Total Deposition of Ultrafine Hydrophobic and Hygroscopic Aerosols in the Human Respiratory System

The deposition of ultrafine particles in the human respiratory system was studied under a variety of steady breathing conditions. The monodisperse aerosols tested were hydrophobic kerosene heater, aluminosilicate, and hygroscopic NaCl in the size range of 0.03 to 0.4 μm in diameter. The results for all aerosols show that particle deposition increases with an increase in tidal volume, but with a decrease in breathing frequency. Also, deposition during breath holding increases nearly exponentially with an increase in time. However, particle deposition as a function of particle size is different between hydrophobic and hygroscopic aerosols in the size range tested. The hydrophobic aerosols increase with a decrease in particle size, while hygroscopic aerosols show minimum value in the size range of 0.06 to 0.09 μm. The hydrophobic kerosene heater and aluminosilicate particle deposition confirms the recent theoretical calculations of Yeh and Schum (1980), Yu and Diu (1982), and Yu and Hu (1983). The NaCl particles show a 3.5 to 4.5 fold growth under conditions approximating the respiratory tract.