Total lung deposition of ultrafine particles in elderly subjects during controlled breathing

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 microm in number median diameter) in the lungs of healthy, elderly subjects (age = 69 +/- 5 yr) 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 +/- 0.02 for NMD = 0.04, 0.06, 0.08, and 0.1 microm, respectively, for V(t) = 500 ml and Q = 250 ml/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.