In a rural, remote village in the southeastern part of Bangladesh, an aid worker
stands in the yard of a villager who wants to install a well for drinking water.
The worker pulls out a cell phone and calls up statistical data that indicates
how deep to drill the well to reach clean water. Workers then manually drill
an exploratory well to that depth and send a sampling “needle” deep
into the ground. Like drawing blood from a vein, the needle “pricks”
the aquifer and draws up a vial of water, which the aid worker then tests for
contaminants, such as arsenic, at the surface. If the water proves safe, people
can install a well there. If not, they drill deeper and retest, until they reach
safe water. All told, the testing process, which should provide a clean source
of water for drinking and cooking for the villager’s family, adds about
an hour to the well-installation process.
Although
this particular scene has happened only in a pilot test, the technology is already
available and it hopefully will be deployed more widely soon, says Alexander
van Geen, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory
in Palisades, N.Y. The needle sampler and cell-phone system are only one idea
for finding safe water in Bangladesh, where naturally occurring arsenic is a
huge problem, he says, as well as in other South Asian developing countries
such as Cambodia, Vietnam, China and West Bengal in India, where altogether
at least 100 million people are exposed to arsenic in high doses, according
to the World Health Organization (WHO).
Researchers recently developed the arsenic
needle sampler — the big needle and transparent tube that the man in the
picture is holding — to test the groundwater before a well is installed.
They hope that figuring out where to install a well before drilling will help
Bangladeshi villagers have a clean water source. Photo by Alexander van Geen.
WHO considers concentrations over 10 micrograms of arsenic per liter of water
to be too high. Bangladesh’s standard is 50 micrograms per liter. At least
90 percent of the country’s population of 130 million people drink well
water, according to WHO, and there are at least 10 million wells in the country,
van Geen says. Studies by the British Geological Survey over the last decade
show that at least one-third of those wells have arsenic concentrations above
the Bangladesh standard, and more than half are above the WHO standard. Those
studies mean that at least 50 million people in Bangladesh alone are drinking
water with potentially dangerous arsenic levels.
Arsenic poisoning in Bangladesh is a problem of epidemic proportions, says Joseph
Graziano, associate dean for research at the Mailman School of Public Health
at Columbia University. It increases rates of skin, bladder, lung and liver
cancer, as well as strokes, heart attacks, cardiovascular disease and skin lesions.
And “now we’re beginning to see lesions on children as young as 6
months old, and developmental and neurological effects — similar to those
associated with lead poisoning — on children as young as 10,” Graziano
says (see story, page 22). Generally, it takes about a
decade or more for cancers and heart problems to start showing up in people
who have been exposed to arsenic.
In Bangladesh, people used to collect most drinking and cooking water from a
plethora of surface sources such as ponds and streams. But in the 1970s, health
officials determined that the surface water was contaminated with pathogens
and was spreading diseases, including diarrhea, dysentery, typhoid, cholera
and hepatitis. To solve the problem, they drilled wells and encouraged households
to switch to groundwater, which was clear of disease. These community wells
were so popular, van Geen says, that individual households followed suit by
installing personal wells, thus doubling the number of wells in the country
every five years. But in 1993, arsenic was discovered in the groundwater. By
then, people had been exposed to varying levels of the poisonous metal for close
to two decades, and some health officials worry that arsenic-based diseases
may reach epidemic proportions in years to come.
Academia, the government of Bangladesh and international nongovernmental organizations
have been studying the problem ever since, trying to figure out how widespread
the problem is, as well as come up with a solution, van Geen says. They have
considered a number of approaches, including installing household water filters,
remediating surface water, collecting rainfall and building reservoirs to hold
it, or removing arsenic from the groundwater.
But problems exist with each of these suggestions, says Charles Harvey, a hydrologist
in the civil and environmental engineering department at MIT. Studies indicate
that people may be reluctant to use water filters regularly, for example, and
the filters also create waste sludge that has to be disposed of somewhere else,
he says. The best option for at least the next decade or two, van Geen and colleagues
say, is to get the people of Bangladesh to switch to cleaner wells.
“The people of Bangladesh know that arsenic is a problem and will do what
they can — what is practical — to solve the problem” on an individual
basis, van Geen says. “And there is a lot of clean, safe groundwater in
the country,” he says; “it just has to be found.”
Research has shown that deeper aquifers — at depths varying from 30 to
more than 150 meters — appear to be relatively safe. But part of the problem
with simply switching everyone to deeper wells, Harvey says, is that very little
is known about the subsurface. “The technologies used in the developed
world to study groundwater are not being employed there,” he says, such
as multilevel sampling of an aquifer and building detailed groundwater flow
models.
Van Geen and colleagues have developed the cell-phone-based system to call up
information onsite and in real time about any given well, and they already have
a database of arsenic concentrations in groundwater in close to 300,000 wells
in 300 villages in Bangladesh that were tested through a World Bank-sponsored
program. They hope, van Geen says, to add arsenic concentration levels into
the accessible database from an additional 5 million wells.
Automatically plugging in data from nearby wells from the database, the system
utilizes a statistical algorithm developed by Columbia statistics professor
Andrew Gelman to estimate the probability that a particular location will have
low-arsenic water at a particular depth, as presented in a paper in the December
2004 Risk Analysis. Via cell phone, consultants then receive a text message
with the automated calculation of how deep to drill to reach safe water.
Workers then drill to that depth and use the needle sampler, prototypes of which
have been made from components that could be easily produced in Bangladesh,
van Geen says, to draw up the water for final testing. The needle sampler is
composed of a clear PVC sample chamber, an 18-inch needle and a unit to connect
the needle to the sample chamber. The consultants then test the water using
an arsenic field kit (that has been in use for years) to directly measure the
arsenic concentration in the water before installing a well or digging to a
deeper aquifer in an existing hole. The whole system is easy enough to use that
the local drillers in individual communities could be trained to use it eventually,
van Geen says. The researchers published the results of this pilot project in
the December 2004 edition of Environmental Science & Technology.
“Actually, the arsenic needle is a cheap and simple model of what is used
in the United States to sample groundwater,” says Harvey, who was not involved
in the project. It is a tool, he says, to “help us to learn more about
the geochemistry of the water.”
Still, some scientists remain convinced that the best solution is yet to be
found. The U.S. National Academy of Engineering (NAE), for example, recently
announced a competition (sponsored by the Grainger Foundation)
to find a treatment option for the arsenic-laced water in Bangladesh and other
affected developing countries. Jack Fritz, senior program officer at NAE, says
that $1 million will go to the person or group who develops the best “practical
technology” to treat the water. Although the winners are allowed to do
whatever they want with the prize money, the hope is that they will put the
money to use on implementing their technology in a developing country, Fritz
says. “We’re trying to energize the American engineering community”
to help the developing world, he says.
Getting and keeping the developed world involved is important, Harvey says,
but funds are tight. And, Graziano adds, while the developed world now accepts
that arsenic poisoning is a huge problem, high impending cancer rates may not
be a compelling enough reason to get them to act. Nonetheless, Graziano says,
“I hope that there’s a more concerted effort in the next 10 years
to curb this problem than there has been over the last 10 years.”
Megan Sever
Links:
"Lead’s Toxic Urban Legacy and
Children’s Health," Geotimes, May 2005
U.S.
National Academy of Engineering (NAE) competition (sponsored by the Grainger
Foundation)
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