Inhaled aerosol dosimetry update.

Abstract

To evaluate recent advances and current challenges in inhaled aerosol dosimetry research, with a focus on understanding how particles affect human health through deposited doses, and to identify key research needs for improving exposure assessment and risk evaluation. The findings were based on discussions and presentations from the Fourth International Aerosol Dosimetry Conference held in 2024 in Irvine, California. The conference used plenary sessions to promote cross-disciplinary communication and collaboration. Topics included computational models and simulations, in vitro and in vivo aerosol exposure systems, and variability in inhaled aerosol deposition. State-of-the-art research was presented, followed by open discussions to identify knowledge gaps and future priorities. Significant advances were reported in computational modeling, particularly in integrating different model types to better represent all major regions of the respiratory tract. Improvements in in vitro exposure systems enhanced particle delivery, dose measurement, and applicability to human health studies. Research also highlighted the importance of the upper airways as entry routes for inhaled medications. Dose variability emerged as a critical issue across aerosol dosimetry studies. New findings showed that inhaled ultrafine particles may acquire surface coatings after deposition and can penetrate tissues, including fetal tissues. Standardization and validation of in vitro approaches were identified as essential steps for reducing reliance on animal testing and improving human risk assessment. Internal aerosol dosimetry research continues to advance through improved models, exposure systems, and mechanistic understanding of deposited particle behavior. However, addressing dose variability, standardizing alternative testing methods, and improving data sharing remain essential for advancing risk assessment and supporting more accurate evaluations of inhaled particle effects on human health.