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ANALYSIS AND MODELING OF TARGET SITE DOSE OF HETEROGENEOUS AMBIENT PARTICLES: DEVELOPMENT OF COMPREHENSIVE MATHEMATICAL MODELS FOR RESPIRATORY DEPOSITION OF INHALED PARTICLES
Impact/Purpose:
The goal of this project is to develop empirical exposure-dose models based on extensive human data collected in EPA and to refine mathematical models such that specific dose at the target sites in the human respiratory airways can be accurately predicted for heterogeneous ambient aerosols with different size particles and chemical components.
Description:
Ambient PM is composed of various particles with different sizes and chemical components. Although health effects of PM appear to be different for different size particles, it is not clear what size fractions are more potent in causing health effects or if such a distinction is consistent in time and space. Detailed dosimetry studies are necessary to provide insights into the questions associated with heterogeneous ambient PM. Human experimental data will be compiled for total respiratory and regional deposition in the lungs of healthy individuals and analyzed with respect to particle size and inhalation mode. Sensitivity analysis will be conducted for each of the factors affecting lung deposition and a universal composite parameter will be identified to consolidate all experimental data as a single empirical function. The analysis will include personal information (age, sex and height) and inhalation conditions (breathing pattern and duration). Empirical model will provide a convenient means of estimating lung deposition dose of specific size particles under various inhalation conditions and also will serve as the basis of validating mathematical models to be developed. Mathematical models will be developed initially based on Weibel’s lung morphology of healthy adult humans. Morphologic variations will be imposed later to accommodate for certain types of abnormality associated with respiratory disease. The model will use mass transport equations during continuous breathing and a complete size distribution will be used for the input aerosol. Thus detailed deposition dose will be calculated for realistic ambient aerosols including bimodal aerosols. The model will predict deposition dose of specific size fractions such as ultrafine, fine and coarse fractions or any size fractions of interest. Chemical composition of specific size fractions will be incorporated with the input aerosols and the dose can be calculated for specific chemical components.