Urban 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.Methods:
The 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.Results:
Exposure 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 μg/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.Conclusions:
Exposure 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.