Advancements in aerosol dosimetry modeling
D. Broday, P. Kevrekidis, P.G. Georgopoulos (EOHSI, UMDNJ - R.W. Johnson Medical School and Rutgers University)
MENTOR-OPERAS provide a set of novel, mechanistically-based, modeling tools for fine airborne particle inhalation dosimetry calculations. These tools are designed to maintain consistency with the physical and chemical attributes considered in the environmental and microenvironmental components of the integrated MENTOR framework. Thus, modeled particles can have properties that (a) reflect real-world conditions (variable size, chemical composition, shape, hygroscopicity, electrical charge, etc.) and (b) affect their interactions with environmental, microenvironmental, and physiological (specifically the human respiratory tract) systems.
Two complementary types of modeling approaches are used in MENTOR-OPERAS: (1) Macromodeling, where the aerosol general dynamic equation (GDE), with terms accounting for growth, transport, and deposition, is solved numerically to track the evolution of the size distribution and composition of the inhaled aerosol along the successive generations of an idealized human lung model, and (2) micromodeling, which utilizes a Computational Fluid Dynamics (CFD) type of approach to study individual particle trajectories (as affected by inertial impaction, gravitational sedimentation, diffusional deposition, electric charge, etc.) in a single tracheobronchial bifurcation of the human airways.
In the case studies presented here, the CFD micromodel is used to study the relative importance of different physical processes in local lung deposition phenomena, whereas the GDE macromodel is used to study effects of chemical composition and particle hygroscopicity on delivered dose. Here the macromodel employs discretized bimodal lognormal distributions for the initial particle number and mass distributions, where each mode can have different initial physicochemical properties (chemical composition and thermodynamic state). The simulation results reveal the significance of the initial parameters of the size distribution, the particle composition, and the thermodynamic state for lung dosimetry calculations.