Super-Emitters On California Roads -On-road VOC fingerprinting from Mobile Monitoring

Various programs, regulations, and technologies targeting emissions from the vehicle fleet on roadways around the world have made significant air quality gains over the past few decades. However, recent monitoring in the San Francisco Bay and surrounding areas by the UC Berkeley Mobile Air Pollution Laboratory (CalMAPLab) has shown that high- emission vehicles (“super-emitters”) are likely now having an outsized impact on total fleet emissions. Fingerprinting and bounding the emission factors for these super-emitters is therefore critical in assessing the overall impact on air toxics from these vehicles. Here we present extensive chemical speciation (VOCs, combustion tracers, GHGs) from on- road and on-highway emissions measurements around the Bay Area performed by the CalMAPLab in 2025. We present and compare the speciated fingerprints for vehicles powered by gasoline and diesel, and super-emitters in these classes.