California Air Resources Board

Exhaust emissions have steadily decreased due to legislative efforts and advancements in engine and control technologies. Further reduction of tailpipe emissions is expected by implementing a California Governor’s executive order (N-79-20) that, by 2035, new gasoline-powered cars and passenger trucks will not be sold in California. Meanwhile, brake and tire-wear will become dominant sources of vehicular PM_2.5 and PM₁₀ emissions. It is critical to understand their physical and chemical characteristics in examining near-road community exposure and potential adverse health effects. University of California Riverside measured brake and tire-wear emissions collected near two major highways: I-710 at Long Beach and I-5 at Anaheim, and characterized their roadside PM contributions, particle size distributions, and chemical compositions. The contribution from non-exhaust sources to total roadside PM_2.5 was 1 to 1.5 times greater than the exhaust PM_2.5 without including secondary PM_2.5 such as sulfates and nitrates. The main components of near-road PM_2.5 were organic matters, elements (Al, Si, Ca, Fe, Ti, Zn), and elemental carbon. These elements would be associated with road dust, brake-wear, tire-wear PM with markers of Al, Si and Ca, Fe and Ti, and Zn, respectively. Some of the heavy metals could associate with adverse health impact when exposed, which requires further comprehensive health risk and impact study.  

Please join us for a research seminar to hear an update on University to California, Riverside’s research that highlights the near-roadside brake and tire-were PM emission measurements and the contribution of non-exhaust PM in real-world environment along with their chemical and physical characteristics.