Long-Term Exposure to Primary Traffic Pollutants and Lung Function in Children: Cross-Sectional Study and Meta-Analysis

BACKGROUND: There is widespread concern about the possible health effects of traffic-related air pollution. Nitrogen dioxide (NO(2)) is a convenient marker of primary pollution. We investigated the associations between lung function and current residential exposure to a range of air pollutants (particularly NO(2), NO, NOx and particulate matter) in London children. Moreover, we placed the results for NO(2) in context with a meta-analysis of published estimates of the association. METHODS AND FINDINGS: Associations between primary traffic pollutants and lung function were investigated in 4884 children aged 9–10 years who participated in the Child Heart and Health Study in England (CHASE). A systematic literature search identified 13 studies eligible for inclusion in a meta-analysis. We combined results from the meta-analysis with the distribution of the values of FEV(1) in CHASE to estimate the prevalence of children with abnormal lung function (FEV(1)<80% of predicted value) expected under different scenarios of NO(2) exposure. In CHASE, there were non-significant inverse associations between all pollutants except ozone and both FEV1 and FVC. In the meta-analysis, a 10 μg/m(3) increase in NO(2) was associated with an 8 ml lower FEV(1) (95% CI: -14 to -1 ml; p: 0.016). The observed effect was not modified by a reported asthma diagnosis. On the basis of these results, a 10 μg/m(3) increase in NO(2) level would translate into a 7% (95% CI: 4% to 12%) increase of the prevalence of children with abnormal lung function. CONCLUSIONS: Exposure to traffic pollution may cause a small overall reduction in lung function and increase the prevalence of children with clinically relevant declines in lung function.