To that score, 24/7 Tempo added each municipality’s average daily PM2.5 (the concentration of particulate matter with a diameter of less than 2.5 micrometers) per cubic meter of air for each city’s county, drawn from the County Health Rankings and Roadmaps, a collaboration between the University of Wisconsin Population Health Institute and the Robert Woods Johnson Foundation. Population figures are from the U.S. Census Bureau’s 2019 American Community Survey five-year estimates. (See how the population of every state has changed since 1880.)
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