Sunscreen Dangers

By Jan TenBruggencate

xWaters sampled off Po‘ipū Beach in 2016 showed levels of oxybenzone of 281-419 parts per trillion, above the 72 parts per trillion that is considered harmful to coral cells. Photo by Ruby Pap

The dangers of certain sunscreens to coral reefs are so serious that some Hawai‘i legislators are considering banning it.

Can it really be that bad? And if it were, wouldn’t reefs where nobody swims be far healthier than those frequented by oil-slathered masses?

As usual, this issue is complicated. Reefs have a lot of challenges in Hawai‘i, and sunscreen is just one of many.

One of the key studies on the subject was published last year in the Archives of Environmental Contamination and Toxicology. It found that if certain corals were exposed to the active ingredient in many sunscreens, oxybenzone, they could harm corals and cause coral bleaching.

Oxybenzone is the chemical in many sunscreens that shields your skin against ultraviolet radiation from the sun.

They found that if you expose coral cells to enough oxybenzone, it will kill them. At lower levels it will deform them, and also at low levels, it will cause reef corals to expel their food-giving algae. When the algae are gone, the corals go white, a process called bleaching. Eventually the coral polyps can starve and die.

The study found that there can be impacts on coral larvae and cells at oxybenzone concentrations in the higher ranges found on Hawai‘i beaches — notably heavily populated O‘ahu beaches.

Thus, the authors wrote, “Oxybenzone poses a hazard to coral reef conservation and threatens the resiliency of coral reefs to climate change.”

But there’s more to it than that. Coral reefs are being hit by all kinds of attacks, and coral reefs are bleaching in the Main Hawaiian Islands as well as in the Northwestern Hawaiian Islands, many of which are uninhabited and presumably sunscreen-free.

“Temperature anomalies, high irradiance, pollution, and bacterial diseases” as well as possibly sunscreen products, are among the culprits, said a 2008 paper in the journal Environmental Health Perspectives.

Hawai‘i is taking coral reef degradation seriously. Earlier this year, the state Department of Land and Natural Resources released its Coral Bleaching Recovery Plan. It focuses on a number of reef threats, primarily warming waters. It does not consider sunscreen issues.

Jan TenBruggencate

That doesn’t mean sunscreen is invisible to the state. The state Division of Aquatic Resources has issued a statement of concern that “Researchers have found oxybenzone concentrations in some Hawaiian waters at more than 30 times the level considered safe for corals.”

Rather than slathering on sunscreens with oxybenzone (read the label), the state recommends other alternatives to prevent sunburn: “water resistant sunscreens, which are more likely to stay on your skin, and sunscreens that use mineral filters, such as zinc oxide or titanium dioxide. Also, rash guards or wet suits will reduce the area of exposed skin, and thus the amount of sunscreen needed for protection.”

But if you care about reefs, limiting your participation in adding harsh chemicals to the surf is important. But you should also be paying attention to some of the more serious threats to reefs — including climate change, sedimentation from the land and overfishing.

• Jan TenBruggencate is a Kaua‘i based writer and communications consultant.