City Pollution Disparity Levels (IMAGE) University of Minnesota Caption This shows the difference in population-weighted mean NO2 concentrations (ppb) between lower-income nonwhites and higher-income whites for U.S. cities (448 urban areas). Credit University of Minnesota Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.