Hanufa Bibi stoops in a worn sari and mismatched flip-flops to work the hand pump on her backyard well. Spurts of clear water wash grains of rice from her hands, but she can never get them clean.
Thick black warts tattoo her palms and fingers, the result of drinking arsenic-laced well water for years. It's a legacy that new research has linked to one in five deaths among those exposed in Bangladesh — an impoverished country where up to half of its 150 million people have guzzled tainted groundwater.
The World Health Organization has called it "the largest mass poisoning of a population in history," as countless new wells continue to be dug here daily without testing the water for toxins.
"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 who was not involved in the study. "But it doesn't have 50 times the attention paid to it."
The issue surfaced about two decades ago, after some 10 million shallow hand-pump wells like Bibi's were sunk across the country in the 1970s with money from international donors.
The wells were meant to provide clean drinking water to help prevent deadly waterborne diseases, such as cholera. But they unintentionally tapped into arsenic deposits in the ground, releasing the odorless, colorless and tasteless toxin into water used for drinking and cooking. Arsenic has been linked to cancers, liver ailments, skin diseases, heart problems and other health issues.
The new research, funded by the U.S. National Institutes of Health and published online June 19 in The Lancet medical journal, is the first to examine how drinking arsenic-contaminated water over time shaves years off lives.
For the nearly 12,000 people followed over 10 years in the country's Araihazar region east of the capital, researchers found that even low doses of arsenic in drinking water could increase the chances of early death. The study also found that damage on all levels appears to be permanent.
"It's similar to tobacco smoking. Once you smoke for 20 years and then you stop smoking, your risk of getting tobacco-induced cancer over the next decade will still be high," co-author Habibul Ahsan from the University of Chicago's Center for Cancer Epidemiology and Prevention said by phone. "Even if, say, for some miracle all the individuals are provided arsenic-free water from tomorrow, these people will also be at a higher risk of dying for many years to come."
More than 75 percent of those studied drank arsenic-contaminated water above WHO's recommended safe limits. About a quarter of deaths from chronic illnesses and a fifth of the total 407 adult deaths were attributed to arsenic.
About half of the 10,000 people living in Bibi's tropical village, which was not part of the study, are drinking arsenic. Victims get sick slowly, and it takes years to develop tiny black or white dots peppering the skin. Most people exposed never develop these classic symptoms at all.
All the tubewells in Chandipur village are contaminated. Red paint once coated every pump's handle as a warning of the danger lurking inside, but the color and message have long faded. None of the tiny palm-shaded shacks have indoor plumbing, and some villagers like Bibi use the well water to avoid walking long distances in the heat to draw foul-tasting surface water from stagnant ponds used for bathing or watering livestock.
"I knew before marriage that there was arsenic in the tubewell, but I decided to take it," says Bibi, who's been drinking the water nearly 20 years. "The water quality of this tubewell is much better than others."
Arsenic poisoning affects some 70 countries, including the U.S., Chile, Vietnam and Cambodia. But the biggest problem by far is in Bangladesh, a country roughly the size of Iowa with about half the U.S. population crammed into it.
It is one of the world's poorest nations, where half the people live on just $1 a day. Few can afford to dig deep wells that draw safe water from aquifers below arsenic-contaminated layers. Filters are expensive or difficult to maintain, and there has been no concerted effort to harness rainwater for daily use. The number of new wells doubled every five years during the study.
Some argue that the international community must help fix the problem created by the wells they first dug.
"They've known about it for at least 20 years, so we expected them to be much more aggressive on this issue," said Dr. Mahmuder Rahman, a retired professor at Dhaka National Medical College and Hospital, who has worked for years on the arsenic issue. "They've got a moral responsibility to do it. Time is running out."
In March, the United Nations and Bangladesh's government announced a plan to provide safe drinking water to all by next year. But the report identified only about 20 million people still drinking high levels of arsenic. It did not address the tens of millions more exposed to lower concentrations.
It also said more research was needed to determine whether arsenic is entering the food chain through rice irrigated with tainted water, and how the poison affects pregnancies and children.
Back in Bibi's village, she digs at her burning hands and the soles of her feet with a razor blade, ripping at the blackened calluses until they bleed. She complains of fevers and constant fatigue, and the 40-year-old's face sags as she shuffles into her small house like a woman twice her age.
She has never seen a doctor. She's more concerned about the damage the arsenic has done to her family's social standing. Her two teenage daughters were recently forced to marry men considered beneath them because of the stigma surrounding the arsenic-infected family.
She worries that if her husband cannot make good on the dowry he promised, the girls will be sent back home forever damaged, like another young woman in the village blighted by arsenic.
"People don't want to eat anything from my hands. They are afraid," Bibi says softly, looking down in shame, her head covered by the red flowered sari. "No one wants to touch me."