where PWMk is the population-weighted mean exposure concentration for group k across n grid cells, Pi,k is the population of group k in grid cell i, and Ci is the concentration of PM2. where fj,k is the fractional contribution from source j on the exposure and disparity for group k, DA,j,k is the absolute disparity from source j for group k, and DA,t,k is the absolute disparity for group k from all on-road mobile sources. ) substantially exceed those experienced on average for the most-exposed racial-ethnic group, Hispanic Californians. Crucially, despite greater than 50% reductions in mobile-source population-weighted mean PM2.5 for all groups (A), relative racial-ethnic disparities increased for Hispanic, Black, and Asian Californians, as well as residents of overburdened communities.