Widespread detection of per- and polyfluoroalkyl substances (PFAS) in our environment and increasing knowledge regarding their toxicity have drawn sharp public, regulatory, and political scrutiny for cleanup. That scrutiny is compounded by increasing treatment and management costs associated with the few technologies proven to achieve extremely low cleanup standards. In response to these challenges, Woodard & Curran has developed a strategy to help determine the sources and associated liabilities for PFAS compounds detected at our client’s sites.
Thousands of PFAS compounds have been developed, using different manufacturing methods, for diverse commercial and industrial applications. This diversity, coupled with recent advances in our ability to detect PFAS in the environment, provides distinctive signatures to identify different PFAS sources and potentially a basis for separating our client’s liabilities from those of other sources.
Woodard & Curran’s strategy builds upon five core elements:
- Conceptual Site Model. The first element of our strategy is a complete and accurate conceptual site model (CSM) including the history and the hydrogeologic and geochemical characteristics of a site. A CSM begins with an understanding of current and past uses of the site to identify processes that may have utilized PFAS or resulted in their discharge to the environment. The hydrogeological and geochemical setting influences the fate and transport of PFAS whether they originate on site or off site. Key elements of a CSM include surface and subsurface features, geology and hydrogeology, geochemistry, exposure pathways, and compliance boundaries. Contaminant characteristics include determining what PFAS are present, their distribution, and concentration.
- PFAS Compound Distribution. The second element of our strategy is a comprehensive analysis of the PFAS compounds present. Specific PFAS or suites of commonly associated PFAS can be linked to certain types of products or industrial uses, or can constrain when they were discharged to the environment. For example, fluorotelomer sulfonates were not widely used until about 2002, after phase-out of long-chain PFAS primarily associated with electrochemical fluorination manufacturing processes. The ratios of different PFAS compounds detected in a sample can also be used to distinguish different PFAS sources, using a wide variety of graphical and multivariate statistical tools.
- Structural Characteristics. The third element of our strategy is to leverage differences in the chemical structures of PFAS compounds imparted by different manufacturing processes. Two primary methods have been utilized to produce PFAS compounds: electrochemical fluorination and telomerization. These processes result in different abundance of branched and linear chemical structures for the same compounds, and different ratios of compounds with even- and odd-numbered carbon chain lengths. These characteristics can be linked to specific types of products and manufacturers, and can help inform when the PFAS were manufactured.
- Fingerprint Compounds. The fourth element of our strategy is to search for PFAS compounds that are diagnostic for specific uses, manufacturers, or in some cases even to specific products. Different PFAS compounds exhibit different chemical properties that affect how they are used in different products. While many of the commonly analyzed PFAS compounds have many uses or are formed by partial transformation of other PFAS in the environment, others are very specific. For example, fluorotelomer thioamido sulfonates such as 6:2 FtTAoS are diagnostic of firefighting foam formulations from very specific manufacturers.
- Non-Target Analysis. The final element of our strategy is to use very sophisticated analytical techniques to search for PFAS compounds for which analytical standards are not available. Non-target analysis can be utilized to detect the presence of compounds with specific atomic masses or repeating chemical units common to PFAS structures, which can be diagnostic of different sources. In very advanced situations, non-target analysis can be extended to determine the specific chemical identity of unknown PFAS compounds detected in a sample, which can provide additional diagnostic information to differentiate sources.
Detection of PFAS at a site does not mean that the compounds were utilized or discharged at the site, or that the property owner is necessarily responsible for their cleanup. Woodard & Curran has developed this five-element strategy to help our clients determine regulatory and financial liabilities. Woodard & Curran is committed to innovative approaches to help solve our client’s site management challenges.
You can learn more about our approach to PFAS Forensics in this free webinar, recorded September 30, 2020.
