A panel of expert on the chemistry and toxicology of per- and polyfluoroalkyl substances (PFAS) as well as on mixtures risk assessment and toxicokinetics in general came together “to provide insight and guidance on [PFAS] grouping for the purposes of protecting human health from drinking water exposures, and how risks to PFAS mixtures should be assessed.” The results from the series of “blind, independent responses to charge questions, and review and comments on co-panelists responses” were published in Regulatory Toxicology and Pharmacology on July 8, 2022. The panelists “represent various stakeholder groups including academia, regulators, and consultants” from four countries. They came to no unanimous conclusions but did have some general majority agreements.
The panelists agreed that “human health risk assessment must be based on the principles of hazard and exposure” and that “compound-specific mode of action or adverse outcome pathway (AOP) information is ‘the gold standard’” for grouping PFAS. However, when comparing ratings of feasibility versus scientific merit of all the methods for grouping chemicals, mode of action had the highest scientific merit score but the lowest feasibility score. Using carbon chain length and chemical structure as the grouping methodology had the highest feasibility score and was in the middle of the range for merit. But “some panelists believed that categorizing PFAS with similar structures was inadequate without consideration of the toxic mode of actions dose-response relationships, and potencies.” The experts note that the current lack of available information for the majority of PFAS also creates a significant challenge for risk assessment.
Persistence as a way of grouping PFAS was discussed but agreement was not achieved. “The application of ‘persistence’ as a means of grouping PFAS seemed to be best supported when applied to a regulatory context of restricting manufacture and use… Overall – the concept of ‘persistence’ to group PFAS [into a single group] was not accepted by most panelists as surrogate for risk or to set human health-based regulations.” Persistence has been considered as a hazard class for European Union regulations including for the classification, labeling and packaging (CLP) of chemicals with support from the Global PFAS Science Council (FPF reported).
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Anderson, JK, et al. July 8, 2022. “Grouping of PFAS for human health risk assessment: Findings from an independent panel of experts.” Regulatory Toxicology and Pharmacology
