The "PFOS and related substances" section is the simplest. It contains the original eight entries for "PFOS plus salts, isomers and PFOSF" listed in the Stockholm Convention Annex B and an extended listing of all content in PubChem matching the "PFOS plus salts, isomers and PFOSF" definition, currently 1,304 entries in total (first node appearing in this section, which can be expanded to see the contributing subsections/categories). This 1,304 comprises PFOS and branched isomers (18), PFOS, PFOSF and salts (239) and a merged PFOS and PFOSF substructure query to find all matching mixtures (1,291 CIDs). An additional section outlines compounds that transform to PFOS (under normal conditions, i.e., excluding advanced treatment transformations) that are in PubChem for information purposes, but these four entries are not included in the extended listing of "PFOS and related substances".