The final section, "Regulatory PFAS collections" was added upon interactions with Andreas Buser from the Federal Office of the Environment (FOEN), Switzerland (see acknowledgements) to support regulatory PFAS efforts. As shown in Figure , inset bottom right, regulation surrounding four cases are covered: long-chain perfluorocarboxylic acids (LC-PFCAs), perfluorohexane sulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and the related substances for all cases. The fifth section deals with exclusions from the PFOA cases, which are separated to avoid "exclusions" being added to the PFOA category totals. Each section is constructed according to definitions from regulatory efforts such as the Stockholm Convention 32 , European Union (EU) Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) and EU Environmental Chemicals Agency (ECHA) . The sections include several lists published with these definitions, as well as various PubChem queries to find matching content in PubChem according to the definitions. Exact details of the PubChem queries are in the respective tool tips (obtained by clicking the "?" next to each heading) and in the documentation . For the LC-PFCAs, the definitions came from reports UNEP/POPS/POPRC.17/7 and UNEP/POPS/POPRC.18/6/Add.1 as well as EU Regulation 2021/1297 , with an indicative list from report UNEP/POPS/POPRC.18/INF/14 . For PFHxS the definitions came from UNEP/POPS/COP.10/CRP.10 39 and a draft ECHA report , while the initial indicative list came from UNEP/POPS/POPRC.15/INF/9 . The definition for PFOA came from Annex A of the Stockholm Convention (2019 revision) , while the initial, updated and exclusions from the PFOA lists were taken from UNEP/POPS/POPRC.17/INF/14/Rev.1 . Finally, the PFOS definition and PFOS listing was taken from Annex B of the Stockholm Convention . The motivation and methods behind these efforts are described further in the documentation , as well as in a presentation at POPRC.18 and a webinar .