Did you say PFAS ?

doi:10.1515/ci-2022-0226

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Did you say PFAS ?

Published/Copyright: April 14, 2022

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From the journal Chemistry International Volume 44 Issue 2

The Organisation for Economic Co-operation and Development (OECD) revises PFAS definition and recommends specific terminology for communicating about PFAS substances (OECD, 2021)

reviewed by Richard M. Hartshorn and Molly A. Strausbaugh

Regulatory agencies, news media, and researchers report daily on new regulations, studies, and insights on per- and polyfluoroalkyl substances (PFAS). These synthetic chemicals have been in use, in many locations across the globe, since the 1940s (U.S. EPA, 2021). PFAS substances are frequently selected for use because of their extreme heat stability and desirable surfactant properties (ECHA, 2021). With the vast range of industries and sectors involved in PFAS use and/or site remediation, together with the environmental persistence profiles of PFAS compounds consistent terminology and nomenclature becomes more critical for effective communication.

OECD Definition and identification process

Recognizing Buck et al (2011) as a starting point for classification and harmonization of terminology, OECD’s recent publication seeks to close four identified gaps. These four gaps include classes and terms that relate to:

Acyclic systems with non-fluorinated functional groups on both ends of a perfluoroalkanediyl moiety
Compounds containing fully fluorinated aliphatic cyclic compounds
PFAS containing functional groups with aromatic rings
The ambiguous meaning and interpretations of “highly fluorinated”

This report summarizes recent efforts by the OECD/UNEP Global PFC Group 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.

The revised PFAS definition is based solely on chemical structure, and the report itself features many structural examples.

Specific and descriptive PFAS terminology is critical

Best practices for communicating about chemical substances are echoed by OECD: be specific, be cautious with generalizations, and be accurate. Table 1 (OECD, 2021) shows the pitfalls of ambiguity and provides examples of good practices with PFAS terminology. The OECD report also provides a diagram (Figure 11) tiered from general to specific that offers advice on when to use different levels of specificity and examples of best terms. The report refers its readers to Buck et al (2011), Barzen-Hanson (2017), CAS Registry, and other reports. As a best practice, it is recommended that, for clarity, when authors desire to leverage acronyms that the full name should be used with the acronym in the first instance.

Beyond chemical names, the importance of leveraging chemical identifiers is discussed. Specifically, the OECD report recommends that chemical identifiers including the CAS Registry Number, InChI (or InChIKey), or SMILES are presented along with the name. The usage of these identifiers, in combination with the chemical name and any relevant (and defined) acronyms, allows for additional review and confirmation of the chemical structure. For substances where a full structural representation is not possible, such as substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs), an identifier may provide additional clarity on the substance identity.

OECD’s Planned future work

As regulatory frameworks for PFAS around the world increase, the importance of consistently identifying and classifying PFAS substances becomes more critical. The OECD report identifies and proposes four areas for future work to support PFAS communication. Two areas specifically involve nomenclature and cheminformatics software for characterization of PFAS substances. These two areas could potentially assist with harmonization of naming and classifying PFAS substances. The other two areas broaden the scope to re-evaluate the OECD definition of polymer and to review terminology for non-PFAS fluorinated aromatic compounds.

Related IUPAC Nomenclature resources

Nomenclature and terminology can certainly be a challenge, but they are critical to successful communication. The OECD report stresses the importance of the chemical structure in identifying classifications and chemical names. The IUPAC Blue Book (formally Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013) and the Brief Guide to the Nomenclature of Organic Chemistry can assist in determining correct IUPAC naming conventions for specific organic small molecules, including some PFAS substances (see https://iupac.org/what-we-do/books/bluebook/). As more regulations around PFAS are developed and enacted, nomenclature and terminology will continue to be vital.

https://www.oecd.org/env/ehs/risk-management/

References

· Barzen-Hanson, Krista A., et al. 2017 “Discovery of 40 Classes of Per- and Polyfluoroalkyl Substances in Historical Aqueous Film-Forming Foams (AFFFs) and AFFF-Impacted Groundwater.” Environmental Science and Techology 51(4): 2047-2057.10.1021/acs.est.6b05843Search in Google Scholar PubMed

· Buck, Robert C, et al. 2011. “Perfluoroalkyl and polyfluoroalkyl substances in the environment: Terminology, classification, and origins.” Integrated Environmental Assessment and Management 7(4): 513-541.10.1002/ieam.258Search in Google Scholar PubMed PubMed Central

· ECHA, 2021. Perfluoroalkyl chemicals (PFAS). October 4, 2021. https://echa.europa.eu/hot-topics/perfluoroalkyl-chemicals-pfas.Search in Google Scholar

· *OECD, 2021. Reconciling Terminology of the Universe of Per- and Polyfluoroalkyl Substances: Recommendations and Practical Guidance. OECD Series on Risk Management, No. 61, Paris: OECD Publishing; online as https://www.oecd.org/chemicalsafety/portal-perfluorinated-chemicals/terminology-per-and-polyfluoroalkyl-substances.pdfSearch in Google Scholar

· U.S. EPA (Environmental Protection Agency), 2021. Basic Information on PFAS. October 4, 2021. https://www.epa.gov/pfas/basic-information-pfas.Search in Google Scholar

Online erschienen: 2022-04-14

Erschienen im Druck: 2022-04-01

©2022 IUPAC & De Gruyter. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. For more information, please visit: http://creativecommons.org/licenses/by-nc-nd/4.0/

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https://doi.org/10.1515/ci-2022-0226