Theoretical Lung Deposition of Hygroscopic NaCl Aerosols

Abstract

Hygroscopic aerosols grow in size as they are inhaled into the humid airways. An empirical formula describing the growth rate is derived from the results of an exact calculation. The approximate particle growth relation is used to calculate total and regional depositions of dry NaCl aerosols in the human respiratory tract for initial particle diameters ranging from 0.01 to 10 μm. Assuming a relative humidity of 99.5% in the airways, total deposition results are found to be in good agreement with recent experimental data, and show a minimum deposition near 0.08 μm. For particles with an initial diameter larger than 0.2 μm, it is found that total deposition is increased due to particle hygroscopicity, whereas an opposite trend is seen for particles initially smaller than 0.2 μm. In most cases, deposition patterns vary appreciably due to the growth of the particles.