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Deposition of fiber and spherical aerosols in the human tracheobronchial airway.

Cheng-YS; Zhou-Y; Su-WC
Proceedings of the AAAR 26th Annual Conference, September 24-28, 2007, Reno, Nevada. Mt. Laurel, NJ: American Association for Aerosol Research, 2007 Sep; :224
Inhalation exposure of fiber aerosol may have serious health consequences including lung cancers. The deposition pattern in the respiratory tract as a function of fiber dimensions is the information critical to understanding respiratory dosimetry and etiology. Controlled studies of fiber deposition in human volunteers are not available because of ethical concerns. The purpose of this study is to investigate the effects of fiber dimension and breathing rate on the deposition pattern in an oral/tracheobronchial airway cast with a defined geometry. Two types of fibers including a carbon fiber and a glass fiber were used for the deposition study. The fiber was generated with a small-scale powder disperser (Model 3433, TSI Inc., St Paul, MN). Regional fiber deposition pattern was measured at a constant inspiratory flow rate of 7.5,15, 30 and 43.5 L min-1. As a comparison we also did deposition experiments in the same cast using polystyrene latex (PSL) test particles tagged with fluorescent. Fiber depositions in different sections of the airway cast and the backup filter were extracted and prepared for optical microscopy and image analysis. From the counting data, deposition efficiency as a function of fiber length /diameter was calculated. Our experimental data of fiber deposition in the tracheobronchial region show large variability but generally agree with the numerical simulation results published by Zhang et al. (1996). The deposition efficiency can be expressed as a function of Stokes diameter, Reynolds number and branching angle. We also show that deposition efficiencies of spherical particles are higher than those of fibers at the same impaction parameter. This can be explained by the orientation of fibers, which tend to align with the flow direction. This information is useful in predicting the deposited dose of inhaled fiber particles.
Fibrous-glass; Fibrous-dusts; Respirable-dust; Respiratory-irritants; Models; Particulate-dust; Particulates; Particle-aerodynamics; Exposure-levels; Exposure-assessment; Dose-response; Dosimetry; Aerosols; Aerosol-particles
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Proceedings of the AAAR 26th Annual Conference, September 24-28, 2007, Reno, Nevada
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Lovelace Biomedical & Environmental Research