Redistribution of continuous airway exposure risk in polluted environments with high- to ultra-high-density dust particles: From nostrils to terminal bronchioles.

Dust particles are typical environmental pollutants. However, the characteristics of airway transportation and deposition of high/ultra-high-density dust remain understudied. In this study, a high-fidelity continuous airway model was constructed from the nostrils to the fine bronchiole ends based on real medical images. The deposition evolution and exposure risk redistribution of high- to ultra-high-density particles of various sizes were then investigated. The results demonstrated that: Particle size determined the spatial deposition pattern, while the deposition center migrated upward with increasing density. Particle deposition results from the coupling of mechanisms such as traditional inertial collision, secondary flow inertial effects, turbulent diffusion transport, and gravitational settling. Ultra-high density had different influences on the interception effect in different regions, and also differentially modulated the risk of bronchioles to particles of different sizes, especially the abnormal increase of PM2.5. These findings reveal the characteristics of deposition redistribution after inhaling high/ultra-high-density harmful dusts, helping clarify and control their risks to human health and the environment. They also provide a basis for further exploring associations between airway lesion locations and exposure preferences for specific particle sizes.