Respiratory Deposition of Fibers in the Non-Inertial Regime—Development and Application of a Semi-Analytical Model

Sofie M. Högberg, Hans O. Åkerstedt, T. Staffan Lundström, Jonathan B. Freund
2010 Aerosol Science and Technology  
A semi-analytical model describing the motion of fibrous particles ranging from nano-to micro scale was developed, and some important differences in respiratory tract transport and deposition between fibrous particles of various sizes and shapes were elucidated. The aim of this work was to gain information regarding health risks associated with inhalation exposure to small fibers such as carbon nanotubes. The model, however, is general in the sense that it can be applied to arbitrary flows and
more » ... rbitrary flows and geometries at small fiber Stokes and Reynolds numbers. Deposition due to gravitational settling, Brownian motion and interception was considered, and results were presented for steady, laminar, fully developed parabolic flow in straight airways. Regarding particle size, our model shows that decrease in particle size lead to reduced efficiency of sedimentation but increased intensity of Brownian diffusion, as expected. If regarding the effects due to particle shape alone, by varying the aspect ratios and diameters of the microfibers simultaneously such that the effect of particle mass does not come into play, our model suggests that deposition both due to gravitational settling and Brownian diffusion decreases with increased fiber aspect ratio. If considering the combined effect of fiber size and shape, our results suggest that for particles with elongated shape, those with diameters in the size-range range 10-100 nm and lengths of several micrometers have the highest possibility to reach the vulnerable gas-exchange region in the deep lung. Note that the popular multi-walled carbon nanotubes fall into this size-range.
doi:10.1080/02786826.2010.498455 fatcat:a5ovjrn2gfgcdidzoc5t6wydke