Redefining Photoinitiator Risk Prioritization by Bridging Environmental Fate and Human Internal Exposure

This study integrates settled indoor dust measurements from multiple functional microenvironments with urinary biomonitoring of corresponding populations to characterize indoor exposure pathway, emission behavior, and internal burdens of photoinitiators (PIs). Total PI concentrations in settled dust exhibited pronounced differences across functional microenvironmental differences, decreasing in the order dormitories (geometric mean (GM): 617 ng/g) > offices (GM: 471 ng/g) ≈ residences (GM: 463 ng/g) ≫ background matrices (GM: 22.6 ng/g). Chamber emission experiments demonstrated that, despite substantial material-specific variability in gas-phase concentrations, adsorbed-phase PI levels converged across materials, suggesting that dust-associated adsorption effectively buffers. Human biomonitoring revealed compound-specific internal exposure patterns that were closely aligned with functional microenvironments. Benzil exhibited consistently elevated urinary concentrations (GM up to 1.50 × 103 ng/mL), whereas ethyl-4-dimethylaminobenzoate (EAB) predominantly characterized office- and dormitory-associated populations. Integration of environmental fate with human internal exposure enabled a dual-dimensional prioritization, identifying 2-ITX as the sole high-priority compound across all scenarios. Reliance on environmental data alone would underestimate the risk of Benzil due to its high internal burden, while overestimating the risk of PI-819, which shows high environmental prominence but negligible internal exposure. Collectively, these findings indicate that, for PIs widely used as green alternatives in UV-curable applications, health-relevant prioritization requires the joint consideration of external contamination and internal metabolic processes.