Childhood Incident Asthma and Traffic-Related Air Pollution at Home and School

TLDR

Traffic‑related air pollution is linked to increased asthma prevalence and other cardiorespiratory effects. The study examined whether traffic exposure near children’s homes and schools predicts new‑onset asthma in a cohort of kindergarten and first‑grade children. Exposure was estimated with a line‑source dispersion model of traffic volume, distance from home and school, and local meteorology, and ambient ozone, NO₂, and particulate matter were continuously measured at central site monitors. Higher modeled traffic pollution near homes (HR 1.51) and schools (HR 1.45) and ambient NO₂ (HR 2.18) were each associated with increased asthma risk, and traffic exposure at both locations remained independently predictive when adjusted for NO₂.

Abstract

Traffic-related air pollution has been associated with adverse cardiorespiratory effects, including increased asthma prevalence. However, there has been little study of effects of traffic exposure at school on new-onset asthma.We evaluated the relationship of new-onset asthma with traffic-related pollution near homes and schools.Parent-reported physician diagnosis of new-onset asthma (n = 120) was identified during 3 years of follow-up of a cohort of 2,497 kindergarten and first-grade children who were asthma- and wheezing-free at study entry into the Southern California Children's Health Study. We assessed traffic-related pollution exposure based on a line source dispersion model of traffic volume, distance from home and school, and local meteorology. Regional ambient ozone, nitrogen dioxide (NO(2)), and particulate matter were measured continuously at one central site monitor in each of 13 study communities. Hazard ratios (HRs) for new-onset asthma were scaled to the range of ambient central site pollutants and to the residential interquartile range for each traffic exposure metric.Asthma risk increased with modeled traffic-related pollution exposure from roadways near homes [HR 1.51; 95% confidence interval (CI), 1.25-1.82] and near schools (HR 1.45; 95% CI, 1.06-1.98). Ambient NO(2) measured at a central site in each community was also associated with increased risk (HR 2.18; 95% CI, 1.18-4.01). In models with both NO(2) and modeled traffic exposures, there were independent associations of asthma with traffic-related pollution at school and home, whereas the estimate for NO(2) was attenuated (HR 1.37; 95% CI, 0.69-2.71).Traffic-related pollution exposure at school and homes may both contribute to the development of asthma.