Accumulation and mother-to-calf transfer of anthropogenic and natural organohalogens in killer whales (Orcinus orca) stranded on the Pacific coast of Japan

Blubber samples were analyzed for anthropogenic and natural persistent organohalogens in nine killer whales (Orcinus orca) stranded on the northern coast of Japan in 2005. Anthropogenic organohalogens were dominated by DDTs (40–240 µg/g lipid weight (lw)), PCBs (19–68 µg/g lw), and chlordanes (trans-nonachlor, 15–80 µg/g lw). Polybrominated diphenyl ethers (PBDEs) were detected at a range of 0.22–0.64 µg/g lw (BDE-47, 42–74% of ΣPBDE). For natural organohalogens, mixed halogenated dimethylbipyrroles (Br4Cl2-DBP, 6.4–26 µg/g lw), heptachlorinated methylbipyrrole (Cl7-MBP, 0.5–1.9 µg/g lw), two methoxylated tetrabromodiphenyl ethers (6-MeO-BDE47, 0.11–0.58 µg/g lw; 2'-MeO-BDE68, 0.02–0.06 µg/g lw), and dimethoxylated tetrabromobiphenyl (2,2'-diMeO-BB80, 0.06–0.20 µg/g lw) were present. These concentrations in the blubber were higher in calves than in lactating females, indicating that large quantities of the persistent organohalogens transferred from the mother to the calf through lactation. The mother-to-calf transfer ratios of PCBs and PBDEs were significantly decreased with increasing number of halogen substituents, suggesting that higher halogenated congeners are less transferable.