Passive sampling of chemical targets in wastewater-based epidemiology: Promise, pitfalls and pathway forward

Wastewater-based epidemiology (WBE) is an increasingly important approach for assessing community exposure to pharmaceuticals, illicit drugs, and biomarkers, yet its reliance on autosamplers limits spatial and temporal coverage due to high cost, maintenance, and infrastructure demands. Passive sampling (PS) offers a power-free, time-integrated alternative for monitoring polar organic contaminants in complex wastewater matrices. This review examines the performance of adsorption- and diffusion-based PS devices, emphasizing how calibration, biofouling, and sorbent-analyte interactions govern quantitative reliability. In situ calibration remains essential for robust uptake estimates, while ion-exchange and mixed-mode sorbents provide enhanced selectivity and broader analyte coverage. Beyond targeted screening, PS enables semi-quantitative, non-targeted analyses through high-resolution mass spectrometry, expanding its analytical scope. Rather than replacing autosamplers, PS should be viewed as a complementary technology capable of improving spatial and temporal resolution in WBE. Ongoing innovations in design, calibration, and data interpretation will shape its integration into future wastewater surveillance frameworks. • Review of 23 studies using passive samplers in wastewater-based epidemiology. • Compared adsorption, gel diffusion, and passive diffusion mechanisms. • Identified challenges for calibration, biofouling, and sorbent selectivity. • Outlook: hybrid calibration, ion-exchange resins, and HRMS non-target tools.