By Daniel DeNoon, WebMD Medical News

April 29, 2005 -- America's air quality is a little bit better. But don't breathe a big sigh of relief -- especially if you're among the 52% of American's whose air is still unhealthy.

The American Lung Association today released its annual State of the Air report, using data collected from 2001-2003. The news is a little better than last year. There was less of the worst kind of air pollution -- small particle pollution -- thanks in part to curbs on coal-fired power plants.

These efforts -- and a cooler, wetter summer in some parts of the nation -- helped reduce ozone levels, too. Ozone is the main ingredient in smog.

That's good news. But not good enough, says ALA president John L. Kirkwood.

"Dirty air threatens the lives and health of far too many Americans," Kirkwood says in a news release.

Why is Kirkwood so grumpy? The ALA report shows that:

• 52% of Americans live in counties with unhealthy levels of either ozone or particle pollution.

• 49% of Americans live in areas with unhealthy ozone levels.

• 1 in 5 Americans live in areas with unhealthy year-round levels of particle pollution.

• 17% of Americans -- more than 50 million people -- live in the 47 counties that have unhealthy levels of ozone, year-round particle pollution, and short-term bursts of particle pollution.

Most at risk from bad air:

• Anyone aged 65 and older
• Children
• Anyone with asthma
• Anyone with chronic bronchitis or emphysema
• Anyone with any long-term lung disease
• Anyone with heart disease
• Anyone with diabetes

Worst Air/Best Air Quality

Keeping its reputation for terrible air quality, Los Angeles once again tops the list of metropolitan areas with the worst long-term particle pollution -- the most dangerous kind of air pollution.

The worst 25 metropolitan areas for year-round particle pollution (cities with the same rank are tied):

1. Los Angeles-Long Beach-Riverside, Calif.
2. Bakersfield, Calif.
3. Visalia-Porterville, Calif.
4. Pittsburgh-New Castle, Pa.
5. Fresno-Madera, Calif.
6. Detroit-Warren-Flint, Mich.
7. Hanford-Corcoran, Calif.
8. Cleveland-Akron-Elyria, Ohio
9. Atlanta-Sandy Springs-Gainesville, Ga.
10. Weirton-Steubenville, W.V.-Ohio
10. Cincinnati-Middletown-Wilmington, Ohio-Ky.-Ind.
12. New York-Newark-Bridgeport, N.Y.-N.J.-Conn.
12. Chicago-Naperville-Michigan City, Ill.-Ind.-Wis.
14. St. Louis-St. Charles-Farmington, Mo.-Ill.
15. Canton-Massillon, Ohio
15. Birmingham-Hoover-Cullman, Ala.
17. Charleston, W.V.
18. York-Hanover-Gettysburg, Pa.
18. Merced, Calif.
18. Lancaster, Pa.
21. Louisville-Elizabethtown-Scottsburg, Ky.-Ind.
22. Indianapolis-Anderson-Columbus, Ind.
22. Columbus-Marion-Chillicothe, Ohio
24. Washington-Baltimore-Northern Virginia, D.C.-Md.-Va.
24. Huntington-Ashland, W.V.-Ky.-Ohio

The best 26 metropolitan areas for year-round particle pollution (cities with the same rank are tied):

1. Cheyenne, Wyo.
2. Santa Fe-Espanola, N.M.
3. Honolulu, Hawaii
4. Great Falls, Mont.
5. Anchorage, Alaska
6. Kennewick-Richland-Pasco, Wash.
7. Farmington, N.M.
8. Tucson, Ariz.
8. Bismarck, N.D.
10. Bellingham, Wash.
11. Rapid City, S.D.
12. Grand Junction, Colo.
12. Colorado Springs, Colo.
14. Palm Bay-Melbourne-Titusville, Fla.
14. Fort Collins-Loveland, Colo.
14. Fargo-Wahpeton, N.D.-Minn.
17. Pueblo, Colo.
18. Albany-Corvallis-Lebanon, Ore.
19. Duluth, Minn.-Wis.
19. Cape Coral-Fort Myers, Fla.
21. Port St. Lucie-Fort Pierce, Fla.
22. Reno-Sparks, Nev.
23. Sarasota-Bradenton-Venice, Fla.
23. Redding, Calif.
23. El Centro, Calif.
23. Deltona-Daytona Beach-Palm Coast, Fla.