Boundaries, Limits, Global Threats - How Can the Impacts of Global Synthetic Pollutants Be Reduced?

The planetary-scale risks posed by "chemicals of global concern" have deep historical roots that predate the literature on the Planetary Boundaries concept. Two largely separate scientific and regulatory tracks emerged from mid-20th-century research: an atmospheric track (exemplified by chlorofluorocarbons and stratospheric ozone depletion) and an aquatic-terrestrial/ecotoxicological track (exemplified by DDT, PCBs and other bioaccumulative organohalogens). Both tracks produced early warnings, scientific consensus, and eventual multilateral environmental agreements (the Montreal Protocol and Stockholm Convention). In this Perspective, we synthesize the historical evidence, link it to the planetary-boundaries and limits-to-growth narratives, highlight why chemical regulation repeatedly failed to prevent widespread contamination, and propose a set of pragmatic policy instruments, including targeted premarket controls such as the application of the Safe and Sustainable by Design framework, class-based phase-outs to speed up the removal of hazardous substances from the market, and global burden sharing to better manage planetary-scale chemical problems.