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

Tristan A Smythe; Guanyong Su; Åke Bergman; Robert J Letcher

doi:10.1016/j.envint.2022.107097

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

Environ Int. 2022 Mar:161:107097. doi: 10.1016/j.envint.2022.107097. Epub 2022 Feb 4.

Authors

Tristan A Smythe¹, Guanyong Su², Åke Bergman³, Robert J Letcher⁴

Affiliations

¹ Ecotoxicology and Wildlife Health Division, Wildlife and Landscape Directorate, Science and Technology Branch, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University, Ottawa, ON, Canada; Department of Chemistry, Carleton University, Ottawa, ON K1S 5B6, Canada. Electronic address: Tristan.Smythe@carleton.ca.
² School of Environmental Science and Engineering, Nanjing University of Science and Technology, Nanjing, China.
³ Department of Analytical Chemistry and Environmental Science, Stockholm University, SE-106 91 Stockholm, Sweden.
⁴ Ecotoxicology and Wildlife Health Division, Wildlife and Landscape Directorate, Science and Technology Branch, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University, Ottawa, ON, Canada; Department of Chemistry, Carleton University, Ottawa, ON K1S 5B6, Canada. Electronic address: robert.letcher@ec.gc.ca.

PMID: 35134713
DOI: 10.1016/j.envint.2022.107097

Abstract

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).

Keywords: Biotransformation; Brominated flame retardants; Emerging BFRs; Metabolism; Non-human animals; Polybrominated diphenyl ethers.

Publication types

Research Support, Non-U.S. Gov't
Review

MeSH terms

Animals
Coturnix
Environmental Monitoring
Flame Retardants* / analysis
Halogenated Diphenyl Ethers / analysis
Hydrocarbons, Brominated* / analysis
Zebrafish

Substances

Flame Retardants
Halogenated Diphenyl Ethers
Hydrocarbons, Brominated