Changes in Lung Function and Airway Inflammation Among Asthmatic Children Residing in a Woodsmoke-Impacted Urban Area

Abstract

Fine particulate matter (PM_2.5) is associated with respiratory effects, and asthmatic children are especially sensitive. Preliminary evidence suggests that combustion-derived particles play an important role. Our objective was to evaluate effect estimates from different PM_2.5 exposure metrics in relation to airway inflammation and lung function among children residing in woodsmoke-impacted areas of Seattle. Nineteen children (ages 6–13 yr) with asthma were monitored during the heating season. We measured 24-h outdoor and personal concentrations of PM_2.5 and light-absorbing carbon (LAC). Levoglucosan (LG), a marker of woodsmoke, was also measured outdoors. We partitioned PM_2.5 exposure into its ambient-generated (E_ag) and nonambient (E_na) components. These exposure metrics were evaluated in relation to daily changes in exhaled nitric oxide (FE_NO), a marker of airway inflammation, and four lung function measures: midexpiratory flow (MEF), peak expiratory flow (PEF), forced expiratory volume in the first second (FEV₁), and forced vital capacity (FVC). E_ag, but not E_na, was correlated with combustion markers. Significant associations with respiratory health were seen only among participants not using inhaled corticosteroids. Increases in FE_NO were associated with personal PM_2.5, personal LAC, and E_ag but not with ambient PM_2.5 or its combustion markers. In contrast, MEF and PEF decrements were associated with ambient PM_2.5, its combustion markers, and E_ag, but not with personal PM_2.5 or personal LAC. FEV₁ was associated only with ambient LG. Our results suggest that lung function may be especially sensitive to the combustion-generated component of ambient PM_2.5, whereas airway inflammation may be more closely related to some other constituent of the ambient PM_2.5 mixture.