Comparison of Glycine and Simulated Mammalian Digestion for Estimating Bioaccessible Cu, Ni, Pb, and Zn in Soils Receiving Smelter Emissions
Bibliographic record
Abstract
MS1-02 Abstract: Risk assessment for contaminated sites frequently identifies ingestion of soil as the largest contributor to exposure of people, in particular children, in part because the default value for transfer of metals from ingested material to the bloodstream is 100%. Values less than this default can be used in a site-specific risk assessment; currently, the determination of an alternate value is achieved using in vivo studies, the cost of which are high. Alternates to in vivo studies are in vitro extractions, which purport to identify the amount of metal in the ingested material that is solubilized by gut passage and is thus available for intestinal transfer. These in vitro extractions are numerous, vary considerably in complexity, and are infrequently validated against in vivo studies of the same matrices. The objective of this work was to estimate the bioaccessible amounts of Cu, Ni, Pb, and Zn in 4 soils, 2 of which had elevated metals from smelter emissions and 2 of which were from similar sites but outside the footprint of smelter emissions. These metals were extracted from the soils either by the SBRC method (glycine at pH 2) or by simulated mammalian digestion (chyme), which included saliva, gastric, and intestinal phases. Total metals in these 4 soils were extracted by digestion with concentrated nitric acid as a comparison. Bioaccessible metals were considered to be that fraction of the total metal as determined by nitric acid digestion, which was solubilized by either the glycine or the simulated mammalian digestion. The amounts of these 4 metals that were solubilized by chyme were smaller than those resulting from nitric acid; the amounts of metals solubilized in chyme were very much smaller than the amounts solubilized by glycine. Part of this is likely due to the effect of pH: the final pH of the chyme (after the intestinal phase) is close to neutral, higher than the final pH of the glycine and nitric acid extractions. Efforts to simulate the selectivity of the intestinal barrier for the digested metals by intestinal epithelial (Caco-2) cells were not initially successful. The exposure of the cell monolayer to the chyme caused the layer to detach and the cells to lyse; efforts toward success with this system are continuing.
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How this classification was reachedexpand
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 | 0.002 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".