Various studies show that people of color are disproportionately exposed to air pollution in the United States. However, it was unclear whether this unequal exposure is due mainly to a few types of emission sources or whether the causes are more systemic. A new study that models peoples’ exposure to air pollution – resolved by race-ethnicity and income level – shows that exposure disparities among people of color and white people are driven by nearly all, rather than only a few, emission source types.