Waterborne arsenic is colorless, odorless, tasteless, and lethal. In Bangladesh, people have been drinking it for over two decades. The nation drilled millions of wells in the 1970s and '80s (with the help of foreign aid) to stem an epidemic of cholera and dysentery, and the campaign worked-except that the new wells tapped into an aquifer contaminated with naturally occurring arsenic that had leached from the soil over the years.

The problem wasn't realized until the '90s, and by then the health effects were obvious: black spots and lesions on hands and feet, swollen limbs, gangrene. Over time, arsenic poisoning caused heart disease and cancers of the skin, bladder, and lungs. But the long-term impact on the population of Bangladesh is just now taking shape, and the numbers are astonishing.

In a decade-long study of nearly 12,000 citizens, researchers determined that 21 percent of deaths could be attributed directly or indirectly to elevated levels of arsenic in drinking water. Put another way, arsenic is sending one in five Bangladeshis to their graves early. The more contaminated the well water, the higher the mortality rate among those who depend on it. And the situation could be even worse: The study didn't include child or fetal deaths, or poisoning from rice grown using contaminated irrigation.

The Lancet published the study last month and outside experts praised it for its careful methods. Researchers interviewed the 12,000 participants every two years, took urine samples, tested the arsenic concentrations in 5,966 wells, and made concessions for age and health factors like smoking and body weight. Yet the health minister of Bangladesh, A.F.M. Ruhal Haque, immediately criticized it: "The risk that contaminated groundwater poses to the majority of the population has been blown out of proportion by this study." Haque apparently didn't elaborate as to why but pointed to government efforts to paint the hand pumps of poisoned wells red and provide alternate water sources.

International and local activists say the government of Bangladesh is dragging its feet. Mahmuder Rahman, a native expert on the arsenic problem who helped the government develop a plan to solve it, last October told Star Weekend Magazine, a Bangladeshi publication, that the mitigation plan was "not functional," and that the government was playing "a hide and seek game" with the issue. (The private hospital Rahman is associated with, Dhaka Community Hospital, has led a crusade to treat poor people poisoned by arsenic.)

With expertise and a combination of solutions available-deeper wells, surface water treatment, arsenic filters-the new research should be a valid motive for the nation's officials to get serious. By conservative estimates, 20 million Bangladeshis are still drinking tainted water.

Polio problem?

The polio virus isn't dead just yet. An outbreak in Tajikistan that began in April with seven confirmed polio cases surprised health experts by ballooning in five weeks to 560 suspected infections. Tajikistan immunized over 3 million children in an emergency campaign in May and June-even though the nation's average vaccination rate two years ago reached 87 percent. Health experts worry that an outbreak could jump to the West, where vaccination rates are similar in some regions (the U.S. average is about 96 percent). Polio, which is most common among children and can result in paralysis or death, had been eradicated from Tajikistan and Europe since 2002.

Email Daniel James Devine