Air pollution and bronchitic symptoms in Southern California children withasthma

The association of air pollution with the prevalence of chronic lower respi ratory tract symptoms among children with a history of asthma or related sy mptoms was examined in a cross-sectional study. Parents of a total of 3,676 fourth, seventh, and tenth graders from classrooms in 12 communities in So uthern California completed questionnaires that characterized the children' s histories of respiratory illness and associated risk factors. The prevale nces of bronchitis, chronic phlegm, and chronic cough were investigated amo ng children with a history of asthma, wheeze without diagnosed asthma, and neither wheeze nor asthma. Average ambient annual exposure to ozone, partic ulate matter (PM10 and PM2.5; less than or equal to 10 mu m and < 2.5 mu m in aerodynamic diameter, respectively), acid vapor, and nitrogen dioxide (N O2) was estimated from monitoring stations in each community. Positive asso ciations between air pollution and bronchitis and phlegm were observed only among children with asthma. As PM10 increased across communities, there wa s a corresponding increase in the risk per interquartile range of bronchiti s [odds ratio (OR) 1.4/19 mu g/m(3); 95% confidence interval (CI), 1.1-1.8) . Increased prevalence of phlegm was significantly associated with increasi ng exposure to all ambient pollutants except ozone. The strongest associati on was for NO2, based on relative risk per interquartile range in the 12 co mmunities (OR 2.7/24 ppb; CI, 1.4-5.3). The results suggest that children w ith a prior diagnosis of asthma are more likely to develop persistent lower respiratory tract symptoms when exposed to air pollution in Southern Calif ornia.