arsenic probably originates in the Himalayan headwaters of the Ganges
and Brahmaputra rivers, and has lain undisturbed beneath the surface
of the region’s deltas for thousands of years in thick layers
of fine alluvial mud smeared across the area by the rivers.
to David Kinniburgh of the British Geological Survey, who has recently
completed a detailed study of the arsenic’s route into millions
of tube wells, the arsenic concentration in the mud is not extraordinary.
Time is the culprit. The mud in Bangladesh lies thicker, wider and flatter
than almost anywhere on Earth. It can take hundreds or thousands of
years for underground water to percolate through the mud before reaching
the sea. All the while it is absorbing arsenic.
says Kinniburgh, helps explain the diverse pattern of arsenic concentrations
in tube well waters. The contaminated wells almost all take water from
a depth of 20 to 100 metres. Shallower wells are clean because they
contain mostly recent rainwater or water flowing swiftly through the
sediments. Deeper wells tap water in older sediments, which have by
now been flushed clean of arsenic. It will take thousands of years,
says Kinniburgh, before the rest of the arsenic will wash away into
the Indian Ocean.
underground water sources around the world contain arsenic. Parts of
Taiwan, Argentina, Chile and China have all suffered epidemics of skin
diseases, gangrene and cancer as a result. Smith’s analysis of
the Taiwan epidemic in particular helped set the WHO arsenic standards
for water and is the basis for his current predictions. Bangladesh,
he says, is quite unprecedented.
explains today that “at the time, standard procedures for testing
the safety of groundwater did not include tests for arsenic [which]
had never before been found in the kind of geological formations that
exist in Bangladesh.” But many geochemists, such as John McArthur
at University College London, scoff at such a suggestion. They blame
dogma among public health people with no knowledge of geology, and who
equated underground water with safe water.
World Bank announced an emergency three-year program to identify the
killer tube wells using simple tests and to “put in motion concrete
actions [to] combat a major health crisis with devastating effects on
the lives of millions.” With almost every one of the country’s
68,000 villages potentially at risk, the Bank said it would initially
survey 4,000 villages and draw up action plans for each. This “fast-track
project” was to be the first phase in a 15-year program to screen
the country’s tube wells.
Wilson, a leading analyst of the crisis from Harvard University’s
department of public health, says, “The project is stalled.”
He blames the Bangladeshi government’s failure to “decide
how to spend the money” and says that leading officers at the
Bank are privately “most upset about it.”
too Big for NGO
the task is far too big for any NGO. Shahida Azfar, UNICEF’s representative
in Dhaka, told a conference in the city last May that “to date,
only 250,000 tube wells have been tested. If we keep this up it will
take us 30 years to complete the testing.”
few if any action plans have been completed because, says Minnatullah,
scientists have failed to find a “proven, affordable” method
of removing arsenic from village pumps.
is Situation the Worst?
is the situation worst? Chakraborti says “one of the worst villages
I have ever visited” is Stadium Para in Meherpur district, right
on the border with India. Here nine residents have already died of cancerous
ulcers caused by arsenic. One was only 25 years old. But, after five
years of surveying, he nominates the southeastern village of Seladi
as “in all probability the most arsenic-contaminated village in
the world.” Here 72 out of 73 tube wells are contaminated. No
fewer than 21 contain arsenic at more than 1,000 parts per billion,
and the highest at 4,000 ppb, or four hundred times the WHO limit.
of Education a Problem
are some technical solutions to providing safe drinking water for the
people of Bangladesh–albeit hard to execute in such a poor, ill-educated
and rural countryside (see box). But first the millions of dangerous
tube wells have to be identified. The slow progress of the World Bank
program so far could prove a mortal blow. In his September report, Smith
warned that “the worst thing that can possibly be done is nothing.”
But for most Bangladeshis caught up in this disaster, nothing is exactly
what is being done.
the first step of the mammoth task of testing the country’s tube
wells, volunteers, aid workers and officials paint the dangerous ones
red, which should only be used for washing. The villagers are supposed
to use the safe wells exclusively for drinking, but that’s not
easy when the lucky one is found in someone else’s backyard.
the longer run, part of the answer lies in sinking deeper wells to tap
cleaner water. But it will take millions of dollars to install these
wells in addition to the needed surface tanks and distribution pipes.
Also some deep tube wells in West Bengal have started bringing up arsenic
months or years after they were opened.
idea is to adopt traditional methods such as ponds and tanks to “harvest”
rainwater. This will work in some places, says Shahida Azfar from UNICEF,
but “there is not enough rain all year for that to be feasible
as the main strategy.”
the tube well waters be treated? While a large number of ideas for filters
and chemical treatments have been tried out in the past two years, there
is “no proven affordable arsenic removal technology available
yet,” according to Khawaja Minnatullah of the World Bank. Most
experts warn against blanket solutions. Each village needs its own plan.
And none of them can begin planning until it knows which of its tube
wells are pouring poison into villagers’ buckets.