Between 35 and 77 million Bangladeshis have been exposed to toxic levels of arsenic from drinking contaminated water, a public health calamity causing one in five deaths in the country, according to new research published in The Lancet medical journal.

The study, funded by the U.S. National Institutes of Health, monitored 12,000 people over ten years.  In the Araihazar district of the capital Dhaka, they found that more than 20 percent

of deaths in the past decade were caused by arsenic-tainted well water.

water-arsenic-bangladesh-featured.jpgMuch of the contaminated water comes from wells dug into layers of soil with naturally occurring arsenic. Tragically, and ironically, those wells were constructed as part of an effort to provide safe drinking water by tackling waterborne pathogens like cholera in the 1970s.

Though there have been significant reductions in microbial contamination, the wells have brought on a new public health burden.

The findings confirm concerns in the international public health community about the impact of arsenic-tainted water. The World Health Organization has long called the widespread contamination in Bangladesh “the largest mass poisoning of a population in history.”

“The magnitude of the arsenic problem is 50 times worse than Chernobyl,” said Richard Wilson, president of the nonprofit Arsenic Foundation and a physics professor emeritus at Harvard University.

Leading public health officials in Bangladesh responded cautiously to the study’s findings late last month. “To be frank, I have my doubts about these findings–I would like to examine their methodology more closely,” Bangladeshi Health Minister A.F.M. Ruhal Haque told a foreign news wire service.

“Arsenic is a problem in Bangladesh, there is no question about that, but the risk that contaminated groundwater poses to the majority of the population has been blown out of proportion by this study,” he said.

According to the WHO, chronic exposure to arsenic may increase cancers of the liver, kidney, bladders, and skin, as well as heart disease, and the problem is widespread. Argentina, Chile, China, India, Mexico, Taiwan, Thailand, and the U.S are all struggling to address arsenic contamination in drinking water.