Every time I go swimming, I end up with a little bit of sunscreen left behind.
Estimated 25% of sunscreen applied According to a study by Environmental Health Perspectives, about 5,000 tons are washed away during recreational water play and are released annually in coral reef areas alone. This is equivalent to the weight of about 1,000 elephants, and many of these chemicals are toxic to corals. Some researchers argue that this may be a low estimate; They noted that the experiment did not replicate the friction caused by swimming, which could cause more sunscreen to rub off.
Coral reefs support about a quarter of all marine species Even though only 0.1% of the Earth’s oceans are covered. Coral reefs, already under increasing pressure from rising ocean temperatures, pollution, overfishing and coastal development, face additional threats from sunscreen chemicals that can damage coral larvae, cause bleaching and inhibit growth. Scientists say it’s a smaller stressor than climate change, but one that consumers can actually deal with.
Pollution doesn’t just come from swimming. Sunscreen chemicals can enter waterways when you shower, wash towels, or urinate after a trip to the beach. Studies have shown that sewage is the largest source of sunscreen contamination in the ocean, as traditional treatment facilities cannot effectively remove many UV filter compounds. Chemicals flow from sewage plants into rivers and eventually into the ocean.
Approximately 25% of applied sunscreen washes away into the water, releasing thousands of tons of toxic chemicals into coral reef areas each year.
Certain chemicals have been documented to pose a risk to coral reefs
Sunscreens protect against sunburn and reduce the risk of skin cancer, but not all formulations have the same environmental footprint.
The strongest evidence of harm centers on two widely used chemical UV filters: oxybenzone and octinoxate. 2016 study published in Archives of Environmental Contamination and Toxicology Oxybenzone has been found to transform coral larvae from healthy, mobile creatures to deformed, immobile creatures. This chemical causes the algae that provide much of the coral’s food and color to be expelled, a stress response known as bleaching. Bleached corals become weaker and more susceptible to disease, and can starve or die if stressful conditions persist. Researchers also found that oxybenzone damages DNA and causes early skeletal formation that envelops the entire larva. In addition, coral bleaching can occur at low temperatures, potentially exacerbating the effects of ocean heatwaves caused by climate change.
Bleached coral is seen while scuba diving at Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico, Sunday, Sept. 17, 2023. (AP Photo/LM Otero, File)
Bleached coral is seen while scuba diving at Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico, Sunday, Sept. 17, 2023. (AP Photo/LM Otero, File)
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The chemical was found to be toxic at concentrations as low as 62 ppt, the equivalent of one drop from six Olympic-sized swimming pools. At Hawaii’s popular snorkeling spot, Hanauma Bay, nearly 2,600 visitors leave about 412 pounds of sunscreen in the ocean each day, according to a 2017 study by the nonprofit Haereticus Environmental Research Institute.
Scientists are also growing concerned about octocrylene, avobenzone, and homosalate.
These chemicals do not remain as they are. UV filters have been detected in fish and other marine life, raising questions about the safety of seafood.
“We measured oxybenzone levels in locally caught fish, and it was scary,” said Craig Downs, executive director of the nonprofit Haereticus Environmental Research Institute, which led the 2016 study. “These chemicals move through the food chain and we eat them.”
Even mineral sunscreens aren’t always safe.
A man applies sunscreen to a woman’s arm before a spring training baseball game between the San Diego Padres and Chicago White Sox in Phoenix on February 28, 2024. (AP Photo/Ashley Landis, File)
A man applies sunscreen to a woman’s arm before a spring training baseball game between the San Diego Padres and Chicago White Sox in Phoenix on February 28, 2024. (AP Photo/Ashley Landis, File)
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Zinc oxide and titanium dioxide are generally considered safer alternatives to chemical UV filters, but there are caveats. Experts say it should be in non-nano form, as its larger particle size makes it less likely to be inhaled or absorbed by marine life.
Zinc oxide can also contain traces of heavy metal impurities such as lead, chromium and mercury, Downs said, and few products have undergone comprehensive ecotoxicity testing.
AP Audio: Most sunscreens are harmful to corals. Here’s what you can do
AP correspondent Haya Panjwani reports that sunscreen can harm coral reefs.
Consumers should also pay attention to inert ingredients, as oils, fragrances, and other additives can have a negative impact on marine life.
Some mineral sunscreen manufacturers add UV filters such as butyloctylsalicylic acid or ethylhexylmethoxycrylene to prevent zinc oxide from lowering SPF levels, but Downs links this to potential cancer risks and coral toxicity.
The most effective step is to reduce sunscreen use
A resort employee folds up a beach umbrella, South Yarmouth, Massachusetts, Aug. 16, 2025 (AP Photo/David Goldman, File)
A resort employee folds up a beach umbrella, South Yarmouth, Massachusetts, Aug. 16, 2025 (AP Photo/David Goldman, File)
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Experts recommend covering your body with clothing, rash guards, hats, and sunshades.
“When you wear a rash guard or a long-sleeved swim shirt, you’re basically covering 50% of your body, which means you don’t need to wear 50% of your sunscreen,” says Downs. “From a conservation perspective, this is a huge win.”
If you need sunscreen, look for products that contain non-nano zinc oxide or titanium dioxide as active ingredients. Although research continues into how these minerals behave in the marine environment, many experts believe they are preferable to chemical UV filters.
Mineral sunscreens have a reputation for leaving a white cast, but newer formulations offer purer alternatives.
Experts also recommend avoiding aerosol sprays that can disperse sunscreen into the air and surrounding environment. Waiting at least 15 minutes after applying sunscreen before swimming allows it to adhere to your skin better than washing it off immediately.
Some places have banned harmful ingredients, but regulations still vary.
A man showers near the beach during a hot day in the suburb of Palaio Faliro, south of Athens, Greece, July 6, 2025. (AP Photo/Yorgos Karaharis, File)
A man showers near the beach during a hot day in the suburb of Palaio Faliro, south of Athens, Greece, July 6, 2025. (AP Photo/Yorgos Karaharis, File)
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In 2018, Hawaii became the first US state to ban the sale of sunscreens containing oxybenzone and octinoxate, citing harm to coral reefs. Key West, Florida, has taken similar measures. Palau and the U.S. Virgin Islands have gone further, restricting a broader list of chemicals linked to coral reef damage.
Apart from these prohibitions, the market remains largely unregulated. Labels such as “reef safe” and “reef friendly” do not have universal definitions or standards.
“People are free to write whatever they want on the bottle, there’s no validation, there’s no testing, there’s no standardization,” said Michael Sweet, director of the Nature-Based Solutions Research Center and Aquatic Research Facility at the University of Derby in the UK.
In lab experiments, he said, some formulations “destroyed corals right before my eyes.” “When you look at this, you wonder what’s being put into our oceans every day: shampoo, skin care, conditioners, shower gels. All of this ends up in our rivers and ultimately into the ocean.”
Several independent certifications have emerged to help consumers make informed decisions. As an example, protect land and seaa label created by Downs Research Institute to ensure the product is free of ingredients such as oxybenzone, octinoxate, and parabens. Experts note that while ingredient screening can be useful, it is not the same as comprehensive ecological safety testing of the entire formulation.
“Reefs are being pounded left, right and center,” Sweet said. “Everything we can do to tip the balance a little bit more and hopefully give them a little bit of a fighting chance.”
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Follow Annika Hammerschlag on Instagram: @ahammergram.
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