A Roadmap to the Structure-Related Metabolism Pathways of Per- and Polyfluoroalkyl Substances in the Early Life Stages of Zebrafish
By Jiajun Han, Wen Gu, Holly Barrett, Diwen Yang, Song Tang, Jianxian Sun, Jiabao Liu, Henry M Krause, Keith A Houck, and Hui Peng
Environ Health Perspect
July 27, 2021
DOI: 10.1289/EHP7169
Background
Thousands of per- and polyfluoroalkyl substances (PFAS) with diverse structures have been detected in the ambient environment. Apart from a few well-studied PFAS, the structure-related toxicokinetics of a broader set of PFAS remain unclear.
Objectives
To understand the toxicokinetics of PFAS, we attempted to characterize the metabolism pathways of 74 structurally diverse PFAS samples from the U.S. Environmental Protection Agency's PFAS screening library.
Methods
Using the early life stages of zebrafish () as a model, we determined the bioconcentration factors and phenotypic toxicities of 74 PFAS. Then, we applied high-resolution mass spectrometry-based nontargeted analysis to identify metabolites of PFAS in zebrafish larvae after 5 d of exposure by incorporating retention time and mass spectra. enzymatic activity experiments with human recombinant liver carboxylesterase (CES1) were employed to validate the structure-related hydrolysis of 11 selected PFAS.
Results
Our findings identified five structural categories of PFAS prone to metabolism. The metabolism pathways of PFAS were highly related to their structures as exemplified by fluorotelomer alcohols that the predominance of or taurine conjugation pathways were primarily determined by the number of hydrocarbons. Hydrolysis was identified as a major metabolism pathway for diverse PFAS, and perfluoroalkyl carboxamides showed the highest hydrolysis rates, followed by carboxyesters and sulfonamides. The hydrolysis of PFAS was verified with recombinant CES1, with strong substrate preferences toward perfluoroalkyl carboxamides.
Conclusions
We suggest that the roadmap of the structure-related metabolism pathways of PFAS established in this study would provide a starting point to inform the potential health risks of other PFAS. https://doi.org/10.1289/EHP7169.
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