The most polluted cities in America

Bryan Walsh has a Time article about places not to live:

(three-way-tie): Cincinnati, Ohio; Middletown, Kentucky; Wilmington, Indiana
El Centro, California
(tie): Pittsburgh, Pennsylvania & New Castle, Pennsylvania
(tie): Visalia, California & Porterville, California
Modesto, California
(three-way-tie): Los Angeles, California; Long Beach, California; Riverside, California
(tie): Hanford, California; Corcoran, California
(tie): Fresno, California; Madera, California
(tie): Merced, California; Bakersfield, California

Rico says he's surprised that so many of them were in California, and so few in Ohio...