A numerical study on airflow and particle transport characteristics of subjects with cement dust exposure

Exposure to cement dust can cause respiratory problems and structural changes in respiratory airways. Computed tomography (CT) has shown that the airways of individuals with cement dust exposure (CDE) exhibit narrowing, wall thickening, and altered bifurcation angles. This study aimed to investigate the differences in airflow structure and particle transport between individuals with CDE and those with non-cement dust exposure (NCDE). To this end, computational fluid dynamics and Lagrangian particle tracking specialized for the respiratory system were employed, and two particle models representing cement dust and microdust were established. To construct three-dimensional airway models, CT images were obtained from four subjects with CDE and four with NCDE. Physiologically accurate small airways were virtually established to explore the flow structures in CT-unresolved regions. Subjects with NCDE showed higher wall shear stress and pressure drops in the lower lobes than in the upper lobes of the lungs. Conversely, subjects with CDE showed higher wall shear stress and pressure drops in the upper lobes than in the lower lobes. Furthermore, the narrowed airways of subjects with CDE caused strong dissipation, turbulence, and secondary flows, exacerbating the deposition of cement dust in the corresponding regions. However, the microdust model showed consistently low deposition fractions in all airway models, indicating deep penetration into the lungs, regardless of respiratory health. Thus, CDE alters the airway structure and parenchymal function, which further affects fluid dynamics and particle deposition characteristics. This study elucidates the fluid flow and particle deposition patterns within airways narrowed by CDE.