First assessment of the ecotoxicological effects of the tire antioxidant 6PPD on early life stages of the popular sport fish species, the largemouth bass ( <i>Micropterus nigricans</i> )
Bibliographic record
Abstract
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is a widely used rubber antioxidant, entering aquatic ecosystems through roadway runoff of tire wear particles. A transformation product of 6PPD, 6PPD-quinone, has been detected in watersheds at concentrations acutely toxic to some salmonid fish species. We evaluated the toxicity of 6PPD to early-life stage largemouth bass (Micropterus nigricans) in a series of outdoor aquatic microcosm experiments. Wild-collected embryos were chronically exposed to 6PPD and its potential transformation products in natural lake water under ambient environmental conditions. In a preliminary 96-hr experiment, 6PPD was toxic to largemouth bass embryos with a 96-hr median lethal concentration of 42.8 µg/L. Interestingly, we found that exposure to 6PPD-quinone did not cause mortality in largemouth bass embryos beyond concentrations of maximum solubility in water. To further investigate the developmental toxicity of 6PPD, largemouth bass were exposed to 6PPD (modeled time-weighted average concentrations ranging from 0.1-3.7 µg/L) for 10 days, which spanned the embryonic to yolk-sac larval life stages. We observed a concentration-dependent increase in yolk sac area as well as the occurrence and severity of malformations in largemouth bass exposed to 6PPD. As the first toxicological assessment of 6PPD with largemouth bass, our findings provide an important first step in understanding how 6PPD affects the early development of this popular sport fish species under environmentally realistic conditions.
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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".