The purpose of this study was to estimate cancer risks from air toxics in Southwest Chicago. The study area is approximately 16 square miles, and about 93,854 people live in the study area. The emissions inventory included 174 industrial point sources, area sources, road vehicles, emissions at Midway Airport, and nonroad mobile source emissions, such as lawn mowers and snowblowers. Air dispersion modeling was then used to estimate the concentration of the pollutants in the area and these modeled estimates were compared to monitored concentrations. Cancer risk was estimated for each pollutant based on the unit risk of each chemical, and these were summed up for all pollutants and source categories to determine lifetime risk.