Decades of heavy industrial development along the Milwaukee River has contributed to significant amounts of PCBs and heavy metals polluting groundwater and draining towards Lake Michigan. The 1.5 million residents of the Milwaukee-Waukesha metro endure air that's ranked 20th for short-term particle pollution. Sperling Air Quality Index:
26 Sperling Water Quality Index:
(AP Photo/Roger Schneider) More from Forbes
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