Traffic-related air pollution and lung function in children at 8 years of age: a birth cohort study.

RATIONALE Long-term exposure to air pollution has been related to lung function decrements in children, but the role of timing of exposure remains unknown. OBJECTIVES To assess the role of long-term exposure to air pollution on lung function in school-age children. METHODS More than 1,900 children in the Swedish birth cohort BAMSE were followed with repeated questionnaires, dynamic spirometry, and IgE measurements until 8 years of age. Outdoor concentrations of particulate matter with an aerodynamic diameter less than 10 μm (PM(10)) from road traffic were estimated for residential, day care, and school addresses from birth and onward using dispersion modeling. The relationship between time-weighted average exposure during different time windows and FEV at 8 years was analyzed by linear regression, adjusting for potential confounding factors, including short-term exposure to air pollution. MEASUREMENTS AND MAIN RESULTS A 5th to 95th percentile difference in time-weighted average particulate matter less than 10 μm in aerodynamic diameter exposure during the first year of life was associated with a reduced FEV(1) of -59.3 ml (95% confidence interval, -113 to -5.6) at 8 years of age. The negative association was particularly pronounced in children concomitantly sensitized to common inhalant or food allergens (-136.9 ml; 95% confidence interval, -224.1 to -49.7). Exposure after the first year of life seemed to have less impact on lung function at 8 years. CONCLUSIONS Our results indicate that exposure to traffic-related air pollution during infancy affects lung function in children up to 8 years of age and particularly in those sensitized to common inhalant or food allergens.