This study aims to investigate the physical properties of particles and their implications for source apportionment and health human exposure studies. A wide range of particle number size distribution (PNSD) measurements was conducted in selected environments using state-of-the-art high time resolution instruments. It is found that PNSD varied in different environments, depending on emission sources and atmospheric processes. A mass balance model was used to predict the penetration, infiltration factors, deposition and loss rates of indoor particles. The loss rates of indoor particles, which are mainly subject to deposition, coagulation and evaporation, were found to be a function of particle size and time. Moreover, HTDMA measurements were performed to study the hygroscopic properties of particles in outdoor and indoor environments, and from five major indoor sources. The particles emitted from indoor sources were mostly hydrophobic. An enhanced lung deposition model based on the ICRP and MPPD models was developed to predict the deposition fraction of particles in the human respiratory tract, with consideration of their hygroscopicity. Furthermore, a combination of lung deposition models and the PMF technique was applied to identify which sources are mostly responsible for deposited particles in the different regions of lung
