Effects of airborne particulate matter on respiratory morbidity in asthmatic children.

Background: 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.

Methods: 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 mum in diameter (PM(2.5)) were monitored at a monitoring station proximal to the hospital. Moreover, PM(2.5) concentrations inside and outside the hospital were measured using the dust monitor with a laser diode (PM(2.5(LD))). The changes in PEF and wheezing associated with PM concentration were analyzed.

Results: The changes in PEF in the morning and evening were significantly associated with increases in the average concentration of indoor PM(2.5(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-mug/m(3) increases). The change in PEF was also significantly associated with outdoor PM(2.5(LD)) concentrations, but the changes were smaller than those observed for indoor PM(2.5(LD)). Changes in PEF and concentration of stationary-site PM(2.5) were not associated. The prevalence of wheezing in the morning and evening were also significantly associated with indoor PM(2.5(LD)) concentrations (odds ratios = 1.014 [95%CI: 1.006, 1.023] and 1.025 [95%CI: 1.013, 1.038] respectively, for 10-microg/m(3) increases). Wheezing in the evening was significantly associated with outdoor PM(2.5(LD)) concentration. The effects of indoor and outdoor PM(2.5(LD)) remained significant even after adjusting for ambient nitrogen dioxide concentrations.

Conclusion: Indoor and outdoor PM(2.5(LD)) concentrations were associated with PEF and wheezing among asthmatic children. Indoor PM(2.5(LD)) had a more marked effect than outdoor PM(2.5(LD)) or stationary-site PM(2.5).