Microbial biotransformation of aqueous film-forming foam derived polyfluoroalkyl substances

• Published in: The Science of the total environment 2022-06, Vol.824, p.153711-153711, Article 153711
• Main Authors: Choi, Youn Jeong, Helbling, Damian E., Liu, Jinxia, Olivares, Christopher I., Higgins, Christopher P.
• Format: Article
• Language: English
• Subjects: Biotransformation; Degradation database; Environmental Monitoring; Fluorocarbons - analysis; Microbial degradation; Pathway; Polyfluorinated substance biotransformation; Water - analysis; Water Pollutants, Chemical - analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.153711

Per- and polyfluoroalkyl substances (PFASs) used in aqueous film-forming foam (AFFF) comprise some perfluoroalkyl substances but a larger variety of polyfluoroalkyl substances. Despite their abundance in AFFF, information is lacking on the potential transformation of these polyfluoroalkyl substances. Due to the biological and chemical stability of the repeating perfluoroalkyl -(CF2)n- moiety common to all known AFFF-derived PFASs, it is not immediately evident whether the microbial biotransformation mechanisms observed for other organic contaminants also govern the microbial biotransformation of polyfluoroalkyl substances. Herein, we aim to: 1) review the literature on the aerobic or anaerobic microbial biotransformation of AFFF-derived polyfluoroalkyl substances in environmental media; 2) compile and summarize proposed microbial biotransformation pathways for major classes of polyfluoroalkyl substances; 3) identify the dominant biotransformation intermediates and terminal biotransformation products; and 4) discuss these findings in the context of environmental monitoring and source allocation. This analysis revealed that much more is currently known about aerobic microbial biotransformation of polyfluoroalkyl substances, as compared to anaerobic biotransformation. Further, there are some similarities in microbial biotransformations of fluorotelomer and electrochemical fluorination-derived polyfluoroalkyl substances, but differences may be largely due to head group composition. Dealkylation, oxidation, and hydrolytic reactions appear to be particularly important for microbial biotransformation of AFFF-derived polyfluoroalkyl substances, and these biotransformations may lead to formation of some semi-stable intermediates. Finally, this review discusses key knowledge gaps and opportunities for further research. [Display omitted] •Microbial biotransformation of AFFF-derived PFASs was reviewed.•ECF-derived and fluorotelomer-derived PFASs share head-group transformation pathways.•Dealkylation at N- and S-head groups are dominant biotransformation mechanisms.•FASAs are semi-recalcitrant transformation products, and not all microcosm transformation products are found in the field.•Further research is needed for transformation mechanisms on secondary amide and sulfonamides adjacent to fluorinated tails.