Widening the Lens on PFASs: Direct Human Exposure to Perfluoroalkyl Acid Precursors (pre-PFAAs)

Abstract

Determining health risks associated with per-/polyfluoroalkyl substances (PFASs) is a highly complex problem requiring massive efforts for scientists, risk assessors, and regulators. Among the most poorly understood pressing questions is the relative importance of pre-PFAAs, which are PFASs that degrade to highly persistent perfluoroalkyl acids. How many of the vast number of existing pre-PFAAs are relevant for direct human exposure, and what are the predominant exposure pathways? What evidence of direct exposure to pre-PFAAs is provided by human biomonitoring studies? How important are pre-PFAAs and their biotransformation products for human health risk assessment? This article outlines recent progress and recommendations toward widening the lens on human PFAS exposure to include the pre-PFAA subclass.

The Need for Testing Isomer Profiles of Perfluoroalkyl Substances to Evaluate Treatment Processes

“…In contrast, most wildlife studies report lower contributions from branched isomers (Figure ). This may indicate greater direct exposure of humans to PFAS precursors, which are transformed in vivo to form perfluoroalkyl acids (PFAAs), with preferential formation of branched isomers. , This elevated exposure likely arises from sources other than drinking water, such as certain foods, paper products, textiles, and other consumer products. − …”

“… 26 , 63 This elevated exposure likely arises from sources other than drinking water, such as certain foods, paper products, textiles, and other consumer products. 64 − 66 …”

Volatility and Nonspecific van der Waals Interaction Properties of Per- and Polyfluoroalkyl Substances (PFAS): Evaluation Using Hexadecane/Air Partition Coefficients

“…PFAS contain perfluorinated carbon atoms, which are highly resistant to degradation in the environment and ecosystems. Some PFAS such as perfluorooctane sulfonate and perfluorooctanoic acid have adverse health effects in humans, and many precursors exist that can transform into these or other potentially harmful PFAS. − In 2018, the Organisation for Economic Co-operation and Development published a list of 4730 CAS-registered PFAS . Since then, the definition of PFAS has been expanded to include basically any compound that contains a perfluorinated methyl (−CF 3 ) or methylene (−CF 2 −) moiety .…”

Impacts of Environmental and Engineered Processes on the PFAS Fingerprint of Fluorotelomer-Based AFFF

“…The presence of precursors worsens a contaminated site as they may indicate long-term release of PFAAs. Additionally, the precursors themselves may cause harmful effects in humans . Quantification of precursors is often omitted from environmental analyses and thus characterization solely of terminal PFAAs may underestimate the long-term potential of PFAS release.…”