[Report] Reconciling Terminology of the Universe of Per- and Polyfluoroalkyl Substances: Recommendations and Practical Guidance

July 20, 2021

This report summarizes recent efforts by the OECD/UNEP Global PFC Group between June 2018 and March 2021 in reviewing the universe and terminology of per- and polyfluoroalkyl substances (PFASs) to provide recommendations and practical guidance to all stakeholders with regard to the terminology of PFASs. In particular, this report highlights (1) a revised PFAS definition to comprehensively reflect the universe of PFASs and a comprehensive overview of the PFAS universe (Chapter 2), (2) practical guidance on how to use the PFAS terminology (Chapter 3), (3) a systematic approach to characterization of PFASs based on molecular structural traits to assist stakeholders, including nonexperts, in making their own categorization based on their needs (Chapter 4), and (4) areas in relation to the PFAS terminology that warrant further development (Chapter 5). It should be noted that this report does not address the nomenclature and understanding of individual PFASs, including the sources of exposure and the actual composition of commercial products.

PFASs comprise a class of synthetic compounds that have attracted much public attention since the late 1990s and early 2000s, when the hazards and ubiquitous occurrence of two PFASs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), started to be reported and recognized. Since then, research and risk management measures have expanded from these two PFASs to a wider range of PFASs. Early communications used many different terminologies (e.g. perand polyfluorinated chemicals, perfluorinated organics, perfluorochemical surfactants, highly fluorinated compounds). In 2011, to unify and harmonize communication on PFASs, Buck et al. published a milestone paper, providing a first clear structural definition of PFASs and recommendations on names and acronyms for over 200 individual PFASs.

Currently, there is a growing interest by regulators and scientists across the globe to assess legacy and novel PFASs. In 2018, the OECD/UNEP Global PFC Group prepared a new list of PFASs that may have been on the global market. In total, a set of substances with over 4730 CAS numbers have been identified, including substances that contain such fully fluorinated carbon moieties, but do not meet the PFAS definition in Buck et al. (2011) due to a lack of a –CF3 group in the molecular structures. In addition, recent advancement of non-target screening analytical techniques using high-resolution mass spectrometry has enabled identification of many unknown substances in different environmental and product samples. The identification of these substances motivates the present work to reconcile the terminology of the universe of PFASs, including a renewed look at the PFAS definition in Buck et al. (2011).

Read the report here.