Untargeted mass spectrometric analysis of per- and polyfluoroalkyl substances (PFAS) in rat matrices following exposure to aqueous film-forming foams (AFFFs)

Abstract

AFFFs contain proprietary mixes of surfactants and numerous PFAS. PFAS are released into ground water and drinking water supplies and hence are ubiquitous contaminants. To investigate which PFAS bioaccumulate in rats following exposure to AFFF formulations, untargeted analysis was conducted using high resolution mass spectrometry following liquid chromatographic separation. Male Hsd: Sprague Dawley SD rats were administered a daily dose of 1% dilution of 5 MIL-SPEC-qualified AFFF formulations for 1 or 14 days. Plasma and liver were collected 24 h after the last dose, and urine was collected at 24 h after the first and seventh dose. A pilot assessment was done using a limited number of liver and plasma samples followed by a definitive assessment using liver from 5 animals per exposure duration (i.e. control, single dose, 14 doses). Samples were extracted with 300 µL of methanol, frozen at -80°C to separate phospholipids prior to analysis of the supernatant in both positive and negative ion modes. Data were processed with Compound Discoverer 3.2 using an untargeted approach against a library of standards, and against libraries including PFAS compounds from US EPA’s Chemical Dashboard, from Luo et al. (2020), McDonough et al. (2020) and Ruyle et al. (2020). Compounds were identified/annotated using exact mass, isotope ratio, adducts, and comparison of retention time with standards, including 6:2 fluorotelomer sulfonic acid (FTS), N,N-dimethyl-3-((perfluorohexyl)ethylsulfonyl)amino-propanamine N-oxide (FTNO), and 6:2 fluorotelomer sulfonamide betaine, as well as
perfluorocarboxylic acids and sulfonates. A limited number of PFAS were detected in liver with levels increasing with exposure duration. FTS was readily detected in all matrices from exposed animals. FTS bioaccumulated in liver from rats administered each AFFF, accumulating 3.6-7.1 fold between 1 and 14 days. FTS was the major analyte (highest peak area) detected in urine, with all AFFFs investigated. FTNO was found in urine from one AFFF. FTNO was not detected in liver, but several possible metabolites were detected. Other compounds detected in liver and plasma included 6:2 fluorotelomer sulfinyl amido sulfonic acid, 6:2 fluorotelomer thioether amido sulfonic acid, and 6:2 fluorotelomer thiohydroxyl ammonium. Perfluoropentanoic, -hexanoic, and -heptanoic acids, which may arise from metabolism of 6:2 fluorotelomers, were found in urine samples from all treated rats. FTS was the major component found to bioaccumulate in liver.