119 Contamination Status of Brominated Flame Retardants (BFRs) in Baikal Seals (Pusa sibirica) Tomohiko ISOBE 1 , Yoko OCHI 1 , Daisuke IMAEDA 1 , Hiroki SAKAI 1 , Shusaku HIRAKAWA 1 , Oyuna TSYDENOVA 1 , Masao AMANO 2 , Evgeny PETROV 3 , Valeriy BATOEV 4 , Hisato IWATA 1 , Shin TAKAHASHI 1 and Shinsuke TANABE 1 1 Center for Marine Environmental Studies (CMES), Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan 2 Faculty of Fisheries, Nagasaki University, Bunkyo-cho 1-14, Nagasaki 852-8521, Japan 3 The Eastern-Siberian Scientific and Production Fisheries Center, Russia 4 Baikal Institute of Nature Management, Russia (Received 28 January 2009; accepted 11 March 2009) Abstract—Brominated flame retardants (BFRs) including polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) were determined in Baikal seals (Pusa sibirica) collected from Lake Baikal to reveal their contamination status, accumulation features and temporal trends. Organohalogen compounds analyzed were detected in all the blubber samples of Baikal seals. DDTs were the most abundant contaminants followed by PCBs, CHLs, HCHs, PBDEs, HBCDs, and HCB. BFR levels found in Baikal seals were lower than those in other marine mammals from European or American coastal waters, implying that seals in this region were less exposed to BFRs. This suggests that there is no heavy industry producing or using BFRs in the watershed of Lake Baikal and the contamination might have resulted from long-range atmospheric transport. Concentrations of PBDEs and HBCDs in the blubber of Baikal seals collected in 2005 were significantly higher in males than in females. This gender dependent difference could be due to transfer of these contaminants from mother to pup during gestation and lactation. In addition, temporal trends of organohalogen contamination in Baikal seals were investigated using the blubber of male juvenile seals collected in 1992, 1995, 1998, and 2005. No obvious trend was observed for PBDEs, whereas HBCDs showed a significant increasing trend during this period, suggesting that contamination by these organohalogen compounds, particularly HBCDs, is ongoing. Keywords: Bikal seal, PBDEs, HBCDs INTRODUCTION Many incidents of mass mortalities of marine mammals have been observed worldwide since 1980’s. In Lake Baikal, a severe mass mortality of 8,000 Baikal seals (Pusa sibirica) was reported in 1987/88. Although morbillivirus infection Interdisciplinary Studies on Environmental Chemistry — Environmental Research in Asia, Eds., Y. Obayashi, T. Isobe, A. Subramanian, S. Suzuki and S. Tanabe, pp. 119–124. © by TERRAPUB, 2009.