The American Lung Association’s annual “State of the Air” report gave Polk County an “A.” The association, using U.S. Environmental Protection Agency data, grades metro areas on smog and particle pollution. The report indicates that more than four in 10 Americans live in counties where ozone or particle pollution levels make the air unhealthy to breathe. Among the few other Iowa counties ranked, Story got an “A,” Linn received a “B,” and Clinton and got a “C.” The full report can be found online.