| Abstrakt: |
Exposure to particulate matter (PM) air pollution has been shown to exacerbate children's asthma, but the exposure sources and temporal characteristics are still under study. Children's exposure to PM is likely to involve both combustion-related ambient PM and PM related to a child's activity in various indoor and outdoor microenvironments. Among 19 children with asthma, 9-17 years of age, we examined the relationship of temporal changes in percent predicted forced expiratory volume in 1 sec (FEV[1]) to personal continuous PM exposure and to 24-hr average gravimetric PM mass measured at home and central sites. Subjects were followed for 2 weeks during either the fall of 1999 or the spring of 2000, in a southern California region affected by transported air pollution. FEV[1] was measured by subjects in the morning, afternoon, and evening. Exposure measurements included continuous PM using a passive nephelometer carried by subjects; indoor, outdoor home, and central-site 24-hr gravimetric PM[2.5] (PM of aerodynamic diameter < 2.5 microm) and PM[10]; and central-site hourly PM[10], nitrogen dioxide, and ozone. Data were analyzed with linear mixed models controlling for within-subject autocorrelation, FEV[1] maneuver time, and exposure period. We found inverse associations of FEV[1] with increasing PM exposure during the 24 hr before the FEV[1] maneuver and with increasing multiday PM averages. Deficits in percent predicted FEV[1] (95% confidence interval) for given PM interquartile ranges measured during the preceding 24-hr were as follows: 128 microg/m[3] 1-hr maximum personal PM, -6.0% (-10.5 to -1.4); 30 microg/m[3] 24-hr average personal PM, -5.9% (-10.8 to -1.0); 6.7 microg/m[3] indoor home PM[2.5], -1.6% (-2.8 to -0.4); 16 microg/m[3] indoor home PM[10], -2.1% (-3.7 to -0.4); 7.1 microg/m[3] outdoor home PM[2.5], -1.1% (-2.4 to 0.1); and 7.5 microg/m[3] central-site PM[2.5], -0.7% (-1.9 to 0.4). Stronger associations were found for multiday moving averages of PM for both personal and stationary-site PM. Stronger associations with personal PM were found in boys allergic to indoor allergens. FEV[1] was weakly associated with NO[2] but not with O[3]. Results suggest mixed respiratory effects of PM in asthmatic children from both ambient background exposures and personal exposures in various microenvironments. [ABSTRACT FROM AUTHOR] |
