• Emma Nordling, Niklas Berglind, Erik Melén, Gunnel Emenius, Jenny Hallberg, Fredrik Nyberg, Göran Pershagen, Magnus Svartengren, Magnus Wickman, and Tom Bellander.
• Department of Occupational and Environmental Health, Stockholm County Council, Stockholm, Sweden.
• Epidemiology. 2008 May 1;19(3):401-8.

BackgroundUrban air pollution can trigger asthma symptoms in children, but there is conflicting evidence on effects of long-term exposure on lung function, onset of airway disease and allergic sensitization.MethodsThe spatial distribution of nitrogen oxides from traffic (traffic-NOx) and inhalable particulate matter from traffic (traffic-PM10) in the study area was assessed with emission databases and dispersion modeling. Estimated levels were used to assign first-year exposure levels for children in a prospective birth cohort (n = 4089), by linking to geocoded home addresses. Parents in 4 Swedish municipalities provided questionnaire data on symptoms and exposures when the children were 2 months and 1, 2, and 4-year-old. At 4 years, 73% of the children underwent clinical examination including peak expiratory flow and specific IgE measurements.ResultsExposure to air pollution from traffic during the first year of life was associated with an excess risk of persistent wheezing (odds ratio [OR] for 44 microg/m3 [5th-95th percentile] difference in traffic-NOx = 1.60; 95% confidence interval [CI] = 1.09-2.36). Similar results were found for sensitization (measured as specific IgE) to inhalant allergens, especially pollen (OR for traffic-NOx = 1.67; 95% CI = 1.10-2.53), at the age of 4 years. Traffic-related air pollution exposure during the first year of life was also associated with lower lung function at 4 years of age. Results were similar using traffic-NOx and traffic-PM10 as indicators.ConclusionsExposure to moderate levels of locally emitted air pollution from traffic early in life appears to influence the development of airway disease and sensitization in preschool children.

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