A new advance in the potential exposure to "old" and "new" halogenated flame retardants in the atmospheric environments and biota: From occurrence to transformation products and metabolites

The atmosphere occurrence of the most frequency used halogenated flame retardants (HFRs), including "old" chemicals such as polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A, hexabromocyclododecanes, and "new" chemicals such as decabromodiphenyl ethane, dechlorane plus, and short-chain chlorinated paraffins (SCCPs) were mainly reviewed. From data collected, these chemicals have reached all corners of the globe, and the atmospheric concentrations of HFRs were closely associated with production and usage of commercial products. The highest air concentrations of HFRs were measured at industrial and urban area with higher population density. The levels of "old" HFRs are decreasing or leveling off, while the "new" groups continue to grow. In addition, a large number of potential transformation products were also tentatively discovered and a few were structurally identified in both atmosphere and biota. Dehalogenation appears to be the most important atmospheric degradation processes. While, in animals and human body, the hydroxylated metabolites are of significant concern due to enhanced toxicological effects. However, due to limited availability of authentic standards, only a few compounds, such as hydroxylated PBDEs have been identified in the atmospheric environments and biota. Further studies are needed to elucidate possible transformation pathways and to enhance the monitoring of transformation products. [GRAPHICS] .