Residents who live in the vicinity of industrial land and major highways bear the brunt of the city's poor air quality and have higher rates of asthma, according to new research from Rowan University. The study sought to trace the connections between air pollution, asthma and the history of redlining laws that led to disinvestment in minority neighborhoods. Philadelphia's air quality generally has improved since the 1980s, partly due to regulatory policies that reduce particulate matter, but more frequent wildfires that bring smoke from New Jersey and Canada are contributing to an increase in acute periods of poor air quality. Compared to last year's report from the American Lung Association, Philadelphia's air quality rank plummeted 11 spots among U.S. metro areas. Nationally, the State of the Air report found 4 in 10 Americans live in places with unhealthy levels of air pollution, including nearly half of children in the United States.