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Leaking lead

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1:06pm, May 23, 2006
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A disinfectant used by U.S. water utilities dissolves lead in laboratory experiments. The finding bolsters the notion that the disinfectant, called monochloramine, may be responsible for increased lead in some drinking-water supplies.

Utilities have traditionally disinfected drinking water with chlorine. However, the chemical can react with organic compounds in water, generating by-products that include suspected cancer-causing agents. So, some utilities have switched to monochloramine, a compound of chlorine, nitrogen, and hydrogen.

But with the swap came reports of higher concentrations of lead in some water supplies. For example, Washington, D.C.'s water contained lead levels as high as 48,000 parts per billion (ppb) in 2003, 3 years after the city began using monochloramine. The Environmental Protection Agency limits lead in drinking water to 15 ppb. Sources of lead contamination include corroding pipes and solder.

To investigate monochloramine's effect, Jay A. Switzer of the University of Missouri–Rolla and his colleagues measured changes to the mass of lead film after treatment.

A 112-microgram film exposed to a monochloramine solution for 20 hours lost 96 percent of its mass. "The film just about completely dissolves," says Switzer. A similar film immersed in chlorine for the same amount of time dropped only 4 percent of its mass, the researchers report in the May 15 Environmental Science & Technology.

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