PARENT SESSION
PS14 - Environmental Contaminants in Marine Mammals
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P140) Toxicokinetic behavior of polychlorinated dibenzo-p-dioxin, dibenzofuran and biphenyl congeners in Baikal seals.
Iwata, Hisato*,1, Watanabe, Mafumi1, Okajima, Yuka1, Tanabe, Shinsuke1, Amano, Masao2, Miyazaki, Nobuyuki2, 1 Center for Marine Environmental Studies, Ehime University, Japan2 Marine Research Center, Ocean Research Institute, The University of Tokyo, Japan
ABSTRACT- To assess the toxicokinetic behavior and potential toxicity of dioxins in Baikal seal (Phoca sibirica), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (PCBs) were analyzed in the liver and blubber. Congener-specific tissue distribution was clarified, and the potential effects of biological factors including sex and growth on the toxicokinetics were discussed. Among PCDDs/DFs, the 2,3,7,8-chlorine substituted congeners were only detected. The total 2,3,7,8-TCDD toxic equivalents (TEQs) of PCDDs/DFs and coplanar PCBs were found in the range of 210-920 pgTEQ /g fat wt (180-800 pgTEQ/g wet wt) in the blubber and 290-7800 pgTEQ/g fat wt (9.9-570 pgTEQ/wet wt) in the liver. Non-ortho chlorine substituted coplanar PCB126 was the most TEQ-contributed congener, accounting for 36-50 % of the total TEQs in the blubber and 50-80 % in the liver. The liver-blubber distribution ratios of the dioxin concentrations expressed on fat weight basis exhibited that the congeners with higher toxic equivalency factors (TEFs) tend to be more abundant in the liver. There was an age trend of hepatic dioxin accumulation, in which mature male consistently had higher dioxin concentrations than immature male, but the increasing rate was congener-specific, showing higher rates for penta- and hexa-CDDs than other congeners. Male-female differences in dioxin congener profiles in the livers from mature seals revealed that tetra-, penta- and hexa-CDDs and non-ortho coplanar PCB 77, 81 and 126 congeners in mothers are more preferentially transferred to their pups through lactation. These results indicate that toxicokinetic behavior of dioxin congeners in Baikal seals is governed by complex factors including lipophilicity, hepatic sequestration by CYP and rates of metabolism/excretion. The differences in toxicokinetic behavior between individual dioxin congeners suggest that the determination of tissue- and growth stage-specific TEFs is necessary for the accurate evaluation of dioxin toxicity.
Key words: Dioxins, Baikal seal, Toxicokinetic behavior, Toxic equivalency factor