Total Lung Deposition of Ultrafine Particles in Elderly Subjects During Controlled Breathing

Abstract

Ultrafine particulate matter (PM) in the air may be harmful to health, particularly in elderly subjects. From the dosimetry point of view, it is not known if the elderly subjects are more susceptible to exposure to ultrafine PM. We measured the total deposition fraction (TDF) of ultrafine PM (NMD = 0.04–0.1 μm in number median diameter) in the lungs of healthy, elderly subjects (age = 69 ± 5yr) and compared the results with those obtained from young adults (age = 31 ± 4 yr) in an earlier study. Subjects inhaled the aerosols with six different breathing patterns: three different tidal volumes (V_t = 500, 750, and 1000 ml) and two flow rates (Q) for each V_t. TDF was measured breath by breath in situ by measuring aerosol concentrations on inhalation and exhalation using an ultrafine condensation particle counter. Mean TDF (±SD) of the elderly subjects was 0.43 ± 0.03, 0.36 ± 0.04, 0.31 ± 0.03, and 0.27 ± 0.02for NMD = 0.04, 0.06, 0.08, and 0.1 μm, respectively, for V_t = 500ml and Q = 250ml/s. These and all other results were very similar to those of young adults. The results suggest that healthy, elderly subjects are not subjected to a greater respiratory dose of ultrafine PM than young adults under the same exposure conditions.