Slideshow: 10 Worst Cities for Asthma, 2008

Asthma affects more than 22 million Americans and is on the rise.

No. 10 Worst Asthma City: Greensboro, North Carolina.

No. 9 Worst Asthma City: St. Louis, Missouri.

No. 8 Worst Asthma City: Greenville, South Carolina.

No. 7 Worst Asthma City: Charlotte, North Carolina.

No. 6 Worst Asthma City: Allentown, Pennsylvania.

No. 5 Worst Asthma City: Memphis, Tennessee.

No. 4 Worst Asthma City: Atlanta, Georgia.

No. 3 Worst Asthma City: Milwaukee, Wisconsin.

No. 2 Worst Asthma City: Tulsa, Oklahoma.

No. 1 Worst Asthma City: Knoxville, Tennessee.

Did your city make the list?

Asthma is a chronic disease of the airways that makes breathing difficult. Many things in the environment can trigger an attack, including air pollution, secondhand smoke, and pollen. While there are no asthma-free cities, some are more challenging than others for people living with asthma. The Asthma and Allergy Foundation of America (AAFA), a nonprofit patient organization, has released their "2008 Asthma Capitals." Here are the top 10.

No. 10: Greensboro, N.C.

Greensboro may be situated among gently rolling hills, but there's nothing pretty about the asthma picture here. It comes in at No. 10 on the list of "worst" asthma cities. Twelve factors were used to formulate the list, including air quality, asthma prevalence, pollen scores, poverty levels, and asthma death rates. "Each factor is given a weighted value by medical and research experts according to its effect on 'quality of life' for asthma patients," says the AAFA.

No. 9: St. Louis, Mo.

The Gateway Arch is not the only thing in the air in St. Louis. High pollen levels and poor air quality contribute to big asthma issues -- and brings it in at No. 9. That's a significant leap from the No. 28 spot it held in 2007.

No. 8: Greenville, S.C.

Poor air quality and an above average use of controller medications by asthma suffers contribute to Greenville's ranking as one of the worst cities for asthma in the U.S. It jumped to No. 8, from No. 34 in 2007.

No. 6: Allentown, Pa.

This small Rust Belt city has big asthma issues, jumping to sixth place from No. 16 in 2007. A high prevalence of asthma and a low number of asthma specialists in the area are contributing factors.

No. 5: Memphis, Tenn.

This Mississippi river town has many asthma sufferers singing the blues. Memphis has skyrocketed from the No. 30 spot in 2007 to the top five this year, with high poverty rates and poor air quality partly to blame. While asthma doesn't discriminate based on socio-economic status, people living in poverty often have less access to health care and medications needed to manage their condition.

No. 4: Atlanta, Ga.

Southern hospitality? While Atlanta wasn't so hospitable for asthma sufferers this past year, things do seem to be improving. Atlanta edged its way down the list a little, from its starring No. 1 spot in 2007.

No. 3: Milwaukee, Wis.

Asthma problems are brewing in this Lake Michigan city. Milwaukee bubbled up from the No. 7 spot in 2007 to third place this year. The town gets low marks for air quality and is worse than the national average for the use of "rescue" asthma medications.

No. 2: Tulsa, Okla.

Once dubbed the "Oil Capital of the World," Tulsa is now ranked as the No. 2 "Asthma Capital" of the United States, rocketing up from No. 25 in 2007. The city has a high prevalence of asthma and a low number of asthma specialists, according to data compiled by the AAFA..

No. 1: Knoxville, Tenn.

For the third time in five years, Knoxville has been ranked by the AAFA as the worst asthma city in America. High pollen counts, poor air quality, the lack of a smoking ban in all public places, and the above average usage of asthma medications all contribute to this distinction.