Metabolic transformation of environmentally-relevant brominated flame retardants in Fauna: A review

• Published in: Environment international 2022-03, Vol.161, p.107097-107097, Article 107097
• Main Authors: Smythe, Tristan A., Su, Guanyong, Bergman, Åke, Letcher, Robert J.
• Format: Article
• Language: English
• Subjects: Animals; Biotransformation; Brominated flame retardants; Chemistry; Coturnix; Emerging BFRs; Environmental Monitoring; Flame Retardants - analysis; Halogenated Diphenyl Ethers - analysis; Hydrocarbons, Brominated - analysis; Kemi; Metabolism; Non-human animals; Polybrominated diphenyl ethers; Zebrafish
• ISSN: 0160-4120; 1873-6750; 1873-6750
• DOI: 10.1016/j.envint.2022.107097

[Display omitted] •Fifty-one studies on E/BFR metabolism have been mostly on PBDE, HBCDD and TBBPA.•More E/BFR studies on metabolism shown in e.g. fish, birds, rodents and mammals.•The metabolism and toxicokinetics are critically understudied for 30 E/NBFRs.•Species-specific differences in metabolic capacity of BFRs exists across species.•In vitro metabolism studies often lack, e.g. active controls, ignore enzyme activity. Over the past few decades, production trends of the flame retardant (FR) industry, and specifically for brominated FRs (BFRs), is for the replacement of banned and regulated compounds with more highly brominated, higher molecular weight compounds including oligomeric and polymeric compounds. Chemical, biological, and environmental stability of BFRs has received some attention over the years but knowledge is currently lacking in the transformation potential and metabolism of replacement emerging or novel BFRs (E/NBFRs). For articles published since 2015, a systematic search strategy reviewed the existing literature on the direct (e.g., in vitro or in vivo) non-human BFR metabolism in fauna (animals). Of the 51 papers reviewed, and of the 75 known environmental BFRs, PBDEs were by far the most widely studied, followed by HBCDDs and TBBPA. Experimental protocols between studies showed large disparities in exposure or incubation times, age, sex, depuration periods, and of the absence of active controls used in in vitro experiments. Species selection emphasized non-standard test animals and/or field-collected animals making comparisons difficult. For in vitro studies, confounding variables were generally not taken into consideration (e.g., season and time of day of collection, pollution point-sources or human settlements). As of 2021 there remains essentially no information on the fate and metabolic pathways or kinetics for 30 of the 75 environmentally relevant E/BFRs. Regardless, there are clear species-specific and BFR-specific differences in metabolism and metabolite formation (e.g. BDE congeners and HBCDD isomers). Future in vitro and in vivo metabolism/biotransformation research on E/NBFRs is required to better understand their bioaccumulation and fate in exposed organisms. Also, studies should be conducted on well characterized lab (e.g., laboratory rodents, zebrafish) and commonly collected wildlife species used as captive models (crucian carp, Japanese quail, zebra finches and polar bears).