<scp>PFAS</scp> Forensics, Part 1: Identifying Source‐Specific Signatures

Abstract Environmental forensics employs a variety of analytical tools and techniques to evaluate contamination sources and assess the scope and impact of contamination in environmentally relevant media. The key questions for an environmental forensics analysis are where, when and how contamination occurred. This paper, the first in a series on per‐ and polyfluoroalkyl substances (PFAS) forensics, presents some considerations for understanding and identifying source‐specific PFAS signatures. Because different PFAS applications utilize distinct properties of these compounds, the composition of PFAS, the potential for their release and their fate and transport in the environment will vary based on industry and consumer products. Information critical to understanding and identifying PFAS sources include: (1) source type(s) (i.e., primary vs. secondary), (2) the manufacturing process, (3) formulations used, (4) how formulations may have changed over time, (5) how PFAS or PFAS formulations were used or applied, (6) relative magnitude of known or suspected releases and (7) potential precursor transformation products. This information will help develop a source‐specific signature that can then be compared to documented contamination. In addition, the widespread usage of PFAS across numerous products, materials, and industries has potentially created a large, non‐attributable source of PFAS (i.e., anthropogenic background). As a result, an understanding of baseline or “background” PFAS levels in our environment may be needed in an environmental forensics analysis. The combined information of potential source‐specific signatures and anthropogenic background are essential for making informed and defensible decisions on where, when and how PFAS contamination occurred.