Aerosol deposition in nasal passages of burrowing and ground rodents when breathing dust-laden air

Abstract

The adaptation of subterranean rodents, which dig passages with their front teeth, to underground life presumes the formation of protection mechanisms against inhaling dust particles of different size when digging. One such mechanism can be a specific pattern of air-flow organization in the nasal cavity. To verify this assumption, we conducted a comparative study of the geometry and aerodynamics of nasal passages of a typical representative of subterranean rodents, the mole vole, and a representative of ground rodents, the house mouse. Numerical modeling of air flows and the deposition of micro- and nanoparticle aerosols indicate that sedimentation of model particles over the whole surface of the nasal cavity is higher in the mole vole than in the house mouse, while, on the contrary, particle deposition on the surface of the olfactory epithelium is much less in the burrowing rodent as compared to the ground rodent. The adaptive significance of the latter was substantiated by an experimental study on the inflow of hydrated manganese oxide MnO · (H2O)x and Mn ion nanoparticles from the nasal cavity into brain. It has been shown with use of magnetic resonance tomography (MRT) that there is no difference between the studied species with respect to the inflow of particles or ions by the olfactory bulb when they are introduced intranasally. Meanwhile, when inhaling a nanoparticle aerosol of MnCl2, the Mn deposition in the house mouse’s olfactory bulbs significantly exceeds that in the mole vole’s bulbs. Thus, the morphology of nasal passages as a factor determining the aerodynamics of upper respiratory tract ensures more efficient protection of both the lungs and brain against inhaled aerosols for burrowing rodents than for ground ones.