McConnell R, Berhane K, Gilliland F, et al. Am J Respir Crit Care Med. 2003;168:790–797
Purpose of the Study.
To examine the effects of air pollutants, including particulate matter (PM), organic carbon (OC), elemental carbon, and other traffic-related pollutants, on bronchitic symptoms among children with asthma.
Twelve Southern California communities were studied. In 1993, fourth graders and seventh graders were recruited from schools in 12 neighborhoods. Children with a history of asthma who completed ≥2 years of study questionnaires (1996–1999) were included in the analysis. There were 475 children in the study.
Questions regarding bronchitic symptoms were asked each year. Positive responses included daily cough for 3 consecutive months, 3 consecutive months of congestion or phlegm, or the occurrence of bronchitis. Other questions addressed smoke exposure and participation in team sports. A number of demographic questions were also asked. Air pollution monitoring stations were established in the 12 neighborhoods. The following were measured: ozone, PM of <10 μm, nitrogen dioxide (NO2), PM of <2.5 μm (PM2.5), OC, and elemental carbon. Annual averages for these pollutants were calculated, and 4-year mean levels (1996–1999) for each community were established.
Of the 475 children in the study with asthma, 184 (38.7%) experienced bronchitic symptoms during the first year. Children with a history of wheezing in the year before the study or with allergy were significantly more likely to report symptoms. During the 4 years of the study, the average pollutant concentrations varied 4- to 10-fold among the communities. There was very little variation within each community from year to year. The odds ratio (OR) for bronchitic symptoms among children with asthma varied from 0.80 for ozone to 1.81 for PM2.5 among the communities. Within communities, the ORs were >1 for every pollutant. In special models for 2 pollutants, ie, OC and NO2, ORs were only modestly decreased when other pollutants were controlled for and the effects of OC and NO2 were not altered by other pollutants. NO2 effects were modified by participation in team sports, with an increase in the OR for bronchitic symptoms among participating children.
Among children with asthma, there were associations of bronchitic symptoms with PM2.5, OC, NO2, and ozone levels. Importantly, OC and NO2 effects were not confounded by other pollutants. These 2 pollutants deserve greater attention with respect to bronchitic symptoms associated with air pollution among patients with asthma.
This is another important study that helps to establish the effects of air pollution on children with asthma. The study was conducted in California, and the air pollution components that were investigated were derived from vehicular traffic more than industry. This article also demonstrates the need to investigate more extensively the effects of NO2 and OC among children with asthma.