A system boundary in the context of sustainability assessments defines the limits of what is included and excluded in the analysis of a system, product, or process. It determines which stages, processes, flows, and impacts are considered within the scope of the evaluation. For PFAS treatment technologies, clearly defining these boundaries is essential to capture the comprehensive environmental, economic, and social implications associated with each technology. The persistent nature of PFAS necessitates a thorough consideration of the fate of these substances across different treatment methods, yet current literature often overlooks this aspect. Most of the existing studies have defined their system boundaries around the removal of PFAS, with limited attention given to the ultimate destruction of these compounds (e.g., incineration ). This omission is significant, as the destruction phase can entail considerable environmental, economic, and social costs that are not accounted for in current assessments.