PARENT SESSION

PM06 Emerging Pollutants
Exhibit Hall
8:00 AM - Monday

(PM043) Evidence of bioisomerization of - and -hexabromocyclododecane (HBCD) isomers in fish.

Law, K^{1, 2}, Halldorson, T¹, Danell, R¹, Palace, V^{1, 2}, Wautier, K¹, Evans, B¹, Whittle, M³, Alaee, M⁴, Marvin, C⁴, Tomy, G^{1, 2}, ¹ Department of Fisheries and Oceans, Winnipeg, Manitoba, Canada² University of Manitoba, Winnipeg, Manitoba, Canada³ Department of Fisheries and Oceans, Burlington, Ontario, Canada⁴ Environment Canada, Burlington, Ontario, Canada

ABSTRACT- The objective of this study was to follow up on an earlier hypothesis that isomers of HBCD may be biotransforming in fish. Our experimental approach was to expose rainbow trout (Oncorhynchus mykiss) to separate amounts of , , and -HBCD isomers through their diet. This was achieved by holding fish in four tanks and exposing them to spiked food for 56 days, followed by a 112 day depuration phase. Fish were sacrificed on days 0, 7, 14, and 56 of the uptake and days 7, 14, 56, and 112 of the depuration phase. HBCD levels in muscle tissue were analyzed by LC/MS/MS. Significant concentrations of the -isomer were detected in fish (after 56 days) exposed exclusively to the -isomer. The -isomer was also observed but at a much lower concentration than the -isomer. Likewise, fish exposed only to the -isomer showed the presence of both the - and -isomers; similar to the results of the -isomer treatment experiment, the -isomer was least-favoured. To our knowledge, this is the first report of bioisomerization of an halogenated organic pollutant in fish. Selective biotransformation of HBCD isomers will likely play a role in the isomer distribution in environmental samples. These results also help to explain differences in HBCD profiles in fish, compared to those in abiotic matrices.

Key words: Oncorhynchus mykiss, Hexabromocyclododecane, bioisomerization