Inhalation and deposition characteristics of respiratory ultrafine and elongated mineral particles in the all-in-one human respiratory system: A CFD-based Study

Nano-sized particles and elongated mineral particles (EMPs) pose significant inhalation hazards in mineral extraction and processing, and are key contributors to pneumoconiosis, yet their inhalation risks remain inadequately characterized. In this study, a high-fidelity CFD-based modelling framework was developed to systematically investigate inhalation and deposition characteristics of ultrafine and EMPs in an all-in-one human airway model coupled with a breathing region. The size distribution and morphology of mineral dusts were first experimentally examined. A wide range of micro- and nano-sized spherical particles, together with elongated particles with varying aspect ratios, were then numerically simulated with various breathing rates using User-Defined Function. Their transport and deposition patterns were qualitatively visualized and deposition efficiency in total and regional airway areas was systematically evaluated. The outcomes revealed that in the upper airway, micro-sized particles 10 μ m exhibited high deposition (up to ∼ 80 % in the nasal cavity), while nanoparticles remained below 3% and insensitive to breathing rate. In contrast, nanoparticles showed enhanced deep lung penetration, with deposition up to ∼ 4 % in the trachea and individual lobes and ∼ 52 % reaching pulmonary regions. For EMPs, deposition was strongly morphology-dependent and non-monotonic. High-aspect-ratio particles ( β = 50 ) showed up to ∼ 20 % higher deposition in the nasal cavity compared to other β values, while moderate aspect ratio ( β = 5 ) yielded the highest deposition efficiency ( ∼ 7 % ) in the lower airway. This study is expected to highlight the necessity of explicitly accounting for nanoscale effects and particle morphology in assessing inhalation risks associated with mineral dust exposure.