More than three decades after the Clean Water Act, two iconic waterways—the great coastal estuaries Puget Sound and the Chesapeake Bay—are in perilous condition. With polluted runoff still flowing in from industry, agriculture, and massive suburban development, scientists fear contamination to the food chain and drinking water for millions of people. A growing list of endangered species is also threatened in both estuaries. As a new president, Congress, and states set new agendas and spending priorities, FRONTLINE correspondent Hedrick Smith examines the rising hazards to human health and the ecosystem, and why it's so hard to keep our waters clean. Watch "Poisoned Waters" on air and online coming April 21, 2009 to PBS (check local listings).