Twenty years since coming into force, the Stockholm Convention has become a “living” global agreement that has allowed for the addition of substances that are likely, as a result of their long-range environmental transport (LRET), to lead to significant adverse effects. The recent listing of the phenolic benzotriazole UV-328 in Annex A and a draft nomination of three cyclic volatile methylsiloxanes (cVMS) for Annex B draw attention to the fact that many chemicals are subject to LRET and that this can lead to questionable nominations. The nomination of UV-328 and the draft nomination of cVMS also raise the spectre of regrettable substitutions. At the same time, atmospheric monitoring across the globe reveals that environmental releases of several unintentionally produced POPs listed in Annex C, such as hexachlorobenzene and hexachlorobutadiene, are continuing unabated, highlighting shortcomings in the enforcement of the minimum measures required under Article 5. There is also no evidence of efforts to substitute a chemical whose use has been known for three decades to unintentionally produce polychlorinated biphenyls. These developments need to be rectified to safeguard the long-term viability and acceptance of a global treaty of undeniable importance.