Columbia University Medical Center
In Vivo - The Newsletter of Columbia University Medical Center
Home
Back Issues
Contact Us
Calendar
Contents
In Vivo
PUBLIC HEALTH


New arsenic-free wells dug under the supervision of Columbia researchers have led to a decline in arsenic levels of residents of Araihazar, Bangladesh.
New arsenic-free wells dug under the supervision of Columbia researchers have led to a decline in arsenic levels of residents of Araihazar, Bangladesh.
It’s been called the largest mass poisoning in the world. Millions of wells drilled in the 1970s to supply Bangladesh with clean water have instead been poisoning about a third of the country’s population – about 40 million people – with naturally occurring arsenic. Arsenic, it turns out, is a major problem in the United States, as well, where the toxic chemical is present in many huge former mining and chemical manufacturing sites. Now, the National Institute of Environmental Health Sciences (NIEHS) Superfund Basic Research Program has awarded Columbia researchers a five year, $16.9 million competitive grant renewal to study the situation in Bangladesh, in the hope that what they learn may also help guide risk assessment and clean-up policies at U.S. superfund sites.
   At first, the Bangladesh wells were considered a great success. Before the 1970s, when UNICEF and the Bangladesh government began sinking the wells, most Bangladeshis relied on water collected from ponds or shallow pits contaminated with human and agricultural sewage. Diarrhea and disease killed a quarter million children each year. With improvements in sanitation and healthcare, the new wells slashed child mortality in half.
   But by the 1990s it became apparent that many wells were contaminated with naturally elevated levels of arsenic, a known carcinogen. When The New York Times wrote about the situation in 1998, several Columbia scientists decided to act. Within weeks, Habibul Ahsan, M.D., M.M.Sc., associate professor of epidemiology in the Mailman School and a native of Bangladesh; Joseph Graziano, Ph.D., associate dean of environmental health sciences at Mailman and a noted expert in lead poisoning; and several geologists from Columbia’s Lamont-Doherty Earth Observatory had formed a group and were on their way to Bangladesh to assess the problem.
   Nine months later, with a first grant from NIEHS, the researchers set up in a town near the capital city of Dhaka, where arsenic in the wells ranges from less than 10 micrograms per liter, the World Health Organization’s standard, to well over 900 micrograms per liter.
   Dark, thick, pre-cancerous skin lesions are the first outward signs of arsenic poisoning, but it was not known how much arsenic would cause such lesions. “On our first visit, we were looking at people’s hands to check for lesions, when we saw them on the hands of a 6-year-old girl,” says Dr. Graziano, the project’s principal investigator. “That conflicted with the dogma about arsenic that it takes 20 years to develop lesions.”
   Dr. Ahsan’s studies, published this year in the American Journal of Epidemiology, show that in adults the chronic consumption of even relatively small amounts of arsenic – between 10 and 50 micrograms per liter – can cause skin lesions. Arsenic in adults also causes bladder cancer, lung cancer and cardiovascular disease, which the researchers will investigate more thoroughly. Dr. Graziano has also found that low concentrations of arsenic, just like lead, are associated with lower intelligence in children.

No Easy Answers
The solution is arsenic-free water, but how to implement this solution is still far from clear. To date, there has not been a systematic effort across Bangladesh to provide safe water. Though many wells have been tested and people are encouraged to drink from safe wells, the wells are privately owned and it is not always easy to gain access to them. Filters are also problematic. “Technically they work, but they are costly and filtering takes time, so people tend to give up on them,” Dr. Graziano says.
   In 2003, the Columbia researchers began supervising the digging of wells for entire communities that tap into deeper arsenic-free water. There are now 55 in place. “Since these wells were installed, we have very clear evidence that arsenic levels in people’s bodies are going down,” Dr. Graziano says.
   Digging deeper wells, however, is only a solution for a couple of decades because such wells may cause the earth to sink or pull arsenic-laden shallow water into deep aquifers. In the long run, Bangladesh must find a way to collect and treat surface water – a huge problem in an area that is constantly flooded.
   The Columbia team has already observed one result with relevance in the United States. It turns out that in addition to arsenic, high levels of manganese are also present in the Bangladesh wells. The researchers found that children who drank from wells with manganese levels two to three times greater than the U.S. guideline of 300 micrograms/liter showed about the same intelligence deficits as children who were exposed to high arsenic levels. About 6 percent of wells in the United States have levels of manganese that exceed this level; the problem is particularly prevalent in New Hampshire, Maine, and in the Southwest.
   With the University of New Hampshire, the Columbia researchers are recruiting children in New Hampshire into a study to look at the effects of both arsenic and manganese in drinking water. Dr. Graziano says it is highly likely that these elements are putting some children at risk for neurotoxicity.
   “Announcing that arsenic causes cancer in adults doesn’t convey the same urgency as telling people, ‘children are suffering,’” Dr. Graziano says “so if there’s any hope in this new information, it’s that if people know children are being adversely affected, greater action may be taken both in the U.S. and in Bangladesh.”

—Susan Conova

Top