Traffic-related air pollution and asthma onset in children: a prospective cohort study with individual exposure measurement

Environ Health Perspect. 2008 Oct;116(10):1433-8. doi: 10.1289/ehp.10968. Epub 2008 Jun 18.


Background: The question of whether air pollution contributes to asthma onset remains unresolved.

Objectives: In this study, we assessed the association between asthma onset in children and traffic-related air pollution.

Methods: We selected a sample of 217 children from participants in the Southern California Children's Health Study, a prospective cohort designed to investigate associations between air pollution and respiratory health in children 10-18 years of age. Individual covariates and new asthma incidence (30 cases) were reported annually through questionnaires during 8 years of follow-up. Children had nitrogen dioxide monitors placed outside their home for 2 weeks in the summer and 2 weeks in the fall-winter season as a marker of traffic-related air pollution. We used multilevel Cox models to test the associations between asthma and air pollution.

Results: In models controlling for confounders, incident asthma was positively associated with traffic pollution, with a hazard ratio (HR) of 1.29 [95% confidence interval (CI), 1.07-1.56] across the average within-community interquartile range of 6.2 ppb in annual residential NO2. Using the total interquartile range for all measurements of 28.9 ppb increased the HR to 3.25 (95% CI, 1.35-7.85).

Conclusions: In this cohort, markers of traffic-related air pollution were associated with the onset of asthma. The risks observed suggest that air pollution exposure contributes to new-onset asthma.

Keywords: air pollution; asthma onset; children; nitrogen dioxide.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Age of Onset
  • Air Pollution*
  • Asthma / etiology*
  • Asthma / physiopathology
  • Child
  • Cohort Studies
  • Confounding Factors, Epidemiologic
  • Environmental Exposure*
  • Female
  • Humans
  • Male
  • Models, Statistical
  • Seasons
  • Vehicle Emissions


  • Vehicle Emissions