LC–IMS–HRMS Detects Forever Chemicals in Elephant Seal Milk

PFAS, often called "forever chemicals," are known to be everywhere in the environment and to last a very long time. Still, scientists do not fully understand where they end up in nature or how people and animals are exposed to them in harmful ways, especially early in life.

The milk of marine mammals offers a rare look at both how much PFAS is in the environment and how these chemicals pass from one generation to the next. This is especially true for species whose mothers stop eating while nursing and live off their stored fat, which they break down quickly to make milk.

To learn more, researchers studied PFAS levels in northern elephant seals and how mothers pass the chemicals to their pups. Elephant seals make a good early-warning species because scientists already know a great deal about how they nurse and where they feed. That makes them useful for tracking how PFAS move through mother's milk and for measuring PFAS levels in the deep ocean, where the seals hunt. The team tested blood from 14 mother-pup pairs and milk from 9 mothers, using an advanced technique that combines liquid chromatography, ion mobility spectrometry, and high-resolution mass spectrometry (LC–IMS–HRMS) to detect a wide range of chemicals without having to know in advance what to look for. A paper based on their study was published in the journal Environment & Health.¹

Why Study PFAS in Marine Mammal Milk?

Testing mammal milk for PFAS is a powerful way to find out where these chemicals end up in the environment and how living things are exposed to them in ways that affect health. Milk can show scientists how long PFAS stick around and how they're passed down from one generation to the next. Studying the milk of ocean mammals can also reveal where these chemicals are found across the seas. That information is otherwise hard to get, because ocean water is always moving and marine ecosystems are complicated. Marine mammals are widely considered good early-warning signs for long-lasting pollutants, tracking them across both place and time. That's because they live a long time, sit near the top of the food chain, carry large fat stores where these fat-loving chemicals collect, and travel great distances to feed.^2-6

Northern elephant seals are widely seen as a good way to keep watch on the open ocean, because scientists know a great deal about their long journeys offshore and how they hunt for food in deep, open waters.^7-9

How Much PFAS Do Marine Mammal Pups Carry, and Where Does It Come From?

The researchers found 27 different PFAS, often called "forever chemicals," in the samples from mothers and pups of all ages. The levels in both the milk and the blood were higher than the amounts considered safe for people to be exposed to or to consume.1

In every mother-pup pair, the pup had more PFAS in its blood than its mother did. The highest levels showed up in pups that had just finished nursing, suggesting that these chemicals build up quickly early in life, or that they shift around in the body while the pups go without food after weaning.¹

The amount of PFAS in a mother's milk tracked closely with the levels in both her blood and her pup's blood, meaning each pair had its own distinct chemical fingerprint. A broader search for other possible PFAS showed that the types of chemicals varied depending on the sample and the family line. This fits with mothers and pups sharing the same feeding grounds and with mothers passing the chemicals to their young through their milk.¹

“These findings,” write the authors of the paper,¹ “indicate that neonatal marine mammals in extreme capital-breeding systems experience elevated PFAS body burdens during sensitive developmental windows.”

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References

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2. Bossart, G. D. Marine Mammals as Sentinel Species for Oceans and Human Health. Vet. Pathol2011, 48(3), 676-690. DOI: 10.1177/0300985810388525
3. Plön, S.; Andra, K.; Auditore, L. et al. Marine Mammals as Indicators of Anthropocene Ocean Health. Npj Biodiversity 2024, 3 (1), 24. DOI: 10.1038/s44185-024-00055-5
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7. Beltran, R. S.; Payne, A. R.; Kilpatrick, A. M. et al. Elephant Seals as Ecosystem Sentinels for the Northeast Pacific Ocean Twilight Zone. Science 2025, 387 (6735), 764-769. DOI: 10.1126/science.adp2244
8. Robinson, P. W.; Costa, D. P.; Crocker, D. E. et al. Foraging Behavior and Success of a Mesopelagic Predator in the Northeast Pacific Ocean: Insights from a Data-Rich Species, the Northern Elephant Seal. PLoS One 2012, 7 (5), e36728. DOI: 10.1371/journal.pone.0036728
9. Petersen, S. H.;Peterson, M. G.; Ackerman, J. T. et al. Foraging Behavior and Age Affect Maternal Transfer of Mercury to Northern Slephant Seal Pups. Sci. Rep. 2024, 14 (1), 4693.DOI: 10.1038/s41598-024-54527-6