Traffic-related Air Pollution and Incident Obesity during Ages 10-18 years in the Southern California Children’s Health Study

Abstract

Childhood obesity is a global public health crisis, often continuing into adulthood and contributing to increased morbidity and mortality. A growing literature suggests traffic pollution may contribute to increased BMI in childhood, but few studies have examined whether this translates to an increased risk of obesity. In this study we evaluated how traffic-related air pollution relates to incident obesity in a prospective study of schoolchildren from ages 10 to 18 years.The study population comprised 3430 children from eight Southern California communities who were not obese at study entry, recruited over three waves in 1992-93, 1995-96, and 2002-03. Children were followed until age 18 or high school graduation, and height and weight measurements were collected longitudinally. Residential traffic pollution exposure at baseline was estimated as nitrogen oxides (NOx) using the California line-source dispersion model. Multilevel Poisson regression models were fitted to estimate incidence rate ratios (IRR) for obesity associated with traffic-related NOx exposure, adjusting for a set of confounding variables selected a priori using a directed acyclic graph.Participants were primarily non-Hispanic White (44%) or Hispanic (40%). At study entry the median age was 9.7 (IQR: 9.3-10.1) and most children were of normal weight (78%). Traffic-related NOx was associated with increased risk of childhood obesity: IRR=1.10 (1.01-1.19) per average standard deviation within community. Further adjustment for baseline body mass index category increased the risk: IRR=1.14 (1.05-1.24).Exposure to traffic was associated with higher obesity risk in childhood. These findings strengthen the scientific evidence linking childhood obesity and air pollution from near-roadway sources, a modifiable risk factor which could be targeted through vehicular emissions reductions and exposure policies.