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

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.