Plant accumulation and transformation of brominated and organophosphate flame retardants: A review

Plants can take up and transform brominated flame retardants (BFRs) and organophosphate flame retardants (OPFRs) from soil, water and the atmosphere, which is of considerable significance to the geochemical cycle of BFRs and OPFRs and their human exposure. However, the current understanding of the plant uptake, translocation, accumulation, and metabolism of BFRs and OPFRs in the environment remains very limited. In this review, recent studies on the accumulation and transformation of BFRs and OPFRs in plants are summarized, the main factors affecting plant accumulation from the aspects of root uptake, foliar uptake, and plant translocation are presented, and the metabolites and metabolic pathways of BFRs and OPFRs in plants are analyzed. It was found that BFRs and OPFRs can be taken up by plants through partitioning to root lipids, as well as through gaseous and particle-bound deposition to the leaves. Their microscopic distribution in roots and leaves is important for understanding their accumulation behaviors. BFRs and OPFRs can be translocated in the xylem and phloem, but the specific transport pathways and mechanisms need to be further studied. BFRs and OPFRs can undergo phase I and phase II metabolism in plants. The identification, quantification and environmental fate of their metabolites will affect the assessment of their ecological and human exposure risks. Based on the issues mentioned above, some key directions worth studying in the future are proposed.