Ranked alphabetically. Here are the top three.
Linfen, China, where residents say they literally choke on coal dust in the evenings, exemplifies many Chinese cities;
Haina, Dominican Republic, has severe lead contamination because of lead battery recycling, a problem common throughout poorer countries [image];
Ranipet, India, where leather tanning wastes contaminate groundwater with hexavalent chromium, made famous by Erin Brockovich, resulting in water that apparently stings like an insect bite