If the Pittsburgh region could sue American Lung Association (ALA) for defamation of character, it just might have a slam-dunk case.

Since World War II, what was then the "Smoky City" has been transformed remarkably. Still, the impression people elsewhere have of our region always has lagged behind the reality, though the history of that transformation and all those sparkling shots of Downtown from Mt. Washington during national telecasts of Pittsburgh sporting events have helped our region's image.

But whatever progress we've made in battling that archaic, smoky image largely was wiped out on April 30, when people across the nation awoke to headlines, such as "Pittsburgh No. 1 in soot," prompted by ALA's latest air pollution rankings of U.S. metro areas.

And what's really galling is that ALA based that ranking on just one air quality monitoring station among 20 spread across eight counties. That station just happens to be downwind from U.S. Steel's Clairton Coke Works and monitors air quality in only five communities of about 25,000 people total -- about 2 percent of Allegheny County's 1.2 million people, and an even smaller part of the eight-county region's population.

Those details weren't mentioned prominently, if at all, in national-media stories on the rankings. We wish those media outlets would have done a better job of explaining ALA's cherry-picking, but we weren't surprised they didn't.

ALA justified its treatment of the Pittsburgh region by saying it based its rankings on the worst air-quality readings for each metro area included, but to us, that just confirms use of a strategy driven by ALA's desire to advance its own agenda, not by objectivity.

Could Pittsburgh's air be better? Sure. But the six-decade trend that has made today's skies in our region unrecognizable to the parents and grandparents of today's Pittsburghers continues, including environmental upgrades for the Clairton Coke Works.

ALA does much good for those battling lung-related illnesses, but it did a hatchet job on Pittsburgh. Intended or not, that was the effect of the rankings.

Clear facts can be just as important as clear skies, so we'll be clear: Just as soot is a form of air pollution, ALA's rankings are a form of media pollution.

Now, let's get started on more long years of effort to reverse the damage ALA has done to Pittsburgh's image.