Background: Urban air pollution can trigger asthma exacerbations, but the effects of long-term exposure to traffic-related air pollution on lung function, or onset of airway disease and allergic sensitization in children is less clear.
Methods: All 2107 children aged 9-14 from 40 schools in Rome in 2000-2001 were included in a cross-sectional survey. Respiratory symptoms were assessed on 1760 children by parental questionnaires (response rate=83.5%). Allergic sensitization was measured by skin prick tests and lung function was measured by spirometry on 1359 children (77.2%). Three indicators of traffic-related air pollution exposure were assessed, i.e. self-reported traffic outside the child's home, the measured distance between the child's home and busy roads, and the residential nitrogen dioxide (NO2) levels estimated by a land-use regression model (R2=0.69).
Results: We found a strong association between estimated NO2 exposure per 10 μg/m3 and lung function, especially expiratory flows, in linear regression models adjusted for age, gender, height, and weight: -0.62 (-1.05, -0.19) for FEV1 as percentage of FVC, 62 ml/s (-102, -21) for FEF25-75, and -85 ml/s (-135, 35) for PEF. The other two exposure indicators demonstrated similar but weaker associations. The associations appeared stronger in girls, older children, among children of high socioeconomic status and among those exposed to parental smoking. Although lifetime asthma was not an effect modifier there was a suggestion of a larger effect on lung function among subjects with a positive prick tests. Multiple logistic regression models did not suggest a consistent association between traffic-related air pollution exposure and prevalence of respiratory symptoms or allergic sensitization.
Conclusion: The results of this study suggest that residential traffic-related air pollution exposure is associated with reduced expiratory flows in school children.