Isomer-specific accumulation of perfluorooctane sulfonate in the liver of chicken embryos exposed in ovo to a technical mixture
Bibliographic record
Abstract
Prior to its recent phaseout, perfluorooctane sulfonate (PFOS) was produced by electrochemical fluorination processes, which yielded technical mixtures composed of linear isomer (∼65-79%) and several branched isomers (∼21-35%). Because PFOS can biomagnify in wildlife, birds that occupy higher trophic levels are at increased risk of exposure. We hypothesized that the pharmacokinetic properties of PFOS are isomer-specific in developing chicken (Gallus gallus domesticus) embryos exposed to technical grade PFOS (T-PFOS). In the present study, T-PFOS was composed of 62.7% linear isomer (L-PFOS), and 37.3% branched isomer, including six mono(trifluoromethyl)-branched isomers and four bis(trifluoromethyl)-branched isomers. Concentrations of 0.1, 5, or 100 µg/g of T-PFOS were injected into the air cell of chicken eggs prior to incubation. After pipping, compared with T-PFOS, the PFOS isomer profile in embryonic liver tissue for the 0.1 µg/g dose group showed 21% enrichment in the proportion of L-PFOS with a corresponding decrease in the proportion of branched isomers. Not all branched isomers were discriminated against at equal rates. The proportion of two mono(trifluoromethyl)-branched isomers and three bis(trifluoromethyl)-branched isomers decreased to a greater degree than other branched isomers. In contrast, the mono-branched isomer, P6MHpS, was overrepresented in the low-dose group. In the higher dose groups, L-PFOS was still enriched but only by approximately 10%, which indicated a dose-dependent change in isomer composition relative to T-PFOS. These results show that accumulation of PFOS in chicken embryo livers is dependent on the presence and position of branches on the alkyl backbone. This supports the hypothesis that the pharmacokinetics of PFOS are isomer-specific in biota, and may help explain why wildlife PFOS burdens are dominated by L-PFOS relative to T-PFOS mixtures.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".