Scientists and policymakers are puzzling over how to get rid of a group of toxic chemicals found in streams and drinking water. One hope was that the persistent compounds, known as per- and polyfluoroalkyl substances (PFAS), would flow out to sea and stay put. But the ocean, it turns out, is spitting them back out: A new study finds sea spray from waves is tossing PFAS into the atmosphere.
“We typically think of the sea being the final resting place of PFAS,” says Martin Wolf, an atmospheric scientist at Yale University who was not involved with the work. “But this study is one of the first to definitively conclude that we can’t stop worrying about them once they’re in the sea.”
PFAS are found in everything from nonstick cookware to firefighting foam. They are valued for their resistance to water, heat, and oil. But the strong chemical bonds that make PFAS so useful also make them extremely hard to break down, earning them the moniker “forever chemicals.” Lab studies have shown PFAS can damage the livers and immune systems of animals, and lead to birth defects and death. In humans, they’ve been linked to cancer and lower birth weights.
Runoff from military bases, contaminated water released into streams and rivers by wastewater treatment plants and manufacturers, and factory emissions have spread PFAS to soil and drinking water around the globe. Now, scientists say they have identified another critical disseminator of the compounds: sea spray.
Researchers have known the mist created by breaking waves can transport pollutants from the ocean into the atmosphere, says Matthew Salter, a marine biogeochemist at Stockholm University. The white, foamy bubbles don’t just contain air—they also contain microscopic droplets of chemicals that float to the surface of the water. Using sea spray simulators, Salter and other researchers have shown in the lab that aerosol droplets can concentrate PFAS 62,000 times higher than their levels in seawater. But scientists had yet to see whether PFAS-laden sea spray aerosols from the ocean make their way into the atmosphere.
To do so, Salter and colleagues collected air samples every few days from 2018 to 2020 at two monitoring sites in Norway—one on a northern island, the other in a town near the southern coast. The researchers chose these sites because North Atlantic Ocean storms produce a lot of sea spray. Back in the lab, they analyzed the levels of PFAS and sodium ions, a key part of sea spray aerosol, in their samples.
The amount of PFAS in the samples was closely linked to sodium levels—a sign that they both got into the air via sea spray—the team reports this month in Environmental Science & Technology. The correlation was strongest at the more remote island site, which was closer to rough, frothy seas.
The findings, Salter says, provide “pretty convincing evidence” that sea spray aerosol brought some of the PFAS to their sample sites. He estimates that sea spray aerosol might be responsible for bringing 0.1% to 0.4% of all PFOS, a specific type of PFAS no longer used in most countries, back to land each year. “There’s a mechanism by which they can come back to haunt us.”
Still, people shouldn’t worry too much about breathing in the chemicals when they’re at the beach, Salter says. Scientists are more concerned about sea spray aerosols traveling long distances and bringing PFAS from the ocean hundreds of kilometers inland, where it could contaminate food and water.
The findings could also help explain how PFAS have ended up in glaciers, ice caps, and even caribou, says Hayley Hung, a chemical engineer at Environment and Climate Change Canada who was not involved with the work. “It’s superexciting, because in the last decade or so, there has been a lot of discussion about what is the actual mechanism for these PFAS to get into the atmosphere,” she says—and this study helps answer that question.