The final node in the PubChem PFAS Tree, "Regulatory PFAS collections" allows users to investigate several aspects of PFAS regulation, including the impact of different wording in definitions under consideration on the number of compounds potentially covered by the regulation. The following paragraphs cover the different cases one by one. Further details on how to perform the search queries, overlaps, downloads and other functions mentioned below can be found in the tooltips, documentation and webinar .