For years, scientists have warned that sunscreen is killing the world’s coral reefs.
Now, a new study confirms those concerns, revealing that the chemical oxybenzone, found in more than 3,500 sunscreen products worldwide, can be harmful in concentrations as small as 62 parts per trillion — the equivalent of a single drop of water in six-and-a-half Olympic-sized swimming pools.
Published Tuesday in the journal “Archives of Environmental Contamination and Toxicology,” the study measured concentrations of oxybenzone off the coast of Oahu and Maui, as well as the Virgin Islands.
“The use of oxybenzone-containing products needs to be seriously deliberated in islands and areas where coral reef conservation is a critical issue,” said study lead author Dr. Craig Downs, of the Haereticus Environmental Laboratory in Clifford, Virginia. “We have lost at least 80 percent of the coral reefs in the Caribbean. Oxybenzone can come from swimmers, recreational dive operations and resorts. Any effort to reduce oxybenzone pollution could mean a local coral reef survives a long, hot summer, or recovery for a degraded reef. Everyone wants to build coral nurseries for reef restoration, but this is an inconsequential effort if the factors that originally killed off the reef remain or intensify in the environment.”
Downs, a graduate of University of Hawaii at Manoa, said Wednesday morning that measurements taken back in 2011 found concentrations of the chemical in Hawaii waters of between 700 parts per trillion and as high as 19 or 20 parts per billion.
“What was kind of scary is that we saw these toxicological effects within two hours of being exposed,” he said.
Since the initial observations were recorded in 2011, Downs said he has returned to Hawaii to take further measurements each year, and “as of this year, the levels, at least in Maui, are sky high.”
Oxybenzone is especially toxic to juvenile corals, and can work in conjunction with other factors to increase coral mortality. For instance, he said, coral bleaching due to high sea surface temperatures typically occurs around 86 or 87 degrees Fahrenheit. But exposure to the sunscreen chemical can lower that to 78 or 79 degrees.
The chemical damages the DNA of corals, preventing them in some cases from reproducing, and also acts as an endocrine disruptor, causing juvenile coral to encase themselves within their own skeleton, ultimately leading to their death and preventing future generations of coral from repopulating the skeleton.
Spray-on sunscreens appear to be especially damaging, he said.
“Everybody is using these spray-on sunscreens where you only get a small fraction of it on you,” he said.
The rest blows away and lands on the sand, where it remains until high tide.
“We found that oxybenzone is at its highest concentration at high tide,” Downs said.
While the results of the study are sobering, University of Hawaii at Hilo Department of Marine Science Associate Professor Misaki Takabayashi said Wednesday that steps can be taken to prevent further damage to Hawaii’s coral reefs.
“There are several non-oxybenzone and paraben-free sunblocks on the market,” she said. “My worry is that the corals are already under siege by so many stressors, they need to be ‘babied’ as much as possible. If people wear rash-guards, wetsuits and hats as an alternative, that would help.”
Downs added that alternative sunscreens that don’t contain oxybenzone have some benefits that may make the switch easier for people looking to protect themselves from the harmful rays of the sun.
“Oxybenzone is one of the major ingredients (in sunscreen) and absorbs (ultraviolet) radiation. They’re called organics, and they are hydrocarbon-based. They absorb UV and dissipate it as heat. They make you feel hotter. There are alternatives like zinc oxide or titanium or clay-based sunscreens which are UV reflectors. They actually make you feel cooler,” he said.
Downs said he knows of several governments around the world exploring the possibility of banning the importation of oxybenzone-containing sunscreens, including two countries in the South Pacific.
“In Mexico, there are marine eco-reserves where oxybenzone sunscreens are banned,” he said. “The study is extremely strong evidence to have government agencies really talking seriously.”
Email Colin M. Stewart at cstewart@hawaiitribune-herald.com.