Reef-safe and Biodegradable Sunscreen: What You Should Know

diver in coral reefs
Some chemicals in sunscreen could be harmful to coral reefs.

 Westend61 / Getty Images

Biodegradable or reef-safe sunscreen refers to a specific sunblock formula that degrades naturally and doesn’t contain chemicals that could be harmful to the environment, specifically coral reefs. 

In one study, researchers found that just a small amount of sunscreen containing the ingredient oxybenzone could be enough to break down coral, causing it to lose its nutrients, bleach, and often die. Reef-safe or biodegradable sunscreens don’t contain these chemicals and are safer for the marine environment. 

While scientists disagree about the exact impact of chemical sunscreen on reefs, biodegradable and reef-safe sunscreen is popular among consumers who wish to reduce their overall impact on marine life.

How It Works

Sunscreens typically have chemical ingredients, physical ingredients, or a combination of both.

Chemical sunscreens work like a sponge, says the American Academy of Dermatology, absorbing the sun’s rays. They contain at least one of these active ingredients: oxybenzone, avobenzone, octisalate, octocrylene, homosalate, and octinoxate. In some studies, oxybenzone and octinoxate were found to harm coral reefs. Researchers are studying the impact of other chemicals.

By contrast, biodegradable (or reef-safe) sunscreen is a physical sunscreen. Physical sunscreens protect your skin by deflecting the sun’s rays. They contain the active ingredients zinc oxide and/or titanium dioxide, which are considered safer for marine life. Biodegradable sunscreens break down over time, and they don’t contain chemicals that are believed to be dangerous to coral reefs. 

What Does Reef-safe Mean?

The labels “reef-safe” and “biodegradable” sound like a simple way to classify products that won’t harm marine life. However, there’s no exact definition for the terms, and they aren't regulated by the government.

Without regulation, manufacturers aren’t required to do testing to show that the products don’t actually harm the marine environment, Craig A. Downs, Ph.D., executive director of the nonprofit Haereticus Environmental Laboratory, tells Consumer Reports.

Even if the products are safe during testing, high concentrations could pose a problem.

"Even if you have something relatively safe," says Downs, "having 5,000 people getting into the water at a single beach, the oils from most sunscreen products can induce toxicity."

Because researchers don't know for sure that any reef-safe sunscreen is completely harmless, it's important to read the label and examine the ingredients before you make a purchase.

What to Look For in Sunscreen

When shopping for sunscreen, there’s a lot of information on the label. The SPF (sun protection factor) measures how long the product will protect you from the sun’s rays. A sunscreen also may be labeled as water-resistant. If a sunscreen is labeled as “broad-spectrum” it means it protects against both UVA and UVB rays. Sunburn is mostly caused by UVB, while UVA can prematurely age your skin, causing wrinkles and age spots. The AAD suggests choosing a sunscreen that is water-resistant, offers broad-spectrum protection, and has an SPF of 30 or higher.

The National Park Service (NPS) points out that although no sunscreen has been proven to be completely reef-friendly, products with titanium oxide or zinc oxide — which are natural mineral ingredients — have not been found to harm corals. Child-safe sunscreens or those for sensitive skin also may have more gentle active ingredients, which can be safer for marine life. If a sunscreen contains oxybenzone or octinoxate, it is not considered reef-safe.

If you're choosing between spray and lotion sunscreen, you may want to avoid spray, some experts suggest. The Food and Drug Administration (FDA) is reviewing the safety of spray sunscreens. Due to the risks of inhalation, Consumer Reports recommends against using sprays on children and says to avoid them on your face. Because these chemicals can be sprayed into the environment, there may be a risk that they can reach the water even if you don't.

And one other guaranteed reef-friendly measure? Cover up with sun-protective clothing — hats and long-sleeve shirts — when you go out in the sun.

The Environmental Toll of Sunscreen

Up to 6,000 tons of sunscreen are estimated to wash up into coral reef areas each year, according to the NPS. The products are concentrated in popular tourist sites as the sunscreen washes off people and gloms onto the coral.

A 2016 study by a team of international scientists led by Downs found that oxybenzone not only kills coral, it also causes DNA damage in adult coral and coral larvae, making it difficult for them to develop properly. The findings were published in the journal Archives of Environmental Contamination and Toxicology.

“The use of oxybenzone-containing products needs to be seriously deliberated in islands and areas where coral reef conservation is a critical issue,” Downs said in a statement. “We have lost at least 80% of the coral reefs in the Caribbean. Any small effort to reduce oxybenzone pollution could mean that a coral reef survives a long, hot summer, or that a degraded area recovers.”

This study supported earlier research published in 2008 in Environmental Health Perspectives, which found that sunscreen ingredients such as oxybenzone have played a role in coral bleaching events in areas including the Atlantic, Pacific, and Indian oceans.

Because of this research, Hawaii was the first state to ban the sale of sunscreen containing the chemicals oxybenzone and octinoxate. Tourists will be able to buy other sunscreens elsewhere to use on the island. The law goes into effect on January 1, 2021. The city commission in Key West, Florida, voted in favor of a similar bill, which is waiting for the governor’s signature. If signed, it will also go into effect in January 2021.

Some researchers are still debating the impact of sunscreen on coral reefs.

“The major driver of bleaching and coral death around the world is rising ocean temperatures. We see coral bleaching happen thousands of miles from the nearest bottle of sunscreen," says Simon Donner, a climate scientist and professor in the department of geography and the Institute for the Oceans and Fisheries at the University of British Columbia.

"If a coral is exposed to a large concentration of benzophenone-3 (oxybenzone) it might bleach. However, unless you're in a very crowded and very small bay where people are constantly reapplying sunscreen, the concentration in the water won't be consistently high enough to bleach any corals,” he says.

Other researchers contend that the chemicals do add up and eventually cause harm, even in small concentrations. If your goal is to protect marine life and you have your pick of sunscreens, it's a safe bet to opt for a biodegradable sunscreen without potentially harmful ingredients.