Estimating safe doses of perfluorooctane sulfonate (PFOS): an international collaboration
Bibliographic record
Abstract
Many government agencies and expert groups have estimated a safe dose (aka a "reference dose," [RfD]) for perfluorooctane sulfonate (PFOS). Notably, these agencies have derived safe doses that vary over at least 600-fold range. The range is larger still if one includes the U.S. Environmental Protection Agency (USEPA) current science-policy position under the Safe Drinking Water Act, which is that the only safe dose of PFOS is zero. This wide range in safe dose-estimates is surprising, since PFOS is a relatively well-studied, and ubiquitous, chemical. The Steering Committee of the Alliance for Risk Assessment (ARA) called for health-scientists interested in attempting to understand and, if possible, narrow this range of estimates. An advisory committee of eight scientists from four countries was selected from nominations received, and a subsequent invitation to scientists internationally led to the formation of three teams comprised of 24 scientists from nine countries. Each team independently reviewed toxicologic and epidemiologic data, and developed PFOS safe dose-estimates. All three teams concluded that currently available epidemiologic data could not form a reliable basis for PFOS safe dose-assessments. In contrast, results of bioassays of PFOS in laboratory monkeys and rats did provide usable bases from which serum-concentration-based "points of departure" were derived. After applying several, necessarily imprecise, uncertainty factors, the three groups derived PFOS safe dose-estimates that ranged, narrowly, from 20 to 100 nanograms (ng) of PFOS/kg body weight/day. In contrast, USEPA's current (United States Environmental Protection Agency (USEPA) (2024) Human health toxicity assessment for perfluorooctane sulfonic acid (PFOS) and Related Salts. EPA Document No. 815R24007.) estimate of the safe dose is 0.1 ng of PFOS/kg-day.
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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 | 0.128 | 0.039 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.007 | 0.006 |
| Science and technology studies | 0.003 | 0.003 |
| Scholarly communication | 0.009 | 0.008 |
| Open science | 0.003 | 0.009 |
| Research integrity | 0.004 | 0.007 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".