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October 21, 2002
Volume 80, Number 42
CENEAR 80 42 pp. 42-45
ISSN 0009-2347


TACKLING ARSENIC IN BANGLADESH
International team of scientists volunteers its labor to help address major health crisis

REBECCA L. RAWLS, C&EN WASHINGTON

An international team of volunteer scientists from Canada, the U.S., and France has prepared detailed maps of the levels of arsenic and 29 other metals in the drinking water of Bangladesh. Their study suggests that the wide-scale arsenic poisoning that has been devastating much of Bangladesh for the past decade may be exacerbated by the presence of metals besides arsenic in well water used for drinking. Ironically, the poisoning may be exacerbated, as well, by the lack of certain other metals in the drinking water, which, if present, might mitigate some of arsenic's ill effects.

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HELPING HAND Sarkar talks with villagers in Bangladesh.

"Our results may allow scientists, policymakers, and aid workers to initiate programs to assist the areas most affected by the toxic metals documented by these studies," says Bibudhendra Sarkar, leader of the team. Sarkar is a senior scientist at the Hospital for Sick Children in Toronto and professor of biochemistry at the University of Toronto.

The World Health Organization (WHO) calls the arsenic poisoning in Bangladesh the largest mass poisoning of a population in history. In one of the world's poorest and most densely populated countries, tens of millions of people--perhaps as many as half of the country's 137 million people--are drinking water that contains unsafe levels of arsenic. Chronic exposure to arsenic at these levels causes skin changes that include the development of dark spots and thick growths. Over time, it can lead to several types of cancer.

Beginning in the 1970s, international aid organizations helped to dig literally millions of relatively shallow wells, known as tubewells, throughout the country. The intent was to provide a safer source of drinking water than the surface water most people were drinking, which often was contaminated with bacteria that cause waterborne diseases such as cholera and diarrhea. By some measures, the program was successful: 97% of the people in Bangladesh now get their drinking water from tubewells, and infant mortality from these diseases has plummeted.

Unfortunately, much of the groundwater being tapped by the tubewells contains high levels of several toxic metals, particularly arsenic. By 1993, the Bangladesh Department of Public Health Engineering was reporting widespread signs of arsenic poisoning among the population and identifying tubewell water as the source of the arsenic.

Although a great deal of information about arsenic in the water in Bangladesh is available on Internet sites and from international organizations such as WHO and UNICEF (the United Nations International Children's Emergency Fund), much of these data are little more than guesses, Sarkar says. Too often, he says, the information being reported is based on limited sampling or has not undergone careful peer review. It was to address this need for solid scientific data on the extent and nature of the water contamination that he and his colleagues conducted their study [Environ. Health Perspect., 110, 1147 (2002), published online Sept. 20, http://ehpnet1.niehs.nih.gov/docs/2002/110p1147-1153frisbie/abstract.html].

THE PROJECT BEGAN in 1997 when Sarkar, an expert on metal-caused diseases, teamed up with Seth H. Frisbie, an environmental scientist now with Better Life Laboratories, Plainfield, Vt. Frisbie had already done fieldwork measuring the levels of arsenic, iron, and several other metals in tubewell water in Bangladesh. Although now a Canadian citizen, Sarkar was born in eastern India near present-day Bangladesh. In 1997, he traveled to Bangladesh, accompanied by a film crew from Canadian Television, to make a documentary on the health crisis there.

What Sarkar saw in Bangladesh made a profound impression on him. "I have never seen so many sick people as were in many of these villages," he recounts. "There are no doctors, no clinics. They don't even know what is happening to them."

Sarkar was struck, in particular, by the fact that "even small children were coming down with metal-connected sickness. They had the dark spots on their bodies associated with arsenic poisoning." That observation was puzzling, he explains, because arsenic is a slow poison. Ordinarily, physical symptoms of toxicity take at least 10 years to develop.

"When I saw these small children, I started wondering what is happening to them." Sarkar recalls. "Naturally, with my background in bioinorganic chemistry, I started wondering if there were other toxic metals coming to them in the water."


"I have never seen so many sick people as were in many of these villages. They don't even know what is happening to them."


MEANWHILE, quite independently, Frisbie and another scientist who would later join the project, hydrogeologist Donald M. Maynard of Johnson Co., Montpelier, Vt., were in Bangladesh analyzing water from tubewells for arsenic and several other metals in a project funded by the U.S. Agency for International Development. The project's aim was to determine whether an earlier AID-funded program of rural electrification in Bangladesh might have inadvertently contributed to the arsenic problem by installing wooden electrical poles that had been treated with copper, chromium, and arsenic.

The study found no connection between the earlier project and the arsenic in Bangladesh's groundwater, which is of geologic origin. In the process, the researchers analyzed water from some 570 tubewells throughout the country and produced what Frisbie says was the first countrywide map of arsenic contamination of the groundwater. That study concluded that about 45% of Bangladesh's land area contains wells with arsenic concentrations above 50 ppb, which is the standard for safe drinking water in Bangladesh, although WHO advocates a lower standard of 10 ppb.

In the 1997 AID-sponsored survey, water samples were analyzed in Bangladesh using a colorimetric technique, Frisbie explains. Equipment needed for more sensitive analysis, such as atomic absorption spectroscopy, was not available in-country, he notes. Consequently, the study was unable to detect arsenic at levels as low as 10 ppb.

In the course of this initial survey, Frisbie and his colleagues also measured Fe(II) concentrations in some of their samples as part of their effort to identify the source of the arsenic in the groundwater. Many samples contained something that interfered with these Fe(II) measurements, Frisbie says. The results suggested the presence of other metals, although the researchers didn't take the work any further at the time.

When Frisbie saw the Canadian Television documentary, he contacted Sarkar. The two began to put together a follow-up project to find out whether there were other potentially toxic metals in Bangladeshi drinking water and whether some of them might be contributing to the toxic effects Sarkar was seeing in children.

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Khandaker

THE TWO RESEARCHERS returned to Bangladesh in December 1998. Over a period of about a month, they interviewed villagers and collected water samples from 112 tubewells throughout the country. After doing preliminary work on the water samples in Bangladesh, they sent them to Richard Ortega, a former postdoc of Sarkar's, who is now an environmental analytical chemist at the French National Center for Scientific Research (CNRS) laboratory at the University of Bordeaux, where Ortega is also an assistant professor. Ortega analyzed the samples using CNRS's inductively coupled plasma/mass spectrometers. Maynard mapped the resulting data.

Because this was a volunteer effort, the scientists had to make time for it around their regular work schedules or when the analytical instruments were not being used for other projects. Consequently, it took nearly four years to prepare the data for publication.

The study finds that although the most significant health risk from drinking Bangladesh's tubewell water is chronic arsenic poisoning, other metals may be contributing to the problem as well. The team found 48% of the samples contained arsenic above the 10-ppb level recommended by WHO. That means about 60 million people may be drinking this water, the researchers say. Furthermore, 97% of the water samples that contained detectable levels of arsenic also contained detectable levels of antimony, a metal known to magnify arsenic toxicity.

In addition, the team's data suggest that tens of millions of Bangladeshis are drinking water that exceeds WHO guidelines for manganese, a mutagen that has also been associated with neurological damage; lead, a possible carcinogen that also causes other health problems in humans; and nickel and chromium, both carcinogens.

The severity of chronic arsenic poisoning in Bangladesh might be magnified by the lack of selenium, zinc, or both in much of the drinking water, the team suggests. Selenium can inhibit arsenic toxicity, Sarkar points out, but 92% of the water samples that contained detectable levels of arsenic did not have detectable levels of selenium. Less frequently, zinc was also absent. This element promotes the repair of tissues damaged by arsenic. The team could not detect it in 18% of the samples containing arsenic.

THE STUDY DRAWS attention to an important problem, says Joan S. Valentine, professor of chemistry and biochemistry at the University of California, Los Angeles. Valentine, who has known of the project for a number of years, is particularly impressed that these scientists "were willing to give their time and attention for totally humanitarian reasons to something which is not funded."

Yet the findings themselves are not new, says Nadim R. Khandaker, a former head of UNICEF's arsenic mitigation project in Bangladesh who now works at Sandia National Laboratories. In fact, Khandaker is concerned that by drawing attention to other metals in the drinking water, the new study may divert limited resources from what he sees as the principal problem--the arsenic.

Born in what is now Bangladesh and trained as a chemical and environmental engineer, Khandaker worked for UNICEF in Bangladesh for a year, beginning in 1998. His current work focuses on developing and evaluating systems to remove arsenic from water.

The new findings parallel in many respects the results of a much larger study of some 3,500 wells conducted by the British Geological Survey (BGS) and published in 2000, Khandaker says. Sarkar and his colleagues have criticized the BGS study as not being peer reviewed, a criticism that Khandaker disputes. "It's an official document, published jointly by BGS and the government of Bangladesh," he points out. "I don't know what peer review means in that context. This document is the baseline that everybody uses when they talk about arsenic and water quality in Bangladesh."


The wide-scale poisoning that has been devastating much of Bangladesh for the past decade may be exacerbated by the presence of metals besides arsenic in the drinking water.


THE BGS STUDY looked at water from both deep (more than about 300 meters) and shallower wells. Among the shallower wells, the study found 27% had water that contained more than 50 ppb of arsenic and 46% had more than 10 ppb. "Arsenic is not the only groundwater problem," the study concluded, "but it is undoubtedly the most serious." Manganese is the next biggest cause of concern, according to this study, in terms of both the number of wells affected and the degree to which wells exceeded drinking water standards. The study also noted boron and uranium as potentially toxic metals sometimes present at levels high enough to cause health concerns.

UNICEF, in conjunction with the Bangladesh Department of Public Health Engineering, has an ongoing and even larger program to test arsenic levels in water from tubewells throughout Bangladesh, Khandaker points out. Begun in 1996, the program has tested well over 100,000 wells, he says. Results from 51,000 tubewells tested through the end of 1999 have been compiled and distributed by UNICEF, although they have not been published in peer-reviewed journals. The UNICEF study found arsenic above the 50-ppb level in 29% of the wells tested. It estimates that 80% of the people of Bangladesh have access to safe drinking water.

Khandaker also questions Sarkar's report of seeing children who show visible signs of arsenic poisoning. "I didn't see these symptoms, and I don't know of anyone else who is actually working with children who has reported these symptoms," Khandaker says.

Although they have points of disagreement, Khandaker and Sarkar and his colleagues all concur that efforts under way to provide safe drinking water in Bangladesh should be based on good science and focus limited resources in effective ways.

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WILLING VOLUNTEER Frisbie poses with young Bangladeshis.


PROGRAMS ARE under way. Over the past two years, the World Bank has provided $52 million to help find alternative sources of drinking water, and UNICEF has contributed another $2.5 million, according to Associated Press reports. That works out to about $1.00 per affected person, which points out one of the biggest challenges to addressing the problem in Bangladesh. In a country with a per capita annual income of only $230 and limited infrastructure, programs need to be very inexpensive to be effective.

Khandaker points out, for example, that a program to mitigate arsenic in drinking water affecting 500,000 people in New Mexico will cost more than $100 million. "That isn't realistic in Bangladesh," he says.

Among the promising programs under way in Bangladesh are efforts to collect and store rainwater, which is free of both arsenic and pathogens. Deeper wells, which tap a different aquifer, also appear to have safe levels of arsenic, according to the BGS study and several others. However, there are geologic questions that need to be answered before this approach can be applied on a large scale. Although there is evidence that in some parts of the country the water in deep aquifers does not mix with shallower, arsenic-containing water, it's not known whether this geologic separation holds true everywhere. Nor is the rate of replenishment of the deep aquifer known. It's possible that deep wells are mining a limited source of pure water, rather than tapping into a renewable resource. In any case, Khandaker points out, a deep well costs about $1,000 to dig, whereas a shallow one costs less than $100.

Clinics need to be set up in the parts of the country most affected by the poisoning, nearly all observers agree. And people throughout the country need to be better educated about what's causing their illness and what can be done to prevent and treat it. As part of the UNICEF program, for example, tested wells have been painted with either a red or green stripe, indicating whether well water meets the 50-ppb standard for arsenic. Yet Sarkar reports being in villages where the local people have simply cut the red stripe off of a contaminated well and continue to use it.

"I said to them, 'You know there is arsenic here. Why are you still drinking from this tubewell?'" Sarkar recounts. "They said, 'We have no alternative. We have to drink water.'"

And yet often, Sarkar and others report, there are alternatives. Not infrequently, wells only a few hundred feet from each other will have sizable differences in arsenic levels, so that some are safe and others are not. Yet people still drink from their own well, even if it's contaminated. "It's a measure of status," Sarkar says. "Nobody wants to go to somebody else's house to get water." More fundamentally, he believes, it's a question of ignorance, of people not really understanding that their well water is poisoning them.

"We have an obligation to stand up for these people and their plight," Sarkar says. "One can't ignore the fact that they need help. If, out of this work, some benefit comes for those millions of poor people, we will have accomplished something."



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ARSENIC CRISIS SPURS SCIENTISTS
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ARSENIC CRISIS IN BANGLADESH
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World Bank takes on arsenic poisoning
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