The long-term objective of this study is to better understand the fate of inhaled particulate matter (PM) in the human lung. This is important whether PM exposure results from atmospheric pollution, biological warfare, and occupational factors or inhaled drug therapy. More and more evidence links the presence of fine PM in the air with cardiopulmonary diseases. This PM is of great concern because it can penetrate deep into the acinus. To date, the most realistic model of the human acinus consists of a multi-bifurcation structure of two-dimensional alveolated ducts (AD). In the present study we will develop three-dimensional acinar models of children and adult lung with a high degree of anatomical realism. A first type of model will consist of a single bifurcation of AD with rigid walls. A second type of model will address the effects of alveolar wall motions during breathing and will form a realistic structure of up to four successive bifurcations. This will be the most comprehensive acinar models yet developed. PM transport and deposition (DE) will be simulated for particle diameters (dp) ranging 0.005-5 (m and for flow rates ranging from quiet breathing to moderate exercise. For 0.5
