When a Trace Becomes an Ingredient · The FDA's 2026 Threshold-of-Regulation Proposal and the Scientific Limits of Exposure-Based Food Authorisation

An August 2026 U.S. Food and Drug Administration proposal, brought into renewed public debate on 10 October, would extend the Threshold of Regulation (TOR) exemption from substances migrating out of food-contact materials to substances added directly to food. It would also replace a diet-wide concentration benchmark with a body-weight-adjusted exposure threshold. The change is embedded within a separate proposal to require notifications for uses claimed to be generally recognised as safe (GRAS). These measures are neither final nor equivalent to unrestricted ingredient approval. Yet their interaction raises an important question: can an exposure-based exemption designed for incidental migration be applied coherently to intentional technological use? This article distinguishes the proposed legal mechanism from claims made in public debate, examines the toxicological limitations of generic thresholds, compares EU and British positive-list authorisation systems, and develops a proposed Exposure–Function Evidence Matrix. The research agenda focuses on cumulative exposure, susceptible populations, analytical verification and the boundary between risk-based prioritisation and market permission.