July 8, 2019
Per- and polyfluoroalkyl substances (PFAS) in the environment are increasingly the focus of environmental investigations and are subject to significant regulatory activity in the United States. Several states have developed standards or guideline concentrations for some PFAS in drinking water, surface water, groundwater, and/or soils. Our understanding of PFAS in these environmental media and of compliance with the evolving regulatory guidelines is hampered by the lack of standardized and validated analytical methods for all media. Recently, the U.S. Environmental Protection Agency (EPA) identified the development of new analytical methods to understand and manage PFAS risks as one of its short-term goals in the PFAS Action Plan, issued in February 2019 (U.S. EPA 2019a). To address the lack of standardized methods, EPA published a proposed Validated Test Method 8327: Per-and Polyfluoroalkyl Substances (PFAS) Using External Standard Calibration and Multiple Reaction Monitoring (MRM) Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) (U.S. EPA 2019b). The proposed method, along with validation and statistical analysis reports, was published on June 12, 2019, on EPA's website for a 30-day comment period. The proposed method has not yet formally been included in the SW-846 compendium of hazardous waste test methods.
The newly proposed Method 8327 is part of EPA's efforts to develop and validate analytical methods for quantification of PFAS in a variety of relevant environmental matrices, including methods for water, soils and sediments, and biota (Gaines 2019; U.S. EPA 2019a). Recently, analytical laboratories have modified EPA's existing Method 537.1 for determination of PFAS in drinking water to also cover other environmental media, due to a lack of validated methods. The publication of EPA Method 8327 expands the scope of EPA's validated methods for analyzing PFAS in environmental water samples, as Method 8327 is validated for groundwater, surface water, and wastewater.
The proposed Method 8327 provides for the analysis of 24 PFAS analytes, including ten sulfonic acids, eleven carboxylic acids, and three sulfonamides and sulfonamideacetic acids (Table 1). These PFAS compounds include perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), for which EPA has established health advisories (U.S. EPA 2016a,b). With the exception of GenX — a short-chain PFAS used as a fluoropolymer processing aid — the proposed method covers PFAS compounds for which states have provided guidance levels or set standards (ITRC 2019), in addition to several other PFAS analytes. In comparison with existing Method 537.1, Method 8327 expands the analyte list with the addition of ten different PFAS, but does not include four analytes that are on the original Method 537.1 list (Table 1).
The Statistical Report and Data Validation Summary that accompanied the proposed Method 8327 illustrated some of the challenges that are associated with the PFAS analyses. For example, some of the longer-chain PFAS carboxylic acids and amidoacetic acids exhibited more bias and/or lower precision in measurement. EPA also noted that the performance of Method 8327 for 6:2 fluorotelomer sulfonate (6:2 FTS) was erratic, and the agency noted background contamination associated with certain sampling equipment, such as Teflon parts. To address the observed precision and bias issues, EPA included several cautions in Method 8327, particularly for the longer-chain PFAS carboxylic acids and amidoacetic acids. These cautions highlight the care that must be taken during sample collection, storage, handling, and analysis for PFAS.
The evolving state guidance levels or standards pose a challenge for the measurement of PFAS, regardless of the analytical method that is used. The numeric guidelines or standards vary from state to state. For example, state PFOA guideline and standard values in drinking water range from 9 ng/L to 70 ng/L, whereas the federal health advisory level for PFOA and/or PFOS is 70 ng/L (ITRC 2019; U.S. EPA 2016b). The suggested lower levels of quantitation (LLOQ) for the Method 8327 analytes range from 10 ng/L to 50 ng/L, depending on the PFAS. These limits are higher than the lowest concentration minimum reporting levels (0.53 ng/L to 6.3 ng/L) for Method 537.1 (Shoemaker and Tettenhorst 2018; ASDWA 2019). For some PFAS, quantitation and reporting limits may be at or even higher than the levels of some state standards or guidance values, a discrepancy that warrants a careful assessment of analytical capabilities before selecting a commercial laboratory to make sure that the data will meet the requirements for the intended use.
Although the new method represents an increase in the number of PFAS that can be measured and the number of matrices for which validated PFAS analytical methods exist, a remaining challenge is posed by the presence of hundreds, if not thousands, of individual PFAS that may be present in the environment. Estimates of the number of PFAS that have been marketed over time range from more than 3,000 (Wang et al. 2017; KEMI 2015) to more than 5,000 compounds (U.S. EPA 2019c). For example, advanced analytical techniques demonstrated that surface water downstream of a fluoropolymer manufacturing facility exhibited 37 unique PFAS compounds comprising perfluorinated ether acids (McCord and Strynar 2019), which represent just one class of PFAS compound, and which are not currently targeted in either EPA method. Methods currently are lacking to understand the environmental disposition and potential impacts of all of the PFAS that may be present in the environment.
How Exponent Can Help
Exponent's expert consultants in regulatory compliance, contaminant fate and transport, and analytical chemistry help clients navigate the current regulatory landscape and manage their ongoing environmental liabilities. Our multi-disciplinary team of scientists and engineers considers both state and federal regulations when developing strategic solutions for our clients' needs. Exponent can help with selecting appropriate methods and laboratories for PFAS analyses based on the intended use of the data. Further, Exponent's scientists and engineers can assist with source identification, chemical fingerprinting, and fate and transport analyses of PFAS in the environment.
References
ASDWA. 2019. Per- and polyfluoroalkyl substances (PFAS) laboratory testing primer for state drinking water programs and public water systems. Version 2. Association of State Drinking Water Administrators. February 14.
Gaines, L. 2019. What are PFAS, and what are issues with them? Per-and polyfluoroalkyl substances emerging characterization and remedial technologies. Federal Remediation Technologies Roundtable webinar. June 20. Available at https://clu-in.org/conf/tio/FRTRPresents5_062019/default.cfm#tabs-4.
ITRC. 2019. Regulations, Guidance, and Advisories. PFAS Fact Sheet. Interstate Technology and Regulatory Council (ITRC). Available at https://pfas-1.itrcweb.org/fact-sheets/. Last updated May 2019. Accessed on June 25, 2019.
KEMI. 2015. Occurrence and use of highly fluorinated substances and alternatives. Report 7/15. Kemi, Swedish Chemicals Agency. Available at https://www.kemi.se/en/global/rapporter/2015/report-7-15-occurrence-and-use-of-highly-fluorinated-substances-and-alternatives.pdf
McCord, J. and M. Strynar. 2019. Identification of per- and polyfluoroalkyl substances in the Cape Fear River by high resolution mass spectrometry and nontargeted screening. Environmental Science and Technology. Vol. 53: 4717-4727.
Shoemaker, J. and D. Tettenhorst. 2018. Method 537.1: Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). EPA/600/R-18/352. U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Washington, DC. November.
U.S. EPA. 2016a. Health effects support document for perfluorooctane sulfonate (PFOS). EPA 822-R-16-003. Office of Water, U.S. Environmental Protection Agency. May.
U.S. EPA. 2016b. Health effects support document for perfluorooctanoic acid (PFOA). EPA 822-R-16-002. Office of Water, U.S. Environmental Protection Agency. May.
U.S. EPA. 2019a. EPA's per- and polyfluoroalkyl substances (PFAS) action plan. EPA 823R18004, U.S. Environmental Protection Agency. February.
U.S. EPA. 2019b. Validated test method 8327: per- and polyfluoroalkyl substances (PFAS) using external standard calibration and multiple reaction monitoring (MRM) liquid chromatography/tandem mass spectrometry (LC/MS/MS). Available at https://www.epa.gov/hw-sw846/validated-test-method-8327-and-polyfluoroalkyl-substances-pfas-using-external-standard. Last updated on June 12, 2019. Accessed on June 25, 2019.
U.S. EPA. 2019c. PFAS master list of PFAS substances. CompTox Chemistry Dashboard. Available https://comptox.epa.gov/dashboard/chemical_lists/PFASMASTER. Accessed on June 25, 2019.
Wang, Z, J.C. DeWitt, C.P. Higgins, and I.T. Cousins. 2017. A never-ending story of per- and polyfluoroalkyl substances (PFAS)? Environmental Science and Technology. Vol. 51: 2508-2518.
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