Effects of Airborne Particulate Matter on Respiratory Morbidity in Asthmatic Children

Abstract

The effects of airborne particulate matter (PM) are a major human health concern. In this panel study, we evaluated the acute effects of exposure to PM on peak expiratory flow (PEF) and wheezing in children. Daily PEF and wheezing were examined in 19 asthmatic children who were hospitalized in a suburban city in Japan for approximately 5 months. The concentrations of PM less than 2.5 µm in diameter (PM2.5) were monitored at a monitoring station proximal to the hospital. Moreover, PM2.5 concentrations inside and outside the hospital were measured using the dust monitor with a laser diode (PM2.5(LD)). The changes in PEF and wheezing associated with PM concentration were analyzed. The changes in PEF in the morning and evening were significantly associated with increases in the average concentration of indoor PM2.5(LD) 24 h prior to measurement (-2.86 L/min [95%CI: -4.12, -1.61] and -3.59 L/min [95%CI: -4.99, -2.20] respectively, for 10-µg/m3 increases). The change in PEF was also significantly associated with outdoor PM2.5(LD) concentrations, but the changes were smaller than those observed for indoor PM2.5(LD). Changes in PEF and concentration of stationary-site PM2.5 were not associated. The prevalence of wheezing in the morning and evening were also significantly associated with indoor PM2.5(LD) concentrations (odds ratios = 1.014 [95%CI: 1.006, 1.023] and 1.025 [95%CI: 1.013, 1.038] respectively, for 10-µg/m3 increases). Wheezing in the evening was significantly associated with outdoor PM2.5(LD) concentration. The effects of indoor and outdoor PM2.5(LD) remained significant even after adjusting for ambient nitrogen dioxide concentrations. Indoor and outdoor PM2.5(LD) concentrations were associated with PEF and wheezing among asthmatic children. Indoor PM2.5(LD) had a more marked effect than outdoor PM2.5(LD) or stationary-site PM2.5.