How to prevent sunscreen chemicals from hurting coral reefs
Most sunscreens protect swimmers from sunburn, but research cited in an Associated Press report says that some of the chemicals used to block ultraviolet light can end up harming coral reefs. The report describes how sunscreen can wash off during swimming and how UV-filter ingredients can also reach the ocean through wastewater, adding an extra stressor to reefs already hit by warming, pollution, overfishing and coastal development.
The Associated Press story says an Environmental Health Perspectives study estimates that about 25% of applied sunscreen washes off during recreational water activities. It adds that the runoff releases about 5,000 tons annually in reef areas and that many of those released chemicals are toxic to corals. The report also notes that some researchers argue the estimate may be low because the cited experiment did not recreate the friction caused by swimming, which could increase how much sunscreen rubs off.
Coral reefs, the report says, cover just 0.1% of Earth’s oceans but support about a quarter of all marine species. It frames sunscreen-related contamination as an additional threat that can affect coral at early life stages, including through damage to coral larvae and effects linked to bleaching and growth disruption. Scientists, as described by AP, say sunscreen chemistry is smaller than climate change as an overall stressor, but one that consumers can influence.
The Associated Press report says sunscreen pollution does not come only from people swimming. It says sunscreen chemicals can enter waterways when people shower after beach trips or wash towels, and it also points to urine as another route. The report adds that sewage is the largest source of sunscreen contamination in oceans because conventional wastewater treatment plants cannot effectively remove many UV filter compounds, based on studies cited by AP.
AP’s account highlights specific UV filters with stronger evidence of harm, focusing on oxybenzone and octinoxate. It says a 2016 study published in Archives of Environmental Contamination and Toxicology found that oxybenzone can transform coral larvae from healthy, mobile organisms into deformed and immobile ones. The report says the chemical causes corals to expel the algae that provide much of their food and color, describing this as a bleaching response, and it adds that bleached corals can become weaker, more vulnerable to disease, and more likely to starve or die if stressful conditions persist.
The report also says the 2016 study found oxybenzone can damage DNA and trigger premature skeleton formation that can encase entire larvae. It further states that oxybenzone can cause corals to bleach at lower temperatures, potentially worsening the impact of marine heat waves driven by climate change. The report says oxybenzone has shown toxicity at concentrations as low as 62 parts per trillion, and it describes a 2017 study at Hanauma Bay in Hawaii finding that nearly 2,600 daily visitors left about 412 pounds of sunscreen in the ocean each day.
The Associated Press story says researchers have growing concerns about other UV filters as well, including octocrylene, avobenzone and homosalate. It also notes that UV filter compounds have been detected in fish and other marine organisms, raising questions about seafood safety. Craig Downs, executive director of nonprofit Haereticus Environmental Laboratory, is quoted in the report saying, “We measured the level of oxybenzone in locally caught fish. It was scary,” and adding, “These chemicals move through the food chain, then we eat it.”
The report turns next to how consumers can reduce risk while still protecting themselves from sun. Experts quoted by AP say covering up with clothing, rash guards, hats and shade can reduce how much sunscreen is needed—for example, Downs is quoted saying a rash guard or long sleeve swim shirt covers about 50% of the body and therefore reduces the need for about half the sunscreen. When sunscreen is needed, the report says to look for products that use non-nano zinc oxide or titanium dioxide as active ingredients, while noting that research continues into how those minerals behave in marine environments.
AP says experts advise that zinc oxide and titanium dioxide should be in non-nano form because larger particles are less likely to be inhaled or absorbed by marine organisms. It adds that zinc oxide can contain trace heavy metal impurities such as lead, chromium and mercury, and that few products have undergone comprehensive ecotoxicity testing, according to Downs. The report also says some mineral sunscreen manufacturers include additional UV filters—such as butyloctyl salicylic acid and ethylhexyl methoxycrylene—to keep SPF levels from degrading, and that Downs has linked those additives to potential cancer risks and coral toxicity.
The Associated Press report also recommends avoiding aerosol sprays, which it says can disperse sunscreen into the air and surrounding environment. It further states that waiting at least 15 minutes after applying sunscreen before swimming may help the product adhere to skin rather than washing off immediately. It notes that while mineral sunscreens have a reputation for leaving a white cast, newer formulations may offer sheerer alternatives.
The report says some governments have moved to restrict specific ingredients. It notes that 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, and that Key West, Florida, has followed a similar measure. The report also says Palau and the U.S. Virgin Islands have gone further by restricting a broader list of chemicals linked to reef damage, while adding that labeling and marketplace regulation remain spotty beyond those bans.
It says labels such as “reef safe” or “reef friendly” have no universal definition or standard, and it quotes Michael Sweet, head of the Nature-based Solutions Research Centre and the Aquatic Research Facility at the University of Derby in England, saying: “People can just write whatever they want on a bottle, and there’s no validation, no testing, no standardization.” Sweet is also quoted saying in lab experiments some formulations “have decimated corals before my very eyes,” and he adds that looking at what goes into oceans daily raises questions about inputs coming from products used on land.
AP says independent certifications have emerged to help consumers, including Protect Land + Sea, a label created by Downs’ laboratory that verifies products are free of ingredients such as oxybenzone, octinoxate and parabens. The report says experts note that ingredient screening can help, but it is not the same as comprehensive ecological safety testing of an entire formula. Sweet is quoted concluding that reefs are “being hammered left, right and center,” and that “Every little bit we can do tips the balance a little bit further up and hopefully gives them that bit of a fighting chance.”