Study finds "forever chemicals" in dolphin milk, raising early-life exposure concerns

Every time a dolphin nurses her calf, she may also be passing along industrial chemicals that persist for years in the body.

A new study has found that per- and polyfluoroalkyl substances (PFAS), often called “forever chemicals,” were present in dolphin milk across a 2-year nursing period. One compound, perfluorooctanesulfonic acid (PFOS), exceeded international safety benchmarks, adjusted for dolphins, by more than 25-fold.¹ The findings add to growing evidence that PFAS circulate through ecosystems, exposing animals at early life stages, and raise concerns about global environmental health.²

For the study, researchers analyzed archived milk samples from a single dolphin collected between 103 and 706 days into lactation. In total, they detected 30 PFAS compounds, 20 of which appeared continuously throughout the full nursing window, suggesting ongoing transfer from mother to calf throughout nursing.¹

PFOS levels exceed safety benchmarks

Among the compounds detected, PFOS drew the most concern. After adjusting human safety thresholds to account for differences in body size, researchers found levels in dolphin milk well above recommended intake levels.¹ PFOS concentrations declined slightly over time, which the authors suggest may reflect transfer to the calf through repeated feedings. The analysis also identified chemicals not typically captured in standard testing, including compounds that can break down into PFOS in the body, potentially adding to overall exposure.¹

Why dolphins matter

PFAS accumulate as they move up the food chain, leaving marine mammals like dolphins especially exposed. Their long nursing periods and high-fat milk make them a useful model for studying how contaminants move through marine ecosystems and reach developing animals.²

“Dolphins are a potential sentinel of global contamination; changes in their health can reveal broader environmental problems that may eventually affect other wildlife and humans,” Weihsueh Chiu, PhD, a professor in the Department of Veterinary Physiology and Pharmacology at Texas A&M University College of Veterinary Medicine and Biomedical Sciences and a coauthor on the study, said in a report by Texas A&M.² “Marine mammals can provide insight into how widespread these contaminants are in the environment.”

PFAS have been used since the late 1940s in products such as nonstick cookware, food packaging, and firefighting foams. The strength of their chemical bonds makes them useful but also difficult to break down. As a result, they persist in water, soil, wildlife, and people.³

They’ve been detected in a range of species, including penguins, seals, river otters, and bald eagles, as well as in remote regions far from known sources.³

What PFAS exposure does to animals

Research on PFAS in animals is still evolving, but a consistent picture has begun to emerge. Across species, exposure has been linked to effects on the liver, thyroid, immune system, and reproduction.³

Cats and dogs

In companion animals, some studies have found higher PFAS levels in cats with hyperthyroidism than in healthy controls, whereas dogs have shown measurable blood markers associated with exposure.³ These findings don’t establish cause and effect, but they raise questions about potential clinical relevance.

Livestock

Livestock studies point to similar patterns of exposure. PFOS has been detected across farm species, with animals picking up contaminants through water, feed, soil, and even packaging.³

In sheep fed contaminated forage, PFOS was excreted more quickly in milk than in urine. This pattern may have implications for nursing young.³

Rodents

Early-life exposure appears to be a particular concern. In rodent models, prenatal PFAS exposure has been associated with reduced survival, altered development, and hormonal disruption.³ Because these chemicals build up in the body over time, lactation can become a second pathway of exposure, transferring accumulated contaminants from mother to offspring.

Humans

In humans, studies indicate that breastfeeding can be a notable route of PFAS exposure for infants, which is why regulatory standards for drinking water are developed with the protection of breastfed babies kept in mind.²

“One of the concerns with PFAS exposure is immunotoxicity,” Chiu said.² “It can suppress the immune system.”

Looking beyond standard testing

The recent study also highlights the limits of conventional PFAS testing, which typically screens for a fixed list of known compounds.

By combining multiple analytical techniques, the researchers were able to detect a broader range of chemicals, including ones not routinely measured.¹ That approach may be especially useful when evaluating environmental contamination from complex or unknown sources.

A persistent problem—without borders

The dolphin samples analyzed in the study, collected in the early 1990s, show that PFAS exposure in marine mammals is not new and has likely been occurring for decades.¹

“This is a global contamination problem,” Chiu said.² “It doesn’t have borders.”

PFAS-related effects are often subtle—changes in immune function, reproduction, or other physiological processes rather than acute illness.³ But across populations, those small shifts can add up.

References

1. Joseph KM, Falls AT, Rehm SJ, et al. Maternal PFAS transfer through lactation: dolphin milk reveals routes of early-life exposure. Anal Bioanal Chem. Published online February 3, 2026. doi:10.1007/s00216-026-06342-3
2. Haines C. ‘Forever chemicals’ detected in dolphin milk, study by Texas A&M Superfund Center shows. Texas A&M University. April 14, 2026. Accessed April 17, 2026. https://vetmed.tamu.edu/news/press-releases/pfas-dolphin-milk-texas-am-study/
3. Peritore AF, Gugliandolo E, Cuzzocrea S, Crupi R, Britti D. Current review of increasing animal health threat of per- and polyfluoroalkyl substances (PFAS): harms, limitations, and alternatives to manage their toxicity. Int J Mol Sci. 2023;24(14):11707. doi:10.3390/ijms241411707