“I know this water is not good for my health, but there is nothing to do,” says Uddin. He tried installing another shallow well himself, but it was contaminated too. A deep well would have safe water, but at $1,000, it’s 10 times the cost of a shallow well and too expensive for villagers to dig without government or other outside support. He asked the local governing council for a new well, but they refused. “They told me to get better water.”

One villager who did get a new well is Piar Ali Shaheb, a building contractor who is also the local representative of the ruling party. When asked if his political connections helped, he smiles: “Yes, definitely.” As he is talking, a neighbor glistening with sweat just in from the fields approaches and begins shouting at him. He says he paid money to a local politician in order to get a safe well, but it had never been delivered. Many of the other villagers have the same story, and are also frustrated.

Shaheb, relaxed in his tank top and sarong, shrugs: “You gave the money to the wrong guy.”

Left with no alternative water source, Uddin, like most of his neighbors, is still drinking from his contaminated well. He spreads his hands before him and looks heavenward as his grandchildren play at his feet. “I have no alternative.”

Bangladesh’s contaminated well water is considered one of the largest public-health crises in the world, and yet it remains relatively unknown outside of scientific circles. An estimated 40 million people—one quarter of the population—are exposed to drinking water contaminated with arsenic. While many people think of arsenic as the fast-acting homicidal agent beloved by the Borgias and their ilk, at the diluted levels found in drinking water, arsenic becomes a different kind of hazard: a tasteless, odorless, pernicious poison. Chronic exposure may lead to only a few visible symptoms (skin pigmentation on the chest, hands, and feet occurs in a minority of cases), but the poison is exceptional in its ability to silently attack multiple organs over the course of years, or even decades.

The result is that trace arsenic exposure in Bangladesh appears to have led to dramatic increases in cancers ranging from skin to liver to lung, in cardiovascular disease, and in developmental and cognitive problems for children. The Bulletin of the World Health Organization estimates that the invisible taint of arsenic in the country’s well water could now be responsible for as many as 43,000 deaths per year in the country.

A naturally occurring metallic element, arsenic was first discovered in the country’s drinking water more than two decades ago. At that point, dismay led to widespread water testing, but relatively little has been done to directly address the problem in recent years. Yet researchers say there is no question that the mass arsenic contamination is solvable in most cases by drilling wells deeper than 500 feet. Some deep wells could provide for several hundred villagers, while the shallow wells they would replace usually serve only one household. Geologists say that enough wells and other types of safe water projects to supply water to the worst-exposed 20 million people could be provided relatively quickly—and that such improvements could gradually be expanded to other at-risk populations.