Investigation of inter-subject variation in ultrafine particle deposition across human nasal airways: A study involving children, adults, and the elderly

The airflow and particle dynamics in adult nasal airways have been extensively investigated, but the impact of age-related anatomical changes in children and the elderly remains underexplored. This study systematically investigates age-related anatomical variations and associated influence on nasal airflow dynamics and ultrafine particle deposition characteristics by using Computational Fluid-Particle Dynamics (CFPD) approach. Numerical simulations were conducted for 9 healthy nasal subjects spanning a wide age range. 6 Nasal subjects from the Development Group were used as the primary models for data analysis and deposition correlation development, while 3 subjects from the Validation Group were used to validate the reliability of the derived total and subregional deposition correlations. Our results reveal distinctive variations across age groups. Specifically, the elderly and children exhibit unique patterns that differ from those of young adults. While total deposition efficiency differs significantly between children and adults, filtration efficiency in the subregion with most deposition, main respiratory, remains consistent. Lastly, overall and subregional empirical equations for deposition efficiency were developed by incorporating the combined diffusion parameter, Sc^a∆^b, corroborating the use of geometrical characteristic parameters for each specific subject in predicting nasal deposition efficiency across different age groups. Our findings are expected to improve the predictive nanoparticle exposure analysis in nasal airways across different age groups, thereby improving the respiratory health for individuals throughout the life span.