The report’s overall findings that uses federal, state, local and tribal data, posit that from 2015-2017, more cities faced bad pollution days than measurements from 2014-2016. The data in the report says more than 141 million Americans, or 4 out of 10, live in counties that had at least one F grade for unhealthy air, an increase from 133.9 million in 2018’s report and 125 million in 2017.