Samuel Lowenberg - Independent Journalist biography articles articles

Scientists tackle water contamination in Bangladesh

The Lancet  August 11, 2007
A diverse group of scientists is trying to make Bangladesh's polluted waters safe. But even with this innovative, multidisciplinary research effort, the indifference of the world's wealthy countries means that no long-term solutions are being implemented.


More than 70 million people in Bangladesh are estimated to be exposed to toxic levels of arsenic from their drinking water in what WHO has called the “largest mass poisoning of a population in history”.

The sad irony is that the problem is the unintended consequence of a campaign in the 1970s and 1980s by international development organisations, including UNICEF, to get villagers to stop drinking dirty surface water. More than 10 million wells were installed in Bangladesh. Unfortunately, nobody thought to test the wells for the presence of arsenic, which has since been found in a large percentage of the wells at amounts sometimes five, and even ten times over, what is deemed safe by WHO. The arsenic is thought to be naturally occurring, possibly drawn down from the Himalayas over thousands of years, and then released by the sudden and massive withdrawal of water from the aquifers.

Estimates vary widely about how many people are affected. A 1999 survey found that some 27 million people were drinking water tainted with 50 parts per billion (ppb) arsenic. Another 50 million were exposed to over 10 ppb—the WHO safety limit that many now say is out-of-date. Some estimates based on arsenic tests in Taiwan have put the safe amount at 1·7 ppb.

Although the world's international institutions have paid scant attention to this continuing catastrophe, it has drawn the interest of public-health experts and scientists from among the world's elite research institutions.

Joseph H Graziano vividly remembers the first time he went to Bangladesh to assess the crisis with a small team from Columbia University. “We saw with our own eyes for the first time some of the epidemiology associated with arsenic exposure. We all came away saying that this was a life altering experience”, said Graziano, the associate dean for research and a professor of environmental health sciences at Columbia University's Mailman School of Public Health.

The symptoms of long-term exposure to arsenic begin with the blackening of the hands and feet, progressing to nodular growths, and later to open sores and gangrene. Eventually, it can lead to cardiovascular and reproductive damage and to virulent cancers of the bladder, skin, lungs, and liver. In children, the exposure is also thought to lead to learning disabilities and other neurological effects. Researchers at Columbia University say that the arsenic poisoning could double Bangladesh's cancer mortality rate within two decades.

For such a massive disaster, the response by international aid agencies has been small, especially since researchers estimate that substantial mitigation could be achieved for less than US$100 million.

Arsenic poisoning from drinking water occurs to a much lesser extent in 60 countries around the world, from Taiwan to the USA. Worldwide, over 150 million people are estimated to be drinking the poisonous water. Bangladesh is one of the world's poorest countries. The cash-strapped government does not have the capacity to deal with this problem, and recent political upheavals have not helped the situation.

But along with this exceptional disaster has come an unusual opportunity for collaboration between researchers from myriad branches of science, including experts in epidemiology, environmental health, medicine, economics, statistics, sociology, hydrology, and geochemistry. “This is a really good example of true multidisciplinary work”, said David C Christiani, a professor at Harvard's Schools of Public Health and Medicine who is developing a research project with researchers from the Massachusetts Institute of Technology (MIT). “Everybody comes with their different perspective on these things. This cross-talk gives you a holistic perspective”, says Christiani.

At Columbia, one of Graziano's principal collaborators is Alexander van Geen, a senior research scientist at the university's Lamont-Doherty Earth Observatory, who specialises in geochemistry. He says that his team of earth scientists worked closely with the public-health researchers and the two sides realised that they could not only study the problem, but also that it was fixable most immediately by creating new, safe wells for their research participants and actively testing and labelling the contaminated wells.

Other researchers are looking at how to mitigate the effects of arsenic ingestion. Once people have been exposed for several years, conservatively estimated at a decade, the DNA damage almost guarantees that cancer is imminent, said Habibul Ahsan, a cancer researcher at the University of Chicago. Ahsan's research is now focused on how to undo the genetic damage caused by arsenic. Supplements of micronutrients such as selenium and vitamin E are showing positive effects.

Scientists have been working on the arsenic problem for less than a decade, but they have already developed innovative solutions like inexpensive filters, methods to cheaply test wells for contamination, and more elaborate programmes to map out the extent of the arsenic contamination, so that safe water can be drawn from either existing wells or new ones that tap into deeper, uncontaminated aquifers.

Graziano and Christiani's teams have assessed arsenic removal strategies, and have found that seemingly simple solutions may have unintended side-effects. Scientists in both Bangladesh and the USA, for instance, have come up with cheap and easy ways to make filters that can safely remove arsenic, using such commonly available ingredients as rusty nails and coal ash. But there are drawbacks to these approaches; the filters eventually get clogged up and need to be disposed of, which could put the arsenic back into the ground.

Although in practice many of the solutions have technical and effectiveness hurdles, everybody working on the problem agrees it is solvable. What is lacking is political will to act. And, even more importantly, the hundred million or so dollars in funding needed to put the fixes into practice—a relatively small amount to save millions of lives.

Meanwhile, the search for a solution, and even to understand the source and means of distribution of the arsenic, continues. Peter Ravenscroft, who is working on a book about the subject at Cambridge University for the Royal Geographic Society, cites research from west Bengal that Bangladeshis might be getting much of their arsenic intake not only from drinking water, but also from food—mostly rice that is irrigated and then cooked in contaminated water.

These types of complications have further emphasised the need for epidemiological studies. “We know a lot about arsenic as a classic poison but there is a lot we still do not know about how it operates in people”, said Christiani.

Christiani's work has focused on using biological markers of cumulative exposure, like toenails and urine, to get a more accurate measure of how much arsenic Bangladeshis are actually exposed to. Bangladeshi men, for example, may get water from many different sources when they go out to work, and the hard physical labour they do means they may consume nearly twice as much water as the average person.

Christiani has been sharing his findings with Charles Harvey, a professor of hydrogeology at MIT. The two are putting together a collaborative project that would link their seemingly disparate research activities.

In two separate locales, Harvey and his team from MIT are surveying wells to learn about factors such as the prevalence of arsenic in wells, how the rates vary with the season, and the effects of irrigation in spreading arsenic. Meanwhile, Christiani's team is working with researchers from a local non-governmental organisation—the Dhaka Community Hospital Trust—to measure the effects of arsenic on pregnant women and small children.

Along with the scientific advances that could lead to mitigation, the research could also have another effect—a political one. “Having the academic research lends the issue credibility and helps put pressure on the government and the international community to set stricter standards on arsenic and to start coming up with innovative technologies to provide safe water to people”, said Christiani.

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