In vivo measurement of fine and coarse aerosol deposition in the nasal airways of female Long-Evans rats.

Experimental data on fine and coarse aerosol deposition in the nasal airways of animals are essential in appropriately using toxicological studies to assess the potential risk to human health from exposure to airborne pollutants. However, such data are scarce. The objective of this study was to determine aerosol deposition efficiencies for the nasal airways in Long-Evans rats for particles with diameters ranging from 0.5 to 4 microm. Polystyrene latex (PSL) microspheres in steady-state and pulsatile flows were passed through the nasal airways for simulated inspiratory and expiratory scenarios. Average flow rates ranged from 220 to 640 ml/min. Deposition increased sharply with increasing particle inertia for all exposure scenarios. Expiratory deposition efficiency appeared to be somewhat higher than inspiratory deposition efficiency for both steady-state and pulsatile flow conditions. Pulsatile flow yielded significantly higher deposition than steady-state flow. This result emphasizes the importance of considering fluid accelerations inherent in normal breathing when determining aerosol deposition that is dominated by inertial impaction. Variability in the data, which was suspected to result primarily from the difficult surgical procedure, was in excess of expected intersubject variability. The results of this study will be incorporated into extrapolation-modeling and risk-assessment activities for inhaled pollutants.