Assessing the Contribution of Noise to the Association between Traffic-Related Air Pollution and Children's Respiratory Health

Abstract

Traffic emissions are comprised of a complex mixture of components including tailpipe emissions, non-tailpipe emissions, and noise. While regulations have resulted in drastic reductions in tailpipe emissions, growing vehicle fleets and miles traveled have contributed to increased noise and non-tailpipe emissions such as brake wear, tire wear, and associated resuspended road dust. It is critical to assess effects of these lesser-studied non-tailpipe exposures particularly of noise, which can amplify the detrimental health effects associated with near-roadway exposure.Exposures to traffic noise, estimated from the Federal Highway Administration Traffic Noise Model (TNM), and NOx, estimated from a line-dispersion model, were spatially linked to the residential locations of children in the Southern California Children’s Health Study. Lung function and asthma status were assessed for 1,397 children, and additional personal characteristics were recorded. Generalized additive mixed effects models were fit to assess the marginal and joint associations between NOx, noise and respiratory outcomes.In an adjusted model we found a 14.5 mL (95 % CI: -40.0, 11.0 mL) decrease in forced vital capacity (FVC) per interquartile range (13.6 ppb) increase in NOx that was strengthened to a statistically significant 34.6 mL decrease (95% CI: -66.3, -2.78 mL) after adjusting for a non-linear function of noise. The associations with FEV showed a similar result.Without taking noise into account we would have drastically underestimated the detrimental effects of exposure to traffic-related pollution, indicating the importance of jointly assessing multiple traffic-related pollutants. Further contributions of noise measured at intersections, as well as other important factors including particulate matter metals and neighborhood greenspace, enhanced our assessment of the full effects this multipollutant mixture on respiratory outcomes in a children.