These UV filters cause whitening and deformities in corals, threatening ecosystems that host a quarter of the world’s marine biodiversity. Emerging solutions exist, but regulation remains insufficient.
When Sunscreen Poisoned the Oceans
Between 6,000 and 14,000 tonnes of sunscreen flow into coral waters each year. This invisible tide directly threatens the survival of reefs, already weakened by warming seas. As the global market for these products is expected to reach $13.6 billion by 2028, scientists reveal the scale of a pollution that has long been overlooked.
“We have only scratched the surface of understanding how these chemicals can affect marine life,” warns Anneliese Hodge, a researcher at the Plymouth Marine Laboratory. This specialist analyzed more than 110 scientific publications for a study published in Marine Pollution Bulletin, which underscores the urgency of acting on this contamination.
Toxic Molecules at Infinitesimal Doses
About 25% of sunscreen applied to the skin ends up in the water during aquatic activities, according to a study published in Environmental Health Perspectives. That share could be underestimated, as laboratory experiments do not faithfully reproduce the friction generated by swimming.
Oxybenzone and octinoxate, two UV filters ubiquitous in the cosmetics industry, literally transform coral larvae into deformed, immobile organisms. These substances also trigger coral bleaching, the process by which corals expel the algae that provide them with food and color.
The toxicity of oxybenzone shows up at minute concentrations: 62 parts per billion are enough to damage corals, equivalent to a drop diluted in six Olympic-sized swimming pools. At Hanauma Bay, a popular diving site in Hawaii, the 2,600 daily visitors leave behind 187 kilograms of sunscreen residues in the ocean every day.
Innovations Struggle to Emerge
At the University of Derby in the United Kingdom, Professor Michael Sweet’s team has developed what they describe as “the world’s first coral-friendly sunscreen.” Their experiments yield encouraging results: some reef species exposed to their nutrient-enriched formula experienced 29% growth over sixteen weeks.
“We’re not just avoiding damage; we’re feeding the corals,” explains Professor Sweet to the BBC. This revolutionary approach relies on a rigorous accreditation system, with reef-protection factors (RPF) rated gold, silver, and bronze. These innovations, however, remain marginal in the face of the scale of the global market.
The mineral sunscreens based on zinc oxide and titanium dioxide offer a more eco-friendly alternative, provided you use non-nano particles. These formulations do not guarantee total safety, especially when they contain traces of heavy metals such as lead or mercury. To better understand the issues surrounding choosing a planet-friendly sunscreen, several criteria are to be considered.
Less Is More: Applying Less to Protect More
The most radical solution is to limit sunscreen use. Indeed, if you wear a UV-protective garment or a long-sleeve swim shirt, you essentially cover 50% of your body, which means you don’t need 50% sunscreen. This strategy should be accompanied by other simple steps: seek shade and avoid aerosol sprays that disperse chemicals, wait fifteen minutes before swimming to allow better skin adhesion, or choose non-nano zinc or titanium formulations.
These recommendations could dramatically reduce the daily pollution load flowing into the oceans. UV filters also reach aquatic environments through other pathways: post-beach showers, washing towels, or discharges of untreated wastewater.
A Fragmented Regulation
A few pioneering jurisdictions have taken restrictive steps. Hawaii has banned the sale of products containing oxybenzone and octinoxate since 2018, while Palau and the U.S. Virgin Islands have broadened this prohibition to other harmful substances. Key West, Florida has followed suit, but these moves remain fragmented on a global scale.
The problem lies in the absence of universal standards. The labels “reef-friendly” or “ocean-friendly” do not correspond to any harmonized legal definition. “People can write whatever they want on a bottle, with no validation, no testing, no standardization,” laments Michael Sweet.
Some independent labels try to fill this regulatory gap. The Protect Land + Sea certification, developed by the Haereticus Laboratory, guarantees the absence of problematic ingredients like oxybenzone, octinoxate, and parabens. This exclusion-based approach does not replace comprehensive ecotoxicological testing on formulations.
A Contamination Moving Up the Food Chain
The impact of sunscreen goes beyond corals. These “pseudo-persistent” pollutants accumulate in the tissues of fish and other marine organisms, raising questions about food safety. “We measured the level of oxybenzone in locally caught fish. It was terrifying,” testifies Craig Downs.
This contamination extends to farming practices, when treated wastewater from wastewater treatment plants is used for irrigation. UV filters reach crops before re-entering waterways via runoff, creating a particularly pernicious pollution cycle.
Conventional wastewater treatment technologies, including ozonation, prove inadequate at effectively removing these complex chemical compounds. “There are increasing quantities and varieties of sunscreens entering the environment, and contaminants show up in all possible combinations,” explains Professor Awadhesh Jha, of the University of Plymouth.
This silent crisis demands urgent mobilization from all stakeholders. Because while sunscreens pose a stress factor to reefs that is smaller than climate warming, they represent one of the few levers we can act on immediately. “Reefs are under assault from all sides,” laments Michael Sweet to the BBC. “Every small step we can take tips the balance a little higher and, hopefully, gives them a fighting chance.”
Further reading:
Coral: the tipping point for its survival has been reached.
