Naucalpan de Juárez, Mexico

With a population of 872,320, Naucalpan de Juárez is an industrial powerhouse just outside Mexico City - and a polluted, congested headache for residents. The city's growth has come at a cost, as the booming economy and urban sprawl have strained resources and the environment. Illegal settlements have encroached on the once-pristine Los Remedios National Park, while small businesses routinely flout environmental laws. Commuting is a constant battle, with automobiles accounting for 70% of the area's air pollution. But for those undeterred by bureaucratic obstacles and persistent infrastructure woes, Naucalpan offers abundant job opportunities and proximity to Mexico's vibrant capital.