In October 2021, the EPA developed a new national testing strategy for PFAS that attempts to bypass some difficulties in screening for the thousands of PFAS in the environment. The EPA is now adopting a strategy of categorizing PFAS according to chemical structure and toxicity. In categorizing PFAS, EPA hopes to select a few specific PFAS that are representative of all PFAS, which allows sample testing to provide more substantive information. In this post, I’ll unpack how EPA proposes doing so.
The EPA has a large database of chemicals called DSSTox, which provides extensive chemical-related data on over 800,000 compounds. From DSSTox, EPA has applied structural filters to weed out all chemicals that generally cannot be classified as PFAS. From there, EPA applies “primary structural categories,” which divide the selected PFAS into specific categories depending on chemical structure. After that, each primary category is divided into secondary categories that classify PFAS based on length. In literature, the length of PFAS have shown to affect how long they spend in the human body, in addition to adverse health effects.
When the PFAS has been categorized by structure, the EPA then applies filters based on whether a specific chemical has toxicity data and is industrially prevalent. On its initial selection run, the EPA selected 24 PFAS candidates that were representative of the numerous PFAS categories.
I believe that the categorization of PFAS based on structure and toxicity is a step in the right direction. Currently, official EPA drinking water testing methods analyze for ~30 PFAS, which were picked based on their industrial prevalence. In selecting specific PFAS candidates, EPA testing methods can be improved to provide more information about all PFAS in a sample, not just a select few.
Furthermore, I think that systematically categorizing PFAS by a central authority has implications beyond sample testing. If this standard of PFAS grouping is established in academia, the health effects of PFAS can be more extensively studied. In addition, adopting standards by which PFAS can be categorized will prevent chemical companies from avoiding regulations by inventing new PFAS.
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