Knoxville, Tenn., tops the list of the 100 most challenging U.S. cities for people living with asthma (search).

Memphis, Tenn., and Louisville, Ky., took the second and third spots in the second annual ranking of U.S. asthma cities. Washington, D.C. jumped from number 50 last year to number five in this year’s list.

Researchers say more than half of the 20 million Americans with asthma suffer from the allergic form of the disease, which is aggravated by exposure to allergens like pollen, dust mites, and mold.

In compiling the 2005 U.S. asthma cities list, the Asthma and Allergy Foundation of America (search) ranked the top 100 metropolitan areas in the country based on 12 asthma risk, medical, and prevalence factors, such as:

Estimated and reported prevalence of asthma Asthma-related deaths Annual pollen level Annual air quality Public smoking laws Number of asthma specialists School asthma-inhaler access laws Uninsured rate Poverty rate

Based on those factors, the following cities were ranked the top 100 worst cities for asthma sufferers:

Top 100 Asthma Cities:

1. Knoxville, Tenn.
2. Memphis, Tenn.
3. Louisville, Ky.
4. Toledo, Ohio
5. Washington, D.C.
6. St. Louis, Mo.
7. Allentown, Pa.
8. Springfield, Mass.
9. Grand Rapids, Mich.
10. Scranton, Pa.
11. Indianapolis
12. Columbus, Ohio
13. Pittsburgh
14. Phoenix-Mesa, Ariz.
15. Birmingham, Ala.
16. Chattanooga, Tenn.
17. Detroit
18. Atlanta
19. Lancaster, Pa.
20. Fresno, Calif.
21. Little Rock, Ark.
22. Hartford, Conn.
23. Oklahoma City
24. Johnson City, Okla.
25. Milwaukee
26. Harrisburg, Pa.
27. Charlotte, N.C.
28. Madison, Wis.
29. Philadelphia
30. Canton, Ohio
31. Kalamazoo, Mich.
32. Lexington, Ky.
33. Greensboro, N.C.
34. Youngstown, Ohio
35. Nashville, Tenn.
36. Tulsa, Okla.
37. Dayton, Ohio
38. Lansing, Mich.
39. Modesto, Calif.
40. Augusta, Ga.
41. Wichita, Kan.
42. Los Angeles
43. Cincinnati
44. Chicago
45. Omaha, Neb.
46. Syracuse, N.Y.
47. Jackson, Miss.
48. Raleigh, N.C.
49. Cleveland
50. Baltimore
51. Minneapolis-St. Paul, Minn.
52. Kansas City, Mo.
53. Bakersfield, Calif.
54. Boise City, Idaho
55. Fort Wayne, Ind.
56. Mobile, Ala.
57. Spokane, Wash.
58. Greenville, S.C.
59. Buffalo, N.Y.
60. Portland, Ore.
61. Tucson, Ariz.
62. Richmond, Va.
63. Salt Lake City
64. Columbia, S.C.
65. Providence, R.I.
66. Boston
67. El Paso, Texas
68. Charleston, S.C.
69. Las Vegas
70. Rochester, N.Y.
71. Sacramento, Calif.
72. New York
73. Stockton, Calif.
74. McAllen, Texas
75. Tampa, Fla.
76. Austin, Texas
77. Albuquerque, N.M.
78. Orlando, Fla.
79. New Orleans
80. Des Moines, Iowa
81. Baton Rouge, La.
82. San Diego
83. Albany, N.Y.
84. Jacksonville, Fla.
85. Pensacola, Fla.
86. Houston
87. Lakeland, Fla.
88. Norfolk, Va.
89. San Antonio
90. Sarasota, Fla.
91. Melbourne, Fla.
92. Colorado Springs, Colo.
93. Fort Meyers, Fla.
94. Dallas-Ft. Worth, Texas
95. West Palm Beach, Fla.
96. Seattle
97. Denver
98. Daytona Beach, Fla.
99. Miami
100. San Francisco

By Jennifer Warner, reviewed by Michael W. Smith, MD

SOURCES: The U.S. Asthma Capitals, Asthma and Allergy Foundation of America. News release, Asthma and Allergy Foundation of America.