Deposition of ultrafine aerosols in human tracheobronchial airways

Theoretical modeling of ultrafine particle deposition in human airways can be employed as a valuable complement to difficult and expensive in vitro and in vivo experimental studies. If such modeling can be shown to be reasonably accurate (compared with laboratory data), versatile (simulate different conditions), and compact (easy to use), it would then be warranted to use it for the extrapolation of theoretical results in risk assessment applications. In this study, a closed-form solution proposed by Martonen et al. (in press), which quantitatively describes convective particle diffusion in a conduit including wall irregularities and entrance effects, has been validated by experimental data from the literature. Theoretical predictions of particle deposition efficiencies are not only in agreement with the best-fit empirical correlation presented by Cohen and Asgharian (1990) over a wide range of dimensionless diffusion parameters but also march individual experimental measurements with regard to effects of the parameters of particle size, flow rate, and airway dimensions. Indeed, the model presented in this work is in much better agreement with actual data than the theory of Ingham (1975) used by Cohen and Asgharian (1990). For instance, the mean ratio of experimental-to-theoretical particle diffusion values using our model is 1.1 (i.e., the difference is only about 10%), while the mean ratio using Ingham's (1975) theory is 2.1 (i.e., the difference can exceed 100%).