Nanoplastics at the Science-Policy Interface: Strengthening the Evidence Base for Decision-Making

Abstract Despite a rapid expansion of research on nanoplastics, substantial scientific gaps continue to limit the reliability and policy relevance of the available evidence on their hazards and exposure. Much of the existing literature is constrained by inconsistent terminology, insufficiently validated analytical methods, and uncertain biological relevance, reducing its utility for robust risk assessment and regulatory decision-making. While these challenges are increasingly recognized, current research practices and incentive structures often favor continued data generation over the resolution of foundational methodological and interpretative limitations. As a result, scientific narratives surrounding nanoplastics have, in some cases, advanced more rapidly than the supporting evidence, contributing to uncertainty in exposure characterization, toxicological inference, and health relevance. This Perspective critically examines the roots of these uncertainties, with particular attention to definitional ambiguity, analytical constraints, surrogate use, and the translation of emerging findings into policy-relevant claims. Rather than presenting new empirical data, we assess how structural weaknesses in the current evidence base affect scientific credibility, public trust, and regulatory interpretation. We highlight recent methodological progress in the field while identifying the remaining barriers that prevent its effective consolidation for risk assessment purposes. Finally, we outline pragmatic directions for strengthening the science-policy interface, emphasizing uncertainty-aware regulatory approaches, operational definitions linked to analytical capability, and transparent communication as prerequisites for proportionate and defensible policy action on nanoplastics, with the aim of providing a critical yet constructive synthesis to help move the field forward and better support decision-makers.