CALCULATION OF TOTAL DEPOSITION FRACTION OF ULTRAFINE AEROSOLS IN HUMAN EXTRATHORACIC AND INTRATHORACIC REGIONS

Total deposition fraction during inspiration and expiration can be con sidered as an index of cumulative doses of inhaled particles. We have calculated the total deposition fraction of ultrafine aerosols for the 5-200-nm-diameter range in the extrathoracic and intrathoracic airway s for two breathing rates, 7.5 and 15 L min-1, based on the total resp iratory deposition measurements of Schiller et al. (1988) and the empi rical extrathoracic aerosol deposition equations of Cheng et al. (1993 ) and Swift et al. (1993). Our results indicate that extrathoracic par ticle deposition during expiration is an important component of total extrathoracic deposition fraction for particle diameters less than 20 nm. The intrathoracic deposition fraction increases as particle diamet er increases from 5 to 20 nm, and decreases with increasing particle d iameter from 20 to 200 nm. These trends were observed for both oral an d nasal breathing for both respiratory flow rates.