Respiratory deposition of atmospheric aerosols

While filtration occurs in a fixed system at a steady flow rate, respiratory deposition occurs in a system of changing geometry, with a flow that changes with time and cycles in direction. An understanding of how and where particles deposit in our lungs is necessary in order to evaluate properly the toxicity of aerosols. In this study the effect of particle size, wind speed and direction on respiratory deposition was investigated. The inhalable fraction (IF), which gives an indication of the efficiency of particle entry into the nose or mouth, as well as the total deposition fraction (DF) in the respiratory system, showed an increase as particle diameter decreased. Both the IF and DF showed an increase as ambient air velocity increased above 4 m.s-l for particles with aerodynamic diameters 10, 2.5, 1.0 and 0.4 mu m. A reasonable correlation between mass concentrations and wind speed was obtained for all the sizes investigated.