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 i n vitro and in vivo experimental studies. If such modeling can be show n 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 resul ts in risk assessment applications. In this study, a closed-form solut ion proposed by Martonen et al. (in press), which quantitatively descr ibes convective particle diffusion in a conduit including wall irregul arities and entrance effects, has been validated by experimental data from the literature. Theoretical predictions of particle deposition ef ficiencies are not only in agreement with the best-fit empirical corre lation presented by Cohen and Asgharian (1990) over a wide range of di mensionless diffusion parameters but also march individual experimenta l measurements with regard to effects of the parameters of particle si ze, flow rate, and airway dimensions. Indeed, the model presented in t his 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 u sing 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 differen ce can exceed 100%).