Cincinnati Engineering Study Finds Clue to Bangladesh's Poisoned Water

Irrigation pumping used to grow rice during dry seasons is one of the culprits in what has been called “the worst case of natural contamination in human history,” a study led by University of Cincinnati engineering professor Shafiqul Islam has shown.

An article in a special water-themed issue of the journal Nature focuses on Islam’s work in Bangladesh, where naturally occurring arsenic is poisoning the drinking water of millions of people. (See issue at  http://www.nature.com/nature/focus/water/).

Islam and colleagues at the Massachusetts Institute of Technology, University of British Columbia and the Bangladesh University of Engineering and Technology have been working to solve the problem of mass arsenic poisoning in Islam’s native country, Bangladesh. An estimated 75 million people in Bangladesh and neighboring areas of West Bengal in India are at risk of increased cancer rates and other health problems caused by arsenic in groundwater drinking supplies.

 Tragically, the problem is an unforeseen consequence of shifting Bangladesh from a drinking water supply that used surface water to one that uses groundwater.  To prevent the spread of water-borne diseases such as cholera and other life-threatening diseases, Bangladesh and international aid agencies installed 6-10 million wells throughout the nation. 

Unfortunately, many of these new wells contain unsafe levels of arsenic. While the allowable standard for arsenic in the United States is 50 parts per billion, in many of the Bangladesh wells, arsenic levels reach to 500-1000 parts per billion, with the worst at 2,400 parts per billion. It takes several thousand parts per billion to cause immediate death. The cumulative impact of the tainted water supply, however, can lead to skin cancers and other disorders.

Islam and his colleagues find that these elevated arsenic levels appear to be linked to dry-season irrigation pumping, which carries water from below ground to where it is needed to grow rice to feed the country’s population. Islam surmises that “deep groundwater is being replaced by surface water that is rich in organic material, which then mobilizes previously insoluble arsenic,” the Nature article states. Monsoon season, which deluges the countryside from July to October, carries organic materials and rainwater down into the wells to replace what has been pumped out and creates favorable conditions for biogeochemical reactions that take the arsenic from a safe solid state to an unsafe liquid state, says Islam.

One possible remedy that has already begun to be used is to dig deeper wells, Islam and his co-researchers say. Unsafe levels of arsenic are associated with wells that are about 100 feet deep or about 40 meters. The team suggests that a safer depth may be more than 400 feet. “This is a good solution as long as we can establish that these deeper wells will not also become contaminated,” he says. A drawback to the deeper wells is their greater expense, he adds. “It can be five to 10 times more expensive to make these deeper wells.”

In addition to their research, Islam and his partners have been holding workshops in South Asia so that intellectual expertise can be developed closer to home and nearer to the communities where problems arise. The workshops are held through U.S.-Bangladesh partnerships and the South Asian Consortium of Interdisciplinary Water Studies.

Study results were published in a recent issue of Science. The work has been funded by a $400,000 National Science Foundation grant. Islam also received a Fulbright to research the problem in fall 2001.