There are 7 million distinct PFAS registered in a chemical database.

[NNadir]

Last edited Fri Nov 10, 2023, 04:34 PM - Edit history (1)

The paper to which I'll briefly refer is this one: Per- and Polyfluoroalkyl Substances (PFAS) in PubChem: 7 Million and Growing
Emma L. Schymanski, Jian Zhang, Paul A. Thiessen, Parviel Chirsir, Todor Kondic, and Evan E. Bolton Environmental Science & Technology 2023 57 (44), 16918-16928

The full paper is available for the public to read for free, a gift from the American Chemical Society.

Nonetheless, some excerpts are in order. From the introduction:

Per- and polyfluoroalkyl substances (PFAS) are a group of substances of such high environmental, health, and toxicological concern that there is now a drive to treat PFAS as a class for environmental regulation. (1) The 2011 definition of PFAS by Buck et al. (2) included substances as PFAS if they contained two (or more) connected saturated CF2 groups. In 2021, the Organisation for Economic Co-operation and Development (OECD) revised the definition of PFAS in ENV/CBC/MONO(2021)25 (3) as follows: “PFAS are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (?CF3) or a perfluorinated methylene group( ?CF2? ) is a PFAS.”

While early research efforts focused mainly on a very limited list of PFAS, the numbers of documented PFAS are increasing. With the emergence of high-resolution mass spectrometry (HRMS) and the potential for so-called “suspect screening” for contaminants of interest using nontarget analytical techniques, (4,5) more extensive lists of PFAS became available. The first PFAS list hosted by the NORMAN Suspect List Exchange (6,7) (hereafter NORMAN-SLE) was the 2015 list contributed by Trier et al., (8) which became the basis for the OECD list of ?4700 PFAS released in 2017. (9,10) The NORMAN-SLE currently (September 2023) contains 12 PFAS lists. (6,7) The United States Environmental Protection Agency (US EPA) CompTox Chemistry Dashboard (11) also hosts chemical lists (12) and presently (September 2023) hosts 424 lists, including 51 lists matching the PFAS search term, (13,14) 41 of which contain exclusively fluorinated content. The National Institute of Standards and Technology (NIST) recently coordinated a list (hereafter the “NIST PFAS Suspect List”) of 4948 entries, including expanded homologues and expert contributions. (15) Several other research efforts have described PFAS lists with various degrees of availability. The OECD PFAS collection of ?4700 PFAS (9,10) and the US EPA PFASMASTER list (?10000 PFAS in 2020, currently 12034 entries in September 2023) (16) are two of the most frequently used PFAS lists in suspect screening. Both lists also contain entries that are not discrete chemicals, i.e., they also include polymers and substances of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs). (17) A recent effort with Google and OntoChem investigated the influence of PFAS definition on the number of PFAS extracted from the literature (CORE repository) and patents (Google Patent set), resulting in PFAS lists of between 3457 (CORE, Buck et al. (2) definition) and 1783651 (Patent set, 2021 OECD PFAS (3) definition) discrete chemicals. (18) At the time, over 200000 of these PFAS were not in PubChem, (19,20) one of the largest open chemistry databases, but were deposited soon thereafter... (18)

...While integrating the NORMAN-SLE content into PubChem, (6) it became clear that the number of chemicals within PubChem (116 million chemicals, September 2023) that could satisfy the 2021 OECD PFAS definition dwarfed the several thousand entries in the common PFAS suspect lists. A simple substructure search for “CF2” revealed millions of potential matches in PubChem. Since new PFAS are emerging very rapidly, the need for a manageable, relevant, rapidly updateable open collection of PFAS for the community is increasingly obvious. This article describes efforts to develop an interactive, open, dynamic, and browsable collection of PFAS content in PubChem to serve this purpose...

A graphic from the paper:



The caption:

Figure 1. PFAS and Fluorinated Compounds in PubChem collection showing the six top nodes and the first layer of subnodes; collection available at https://pubchem-ncbi-nlm-nih-gov.proxy.libraries.rutgers.edu/classification/#hid=120. Image created September 16, 2023.

On the basis of this information, I would submit that we need a generic way to break the very strong carbon-fluorine bond.

Have a nice weekend.

On edit: The graphic in this post originally was from another post I wrote on DU about PFAS. This has been corrected.

Also there were changes in the text to accommodate for the fact that DU4 does not import full character sets as of yet.

[oldfart73]

1. Seven million - unimaginable. Just cannot avoid them in our daily living.

[NNadir]

2. Every living thing on this planet has detectable levels of PFAS in its tissues. This obviously includes humans.

It's a big problem.