The slow progress of the World Bank programme 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 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. According to David Kinniburgh of the British Geological Survey, who has recently completed a detailed study of the arsenic s route into millions of tubewells, 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. This, says Kinniburgh, helps explain the diverse pattern of arsenic concentrations in tubewell waters. The contaminated wells almost all take water from a depth of 20 to 100 metres.