Levels, isomeric patterns, and ten-year temporal trends of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexane (DBE-DBCH) in cetaceans from the South China Sea

Abstract

Due to the worldwide restriction on polybrominated diphenyl ethers (PBDEs), several brominated flame retardants (BFRs), such as 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), have been recommended as PBDE replacements used in polystyrene foam products. Information on the occurrence and fate of these emerging BFRs in the environment, especially TBECH, is quite limited. Little is known about levels of HBCD and TBECH in marine biota from China. The present study aims to investigate the stereoisomer-specific patterns and stereoselective behaviours of HBCD and TBECH in two species of marine mammals, finless porpoises (Neophocaena phocaenoides) and Indo-Pacific humpback dolphins (Sousa chinensis), from the Pearl River Estuary (PRE) of the South China Sea. Ten-year trends of the levels of these stereoisomers in these cetaceans were also monitored. HBCD and TBECH were determined in blubber samples of these species. By use of specific chiral columns, α-, β-, γ- and δ-TBECH enantiomers, as well as α-, β- and γ-HBCD enantiomers and two meso forms δ- and ε-HBCD, were successfully separated and quantified by GC-MS and UPLC-MS/MS, respectively. It was found that territorial waters in the PRE has been chronically contaminated by these PBDE replacements in cetaceans over the past ten years. Results also suggested that HBCD and TBECH have similar environmental fates, which warrants further investigation on their potential sources. The α-isomers of both HBCD and TBECH were predominant in the samples, and the significant difference in the enantiomeric patterns of these BFRs were observed in these two species. Further studies have to be carried out to verify the mechanisms.