While early research efforts focused mainly on a very limited list of PFAS, the number 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 non-target analytical techniques , more extensive lists of PFAS became available. The first PFAS list hosted by the NORMAN Suspect List Exchange (hereafter NORMAN-SLE) was the 2015 list contributed by Trier et al. , which became the basis for the OECD list of ~4700 PFAS released in 2017 . The NORMAN-SLE currently (June 2023) contains twelve PFAS lists . The United States Environmental Protection Agency (US EPA) CompTox Chemistry Dashboard 11 also hosts chemical lists and presently (June 2023) hosts 424 lists, including 51 lists matching the PFAS search term , of which 41 contain exclusively fluorinated content. The National Institute of Standards and Technology (NIST) recently coordinated a list (hereafter the "NIST PFAS Suspect List") of 4,948 entries, including expanded homologues and expert contributions . Several other research efforts describe PFAS lists, with various degrees of availability. The OECD PFAS collection of ~4700 PFAS and the US EPA PFASMASTER list (~10,000 PFAS in 2020, currently 12,034 entries in June 2023) 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 polymer and substances of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs) . A recent effort with Google and OntoChem investigated the influence of PFAS definition on the number of PFAS extracted from literature (CORE repository) and patents (Google Patent set), resulting in PFAS lists of between 3,457 (CORE, Buck et al. definition) and 1,783,651 (Patent set, 2021 OECD PFAS 3 definition) discrete chemicals . At the time, over 200,000 of these PFAS were not in PubChem , one of the largest open chemistry databases, but were deposited soon thereafter .