The extent of trophic transfer of the three diastereoisomers of hexabromocyclododecane (HBCD) and seven brominated diphenyl ether (BDE) congeners was examined in components of an Arctic marine food web from eastern Canada. Alpha and gamma-HBCD diastereoisomers were detected in all species and total (sigma) HBCD concentrations ranged from 0.6 +/- 0.2 pg/g (geometric mean +/- 1 x standard error (SE), lipid weight (lw)) in arctic cod to 3.9 +/- 0.9 ng/g (lw) in narwhal. beta-HBCD was below method detection limits in all the samples. Mean sigmaBDE (sum of seven congeners) concentrations ranged from 0.4 +/- 0.2 ng/g (lw) in walrus to 73 +/- 10 ng/g (lw) in zooplankton. The relative trophic status of biota was determined by nitrogen stable isotopes (delta15N), and results indicated clear differences in HBCD isomer and BDE congener profiles with trophic level (TL). Trophic magnification was observed for the alpha-diastereoisomer and BDE-47 as concentrations increased with increasing TL in the food web, whereas there was trophic dilution of gamma-HBCD and BDE-209 through the food web. Only the (-)alpha-enantiomer showed a strong positive relationship between concentration and TL (p < 0.01) with a trophic magnification factor (TMF) value of 2.2. A small but significant increase in the enantiomeric fraction value of the alpha-enantiomers with TL was also observed (r2 = 0.22, p < 0.005), implying that there is an overall preferential enrichment of the (-)alpha-enantiomer relative to the (+)alpha-enantiomer likely due to the greater bioaccumulation potential of the (-)alpha-enantiomer and/or to the greater susceptibility of the (+)alpha-enantiomer to metabolism.

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed in the laboratory to an environmentally relevant dose of 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) via their diet for 49 days, followed by 154 days of untreated food to examine bioaccumulation parameters, potential biochemical effects, and metabolic products. There was a linear increase in the amount of BTBPE in fish during the uptake phase of the experiment, and an uptake rate constant of 0.0069 +/- 0.0012 (arithmetic mean +/- 1 x standard error) nmoles per day was calculated. The elimination of BTBPE from the fish obeyed first-order depuration kinetics (r2 = 0.6427, p < 0.001) with a calculated half-life of 54.1 +/- 8.5 days. The derived biomagnification factor of 2.3 +/- 0.9 suggests that this chemical has a high potential for biomagnification in aquatic food webs. Debrominated and hydroxylated metabolites were not detected in liver extracts and suggest that either biotransformation or storage of BTBPE-metabolites in the hepatic system of fish is minor or that our exposure time frame was too short. Similar concentrations of circulating thyroid hormones, liver deiodinase enzyme activity, and thyroid glandular histology suggest that BTBPE is not a potent thyroid axis disruptor.

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