As a global center for petrochemical manufacturing, Houston, Texas, experiences some of the worst air quality in the country, according to the U.S. Environmental Protection Agency. Evidence suggests that air pollution disproportionately affects low-income, non-white and Hispanic residents, but it’s difficult to directly observe differences in pollutants between neighborhoods. Now, researchers have used airplanes and a satellite to uncover disparities in nitrogen dioxide amounts in the atmosphere above Houston.