Intersections as Hot Spots: Assessing the Contribution of Localized Nontailpipe Emissions and Noise on the Association Between Traffic and Children's Lung Function.

introductionTraffic emissions comprise a complex mixture of pollutants, including tailpipe (exhaust), nontailpipe (e.g., brake and tire wear, resuspended road dust), and noise pollution. While regulations have drastically reduced tailpipe emissions, the growing vehicle fleet and miles traveled have contributed to rising levels of nontailpipe and noise emissions. These under-regulated exposures, often rich in toxic transition metals, may pose significant health risks, particularly when noise acts as a co-exposure that may influence traffic-related effects.

methodsWe examined lung function effects associated with nontailpipe exposures in the Children's Health Study (CHS), a cohort of over 1,200 children from eight Southern California communities. Participants underwent lung function testing for forced expiratory volume in 1 second (FEV Participant-specific estimates of particulate matter (PM) mass and metal exposures were developed by applying spatiotemporal regression models to measurements of quasi-ultrafine (PM Traffic noise exposures were estimated at a 20-m resolution along roadways using two approaches: (1) mobile measurements of A-weighted equivalent noise levels (LAeq in decibels [dB]) collected in Long Beach and modeled using machine learning; and (2) CadnaA, an acoustic model applied to generate LAeq across all communities. We used mixed effects models to evaluate associations between exposures and lung function, adjusting for covariates and accounting for repeated measures.

resultsSpatiotemporal PM models showed strong performance (leave-one-community-out cross-validation coefficient of determination [R Noise models using extreme gradient boosting (XGB) achieved high accuracy (leave-one-route-out cross-validation R Epidemiologically, coarse and fine nontailpipe metals, especially iron (Fe) and copper (Cu) as markers of road dust and brake wear, were consistently and significantly associated with reduced FEV Traffic noise was not independently associated with lung function but strongly confounded the OC

conclusionsThis study highlights the lung function impacts of PM components, the role of traffic noise, and the influence of green space. From an exposure modeling standpoint, a major takeaway is the importance of meteorology and intersection features for PM components, and meteorology, traffic volume, and land use for traffic noise. Nontailpipe metals had the strongest and most consistent associations with reduced lung function, likely via oxidative stress pathways. Noise influenced the associations of tailpipe markers, reflecting a separate stress mechanism. Green space emerged as a protective factor, highlighting its potential to influence adverse associations between traffic-related air pollution and children's respiratory health. As nontailpipe sources grow in importance with increased electric vehicle adoption, mitigation strategies should target brake, tire, and road wear. Regulatory actions, lighter electric vehicle designs, and regenerative braking could help. Simultaneously, expanding green space offers a feasible, co-beneficial intervention to buffer both air and noise pollution and to promote children's respiratory health.