Non-exhaust emissions, including brake and tire-wear particles, have become more significant contributors to traffic-related PM emissions as exhaust emissions have steadily decreased. Thus, it is important to understand their contribution to local and regional air quality and impact on roadside exposure and health effects. This research has measured PM samples at upwind and downwind locations near two major highways: one for truck and car mixed fleet on I-710 (Long Beach Location) and one for car dominant fleet on I-5 (Anaheim Location) in Southern California and evaluated chemical and physical characteristics of the samples such as elements/organic matter and particle size, respectively, which were used for source apportion analysis. Source apportionment analysis showed that the contribution from non-exhaust sources to the roadside PM2.5 was 1 -1.5 that of primary exhaust PM2.5 (i.e., without including secondary PM2.5 formed downwind of the near roadway locations). The relative magnitude of the non-exhaust and direct exhaust PM emissions measured is in good agreement with emission inventory (EMFAC2021) estimation, in which brake and tire-wear PM2.5 emissions are 1.3 times greater than the exhaust emission in 2020. In the study, non-exhaust PM10 emissions were 2-3 times direct exhaust PM10 emissions. It is worth noting that a large amount of the coarse PM was identified as road dust including pavement materials, soil dust, etc. In addition to exhaust and non-exhaust PM, road dust should be considered in future investigation of health effects on the near-road communities.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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