Novel Highly Brominated Methoxylated Contaminants: Exposure, Terrestrial Sources, Bioaccumulation, and Fate in a Great Lakes Avian Model Species
Bibliographic record
Abstract
Brominated flame retardants (BFRs) are a large class of highly persistent and bioaccumulative chemicals with the potential for adverse effects in wildlife exposed to them. This thesis investigated the distribution of polybrominated diphenyl ethers (PBDEs) and several non-PBDE halogenated FRs (HFRs) throughout maternal herring gull tissues (adipose, liver, muscle, red blood cells, plasma) and their eggs (yolk and albumen), and estimated the extent of their in ovo depuration. Methoxylated polybrominated diphenoxybenzenes (MeO-PB-DiPhOBzs) are a class of what are believed to be degradation byproducts recently discovered in herring gull egg homogenate samples collected as part of the annual Great Lakes Herring Gull Monitoring Program. MeO-PB-DiPhOBz tissue distributions and in ovo transfer rates were similarly determined and compared to PBDEs and non-PBDE HFRs. This thesis also conducted a systematic literature review on the metabolism of BFRs in wildlife species, with a focus on emerging and novel (E/N)BFRs. Deficiencies in in vitro assay quality control and assurance practices were highlighted, as well as a paucity in studies conducted on E/NBFRs with most focused on legacy BFRs (i.e., PBDEs and hexabromocyclododecanes). The unmethoxylated form of MeO-PB-DiPhOBzs are reported here for the first time in any environmental medium, present in soil collected from Channel Shelter Island (CSI), Lake Huron. MeO-PB-DiPhOBzs were also measured in the soil and herring gull regurgitant collected on CSI, suggesting that they are bioaccumulative contaminants to which the gulls are exposed, rather than metabolic products produced within them. Lastly, novel in silico methodologies were developed and evaluated to model the CYP-mediated biotransformation of MeO-PB-DiPhOBzs. Five distinct potential binding modes of the CYP3A4-MeO-PB-DiPhOBz complex were predicted, while CYP1A binding modes were limited likely due to their strong preference for coplanar ligands.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".