For millions of people in rural bangladesh, drinking water is like playing Russian roulette. Thousands will die in years to come from cancer caused by arsenic, a natural element in their water. Thousands more will suffer hideous skin lesions. There is no simple, cheap way to test drinking water for contamination. The Bangladesh government―recently named the world's most corrupt by a widely respected international monitoring agency―has received $32.4 million from the World Bank to determine which wells are safe, but is hampered both by its notorious bureaucracies and the sheer scale of the problem: Some 10 million private wells need testing. Existing arsenic-measuring devices are expensive and awkward; some also produce a toxic arsene gas. But Pietro Perona, a Caltech electrical engineer, believes he has a solution. It's called the arsenometer, a gizmo about the size of a Walkman, rigged up from a pair of infrared LEDs, two glass tubes, a couple of photodiode detectors, an LCD display, and a 9-volt battery.
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