Sunscreen Pollution Threatens Coral Reefs, Adding to Environmental Pressures

Every time you go for a swim, some of your sunscreen gets left behind—and the environmental cost is higher than many realize.

An estimated 25% of applied sunscreen washes off during water activities, releasing approximately 5,000 tons annually in reef areas alone, according to research published in Environmental Health Perspectives. That’s equivalent to the weight of about 1,000 elephants. Some researchers believe this could be a conservative estimate, as studies don’t fully account for the friction caused by swimming, which might increase the amount that rubs off.

This chemical runoff poses a significant threat to coral reef ecosystems already struggling to survive. Despite covering just 0.1% of Earth’s oceans, coral reefs support roughly a quarter of all marine species. These vital underwater ecosystems face mounting pressure from warming waters, pollution, overfishing, and coastal development—with sunscreen chemicals now recognized as an additional stressor.

The pollution extends beyond swimming. Sunscreen chemicals enter waterways when people shower, wash beach towels, or even urinate after beach trips. Studies show that sewage treatment plants cannot effectively remove many UV filter compounds, making conventional wastewater facilities the largest source of sunscreen contamination in oceans.

Chemical Culprits Damaging Reefs

While sunscreen remains essential for preventing sunburn and reducing skin cancer risk, not all formulations carry the same environmental footprint.

The strongest evidence of harm centers on two widely used chemical UV filters: oxybenzone and octinoxate. A 2016 study published in Archives of Environmental Contamination and Toxicology found that oxybenzone transforms coral larvae from healthy, mobile organisms into deformed, immobile ones. The chemical causes corals to expel the symbiotic algae that provide much of their food and color—a stress response known as bleaching.

Bleached corals are significantly weakened, more vulnerable to disease, and can starve if stressful conditions persist. Researchers also discovered that oxybenzone damages coral DNA and triggers premature skeleton formation that can encase entire larvae. Perhaps most concerning, it can cause corals to bleach at lower temperatures, exacerbating the effects of marine heat waves driven by climate change.

What’s particularly alarming is how potent these chemicals are. Oxybenzone proves toxic to corals at concentrations as low as 62 parts per trillion—equivalent to a single drop in six Olympic-sized swimming pools. At Hanauma Bay, a popular Hawaii snorkeling destination, researchers from the Haereticus Environmental Laboratory found that nearly 2,600 daily visitors were depositing around 412 pounds of sunscreen into the ocean each day.

Scientists are increasingly concerned about other common sunscreen ingredients as well, including octocrylene, avobenzone, and homosalate.

“We measured the level of oxybenzone in locally caught fish. It was scary,” said Craig Downs, executive director of Haereticus Environmental Laboratory, who led the 2016 study. “These chemicals move through the food chain, then we eat it.”

Mineral Options Not Always a Perfect Solution

Zinc oxide and titanium dioxide are generally considered safer alternatives to chemical UV filters, but they come with important caveats. Experts recommend using products with non-nano mineral particles, as their larger size makes them less likely to be inhaled or absorbed by marine organisms.

However, zinc oxide products can contain trace heavy metal impurities such as lead, chromium, and mercury, according to Downs, and few formulations have undergone comprehensive ecotoxicity testing.

Consumers should also scrutinize inactive ingredients, since oils, fragrances, and other additives can harm marine life. Some mineral sunscreen manufacturers add UV filters such as butyloctyl salicylic acid and ethylhexyl methoxycrylene to prevent SPF degradation in zinc oxide—compounds Downs has linked to potential cancer risks and coral toxicity.

Reducing Impact Through Simple Changes

Experts unanimously recommend the most effective approach: reduce sunscreen use by covering up with clothing, rash guards, hats, and seeking shade.

“If you put on a rash guard or long sleeve swim shirt, you basically cover up 50% of your body, which means you don’t need 50% of the sunscreen,” Downs explained. “From a conservation perspective, that’s a massive win.”

When sunscreen is necessary, look for products with non-nano zinc oxide or titanium dioxide as active ingredients. While research continues into how these minerals behave in marine environments, many experts consider them preferable to chemical UV filters.

Though mineral sunscreens have historically had a reputation for leaving a white cast, newer formulations offer increasingly sheer alternatives. Experts also recommend avoiding aerosol sprays, which disperse sunscreen into the air and surrounding environment, and waiting at least 15 minutes after applying sunscreen before swimming to allow it to better adhere to skin.

Regulation Efforts Underway But Limited

In 2018, Hawaii became the first U.S. state to prohibit the sale of sunscreens containing oxybenzone and octinoxate, citing their harm to coral reefs. Key West, Florida, has implemented similar measures. The Pacific island nation of Palau and the U.S. Virgin Islands have enacted even broader restrictions, banning additional chemicals linked to reef damage.

Beyond these specific bans, the marketplace remains largely unregulated. Labels like “reef safe” or “reef friendly” have no universal definition or standard.

“People can just write whatever they want on a bottle, and there’s no validation, no testing, no standardization,” said Michael Sweet, head of the Nature-based Solutions Research Centre at the University of Derby in England.

In laboratory experiments, Sweet has observed alarming results. “Some formulations have decimated corals before my very eyes,” he noted. “When you see that, you wonder what’s being put into our oceans on a daily basis, from shampoos, skin care, conditioners and shower gels. All this stuff goes into our rivers and ultimately our oceans.”

Some independent certifications have emerged to help consumers make informed choices. One example is Protect Land + Sea, a label created by Downs’ laboratory that verifies products are free of ingredients such as oxybenzone, octinoxate, and parabens.

“Reefs are being hammered left, right and center,” Sweet said. “Every little bit we can do tips the balance a little bit further up and hopefully gives them that bit of a fighting chance.”