VARIABILITY OF FINE-PARTICLE DEPOSITION IN HEALTHY-ADULTS - EFFECT OFAGE AND GENDER

Recent epidemiologic studies suggest increased mortality among the eld erly in association with particulate air pollution. We investigated th e variability in fractional deposition (DF) of inhaled particles (2 mu m mass median aerodynamic diameter [MMAD]) in 62 subjects with normal lung function, aged 18 to 80 yr. Each subject inhaled 2-mu m monodisp erse carnauba wax particles while following a breathing pattern previo usly determined by respiratory inductance plethysmography in that subj ect (i.e., the subject's spontaneous pattern at rest). Breath-by-breat h DF (ratio of particles not exhaled/total particles inhaled) was dete rmined by laser aerosol photometry and pneumotachometry at the mouth. DF (mean DF = 0.29 +/- 0.06 (ages 18 to 40 yr), 0.29 +/- 0.07 (ages 41 to 60 yr), and 0.26 +/- 0.06 (age over 60 yr) was independent Of age. There was a tendency toward greater DF in female than in male subject s; DF = 0.30 +/- 0.07 (females) and 0.27 +/- 0.06 (males) (4 = 0.06); however, because the males had 45% higher minute ventilations than the females, the deposition rate (D-rate), or particles depositing per un it of time, was 30% greater in males than in females (p = 0.004). Mult iple regression analysis showed that among all subjects, the variabili ty in DF was best predicted by variability in the breathing period (T) associated with the pattern used to breathe the particles, and by the subject's specific airway resistance (sRaw). These results may prove useful in determining age- and gender-relative risks that may be assoc iated with the inhalation of pollutant particles in ambient air.