Stanford scientists find new solutions for the arsenic-poisoning cris...( Every day more than 140 million peop...)

Every day, more than 140 million people in southern Asia drink groundwater contaminated with arsenic. Thousands of people in Bangladesh, Cambodia, India, Myanmar and Vietnam die of cancer each year from chronic exposure to arsenic, according to the World Health Organization. Some health experts call it the biggest mass poisoning in history.

More than 15 years ago, scientists pinpointed the source of the contamination in the Himalaya Mountains, where sediments containing naturally occurring arsenic were carried downstream to heavily populated river basins below.

But one mystery remained: Instead of remaining chemically trapped in the river sediments, arsenic was somehow working its way into the groundwater more than 100 feet below the surface. Solving that mystery could have significant implications for policymakers trying to reverse the mass poisoning, said Stanford University soil scientist Scott Fendorf.

"How does the arsenic go from being in the sediment loads, in solids, into the drinking water?" said Fendorf, a professor of environmental Earth system science and a senior fellow at Stanford's Woods Institute for the Environment.

To find out, he launched a field study in Asia in 2004 with two Stanford colleagues: Chris Francis, an assistant professor of geological and environmental sciences, and Karen Seto, now at Yale University. The initial study was funded with a two-year Woods Institute Environmental Venture Projects grant. Five years later, the research team appears to have solved the arsenic mystery and is working with policymakers and government officials to prevent the health crisis from escalating.

"The real thing is, how do we help the people who are there?" Fendorf said. "But first, we have to understand the coupling of hydrology-the way the water is flowing-with the chemistry and biology."

Arsenic-laden rocks in the Himalayas feed into four major river s
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