Dietary biotransformation and bioaccumulation of cyclic siloxanes in rainbow trout (Oncorhynchus mykiss).
Bibliographic record
Abstract
Cyclic volatile methyl siloxanes (cVMS) are commonly used down-the-drain manufactured substances that were assessed for their bioaccumulation (B) potential in Canada and the European Union, which resulted in different regulations. Discrepancies between regulations resulted in part from the unique intrinsic characteristics of cVMS, their log KOW values, which suggests that cVMS partition out of water and into lipids. Modeled simulations and laboratory-based bioconcentration (BCF) values exceed CEPA 1999 B criteria, while field-based analysis of biomagnification factors (BMFs) can produce values that are below CEPA 1999’s B threshold (BCF and/or BMF < 5000) and resulted in biodilution. The current research addressed discrepancies between B values by exploring in vivo dietary somatic biotransformation rate constants (kBM) of two cVMS, octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5), in rainbow trout (Oncorhynchus mykiss). The kBMs were derived using a co-exposure of non-metabolized reference chemicals. Plotting the concentration of fish at time (CF) shows significant but slow somatic depuration rate constants (kBT, d-1) for D4 and D5 (0.045 ± 0.018 (SE); 0.042 ± 0.008 (SE)) and kBM (d-1) (0.039 ± 0.019 (SE); 0.037 ± 0.009 (SE)). The CF also produced significant, but relatively slow dietary uptake absorption efficiencies (ED) for D4 and D5 (0.322 ± 0.034 (SE); 0.079 ± 0.008 (SE)). CF was entered into an Absorption, Distribution, Metabolism, and Excretion Fish Bioaccumulation Calculator (ADME-B) to predict the biotransformation rate constant in the gut (kGM,d-1), resulting in relatively fast rate constants of 1.26 ± 0.61 (SE) and 6.46 ± 1.12 (SE) d-1 for D4 and D5. Results indicate that the exposure route effects the proportional contribution of somatic (φBM) and gut (φGM) biotransformation rate constants on the depuration of D4 and D5. For instance, dietary uptake results in high φGMs for D4 and D5 (61.34 and 93.02%). Furthermore, the ADME-B calculator indicates that D4 and D5 BCF values are below B criteria (2864.6 ± 1112.1 (SE); 2289.6 532.5 (SE)). Results are consistent with measured environmental concentrations that show biodilution.
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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 | 0.000 | 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) | 0.000 | 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".