Assessing chemicals individually also ignores cumulative exposures and risks of groups of substances . Considering primarily the structural similarity and similar properties of PMT/vPvM substances, it may be more feasible and prudent to regulate these substances as a group. The idea of substance grouping based on the relationship between hazard and structural similarity is not new, since many of the very first organic substances to be regulated were groups sharing a similar structure. The successes of regulation in managing substances as groups such as ozonedepleting substances (ODS) under the Montreal Protocol and specific groups of persistent organic pollutants (POPs) under the Stockholm Convention are discussed below. Moreover, successfully grouping substances for regulation not only accelerates but also prevents and reduces inconsistencies in the regulatory process . Grouping substances can enhance chemical safety management, facilitating the identification of regulated substances and potential substitutes for harmful ones .