Interaction of Fine Powders with the Respiratory System

3 INTERACTION OF FINE POWDERS WITH THE RESPIRATORY SYSTEM 

Airborne particles entering the respiratory tract will be deposited on the surface of any part of the airways with which they come into contact. Because the surfaces of the airways are always moist, there is a negligible chance of a particle becoming re-entrained in the air after once having made contact with a surface. Particles which do not make contact with the airway surfaces will be exhaled. The deposition of particles in the airways is a complicated process. Zeng et al. (2001) identify five possible mechanisms contributing to the deposition of particles carried into the respiratory tract. These are sedimentation, inertial impaction, diffusion, interception and electrostatic precipitation. After introducing each mechanism, their relative importance in each part of the respiratory tract will be discussed. 

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