Two organizations set the gold standard for measuring air quality in American cities. The first is the American Lung Association’s “State of the Air 2026”; the second is the IQAir Air Quality in the World study. Both draw on similar datasets.
At a time when the dangers of air pollution are a frequent subject of research and public discussion, clean air rarely makes headlines. Yet the cities on this list have achieved notably good air quality — for reasons that, unfortunately, are difficult to replicate elsewhere. That means the solutions to air pollution are not likely to be found by studying them.
Each study measures some combination of three pollutants: ozone, short-term particle pollution (24-hour PM2.5), and year-round particle pollution (annual PM2.5)…