The P-Sufficient Approach

Why is high persistence alone a major cause of concern?

Persistence is a hazard criterion for chemicals recognized worldwide. This paper argues that the higher the persistence of a chemical, the greater the emphasis that it should be given in chemicals assessment and decision making. It provides case studies for three classes of highly persistent chemicals (chlorofluorocarbons, polychlorinated biphenyls, and per- and polyfluoroalkyl substances) to exemplify problems unique to highly persistent chemicals, despite their otherwise diverse properties. Using evaluative modeling calculations, it demonstrates that if a chemical is highly persistent, its continuous release will lead to continuously increasing contamination and potential exposure, irrespective of the chemical's physical–chemical properties. Increasing exposures will result in increasing risk for known and unknown health effects. Once adverse effects are identified, persistent chemicals will take decades, centuries or even longer to degrade. The findings indicate that high persistence alone should be established as a sufficient basis for management of a chemical, which we term the “P-sufficient approach”.

Strategies for grouping per- and polyfluoroalkyl substances (PFAS) to protect human and environmental health

Most governments still test and evaluate substances on a chemical-by-chemical basis before taking regulatory action. But in the case of the thousands of PFAS now known to be of regulatory concern, chemical-by-chemical testing will be too time- and resource-intensive.  Hence grouping strategies for PFAS are needed. This paper reviews various grouping strategies that could inform actions on these chemicals. Grouping strategies are subdivided into (1) those based on the intrinsic properties of the PFAS (e.g. persistence, bioaccumulation potential, toxicity, mobility, molecular size) and (2) those that inform risk assessment through estimation of cumulative exposure and/or effects. The most precautionary grouping approach suggests phasing out PFAS based on their high persistence alone (the “P-sufficient” approach). The guiding question is: grouping for what purpose? This assessment provides the necessary context for grouping strategies such that they can be adopted as they are, or built on further, to protect human and environmental health from potential PFAS-related effects.