Aquatic Toxicology 95 (2009) 144–151 Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Accumulation and disposition of hexabromocyclododecane (HBCD) in juvenile rainbow trout (Oncorhynchus mykiss) Marianne Haukås a,b,∗ , Espen Mariussen a,c , Anders Ruus d , Knut Erik Tollefsen d,e a Norwegian Institute for Air Research, P.O. Box 100, NO-2027 Kjeller, Norway b Department of Biology, University of Oslo, NO-0316 Oslo, Norway c Norwegian Defence Research Establishment, NO-2007 Kjeller, Norway d Norwegian Institute for Water Research, NO-0349 Oslo, Norway e University of Life Sciences, P.O. Box 5003, N-1432 Ås, Norway article info Article history: Received 16 June 2009 Received in revised form 27 August 2009 Accepted 31 August 2009 Keywords: Brominated flame retardants Hexabromocyclododecane Fish Dietary accumulation Disposition abstract The brominated flame retardant hexabromocyclododecane (HBCD) has been reported in environmental samples worldwide. The three diastereomers, -, - and -HBCD, behave differently in aquatic food webs; likely depending on different factors influencing assimilation efficiency and metabolism. In the present study, two oral exposure experiments with rainbow trout were performed to assess the role of selective uptake on diastereomer-specific accumulation and disposition of HBCD to liver, brain and muscle. In both experiments, juvenile rainbow trout (Oncorhynchus mykiss) were administrated a technical HBCD- mixture in commercial feed (10 mg kg -1 ), followed by up to 21 days of food deprivation. Already 6 h after exposure, the HBCD accumulation was significant, and the concentrations peaked 4–8 days after the exposure. The relative change in HBCD pattern during the accumulation process (0–8 days), suggested that there was a diastereomer-selective uptake of - and -HBCD in the rainbow trout. During the initial 48 h, considerable amounts of all three diastereomers were distributed to liver, brain and muscle. A 70% reduction in HBCD levels after 21 days, indicated elimination of HBCD from brain and liver, but no clear elimination from the muscle was observed. Differences in HBCD pattern between organs at the end of the experiment support a proposal of an organ-specific diastereomer accumulation. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Brominated flame retardants (BFRs) are man-made chemicals produced to reduce fire-related damage of industrial products such as insulation, textiles and electrical equipments. One of the BFRs with highest demand on the global market is hexabromo- cyclododecane (HBCD), which due to its stability, persistence and high production volume has been found in environmental samples worldwide. Aquatic organisms in urban areas have been reported to contain typically 10–1000 ng g -1 wet weight (ww) HBCD, with the highest concentrations found downstream of HBCD production sites (Allchin and Morris, 2003; Guerra et al., 2009; Haukås et al., in press; Janák et al., 2005; Sellstrøm et al., 1998). In biota from more remote areas including Arctic locations, the levels have been shown to be approximately one order of magnitude lower (Frederiksen et al., 2007; Gebbink et al., 2008; Muir et al., 2006; Verreault et al., 2007; Vorkamp et al., 2005). The discovery of HBCD in Arctic marine ecosystems provides compelling evidence of long-range transport ∗ Corresponding author at: Norwegian Institute for Air Research, P.O. Box 100, NO-2027 Kjeller, Norway. Tel.: +47 63 89 81 00; fax: +47 63 89 80 50. E-mail address: mha@nilu.no (M. Haukås). of this compound. Whether this transport is primarily atmospheric, oceanic or via other routes of dispersal, is not yet well established. The three HBCD diastereomers ,  and  behave differently in the environment, and it is well documented that there is a shift in relative diastereomer contribution with increasing trophic level in aquatic food webs (Covaci et al., 2006; Law et al., 2006a; Tomy et al., 2004a). In general, lower trophic level organisms contain mostly -HBCD, while apex predators have an -dominated diastereomer pattern. Intake via food is probably the main exposure pathway of HBCD in wild fish, although transport over gills or other membranes has been shown to contribute significantly (Veith et al., 1979; Zhang et al., 2008). Interestingly, European flounders exposed to spiked sed- iment have been shown to accumulate a proportionally higher level of -HBCD than those administered HBCD through diet (Kuiper et al., 2007). Elevated levels of the -diastereomer found in biota may, thus, be due to diastereomer-selective uptake, depending on the exposure pathway. However, it could also be a result of diastereomer-specific metabolization (Law et al., 2006b; Zegers et al., 2005). In fish and aquatic mammals, HBCD has been observed to accumulate in lipid rich organs such as liver, gonads and adipose tissue (Janák et al., 2005; Peck et al., 2008; Xian et al., 2008). All tissue samples, including muscle, were reported to have a predom- 0166-445X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2009.08.010