Atopic diseases, allergic sensitization, and exposure to traffic-related air pollution in children.

RATIONALE In vitro studies, animal experiments, and human exposure studies have shown how ambient air pollution increases the risk of atopic diseases. However, results derived from observational studies are inconsistent. OBJECTIVES To assess the relationship between individual-based exposure to traffic-related air pollutants and allergic disease outcomes in a prospective birth cohort study during the first 6 years of life. METHODS We studied 2,860 children at the age of 4 years and 3,061 at the age of 6 years to investigate atopic diseases and allergic sensitization. Long-term exposure to particulate matter (PM(2.5)), PM(2.5) absorbance, and long-term exposure to nitrogen dioxide (NO(2)) was assessed at residential addresses using geographic information systems based regression models and air pollution measurements. The distance to the nearest main road was used as a surrogate for traffic-related air pollutants. MEASUREMENTS AND MAIN RESULTS Strong positive associations were found between the distance to the nearest main road and asthmatic bronchitis, hay fever, eczema, and sensitization. A distance-dependent relationship could be identified, with the highest odds ratios (ORs) for children living less than 50 m from busy streets. For PM(2.5) absorbance, statistically significant effects were found for asthmatic bronchitis (OR, 1.56; 95% confidence interval [CI], 1.03-2.37), hay fever (OR, 1.59; 95% CI, 1.11-2.27), and allergic sensitization to pollen (OR, 1.40; 95% CI, 1.20-1.64). NO(2) exposure was associated with eczema, whereas no association was found for allergic sensitization. CONCLUSIONS This study provides strong evidence for increased risk of atopic diseases and allergic sensitization when children are exposed to ambient particulate matter.