A numerical study on sedimentation effect of dust, smoke and traffic particle deposition in a realistic human lung

Inhalation of pollutants can be deadly for respiratory health, as toxic pollutants can penetrate the deep lungs which could occur severe respiratory infection and lead to life-threatening respiratory diseases. The excessive presence of pollutants in the environment increases the concern of potential respiratory health hazards. To date, a microscopic understanding of the sedimentation effect on dust, smoke and traffic (pollutant) particles transported to the airways is missing in the literature. This first-ever study aims to analyse the sedimentation effect in various directions of pollutant particle transport in airways. This study also quantitatively explains how particle size, density, and physical exercise impact pollutant particle transport and deposition (TD) in the human lung airways. The contribution of the sedimentation effect is largely independent of particle size. The sedimentation effect can also be found significant at the trachea region when the fluid flow is horizontal. Overall, traffic particles with large diameters and high flow rates are deposited in the upper lung, whereas dust particles with large diameters and high flow rates are deposited in the deep lung. It is expected that 79.1 % of the particles will reach the deep lung. The difference between the deposition rates of the horizontal and vertical lungs reduces if the particle size reduces, the flow rate increases or the particle density reduces. The deposition rate of a horizontal lung for the heaviest particles (traffic) at 15 L/min flow rate is about 4.5 % higher than that of a vertical lung with the same flow rate.