Last month, three UN human rights experts released a joint letter to the Bangladesh government about the country’s failing response to deadly arsenic in drinking water.

Two decades after the problem came to international attention, an estimated 20 million people in Bangladesh—mostly the rural poor—still drink water with contamination levels above the national standard.

Arsenic in water is colourless, tasteless, and odourless. But exposure to even low doses can have deadly health consequences, although the resulting illnesses—cancers and cardiovascular and lung diseases—take years to develop.

The UN experts—the special rapporteurs on the right to health, on extreme poverty, and on the right to safe drinking water and sanitation—cite research published in the Bulletin of the World Health Organisation in 2012 that estimates an annual death toll of 43,000 people from arsenic-related illnesses in Bangladesh.

After the extent of arsenic in drinking water in Bangladesh was understood in the mid-1990s, successive governments, international donors, and non-governmental organisations oversaw a concerted effort to test shallow wells. From 1999 to 2006, 5 million wells across the country were tested with field kits and the results communicated to their owners.

This national screening found that wells used by an estimated 20 million people yielded water with arsenic above the national standard. Subsequent studies showed that many people switched to a safe well when there was one close by.

But since 2006, such efforts have dissipated. In many cases, the red paint that used to mark wells as contaminated faded years ago.

A nationwide study of drinking water quality published in 2015 found a similar result to the earlier screening — 20 million people exposed to arsenic above the national standard. The result essentially shows no progress. What’s going wrong?

Government wells are vitally important in arsenic affected areas of Bangladesh. Deeper wells drilled down approximately 150 meters into the ground often supply  water without arsenic. They can provide drinking water for hundreds of people.

Deep government wells are a potentially life-saving public good, but they are too expensive for most families in rural villages in Bangladesh to install by themselves.

Some politicians are diverting these life-saving public goods to their political supporters and allies.At the end of a long explanation of who, ideally, should get the water, a government policy states: “50% of the sites for allocation (of new wells) should be finalised after discussion with the relevant member of parliament of that area.”

As one government official told me on condition of anonymity: “If the member of parliament gets 50% (of the new allocation) and the upazila (sub-district) chairman gets 50%, there’s nothing left to be installed in the areas of acute need.”

What does this diversion look like at the village level? I visited one village where more than 90% of all wells were contaminated, but the government wells were behind compound walls in backyards, or even installed inside private houses, used by single families.

As another government official told me (also on condition of anonymity): “This (political interference) happens all over Bangladesh.”

As some members of parliament tap public goods to reward political favours in electorates all over the country, Bangladesh is expending considerable resources in areas where the risk of arsenic contamination is relatively low and where water coverage is relatively good. Put simply, the government’s deep wells that could provide safe water aren’t being put where they are most needed.

The government’s engineering experts are aware of this—in fact, some technical reports have called for targeting areas with the greatest need—but the government has failed to take corrective action.

As the letter by the special rapporteurs to the government notes: “The absence of adequate institutional structures and measures to control arsenic has left millions of the affected population to their own devices.” Underlying the problem, the Bangladesh government has not replied to the joint letter by the three UN special rapporteurs.

Perhaps government denials are to be expected. In response to our report last year that found that 20 million people still drink arsenic-laced water, the local government minister told Bangladesh media that that no one in Bangladesh currently suffers from arsenic.

Effectively addressing arsenic in drinking water requires acknowledging the enormity of the problem and reviving the commitment that the government and international donors displayed after the problem first came to international attention.

While there are technical challenges to be overcome, the real difficulty is poor governance.

The government needs a national plan to end arsenic exposure through drinking water and to install new wells in the areas where the risk of arsenic contamination is high. It should end the pernicious influence of politicians on their allocation.