This dataset corresponds to the research aim: To co-create a Design for Substance Safety (DSS) method with and for design professionals. The DSS Method allows product designers to mitigate the risks generated by hazardous substances throughout the lifecycle of products. Through the sessions, we identified procedural and functional requirements, contextual factors influencing the method's successful application, and actionable insights to produce and refine the new method framework. The resulting DSS Method provides a systematic, lifecycle-oriented approach for addressing SoC across various design scenarios.We conducted two co-creation sessions with three groups of professional designers (six sessions in total) during the months of November and December 2023. Each of the three groups consisted of 2-3 professional designers (total of 6-8 people). The participants were experienced designers (>3 years) working at design agencies in the Netherlands. Experience with circular economy or sustainability was not a requirement. All participants signed an informed consent …