Dietary exposure of 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane to juvenile brown trout (Salmo trutta): bioaccumulation parameters and effects on circulating plasma sex hormones
Bibliographic record
Abstract
1,2-Dibromo-4-(1,2 dibromoethyl)cyclohexane or tetrabromoethylcyclohexane (TBECH) is an additive bromine based flame retardant used primarily in expandable polystyrene beads that are used mainly to produce thermal insulation for housing. Secondary uses include extrusion into polystyrene foam, adhesive in fabric and vinyl lamination, electrical cable coatings and construction materials. The technical formulation contains two diastereoisomers, α- and β-, which are present in equimolar amounts. Under elevated temperatures two other isomers, γ- and δ-, can be formed. The recent detection of TBECH in the environment and suggestions that all four isomers are androgenic prompted me to examine the bioaccumulation and biochemical effects of one of the isomers, β-, in a controlled laboratory environment. I purposely chose to examine this isomer as it has been detected in biota. Juvenile brown trout (Salmo trutta) were exposed to three different amounts of the β-isomer via their to three different amounts of the β-isomer via their food for 56 days (uptake phase). This was followed by a depuration phase in which all fish were exposed to unfortified food for 77 days. A fourth group of fish were exposed to unfortified food for the duration of the experiment. On days 0, 7, 14, 35, 49, 56, 63, 77, 91, 105, and 133 eight fish from each treatment group were sacrificed and liver, plasma, thyroid and gonad gland were collected and whole-fish (carcass minus tissues above) were collected. Residues of β-isomer were analyzed in the whole-fish and in liver extracts by gas chromatography mass spectrometry in the electron ionization while estradiol (E2), 11-ketotestosterone (11-KT) and testosterone (T) were extracted from plasma and analysed by liquid chromatography tandem mass spectrometry. The bioaccumulation of β-isomer was similar in fish from all treatment groups with steady-state occurring before the end of the uptake phase. Depuration of the β-isomer from fish obeyed first order kinetics and there were no statistically significant differences in the depuration half life (t1/2) among the treatment groups: 22.5 ± 10.4 (low), 13.5 ± 5.9 (med) and 13.8 ± 2.2 (high) days. Steady-state biomagnification factors were much smaller than 1 for fish in all treatment groups. I was unable to detect debrominated metabolites in liver or whole-fish extracts and I also found no evidence of isomerization of the β-isomer to other isoforms in vivo. While there were some differences in E2, T and 11-KT levels in plasma of fish from the treated groups relative to plasma in fish from the control group there were no clear, consistent, discerning trends.
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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".