Hazardous substances, or substances of concern (SoC), are present in numerous products and may be the source of significant risks to human health and the environment. In addition, the presence of SoC in products challenges the transition towards a circular economy. By implementing strategies such as reuse or recycling, SoC can be reintroduced in subsequent lifecycles, generating new forms of risk. Addressing SoC in the early stages of the product development process is necessary to mitigate the hazards and risks they may present throughout multiple lifecycles. Product designers hence need appropriate tools and methods to address SoC in products. However, we have observed that current research primarily focuses on the development of non-toxic chemical alternatives and approaches that mitigate the risks of SoC at a chemical and material level (i.e., substitution), lacking the necessary holistic approach to avoid trade-offs or unforeseen consequences. Available design specific methods, tools, and information to address SoC in products are extremely limited and have too a material focus. To address this, we investigated five cases to understand how SoC were dealt with across the product lifecycle and identify mitigation interventions used. We then analyzed the interventions and classified them into five levels of influence, i.e., chemical, material, component, product, and system, and evaluated their respective implications for design, advantages, and drawbacks. Our analysis results in three groups of mitigation strategies that are specifically relevant to product design: Avoid, which entails any modification to the product that eliminates the SoC, Control, in which the SoC remains in use, but its emissions are prevented, and Reduce, which includes any modification that results in the reduction of the volume of the SoC or its emissions. Our findings establish the potential contribution of designers in the mitigation SoC in products and constitute a basis for the development of methods or guidelines to address SoC from a product design perspective.