Deposition of aerosol particles in human lungs: in vivo measurement and modelling.

The deposition dose and site of inhaled particles within the lung are the key determinants in health risk assessment of particulate pollutants. Accurate dose estimation, however, is a formidable task because aerosol transport and deposition in the lung are governed by many factors whose precise workings are often not fully understood. In vivo human data obtained under controlled environment are most important and provide the primary basis of estimating lung doses. The existing database, however, is not sufficient to cover widely varying exposure conditions encountered during daily activities. Mathematical models thus are used to fill the gap or to extend the range of experimental data and are further used as a tool for analysing the exposure-dose relationship under varying inhalation conditions. In this report we briefly review and discuss our recent studies of in vivo measurement of inhaled particles in normal subjects, subsequent analysis of the data for empirical modelling and an improved mathematical model that can be used for a wide range of applications.