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.