Neutral Per- and Polyfluoroalkyl Substances, Butyl Carbitol, and Organic Corrosion Inhibitors in Aqueous Film-Forming Foams: Implications for Vapor Intrusion and the Environment

Abstract

Per- and polyfluoroalkyl substances (PFAS), butyl carbitol, and corrosion inhibitors are components of aqueous film-forming foams (AFFFs). Volatile (neutral) fluorotelomerization (FT)- and electrochemical fluorination (ECF)-based PFAS, butyl carbitol, and organic corrosion inhibitors were quantified in 39 military specification (MilSpec), non-MilSpec, and alcohol resistant-AFFF concentrates (undiluted) from 1974 to 2010. Fluorotelomer alcohols were found only in FT-based AFFFs and N-methyl- and N-ethyl-perfluoroalkyl sulfonamides, and sulfonamido ethanols were found only in ECF-based AFFFs. Neutral PFAS and benzotriazole, 4-methylbenzotriazole, and 5-methybenzotriazole occurred at mg/L levels in the AFFFs, while butyl carbitol occurred at g/L levels. Neutral PFAS concentrations in indoor air due to vapor intrusion of a nearby undiluted AFFF release are estimated to be anywhere from 2 to >10 orders of magnitude higher than documented background indoor air concentrations. Estimated butyl carbitol and organic corrosion inhibitor concentrations were lower than and comparable to indoor concentrations recently measured, respectively. The wide range of neutral PFAS concentrations and Henry’s law constants indicate that field, soil-gas measurements are needed to validate the estimations. Co-discharged butyl carbitol likely contributes to oxygen depletion in AFFF-impacted aquifers and may hinder the natural PFAS aerobic biotransformation. Organic corrosion inhibitors in AFFFs indicate that these are another source of corrosion inhibitors in the environment.

Per- and Polyfluoroalkyl Substances in Field-Collected Light Non-Aqueous Phase Liquids

“…Of note, LNAPL 4 comprises predominately fluorotelomer-based anionic PFAS with detection of three suspects including 6:2 FTTh-PrAd-DiMeEtS, 6:2 FTSO-PrAd-DiMePrS, and 8:2 FTThA (Tables and S8) and the only detection of neutral PFAS (Table ). The three anionic suspects ,,, and 6:2 FTOH are found in fluorotelomer-based AFFFs. All other LNAPLs gave neural PFAS < LOD or < LOQ.…”

“…All other LNAPLs gave neural PFAS < LOD or < LOQ. Neutral PFAS concentrations may be low in LNAPL due to their lower concentrations in AFFF compared to anionic PFAS, , potential volatilization during AFFF application, and subsequent biodegradation …”

“…The liquid–liquid extraction method using methanol as the solvent was developed to screen for 11 neutral PFAS (Table S3). Samples were analyzed using GC–MS. , See the Supporting Information and Tables S3 and S4 for sample preparation and analysis. Quality assurance/quality control details, which include accuracy, precision, limit of detection (LOD), LOQ, for LC–QToF and GC–MS are provided in the Supporting Information.…”

“…Aqueous film forming foams (AFFFs) are used to combat hydrocarbon-fueled fires and contain high concentrations (g/L) of anionic per- and polyfluoroalkyl substances (PFAS) , and lower concentrations of neutral PFAS. , As a result of widespread use of AFFF, PFAS are detected in soil and groundwater at military sites worldwide. − Petroleum products (e.g., diesel, waste oil, lubricants, and gasoline) and chlorinated solvents were co-released with AFFF during fire-fighting exercises and upon waste disposal. , Sufficient quantities of petroleum products or solvents were historically released during emergencies or firefighter training activities to result in the presence of non-aqueous phase liquids (NAPLs). However, comingling of AFFF and NAPL continues with a recent accidental release of AFFF at a US Navy site in the state of Hawaii, , where jet fuel was accidently released in 2021 .…”

Evaluating Neutral PFAS for Potential Dermal Absorption from the Gas Phase

“…The steady-state flux of neutral PFAS across the skin ( J ss ; ng/m 2 /h) can be estimated by multiplying known k p_g with measured indoor air concentrations of neutral PFAS . Of the 19 neutral PFAS with D / I > 5, only indoor air concentrations of N -MeFBSE were available, , resulting in an estimated J ss of 0.77–560 ng/m 2 /h (Table S4).…”