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Total respiratory tract deposition of fine micrometer-sized particles in healthy adults: empirical equations for sex and breathing pattern

¹Human Studies Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina; and ²Life Sciences Operation, IIT Research Institute, Chicago, Illinois

Submitted 10 January 2006 ; accepted in final form 20 April 2006

Accurate dose estimation under various inhalation conditions is important for assessing both the potential health effects of pollutant particles and the therapeutic efficacy of medicinal aerosols. We measured total deposition fraction (TDF) of monodisperse micrometer-sized particles [particle diameter (D_p) = 1, 3, and 5 µm in diameter] in healthy adults (8 men and 7 women) in a wide range of breathing patterns; tidal volumes (VT) of 350–1500 ml and respiratory flow rates () of 175–1,000 ml/s. The subject inhaled test aerosols for 10–20 breaths with each of the prescribed breathing patterns, and TDF was obtained by monitoring inhaled and exhaled aerosols breath by breath by a laser aerosol photometer. Results show that TDF varied from 0.12–0.25, 0.26–0.68, and 0.45–0.83 for D_p = 1, 3, and 5 µm, respectively, depending on the breathing pattern used. TDF was comparable between men and women for D_p = 1 µm but was greater in women than men for D_p = 3 and 5 µm for all breathing patterns used (P < 0.05). TDF increased with an increase in VT regardless of D_p and used. At a fixed VT TDF decreased with an increase in for D_p = 1 and 3 µm but did not show any significant changes for D_p = 5 µm. The varying TDF values, however, could be consolidated by a single composite parameter () consisting of D_p, VT, and . The results indicate that unifying empirical formulas provide a convenient means of assessing deposition dose of particles under varying inhalation conditions.

particulate matter; aerosols; air pollution; inhalation dosimetry