Forever Chemicals Ride the Egg: How PFOS Passes From Quail Mothers to Chicks

Per- and polyfluoroalkyl substances, the famously indestructible class of chemicals known as PFAS, have long been detected in the blood and organs of wildlife across the globe. What has been far harder to pin down is exactly how these compounds move from an exposed mother bird into her developing chick. A new mini review published in the journal Ecotoxicology by researchers at Texas Tech University, Towson University, and AXIS Environmental Intelligence Group brings together years of controlled laboratory data on northern bobwhite quail to answer that question with unusual precision, and the results reveal a striking hierarchy of contamination that runs from the adult liver all the way to the hatchling brain.

The review, led by Kenneth N. Kikanme and senior author Todd A. Anderson, synthesizes tissue-residue data from a series of chronic toxicity studies in which northern bobwhite, a popular gamebird and a standard avian toxicology model, were exposed through drinking water to either perfluorooctane sulfonic acid (PFOS) alone or a binary mixture of PFOS and perfluorohexane sulfonic acid (PFHxS). The birds received an analytically verified dose of 20 nanograms per milliliter over 60 days, after which the researchers measured PFAS concentrations in adult liver and brain, whole eggs, the chorioallantoic membrane, and the liver and brain of 21-day-old hatchlings. In total, 263 samples were collected across the experimental groups, all analyzed with QuEChERS-based extraction, isotopically labeled surrogate standards, and liquid chromatography tandem mass spectrometry.

The clearest signal to emerge from the synthesis is that the liver is the dominant reservoir for PFAS in both adult and hatchling quail. Across all exposure groups, the tissue ranking followed a consistent pattern: adult liver accumulated the most, followed by adult brain, then the post-hatch chorioallantoic membrane, whole egg, hatchling liver, and finally hatchling brain. In males exposed only to PFOS, liver concentrations reached 565 nanograms per gram wet weight, while in the mixture exposure males carried 463 nanograms per gram in liver and females 325 nanograms per gram. The researchers attribute this hepatic dominance to the strong affinity of PFOS for liver-binding fatty acid proteins, which act as molecular docking stations for the long-chain sulfonic acids.

Sex emerged as a surprisingly important variable. Male quail accumulated significantly more PFOS in both liver and brain than females, and bioaccumulation factors calculated from measured water intake were consistently higher in males. Because females can shed a portion of their chemical burden into eggs, the researchers had expected them to show lower tissue concentrations, but the magnitude of the difference was notable. A liver bioaccumulation factor of exactly 1.0 in females under PFOS-only exposure suggests a state of equilibrium between intake and clearance, effectively making the female liver a bioindicator of exposure, whereas the male value of 2.6 indicates genuine net accumulation. The authors suggest that females may also drink more water during egg production, raising their actual daily intake and making the male-skewed pattern even more striking.

Perhaps the most novel contribution of the review concerns the chorioallantoic membrane, or CAM, the highly vascularized structure that forms during embryonic development and mediates gas exchange, nutrient transfer, and waste sequestration between the embryo and the egg. After hatching, remnants of the CAM typically remain attached to the shell, allowing researchers to sample it non-lethally. The data showed that PFOS concentrations in post-hatch CAMs, at 142 nanograms per gram wet weight under PFOS-only exposure, were actually slightly higher than in whole eggs, which averaged 92 nanograms per gram. Because the CAM receives a direct blood supply from the embryo, the authors argue it reflects the PFAS burden genuinely available to the developing chick, whereas whole-egg measurements capture only the total amount the mother deposited.

This finding challenges the conventional focus on yolk and albumen as the primary routes of maternal transfer. Previous work, including studies in mallards, cormorants, and chickens, has emphasized the association of PFOS with very low-density lipoproteins and yolk proteins as the main vehicle carrying the chemical into the egg. The quail data suggest that the CAM, with its dense network of proteinaceous binding sites such as integrins and histones and its continuous exposure to embryonic circulation, may act as an underappreciated reservoir. If confirmed across species, this would make the discarded eggshell membrane a cheap and non-lethal biomonitor for embryonic PFAS exposure in wild bird populations, a tool that could be deployed simply by collecting hatched shells from nests.

The mixture experiments added another layer of complexity. When PFHxS was present alongside PFOS, PFOS concentrations in whole eggs and post-hatch CAMs dropped significantly compared with PFOS-only exposure, falling to 50 and 93 nanograms per gram respectively. PFHxS itself accumulated at lower levels than PFOS in nearly every tissue, consistent with the shorter perfluorinated chain of PFHxS and its weaker hydrophobic interactions with tissue proteins. The researchers propose competitive binding as the likely mechanism: both compounds compete for the same high-affinity sites on albumin, liver fatty acid-binding proteins, and organic anion transporters, and the longer-chain PFOS generally wins, but the presence of PFHxS measurably reshapes how PFOS partitions across organs.

Maternal transfer was confirmed but diluted. Hatchling livers carried PFOS concentrations roughly 4.5 times lower than those of exposed adult females under PFOS-only exposure, and 7 and 14 times lower for PFOS and PFHxS respectively under the mixture. Hatchling brains showed similar dilution, with PFOS about 3.8 times lower than in adult female brains. Because hatchlings received no exposure after hatching, these residues represent the pure signature of in ovo transfer. Notably, PFHxS in hatchling liver was statistically far lower than PFOS, at just 9.5 nanograms per gram, underscoring how selectively the longer-chain compound is mobilized from maternal stores into eggs and embryonic tissues during the breeding cycle.

The brain findings carry their own ecological weight. Birds depend on brain regions such as the dorsal ventricular ridge, which lies outside the blood-brain barrier, for foraging and communication behaviors, making PFAS accumulation in neural tissue a potential route to neurobehavioral disruption. Earlier field studies in glaucous gulls and juvenile seabirds have documented PFOS in avian brain tissue, and the quail data now provide controlled-exposure confirmation that maternally transferred PFOS reaches the hatchling brain. The authors caution that their synthesis relies on relative distribution patterns rather than strict quantitative equivalence across matrices, since extraction protocols varied slightly between studies, but the consistency of the tissue hierarchy across independent trials lends confidence to the overall picture.

The broader implications extend well beyond one gamebird species. PFOS remains the dominant PFAS contaminant at firefighting-foam-affected sites, accounting for roughly 82 percent of targeted PFAS measurements in soils at U.S. Air Force installations, and European soils far from point sources still frequently exceed thresholds that threaten drinking water. As regulators push PFOS and PFHxS toward global elimination under the Stockholm Convention, understanding how residual body burdens translate into next-generation exposure becomes critical for ecological risk assessment. The Texas Tech team argues that risk models should incorporate sex-specific toxicokinetics, since males appear to bear a higher burden of organ-level accumulation, and that the chorioallantoic membrane deserves a formal place in avian monitoring programs. Future work, they note, should dissect the mechanistic drivers of PFAS competition at protein binding sites and further characterize the membrane’s biochemical capacity, steps that could transform a discarded eggshell into one of the most informative and least invasive windows into the invisible chemical inheritance passed from mother birds to their young.

Subject of Research: Bioaccumulation and maternal transfer of PFOS and PFHxS in northern bobwhite quail

Article Title: Bioaccumulation dynamics of perfluorooctane sulfonic acid (PFOS) and a binary mixture of PFOS and perfluorohexane sulfonic acid (PFHxS) in northern bobwhite (Colinus virginianus): a mini review

Article References: Kikanme, K. N., Karnjanapiboonwong, A., Dennis, N. M., Angappan, R., Isukuru, E. J., Salice, C. J., & Anderson, T. A. (2026). Bioaccumulation dynamics of perfluorooctane sulfonic acid (PFOS) and a binary mixture of PFOS and perfluorohexane sulfonic acid (PFHxS) in northern bobwhite (Colinus virginianus): a mini review. Ecotoxicology, 35(8), Article 176. https://doi.org/10.1007/s10646-026-03160-2

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03160-2

Keywords: PFAS, PFOS, PFHxS, bioaccumulation, maternal transfer, northern bobwhite, chorioallantoic membrane, ecotoxicology, avian toxicology, liver, brain, forever chemicals