We estimated statewide group-level exposures to annual average PM2.5 as populationweighted mean (PWM) concentrations, consistent with the air pollution disparity literature . For the metrics below, we consider only on-road mobile source exposure (i.e., we neglect contributions from other source types unless explicitly stated otherwise). To estimate exposure to PM2.5 for each year, we calculate geographic intersections between the 2010 Census tract boundaries and the gridded concentration estimates. Population is down-sampled based on areaapportionment; concentration estimates are assumed to be constant throughout the grid cell.