Modelling the deposition of fine particulate matter (PM2.5) in the human respiratory tract
Robert Sturm
Abstract
Background: Fine particulate matter (PM 2.5 ), which is primarily produced in traffic-loaded urban areas, may represent a considerable health hazard, when it is permanently taken up by inhalation. According to the pneumological research this particulate material is characterized by high inhalability on the one hand and the ability of enhanced accumulation in peripheral lung regions on the other. In the present contribution, deposition of fine dust particles in the human respiratory tract of probands with different ages is subject to a detailed theoretical description. Methods: Theoretical simulations of particle deposition were carried out by assuming (I) a stochastic architecture of the human lung, (II) a random transport of inhaled particles in this specific structure, and (III) the effect of well-defined deposition mechanisms (inertial impaction, interception, sedimentation, Brownian motion). Particles were assigned to five size categories (0.1, 0.5, 1.0, 1.5, and 2.0 µm) and additionally interpreted as objects with mostly irregular geometry. Inhalation of particulate matter was supposed to take place under sitting breathing conditions (uptake through the nasal airways). Results: According to the results provided by the mathematical model total deposition of variably sized particles ranges from 8.5% to 68.4%. Thereby, extrathoracic particle accumulation commonly adopts values ranging from 4.8% to 46.7%, whereas tubular (i.e., bronchial, bronchiolar, alveolar-ductal) accumulation amounts to 2.8% to 12.1%. Alveolar deposition usually varies between 1.0% and 6.5%. With regard to generation-by-generation deposition, highest concentration of deposited particulate mass can be computed for central to peripheral airway generations. Conclusions: Based on the theoretical results presented in this contribution it can be concluded that fine particulate matter indeed plays a significant role in pulmonology. Depending on its main deposition site in the respiratory tract, it may act as trigger for a multitude of lung diseases, for what reason it will stand in the focus of future medical research.