DEPOSITION OF FINE PARTICLES IN CHILDREN SPONTANEOUSLY BREATHING AT REST

Abstract

Recent epidemiological studies suggest that children may be more susceptible than adults to effects of inhaled particulate matter. To determine if children receive an increased lung dose of particles compared to adults we measured fractional deposition (DF) of fine particles in children, age 7-14 yr (n = 16), adolescents, age 14-18 yr (n = 11), and adults, age 19-35 yr (n = 12). Each subject inhaled 2-mum monodisperse Carnauba wax particles while following a breathing pattern previously determined by respiratory inductance plethysmography for that subject (i.e., that subject's spontaneous pattern at rest). Breath-by-breath DF (ratio of particles not exhaled/total particles inhaled) was determined by photometry at the mouth. Among the children there was no variation in DF with subject age or height, but DF was dependent on intersubject variation in tidal volume (Vt) (p < .001). DF for the children versus the adolescents was 0.22 +/- 0.08(sd) and 0.20 +/- 0.03, respectively (NS), also not different from the adults, DF = 0.22 +/- 0.09. On the other hand, the rate of deposition normalized to lung surface area, nDrate, tended to be greater (35%) in the children versus the combined group of adolescents and adults for resting breathing of these particles (p = .07). The variable nDrate is a function of the DF, the subject's minute ventilation, and his or her lung size. The increase in nDrate in the children is due to their higher minute ventilation in relation to their lung size. These results may prove useful in determining age-relative risks that may be associated with the inhalation of pollutant particles in ambient air.