A Comparative Biodegradation Study to Assess the Ultimate Fate of Novel Highly Functionalized Hydrofluoroether Alcohols in Wastewater Treatment Plant Microcosms and Surface Waters.

Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals present in a wide range of commercial and consumer products due to their water-repellency, nonstick, or surfactant properties, resulting from their chemical and thermal stability. This stability, however, often leads to persistence in the environment when they are inevitability released. We utilized microbial microcosms from wastewater treatment plant (WWTP) sludge to determine how employing different functional groups such as heteroatom linkages, varying chain lengths, and hydrofluoroethers (HFEs) will impact the ultimate fate of these novel PFAS structures. A suite of five novel fluorosurfactant building blocks (F7 C3 OCHFCF2 SCH2 CH2 OH (FESOH), F3 COCHFCF2 SCH2 CH2 OH (MeFESOH), F7 C3 OCHFCF2 OCH2 CH2 OH (ProFdiEOH), F7 C3 OCHFCF2 CH2 OH (ProFEOH), and F3 COCHFCF2 OCH2 CH2 OH (MeFdiEOH)) and their select transformation products, were incubated in WWTP aerobic microcosms to determine structure-activity relationships. The HFE alcohol congeners with a thioether (FESOH and MeFESOH) were observed to transform faster than the ether congeners, while also producing second-generation HFE acid products (F7 C3 OCHFC(O)OH (2H-3:2 polyfluoroalkyl ether carboxylic acid [PFECA]) and F3 COCHFC(O)OH (2H-1:2 PFECA). Subsequent biodegradation experiments with 2H-1:2 PFESA and 2H-1:2 PFECA displayed no further transformation over 74 days. Surface water Photofate experiments compared 2H-1:2 PFECA, and 2H-1:2 polyfluorinated ether sulfonate (PFESA) with their fully fluorinated ether acid counterparts, and demonstrated the potential for both HFE acid species to completely mineralize over extended periods of time, a fate that highlights the value of studying novel PFAS functionalization. Environ Toxicol Chem 2024;00:1-9. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Avoiding Regrettable Replacements: Can the Introduction of Novel Functional Groups Move PFAS from Recalcitrant to Reactive?

Per- and polyfluoroalkyl substances (PFASs) are present in a range of commercial and consumer products. These chemicals are often high-performance surfactants or nonstick/water-repellant coatings due to their chemical stability; however, this stability leads to select PFAS being environmentally persistent. To facilitate degradation, new fluorosurfactant building blocks (F7C3-O-CHF-CF2-S-CH2-CH2-OH (FESOH), F3C-O-CHF-CF2-S-CH2-CH2-OH (MeFESOH), F7C3-O-CHF-CF2-O-CH2-CH2-OH (ProFdiEOH), F7C3-O-CHF-CF2-CH2-OH (ProFEOH), and F3C-O-CHF-CF2-O-CH2-CH2-OH (MeFdiEOH)) have been systematically developed with heteroatom linkages such as ethers, thioethers, and polyfluorinated carbons. The room temperature, gas-phase OH oxidation rate constants, and products of these chemicals were monitored in an atmospheric chamber to investigate their fate in the atmosphere. Analysis was performed using online high-resolution chemical ionization mass spectrometry (CIMS) using the iodide reagent ion and via offline UPLC-MS/MS. FESOH and MeFESOH, the thioether congeners, were observed to have the largest rate constants of kFESOH = 2.82 (±0.33) and kMeFESOH = 2.17 (±0.17) (×10-12 cm3 molecules-1 s-1, respectively). First-, second-, and third-generation products of OH oxidation were observed as a function of time, while product quantification yielded ultrashort perfluoropropionic acid (PFPrA) and short polyfluoroether acid species as the terminal products for FESOH and ProFdiEOH. There was evidence for MeFESOH being fully mineralized, demonstrating the potential benign chemical architecture.

In Vivo Transformation of a Novel Polyfluoroether Surfactant.

Per- and polyfluoroalkyl substances are a class of fluorochemicals that can degrade into perfluoroalkyl acids, which are well known to be persistent in the environment. It is thus important that novel fluorinated surfactants be designed to degrade into small, nonbioaccumulative products. We report the biotransformation and elimination kinetics of one such novel polyfluorinated surfactant, di(polyfluoroether thioether(S)-oate) sulfonate (diFESOS), and its metabolites. Biotransformation was investigated in vitro using S9 liver fractions and in vivo in Sprague-Dawley rats. Rats dosed by oral gavage with diFESOS were found to have relatively fast elimination kinetics, with half-lives on the order of hours, compared with legacy fluorinated surfactants such as the disubstituted polyfluoroalkyl phosphates that have half-lives on the order of days. To interrogate degradation of the polyfluorinated chain, rats were then dosed with a polyfluoroether thioether alcohol (a suspected product of carboxylate cleavage of diFESOS) either orally or intravenously, and the novel metabolite 2H-3:2 polyfluoroether sulfonic acid (2H-3:2 PFESA) was identified. Perfluoropropionic acid was detected in rat urine and is likely a terminal product. The blood of orally dosed rats contained higher levels of metabolites than the blood of intravenously dosed rats, suggesting the importance of metabolism in the gut and liver. Elimination kinetics of all the novel metabolites were faster than their fully fluorinated counterparts. Environ Toxicol Chem 2021;40:3328-3336. © 2021 SETAC.