In the US, where people breathe increasingly dirty air, one small city stands out

By Jen Christensen, CNN (CNN) — The American Lung Association calls it a “grim indication of the deterioration of air quality nationwide”: Bangor, Maine, is the last city standing on all three of its “cleanest cities” lists. Bangor has zero days of unhealthy ozone and short-term particle pollution, and some of the lowest year-round concentrations