Dietary and terrestrial exposure to methoxylated polybrominated diphenoxybenzene contaminants in Great Lakes herring gulls.

Methoxylated polybrominated diphenoxybenzenes (MeO-PB-DPBs) are little known contaminants except in North American Great Lakes herring gull tissues and egg samples. MeO-PB-DPBs in gulls originate not via aquatic bioaccumulation pathways but instead likely via transformation of the tetradecabromo-1,4-diphenoxybenzene (TDB-DPB) flame retardant (FR). TDB-DPB was formerly produced as SAYTEX-120 in North America and is still produced in Asia. This study investigates the terrestrial exposure pathway of MeO-PB-DPBs and other FRs in herring gulls. Gull regurgitant and faeces, soil, and earthworms were collected from Channel Shelter Island (Saginaw Bay, Lake Huron), and analyzed for 3 MeO-PB-DPBs, 25 polybrominated diphenyl ethers (PBDEs), and 22 non-PBDE halogenated FRs. MeO-PB-DPBs in soil varied from non-detect to 4 ng/g dw per pentabrominated congener to a remarkably high 53 ng/g dw for the hexabrominated congener and comparable to BDE-209 which accumulates to high levels in Great Lakes sediment. MeO-hexa- to penta-brominated-DPB congener ratios were much greater (> 10x vs. ∼ 2x) than in herring gull tissues or eggs, suggesting possible differences in bioavailability. PB-DPB congeners were detected for the first time in environmental soil samples and confirmed via standard addition of the 2,2',4,4″- and 2,2',2″,4-tetrabromodiphenoxybenzene standards. MeO-PB-DPBs were mostly absent from faeces and not detected in earthworm samples. Combined with the finding of detection in regurgitant samples, indicating dietary intake, this suggests that gull exposure is via terrestrial bioaccumulation of MeO-PB-DPBs.