Traffic-related air pollution and development of allergic sensitization in children during the first 8 years of life.

BACKGROUND: The role of exposure to air pollution in the development of allergic sensitization remains unclear. OBJECTIVE: We sought to assess the development of sensitization until school age related to longitudinal exposure to air pollution from road traffic. METHODS: More than 2500 children in the birth cohort BAMSE (Children, Allergy, Milieu, Stockholm, Epidemiological Survey) from Stockholm, Sweden, were followed with repeated questionnaires and blood sampling until 8 years of age. Outdoor concentrations of nitrogen oxides, as a marker of exhaust particles, and particles with an aerodynamic diameter of less than 10 µm (PM(10)), mainly representing road dust, were assigned to residential, day care, and school addresses by using dispersion models. Time-weighted average exposures were linked to levels of IgE against common inhalant and food allergens at 4 and 8 years of age. RESULTS: Air pollution exposure during the first year of life was associated with an increased risk of pollen sensitization at 4 years of age (odds ratio, 1.83; 95% confidence interval, 1.02-3.28) for a 5th to 95th difference in exposure to nitrogen oxides. At 8 years, there was no general increase in the risk of sensitization; however, the risk of food sensitization was increased, particularly among children free of sensitization at 4 years of age (odds ratio, 2.30; 95% confidence interval, 1.10-4.82). Results were similar by using PM(10). No associations between air pollution exposure after the first year of life and sensitization were seen. CONCLUSION: Traffic-related air pollution exposure does not seem to increase the overall risk of sensitization to common inhalant and food allergens up to school age, but sensitization to certain allergens might be related to exposure during infancy.