Extrapolation Modeling of Aerosol Deposition in Human and Laboratory Rat Lungs

Abstract

Laboratory test animals are often used as surrogates in exposure studies to assess the potential threat to human health following inhalation of airborne contaminants. To aid in the interpretation and extrapolation of data to man, dosimetric considerations need to be addressed. Therefore, a mathematical model describing the behavior and fate of inhaled particulate matter within the respiratory tracts of man and rats has been developed. In the computer simulations, the CO₂ concentrations of inhalation exposure chamber atmospheres are controlled to produce desired breathing patterns in the rat that mimic human breathing patterns as functions of physical activity levels. The Soong et al. (1979) and Yeh et al. (1979) morphologies are used to describe human and rat lungs, respectively Deposition patterns are specifically examined as functions of respiratory intensities and particle parameters. The model is validated with laboratory data from rat inhalation exposure tests. The theoretical model provides a basis for the reevaluation of data from past experiments and, perhaps most importantly, permits new inhalation exposure tests to be designed and conducted in a sound scientific mannec The model has a function complementary to animal testing: specifically, to enhance the extrapolation of laboratory results to physiologically realistic human conditions.