Mapping safer drinking water

by Cassandra Willyard
Thursday, January 5, 2012

Warmer colors represent a higher risk of arsenic-contaminated groundwater, while blues represent low-risk areas. Winkel L., Berg M., Amini M., Hug S.J., Johnson C.A., Nature Geoscience 1, 536-542 (2008)

Beginning in the 1970s, international aid agencies dug hundreds of thousands of wells in Bangladesh to help people access clean drinking water. The effort curbed diarrheal diseases, but it led to a new problem: arsenic poisoning.

Arsenic occurs naturally in some rocks, including formations throughout the Himalayas. When these rocks weather, the groundwater can become contaminated with arsenic. At high doses, arsenic is lethal. But even small doses can cause cancer and other health problems over time.

Southeast Asia, because of its geology and soil conditions, is especially at risk. Testing the groundwater in every village in the region, however, isn’t feasible. So researchers at the Swiss Federal Institute of Aquatic Science and Technology in Dübendorf, Switzerland, created a model that uses geologic variables and soil characteristics to predict arsenic contamination in groundwater. Their work appeared online July 11 in Nature Geoscience.

To develop the model, the researchers relied on groundwater data from Bangladesh, Cambodia and Vietnam. They found eight indicators that influence arsenic contamination, including the age of the surface sediments and the concentration of organic material. Based on the model, the researchers created risk maps.

Not surprisingly, Bangladesh appears to have the highest risk of groundwater contamination in this region. But the eastern coast of Sumatra and the Irrawaddy Delta in Myanmar — where arsenic contamination has never been recognized as a problem — are also at high risk.

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