Interpreting the Microplastics Intake-Detection Gap in Human Biomonitoring

Reports of microplastics (MPs) in human blood and tissues have intensified interest in the relationship between external exposure and internal measurements. This area of research remains poorly understood, with no clear resolution, as the current biomonitoring data still lack a quantitative linkage to environmental sources that could support risk-relevant interpretation. Here, we employ an illustrative pipeline spanning exposure synthesis, probabilistic intake modeling, compositional fingerprinting, and pharmacokinetic compatibility mapping to clarify what existing evidence can and cannot support. While the available data permit an uncertainty-aware assessment of numerical and compositional plausibility, they fall short of enabling mechanistic attribution or reliable pathway ranking. The limitations stem from nonaligned size domains, pervasive analytical heterogeneity, and unresolved toxicokinetic parameters that make inverse modeling nonidentifiable, given current evidence. We therefore argue that the field must move beyond detection and propose a coordinated roadmap centered on size-resolved methodological harmonization, human-relevant kinetic constraints, paired-matrix designs, uncertainty-explicit reporting, and open, interoperable data infrastructure. Resolving the intake-detection gap is essential to transition from a catalog of detections to interpretable internal measurements that can credibly inform exposure-reduction priorities and risk-relevant research without making premature causal or toxicological claims. Our diagnostic approach is intended as an interim interpretability check pending improved toxicokinetic parametrization and the development of multimetric biomonitoring.