Detailed nanoparticle exposure analysis among human nasal cavities with distinct vestibule phenotypes

Despite human exposure to inhaled nanoparticles has been intensively studied, the effect of nasal cavity morphology on the distribution patterns of inhaled particles remains less investigated. This paper compared the total and regional deposition patterns of naturally inhaled nanoparticles among subjects with different vestibule phenotypes (non-notched, unilateral-notched and bilateral-notched vestibules). A sedentary breathing condition with constant flow rate was applied, and the nanoparticle inhalation and transport process were numerically simulated by a computational fluid-particle dynamics (CFPD) approach. The results showed nanoparticle exposure in the nasal cavities was closely associated with anatomical shapes, airflow dynamics, and particle diffusivity. Nanoparticle deposition in the upper passage and olfactory regions was considerably restricted due to the presence of a vestibule notch. However, for the main nasal passage, exposure patterns in all vestibule-notched subjects were similar without significant inter-chamber variations. This indicates the deposition in the main nasal passage was less sensitive to the upstream presence of a notch. This study advances the current understanding of nanoparticle exposure characteristics in human nasal passages with significant inter-subject variations, which play critical roles in assessing particle toxicology following inhalation.