Assessing the environmental impact due to photolytic degradation of ethane-bis(pentabromophenyl) in plastics

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Photolytic degradation of brominated flame retardants is one of the potential decomposition pathways in the environment, and for some flame retardants such as ethane-bis(pentabromophenyl) (EBP), also called decabromodiphenyl ethane, there are concerns that degradation products may be harmful. In this paper, we present photolytic studies of EBP in high-impact polystyrene (HIPS) and polypropylene impact copolymer (PP) using accelerated weatherometry. The half-life of photolytic debromination of EBP in HIPS was estimated to be more than 200 years, which can be contrasted with half-lives of minutes for photolysis conducted on dilute EBP solutions. Perhaps more importantly, there was no subsequent debromination to the octabrominated congeners or lower. No evidence of debromination was seen in PP, which confirms the importance of matrix effects. We also saw no evidence of accelerated resin photooxidation caused by EBP. These studies demonstrate that EBP is much more photolytically stable in resins than structurally-similar decabromodiphenyl ether, and a read-across comparison between the two flame retardant molecules for this degradation pathway is misleading.