In Nepal's agricultural flatlands, women line up at village wells with earthen or metal pots. The water they pump out is sweet and apparently clean. Tragically, it's also often laced with arsenic.
In a scene repeated in more than a dozen countries from Hungary to Chile to the United States, tens of millions of people are drinking from arsenic-tainted wells. Ironically, these wells were dug from the 1970s to the present to provide clean water. Some have called it the largest mass poisoning in history.
Now, researchers are racing to fix this three-decade-old mistake.
"The technology isn't rocket science," says Susan Murcott, an engineering professor at the Massachusetts Institute of Technology. "But we have to translate that knowledge into a system that is viable in these different social settings and in decentralized settings."
It's been anything but easy.
For seven years, Ms. Murcott and her graduate students have traveled to Nepal to devise a foolproof arsenic filter. Such a filter must be cheap, easy to make, and simple to maintain - and local people must want to use it, too, she explains. So far, her team has built and tested seven promising technologies, yet all have failed in one way or another. Some were too costly, one was too heavy, still others didn't filter water fast enough.
Finally, last year Tommy Ngai, an MIT graduate student, bought a round plastic bin at a street market in Kathmandu, Nepal. He and the team filled it with layers of sand, brick chips, gravel, and the magic ingredient - a layer of locally bought iron nails, which chemically bind arsenic to them. The filter may just be the MIT team's silver bullet, a combination arsenic and biological filter. Cost: less than $16.
"We're hopeful we may have found a solution," Murcott says.
A solution is needed. Besides 3 million in Nepal, many millions more drink arsenic-tainted well water in India, Peru, Ghana, Nicaragua, Vietnam, China, Argentina, Mexico, Chile, Taiwan, Hungary, Philippines, New Zealand, Mongolia, the United States, and other nations, Murcott says. The problem is worst in Bangladesh. If the MIT arsenic filter was used there, it might relieve some 35 million people who drink the tainted water - about a quarter of the population, according to published estimates.
Still, variations in water chemistry from country to country make a one-size-fits-all solution difficult. So Murcott's filter for Nepal may not work as well in Bangladesh.
Others are also working on the problem, spurred perhaps by the announcement last month of the first "Grainger Challenge Prize." The National Academy of Engineering in Washington, D.C., is offering $1 million for the first device that can remove arsenic from groundwater and also leap the practical hurdles Murcott's team has faced for years.
Two groups, one at Harvard University in Cambridge, Mass., and another at Columbia in New York, are pursuing well-water arsenic solutions. So are scientists at Lawrence Berkeley National Laboratory, the Centers for Disease Control and Prevention in Atlanta, and the World Bank. At least 50 arsenic-removal technologies are already available, but face various challenges, Murcott says.
Ironically, the problem dates back some three decades in a well-meaning but botched attempt to keep villagers in developing countries from drinking - yes - tainted water.
For years, health authorities had agonized over villagers drinking from bacteria-infested ponds, streams, and lakes. In the 1970s, the United Nations, World Bank, and others mobilized to fix the problem with "tube wells" - a simple and relatively cheap solution that tapped biologically pure groundwater around 20 to 75 feet deep. Within a few years, millions of tube wells were drilled across the developing world.
Things seemed better at first. Villagers, especially women and children who had lugged water from streams and rivers, walked shorter distances and had time for other pursuits. In Bangladesh, health problems from surface water diminished.
Unfortunately, nobody thought to test the water for arsenic.
"We thought 20 years ago that these tube wells were a nice idea, the water was nice and sweet - well, it was because that's the arsenic taste," says Richard Wilson, a Harvard physicist and expert pursuing his own arsenic solution. "This catastrophe is something the whole world is partially responsible for. We here in the US and in England were advising the Bangladeshis. Nobody told them to test for arsenic."
In the US, the new standard for arsenic set by the Bush administration is a maximum of 10 parts per billion (p.p.b.). More than 50 p.p.b. of arsenic in water is considered hazardous by the Bangladeshi and Nepali governments. Many wells in both nations have arsenic levels 10 to 20 times as high as that.
Dr. Wilson proposes avoiding the arsenic filtering problem entirely by returning to surface water. His organization is financing far shallower surface wells that don't reach down into arsenic-tainted aquifers, and then covering them tightly to prevent biological contamination. The cost: about $1,000 for a well that could supply 300 to 500 people, he says. "You could solve the whole problem in Bangladesh with $200 million reasonably spent.... That's only 20 cruise missiles."
Others have proposed digging far deeper wells that tap into nonarsenic aquifers.
Drunk by the cupful, water with arsenic can be ingested for years before severe symptoms show up. Researchers say such symptoms are now appearing in people who drink from tube wells in a number of countries.
Health authorities in neighboring West Bengal, India, reportedly saw arsenic's effects first in the mid-1980s after a rash of diseases. Not until a decade later in the mid-1990s, however, did authorities in Bangladesh declare a widespread problem with the water.
Even researchers like Murcott, who had been focusing on developing wastewater treatment facilities in emerging nations, became aware of the arsenic problem only in the late 1990s. It was 1998 when she heard about and realized the seriousness of the problem - and began work in Nepal.
About the same time, Ashok Gadgil, a research scientist at the Lawrence Berkeley National Laboratory in Berkeley, Calif., was finishing up an innovative water-purification system for the developing world. His inexpensive system uses ultraviolet light to purify biological contaminants in surface water and is deployed in scores of communities, serving 300,000 people so far.
But by 2000, looking for a new challenge, Dr. Gadgil was hearing from friends back in India about the arsenic problem in West Bengal. He began to ponder how to make a simple filter that was also affordable and easy to use. Then inspiration struck: coal ash.
Coal is widely used for fuel in the region. One byproduct is bottom ash (not the same as fly ash, which contains heavy metals and other impurities), which is sanitary, widely available, and cheap. But most important from a physicist's point of view, it's molecular structure provides a huge surface area to gobble up arsenic. To work as an effective filter, all the coal ash required, he realized, was a special chemical coating to get arsenic molecules to cling to it.
To test his theory, he sent away for about 11 pounds of the ash, which shipped in fall 2001 - just in time to get trapped in the post-9/11 security crackdown. His ash package never arrived.
Frustrated, Gadgil traveled to India to get the ash himself. Doubtful that he'd ever be able to explain his odd package to authorities, he wrapped the gray powdery substance in several plastic bags and hid it in his luggage. "Fortunately I didn't get searched," he says. "But I was definitely sweating, I can tell you."
Back at the lab, Gadgil and a group of researchers spent months struggling to coat the ash with ferric hydroxide, a chemical that binds arsenic. The result: a teabag-like pouch, which filters water spiked with 2,400 p.p.b. of arsenic to just 10 p.p.b. Just a few ounces of the coated ash could make three gallons of water with 400 p.p.b. of arsenic safe to drink. Now, the team hopes to receive grant money to develop the full mechanism for doing the coating, and to test it in Bangladesh or West Bengal, maybe winning the Grainger Prize.
In the meantime, California has granted Gadgil's team $250,000 to develop the technology for use in the state. About 600,000 Californians are drinking pumped groundwater that does not meet new Environmental Protection Agency standards, Gadgil estimates. He thinks this work will have spillover benefits for India and Bangladesh.
"There is enough ash at thermal power stations to treat all the water needed in Bangladesh through the end of the century," he says. "We haven't fashioned our silver bullet just yet, but I hope it turns into one."