Toxic foam blights river crucial to Brazil's biggest city

The Tiete river, some 1,100 kilometers long, is crucial for potable water, irrigation and energy production in southeast Brazil, the country's most populated area. But parts of the waterway, including one area just 100 kilometers (62 miles) from the metropolis, have been befouled by phosphate and phosphorus residues from household detergents used by Sao Paulo's 22 million inhabitants and washed down the sewers.