No matter how waterproof your sunscreen claims to be, some will end up washing off as you swim in the sea. As it dissolves, some of its ingredients are known to threaten ocean critters and marine life beneath the water’s surface. Now a new study, published in Environmental Science and Technology on Wednesday, adds another potential environmental risk.
According to the United States National Ocean Service, sunscreen chemicals are already linked to coral stress and death, hormonal changes in dolphins, altered reproductive patterns in fish, and even birth defects in mussels and sea urchins.
The new study, conducted by researchers from the University of Cantabria and the Institute of Marine Sciences of Andalusia, made more startling findings: Sunscreen releases significant amounts of metals and inorganic nutrients into coastal waters, at some times more quickly than others. UV light, they also found, can speed up or slow down this process.
“The model approach described is potentially useful for better understanding the risks associated with sunscreen released in the marine coastal ecosystem,” Araceli Rodríguez-Romero, Ph.D., the study’s lead author, tells Inverse.
Rodríguez-Romero and colleagues added a commercial, titanium-dioxide-containing sunscreen to samples of Mediterranean seawater and observed how droplets of the lotions released various metals and nutrients into the water. Some compounds entered the seawater more quickly after UV treatment, which was meant to simulate sun exposure.
Previous research already linked oxybenzone, a common sunscreen ingredient, to coral damage and harmful oceanic impacts, leading to efforts in Hawaii, Palau, and Key West to ban sales of oxybenzone completely. But the characteristics of other trace chemicals found in sunscreen have remained mysterious until this study.
Looking at the impact of these other chemicals, the researchers found that aluminum, silica, and phosphorus released the fastest from sunscreen under both light and dark conditions. They estimate that on a typical summer day at the beach, beachgoers could increase the concentration of aluminum in coastal waters by 4 percent and of titanium by almost 20 percent.
Other fluctuations were less stark, but the researchers say even small fluctuations of elements like phosphorus (which normally occurs at relatively low concentrations in the ocean) or lead (which is extremely toxic) could be harmful.
The effects of sunscreen runoff in marine ecosystems and on the personal health of swimmers and beachgoers aren’t clear. But we do know high heavy metal concentrations are dangerous in the human body. The health risks vary by specific compound and exposure, but they can include dysfunctions in the kidneys, joints, reproductive system, and cardiovascular system as well as acute and chronic damage to the central nervous system and peripheral nervous system, among others.
Environmentally, higher metal and inorganic nutrient levels in the seawater can cause dramatic changes. The increased levels released from sunscreen can lead to algae blooms, damage phytoplankton, and produce eutrophication, Rodríguez-Romero says. These environmental phenomena could impact tourism and recreation, which drive coastal economies around the world.
This study emerges as sunscreen is being debated like never before. In May, another study published in JAMA found that trace amounts of chemicals were absorbed in the bloodstream, leading to questions about the safety and environmental impacts of sunscreen use. The study triggered a flurry of conversation debating the risks and benefits of sunscreen.
Ultimately, most dermatologists, doctors, and researchers agree with the medical recommendations: Slathering sunscreen, along with other sun protective measures, are required for enjoying the sun safely and preventing skin cancer. The concerns raised in the research do not warrant throwing your sunscreen bottles away. The risks of skin cancer are known, devastating, and widespread, while the risks of chemical exposure are unknown. According to the CDC, everyone should still be applying sunscreen to protect against UV radiation.
Even Rodríguez-Romero doesn’t recommend stopping sunscreen use. “People need to protect themselves against the harmful effects of the sun,” she says. “Marine environmental scientists and cosmetic companies must work together in order to create a sunscreen safe for the marine environment and, of course, for human health.”
Studies detailing the environmental impact of sunscreen products on coastal ecosystems are considered a high priority. In the present study, we have determined the release rate of dissolved trace metals (Al, Cd, Cu, Co, Mn, Mo, Ni, Pb, and Ti) and inorganic nutrients (SiO2, P-PO4 3−, and N-NO3 −) from a commercial sunscreen in seawater, and the role of UV radiation in the mobilization of these compounds. Our results indicate that release rates are higher under UV light conditions for all compounds and trace metals except Pb. We have developed a kinetic model to establish the release pattern and the contribution to marine coastal waters of dissolved trace metals and inorganic nutrients from sunscreen products. We conservatively estimate that sunscreen from bathers is responsible for an increase of dissolved metals and nutrients ranging from 7.54 × 10−4 % for Ni up to 19.8% for Ti. Our results demonstrate that sunscreen products are a significant source of metals and inorganic nutrients to coastal waters. The normally low environmental concentrations of some elements (e.g., P) and the toxicity of others (e.g., Pb) could be having a serious adverse effect on marine ecology in the Mediterranean Sea. This risk must not be ignored.