Toxicity of aqueous and sediment-associated fluoride to freshwater organisms
Why this work is in the frame
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Bibliographic record
Abstract
Inorganic fluorides were declared toxic under the Canadian Environmental Protection Act in 1993 based on their potential to cause long-term harmful effects in aquatic and terrestrial ecosystems, but information on the toxicity of sediment-associated fluoride to freshwater benthic organisms was considered incomplete. The purpose of this study was to determine the toxicity of aqueous and sediment-associated fluoride to several species of freshwater organisms and to determine if toxic effects could be expected under environmentally realistic exposures. Toxicity of fluoride (as NaF) in short-term (48-96-h) lethality tests was greatest for the amphipod Hyalella azteca (median lethal concentration [LC50] = 14.6 mg F-/L), followed by the mayfly Hexagenia limbata (32.3), the midge Chironomus tentans (124.1), the fathead minnow Pimephales promelas (262.4), and the cladoceran Daphnia magna (282.8). Relative toxicity in long-term (10-28-d) growth and survival tests in spiked sediment was similar. Hyalella azteca was the most sensitive species for growth (25% inhibitory concentration [IC25] = 290.2 microg F-/g), followed by C. tentans (661.4), H. limbata (1,221.3), and P. promelas (>5,600); H. azteca was also the most sensitive species for survival (LC50 = 1,114.6 microg F-/g), followed by H. limbata (1,652.2) and P. promelas and C. tentans (>5,600 for both). Concentrations of fluoride measured in sediments near some industrial point sources exceed some of these toxicity thresholds. Fluoride is highly mobile in aquatic systems and could potentially reach toxic levels in the water column during dredging to remove fluoride-contaminated sediment.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.007 | 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 it