Are you breathing dirty air?

Except for those who live in areas well known for polluted air – Los Angeles, say – most of us tend to think that the air's pretty clean where we are. Think again, says the American Lung Association (ALA). About 6 out of 10 Americans – 186.1 million people – are breathing dirty air. And we're not talking just a little pollution. "Forty million Americans live in counties where the air quality has failed every single test," says Charles D. Connor, president and CEO of the ALA, which issued a new State of the Air report card today.

The city with the cleanest air? Fargo, N.D. It's the only place with a passing grade in the three main categories of air pollution: ozone pollution, year-round particle pollution, and short-term (24-hour) particle pollution.

Other cities that ranked high include Billings, Mont.; Bismarck, N.D.; Cheyenne, Wyo.; Colorado Springs, Colo.; Farmington, N.M.; Ft. Collins, Colo.; Honolulu; Lincoln, Neb.; Midland-Odessa, Texas; Port St. Lucie, Fla.; Pueblo, Colo,; Redding, Calif.; Salinas, Calif.; San Luis Obispo, Calif.; Santa Fe-Espanola, N.M.; Sioux Falls, N.D.S.D.; and Tucson, Ariz.

The worst air quality was found in – no surprise – Los Angeles, which has topped this sort of list for years because of ozone pollution. Other cities with big ozone problems are Pittsburgh (despite the widespread belief that the city has licked its air-pollution problem), and three California cities: Bakersfield, Visalia-Porterville, and Fresno-Madera.

Some cities that most would expect to be on the clean-air list received failing grades. Salt Lake City and Logan, Utah, for instance, came in at Nos. 6 and 8 respectively on the list of areas with the most short-term particle pollution.

As you might expect, there were some quibbles about the grades (and no doubt there will be more). Some California officials complained that "the study lumped together areas with heavy smog, such as Los Angeles, with counties that had moderate levels of the pollutants, such as Santa Clara, giving both an 'F,' " reports MercuryNews.com.

You can check the report card for your state by clicking here. It gives grades by counties for high ozone days and particle pollution, but not all counties monitor air pollution.

Added later: Think the smog is bad in L.A.? Read this Monitor article about Bakersfield, Calif.