A decades-long record from North Atlantic pilot whales shows a steep decline in older PFAS chemicals in the open ocean. The findings offer cautious good news for marine ecosystems but highlight growing concerns about newer, less understood PFAS.
For once in the story of “forever chemicals,” there is a bit of good news for the ocean.
A new Harvard study finds that North Atlantic pilot whales now carry about 60% lower concentrations of some of the most notorious PFAS chemicals than they did a decade ago, suggesting that global efforts to phase out these compounds are paying off even in remote marine ecosystems.
At the same time, the research raises an urgent new question: As industry shifts to newer PFAS, where are those replacement chemicals ending up?
PFAS, short for per- and polyfluoroalkyl substances, are a large family of human-made chemicals used since the mid-20th century to make products resistant to water, grease and stains. They are found in items such as nonstick cookware, water-repellent clothing, food packaging, furniture and cosmetics. Because they do not break down easily, PFAS accumulate in the environment and in living organisms, earning them the nickname “forever chemicals.”
Beginning in the early 2000s, some of the best-known and most heavily studied PFAS were phased out through a mix of voluntary industry changes and international regulations. The new study, published in the Proceedings of the National Academy of Sciences, shows that those actions have translated into real declines in contamination in the open ocean.
The research team set out to solve a growing problem in PFAS science.
Older, so-called legacy PFAS are relatively well understood and easier to detect. Newer generations of PFAS, developed to replace them, are far more numerous and often harder to measure.
“With legacy PFAS, we know a lot more about their environmental transport and impacts on organisms,” lead author Jennifer Sun, a recent doctoral graduate and current postdoctoral fellow, said in a news release. “But we have a lot less information about what is going on with many newer compounds that have been produced to replace the phased-out legacy PFAS.”
Instead of chasing individual chemicals one by one, the team used a different strategy. They measured “bulk organofluorine” in whale tissues — essentially capturing the fluorine atoms that are a hallmark of most PFAS compounds. That total organofluorine signal serves as a proxy for overall PFAS contamination, including newer types that are difficult to identify individually.
To apply this approach, the scientists turned to a unique long-term archive of tissue samples from North Atlantic pilot whales, maintained by collaborators in the Faroe Islands. These whales, which live in the subarctic North Atlantic, are apex predators. Because they sit at the top of the marine food web and can live for decades, they accumulate pollutants over time and act as sentinels of ocean contamination.
By analyzing samples collected between 1986 and 2023, the researchers could reconstruct how PFAS exposure in the open ocean has changed over nearly four decades.
They found that overall organofluorine levels in the whales were dominated by four legacy PFAS compounds. Concentrations of those chemicals rose and peaked in the mid-2010s, then dropped sharply. By 2023, levels of the legacy PFAS in whale tissues had fallen by more than 60 percent from their peak.
Sun noted that pattern shows that policy and industry decisions can make a tangible difference, even far from pollution sources.
“Production phase-outs, which were initially voluntary and later driven by regulation, have been quite effective at reducing concentrations of these chemicals in near-source communities as well as more remote ecosystems, which I think is very positive and important to emphasize,” she said.
The decline is especially striking because global production of newer PFAS is still increasing. If those replacement chemicals behaved like the older ones, scientists might expect to see total organofluorine in whales stay the same or even rise. Instead, the open-ocean signal is going down.
That mismatch suggests that many newer PFAS may not be accumulating in the subarctic open ocean in the same way legacy PFAS did — but it does not mean they are harmless.
The findings challenge a common assumption about where human-made chemicals ultimately end up, explained senior author Elsie Sunderland, the Fred Kavli Professor of Environmental Chemistry in the John A. Paulson School of Engineering and Applied Sciences.
“Generally, the ocean is thought to be the terminal sink for human pollution on land. But we are not seeing substantial accumulation of the newest PFAS in the open ocean. So, where are they?” she said in the news release.
One possibility is that newer PFAS are staying closer to where they are used and discharged, building up in rivers, lakes, groundwater or coastal zones. Another is that they behave differently in the environment, perhaps transforming into other compounds or binding to different materials. The study does not pinpoint the answer, but it makes clear that the story of PFAS contamination is shifting.
From a public health and policy perspective, the work delivers a mixed message: It shows that phasing out harmful chemicals can reduce contamination on a global scale, but it also underscores the risks of replacing them with poorly understood alternatives.
“While our results are good news for ocean contamination, it suggests newer PFAS may behave differently from the legacy ones. It underscores the need to place stronger regulations on ongoing PFAS production to mitigate future impacts,” Sunderland added.
The study relied on data and statistical analysis of archived tissues from pilot whales in the Faroe Islands, a rare long-term record that allowed the team to track trends over nearly 40 years. Because these whales integrate pollution from large areas of the North Atlantic, their tissues offer a window into how the broader subarctic marine environment is changing.
More broadly, the research highlights the value of looking at total organofluorine, rather than just a handful of known PFAS, to understand the full scope of contamination. That kind of bulk monitoring could help regulators and scientists keep pace with a fast-evolving chemical marketplace, where new PFAS variants are introduced faster than they can be individually tested.
For students, communities and policymakers concerned about PFAS, the message is both hopeful and cautionary. The steep decline in legacy PFAS in pilot whales shows that regulation and phaseouts can work, even for persistent chemicals that have spread around the globe. But the unknown fate of newer PFAS underscores the need for stronger oversight, better monitoring tools and a more precautionary approach to designing and approving replacement chemicals.
Source: Harvard John A. Paulson School of Engineering and Applied Sciences