Origin of hydroxylated brominated diphenyl ethers: natural compounds or man-made flame retardants?
Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants. The structurally related hydroxylated PBDEs (OH-PBDEs) and methoxylated PBDEs (MeO-PBDEs) occur in precipitation, surface water, wildlife, and humans. The formation of OH-PBDEs in wildlife and humans is of considerable concern due to their greater toxicities relative to PBDEs and MeO-PBDEs. Research to date suggests that OH-PBDEs are formed by hydroxylation of PBDEs, and MeO-PBDEs are then formed by methylation of the OH-PBDEs. Here we show significant metabolic production of OH-PBDEs from MeO-PBDEs while hydroxylation of synthetic PBDEs to OH-PBDEs was negligible. Concentrations of PBDEs, OH-PBDEs, and MeO-PBDEs were analyzed in tuna, albatross, and polar bears collected from marine environments worldwide, and we found a closer relationship between OH-PBDEs and MeO-PBDEs than had been previously reported. Furthermore, for the first time the metabolic relationships between PBDEs, OH-PBDEs, and MeO-PBDEs were elucidated in vitro using rainbow trout, chicken, and rat microsomes. We propose the production of OH-PBDEs from naturally occurring MeO-PBDEs as a previously unidentified mechanism that could be an important contributor for the occurrence of OH-PBDEs found in wildlife from remote areas. Our results suggest that risk assessment paradigms for PBDEs and their metabolites need reevaluation and that human exposure to MeO-PBDEs that occur naturally in marine organisms should be considered.
Department of Biomedical Veterinary Sciences and Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada. yi.wan@usask.ca
Yi
Y
Wan
Steve
S
Wiseman
Hong
H
Chang
Xiaowei
X
Zhang
Paul D
PD
Jones
Markus
M
Hecker
Kurunthachalam
K
Kannan
Shinsuke
S
Tanabe
Jianying
J
Hu
Michael H W
MH
Lam
John P
JP
Giesy
D000818:Animals; D046091:Charadriiformes; D002645:Chickens; D004785:Environmental Pollutants / Q000737:chemistry*; D005411:Flame Retardants / Q000032:analysis*; D055768:Halogenated Diphenyl Ethers / Q000737:chemistry*; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism; D051381:Rats; D014413:Tuna; D001503:Ursidae
D004785:Environmental Pollutants; D005411:Flame Retardants; D055768:Halogenated Diphenyl Ethers