On 1 June 2022, the European Commission’s DG Environment organised an information session on the “1 substance, 1 assessment” (1S1A) initiative, which is part of the CSS (Chemicals Strategy for Sustainability), one of the components of the Green Deal. The aim was to inform stakeholders and citizens of the objectives and actions already undertaken and to be undertaken in this framework. This dossier brings together the reports of all the sessions of this day, as well as the question and answer sessions that followed them.