Andrew Chapin Maizel

Turnout gear protects firefighters from exposure to flames, heat, and liquids and is made from textiles which have been found to contain per- and polyfluoroalkyl substances (PFAS). Previous examinations of PFAS in turnout gear have predominantly utilized targeted analytical approaches, which quantify a limited number of PFAS with established quantitative methods. This NIST Technical Note describes the first use of liquid chromatography high-resolution mass spectrometry combined with suspect screening to search for the presence of over 4,000 PFAS in firefighter turnout gear textiles. PFAS were ionized with negative mode electrospray and the resulting mass spectral features were screened against the NIST PFAS Suspect List as either deprotonated ions ([M-H]-) or acetate adducts ([M+C2H3O2]-), which enabled the detection of a highly chemically diverse set of PFAS. Molecular formulas were assigned to mass spectral features by comparison of precursor ion spectra against predicted isotopic distributions while chemical identities were determined and evaluated by comparison of precursor and product ion spectra against previously collected spectra using the NIST Database Infrastructure for Mass Spectrometry (DIMSpec) application MSMatch. Six PFAS compound identities were confirmed in firefighter gear textiles with high confidence, including four that were not quantified in a previously reported targeted analysis of the same textiles. Additionally, this is the first reported identification of three PFAS (perfluoro butane sulfonamide ethanol, perfluorobutane sulfonamido diethanol, and 6:2 fluorotelomer sulfate) in any outerwear textile. Overall, this NISTTechnical Note demonstrates the need for PFAS screening techniques can discern a broader swath of PFAS than targeted analysis alone and also the capability of DIMspec and MSMatch to provide and evaluate PFAS compound annotations.

Firefighter turnout gear has been found to contain per- and polyfluoroalkyl substances (PFAS) and is a potential source of PFAS exposure to firefighters. However, previous evaluations of firefighter exposure to PFAS through personal protective gear has exclusively examined jackets and pants. In contrast, turnout gear contains other protective articles that contact firefighter skin, including hoods and gloves. Additionally, wildland firefighters typically wear gear that includes a shirt and pants, each made of a single layer, to allow easier movement relative to the heavy jacket and pants worn by structural firefighters. To determine the identity, concentration, and prevalence of PFAS potentially present in unused textiles present in firefighting hoods, gloves, and wildland gear, fifty-five nonvolatile, semivolatile, and volatile PFAS were quantified in thirty-two textiles taken from gloves and hoods used by structural firefighters as well as wildland firefighter shirts and pants. Between zero and nine individual PFAS were observed above their respective reporting limits in each textile, with the highest numbers of detections and highest concentrations of PFAS present in wildland gear textiles, compared to glove textiles, which had the second highest, and hood textiles which had the lowest. 6:2 fluorotelomer methacrylate (6:2 FTMAC) and 6:2 fluorotelomer alcohol (6:2 FTOH) are both fluorotelomerization-derived PFAS with six perfluorinated carbons, which were quantified at the highest concentrations of any PFAS reported here, up to 2980 μg/kg ± 820 μg/kg (mean ± standard deviation of triplicate measurements of single textile) and 1250 μg/kg ± 330 μg/kg, respectively. These two PFAS, however, were only detected in wildland firefighting gear textiles. Also observed in the wildland gear textiles were perfluorocarboxylic acids (PFCAs) with seven or fewer perfluorinated carbons at individual concentrations below 20 μg/kg. Four PFAS were observed in most of the glove layers: perfluorobutanoic acid, perfluorobutane sulfonic acid, perfluorobutane sulfonamide, and N-methyl perfluorobutane sulfonamide, with N-methyl perfluorobutane sulfonamide observed at the highest concentration, up to 117.2 ± 7.0 μg/kg. Five different PFAS were observed across all the hoods, but concentrations were less than 1 μg/kg. PFAS concentrations varied widely among each textile type, suggesting that the amount of PFAS present in unused firefighter gear may depend on the textiles used in gear manufacturing.

Turnout gear is increasingly recognized as a potential source of per- and polyfluoroalkyl substance (PFAS) exposure to firefighters. To determine the type, concentration, and prevalence of PFAS potentially present in new firefighter turnout gear, fifty-three nonvolatile, semivolatile, and volatile PFAS were quantified in twenty textiles used in the construction of firefighter turnout gear. Between one and seventeen PFAS were observed and quantified in each textile, with higher numbers of detections and higher concentrations of PFAS present in moisture barrier and outer shell textiles compared with thermal liner textiles. Three fluorotelomerization-derived PFAS with six perfluorinated carbons, 6:2 fluorotelomer methacrylate, 6:2 fluorotelomer alcohol, and 6:2 fluorotelomer sulfonic acid, were quantified at the highest concentrations of any individual PFAS, up to 1,570 µg/kg ± 140 µg/kg (mean ± standard deviation of triplicate measurements), 613 µg/kg ± 15 µg/kg and 393 µg/kg ± 98 µg/kg, respectively. These three PFAS were not detected in outer shells that had not received fluoropolymer treatments which could indicate they were remnant raw materials from side-chain fluorinated polymer manufacturing. Also widely identified were two compounds with four perfluorinated carbons; perfluorobutane sulfonic acid and perfluorobutane sulfonamide. Perfluorocarboxylic acids, especially those with fewer than six perfluorinated carbons, were nearly universally identified, but entirely at concentrations below 40 µg/kg. In contrast, PFAS with eight or more perfluorinated carbons, such as perfluorooctanoic acid and perfluorooctane sulfonic acid, were present at summed concentrations below 2 µg/kg in all textiles. The wide variation in summed PFAS concentrations among each textile type suggests that the amount of PFAS present in new turnout gear could vary widely based on the specific textiles used in gear manufacturing.

UV-sulfite has been shown to effectively degrade per- and polyfluoroalkyl substances (PFASs) in single-solute experiments. We recently reported treatment of 15 PFASs, including perfluoroalkyl sulfonic acids (PFSAs), perfluoroalkyl carboxylic acids (PFCAs), and fluorotelomer sulfonic acids (FTSs), detected in aqueous film-forming foam (AFFF) using high-resolution liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) targeted analysis. Here, we extend the analysis within those original reaction solutions to include the wider set of PFASs in AFFF for which reactivity is largely unknown by applying recently established LC-QTOF-MS suspect screening and semiquantitative analysis protocols. Sixty-eight additional PFASs were detected (15 targeted + 68 suspect screening = 83 PFASs) with semiquantitative analysis, and their behavior was binned on the basis of (1) detection in untreated AFFF, (2) PFAS photogeneration, and (3) reactivity. These 68 structures account for an additional 20% of the total fluorine content in the AFFF (targeted + suspect screening = 57% of total fluorine content). Structure-reactivity trends were also revealed. During treatment, transformations of highly reactive structures containing sulfonamide (-SO₂N-) and reduced sulfur groups (e.g., -S- and -SO-) adjacent to the perfluoroalkyl [F(CF₂)_n-] or fluorotelomer [F(CF₂)_n(CH₂)₂-] chain are likely sources of PFCA, PFSA, and FTS generation previously reported during the early stages of reactions. The results also show the character of headgroup moieties adjacent to the F(CF₂)_n-/F(CF₂)_n(CH₂)₂- chain (e.g., sulfur oxidation state, sulfonamide type, and carboxylic acids) and substitution along the F(CF₂)_n- chain (e.g., H-, ketone, and ether) together may determine chain length-dependent reactivity trends. The results highlight the importance of monitoring PFASs outside conventional targeted analytical methodologies.

Poly- and perfluorinated alkyl substances (PFASs) frequently co-occur with fuel-derived contaminants because of the use of aqueous film-forming foam (AFFF). Biosparging is a common remediation technology that injects oxygen into the saturated zone to encourage aerobic biodegradation, thereby altering aquifer redox conditions and potentially facilitating the biotransformation of polyfluorinated substances. Between 136 and 280 pore volumes of nitrogen-sparged or oxygen-sparged artificial groundwater amended with toluene were pumped through four saturated, AFFF-impacted soil columns to assess impacts on PFAS release and transformation. Column effluents and soils were analyzed for PFASs by high-resolution mass spectrometry. Significantly higher concentrations of five PFASs eluted from O₂-sparged columns compared to N₂-sparged columns shortly after sparging was initiated. The mass fractions eluted of many zwitterionic, sulfonamide-based PFASs were higher in both sets of columns than unaltered, non-biostimulated columns. Mass balance calculations suggested the transformation of sulfonamide-based precursors to perfluorinated sulfonamides (i.e., perfluorohexanesulfonamide) in oxygen- and nitrogen-sparged columns: recoveries of perfluorinated sulfonamides were 158–235% for C3–C6 homologs but recoveries of several prominent sulfonamide-based zwitterions were low. For example, the recovery of n-carboxyethyldimethyl-ammoniopropyl perfluorohexanesulfonamide was 9–13%. These results suggest biosparging can enhance the transformation and release of PFASs in saturated soils, which has important implications for site characterization and remediation.

Ultraviolet photochemical reaction of sulfite (SO₃²⁻) photosensitizer generates strongly reducing hydrated electrons (e_aq⁻; NHE = −2.9 V) that have been shown to effectively degrade individual per- and polyfluoroalkyl substances (PFASs), including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). However, treatment of complex PFAS mixtures in aqueous film-forming foam (AFFF) remains largely unknown. Here, UV-sulfite was applied to a diluted AFFF to characterize e_aq⁻ reactions with 15 PFASs identified by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) targeted analysis. Results show that reactivity varies widely among PFASs, but reaction rates observed for individual PFASs in AFFF are similar to rates observed in single-solute experiments. While some structures, including long-chain perfluoroalkyl sulfonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs) were readily degraded, other structures, most notably short-chain PFSAs and fluorotelomer sulfonic acids (FTSs) were more recalcitrant. This finding is consistent with results showing incomplete fluoride ion release (up to 53% of the F content in AFFF) during reactions. Furthermore, results show that selected PFSAs, PFCAs, and FTSs can form as transient intermediates or unreactive end-products via e_aq⁻ reactions with precursor structures in AFFF. These results indicate that while UV-sulfite treatment can be effective for treating PFOS and PFOA to meet health advisory levels, remediation of the wider range of PFASs in AFFF will prove more challenging.

Poly- and perfluoroalkyl substances (PFASs) derived from aqueous film-forming foam (AFFF) are increasingly recognized as groundwater contaminants, though the composition and distribution of AFFF-derived PFASs associated with soils and subsurface sediments remain largely unknown. This is particularly true for zwitterionic and cationic PFASs, which may be incompletely extracted from subsurface solids by analytical methods developed for anionic PFASs. Therefore, a method involving sequential basic and acidic methanol extractions was developed and evaluated for recovery of anionic, cationic, and zwitterionic PFASs from field-collected, AFFF-impacted soils. The method was validated by spike recovery experiments with equilibrated soil-water-AFFF and analytical standards. To determine the relative importance of PFASs lacking commercially available analytical standards, their concentrations were estimated by a novel semi-quantitation approach. Total PFAS concentrations determined by semi-quantitation were compared with concentrations determined by the total oxidizable precursor assay. Finally, the described method was applied to two soil cores from former fire-training areas in which cations and zwitterions were found to contribute up to 97% of the total PFAS mass. This result demonstrates the need for extraction and analysis methods, such as the ones presented here, that are capable of quantifying cationic and zwitterionic PFASs in AFFF-impacted source zone soils.

Although electrochemical treatment has received increased attention with respect to treating poly- and perfluoroalkyl substances (PFAS), studies assessing treatment longevity for the wide range of PFAS present in water impacted by aqueous film-forming foam (AFFF) are lacking. A 21-day study was performed in which electrochemical treatment using boron-doped diamond (BDD) anodes was performed in successive 24-h batch cycles on groundwater impacted with AFFF. Results showed substantial defluorination of both the perfluoroalkyl acids (PFAAs) and defluorination of polyfluoroalkyl compounds (based on fluoride generation). Substantial perchlorate generation was observed throughout the study. PFAS treatment effectiveness diminished over time due to scaling, resulting in decreased removal of the PFAAs and generation of perfluorobutanoic acid (PFBA). Based on measured generation of fluoride relative to the concentrations of the PFAAs, defluorination of the polyfluoroalkyl acids decreased 2–3 times more than the PFAAs due to this scaling. This suggests that defluorination of the polyfluoroalkyl acids occurred via a mechanism different from that of the PFAAs. Acid cleaning to remove the accumulated scale resulted in restoration of PFAS treatment. Together, these results suggest that electrochemical treatment of AFFF-impacted waters shows promise. Polyfluorinated compounds and PFBA showed greater adverse impacts from the mass transfer and/or residence time decreases associated with the scaling than what was observed for the other PFAAs. This implies that these compounds may prove to be the greater challenge in long-term full-scale applications.