Multispecies aerosol evolution and deposition in a human respiratory tract cast model

Authored by  M Asgari, F Lucci, A Kuczaj

Published in Toxicology Letters    

Accurate predictions of aerosol transport, evolution, and deposition in the human airways are crucial for inhalation dosimetry investigations. Inhaled aerosol transported through the airways undergoes thermodynamic changes due to changes in temperature and humidity. Aerosol evolution processes are particularly important for liquid multispecies aerosols. These aerosols are sensitive to condensation and/or evaporation dynamics, which can modify gas/liquid partitioning of each species and particle size distribution. In this manuscript, we present computational fluid dynamics simulations of complex aerosol mixtures in a realistic geometry of the human respiratory tract cast model. We used a publicly available computational framework, AeroSolved, developed for simulation of evolving multispecies aerosol mixtures. We evaluated the dynamics of liquid particles in physiologically relevant conditions of 100% relative humidity at the temperature of 37°C. We studied two separate inhalation flow scenarios: in the first case, a warm aerosol at 50°C was inhaled and subsequently cooled down while flowing in the airways. In the second case, an aerosol at room temperature was inhaled and heated up to the temperature of  37°C. Our results demonstrated that aerosol evolution mainly occurs in the upper segments of the airways (throat and trachea) at the very short timescales. Apart from showing the significant influence of temperature and humidity conditions on aerosol dynamics and evolution, we also measured aerosol deposition fluxes investigating the dependence of the delivered aerosol mass on evolution mechanisms. We showed that the delivered regional mass of each species depends on the physico-chemical properties of the mixture, and it is also significantly influenced by the airways’ humidity and thermal conditions. It was also shown that the species-specific properties of the liquid mixture (e.g., activity coefficient) play an important role in gas/liquid partitioning of the species. With AeroSolved such dependencies can be further investigated with greater attention towards specific needs and physiologically important conditions (e.g., transient flow inhalation patterns, aerosol mixture composition and its properties).