," Rigel said. "One in five Americans get skin cancers, and they are something we can prevent. We want to make sure we don't make a radical change in people's behavior based on one study."
Downs told CNBC that some companies have begun to eliminate oxybenzone in their formulations, opting instead for ingredients such as zinc oxide or titanium oxide.
The group published its results in the journal Archives of Environmental Contamination and Toxicology.
Downs is executive director of a nonprofit research institute called the Haereticus Environmental Laboratory, and was employed by the University of Hawaii when he did some of the research. Other scientists on the team came from U.S. National Aquarium and the National Oceanic and Atmospheric Administration, the University of Hawaii, University of Central Florida and two universities in Israel.