Traffic-related air pollution and lung function in children – the ESCAPE project

Abstract

Rationale: There is evidence for adverse effects of outdoor air pollution on lung function of children. Quantitative summaries of the effects of air pollution on lung function, however, are lacking due to large differences between studies. Objectives: To study the association between residential exposure to traffic-related air pollution and lung function in five European birth cohorts with a standardized exposure assessment following a common protocol. Methods: As part of the European Study of Cohorts for Air Pollution Effects (ESCAPE) we analyzed data from birth cohort studies situated in Germany, Sweden, The Netherlands and the United Kingdom with measured lung function at ages 6-8 years. Annual average exposure to traffic-related air pollution [nitrogen oxides (NO2, NOx), mass concentrations of particulate matter with diameters of less than 2.5, less than 10, and 2.5-10 µm (PM2.5, PM10, and PMcoarse), and PM2.5 absorbance], at birth and current addresses was estimated by land-use regression models. Associations of lung function with exposure to air pollution and traffic indicators were first explored by cohort using linear regression analysis. Then, cohort-specific effect estimates were combined by meta-analysis. Results: Estimated levels of NO2, NOx, PM2.5 absorbance and PM2.5 at the current address were associated with small decreases in lung function ranging from 0.86% (95% confidence interval 0.24; 1.48) per 20 µg/m3 NOx to 1.77% (0.18; 3.34) per 5 µg/m3 PM2.5 for forced expiratory volume in 1 second. Conclusions: Exposure to traffic-related air pollution may result in reductions in lung function in school children.