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Groundwater contaminated with soluble arsenic salts is an insidious environmental problem killing thousands each year in the developing world, but, unlike more acute natural disasters, draws little interest from the developed world. New analytical approaches to testing groundwater could help change that. Researchers in Vietnam and Switzerland have developed the first large-scale method for validating the microbial reporter-based test for measuring arsenic concentrations in natural water resources. Their test is based on a modified bacterium (Escherichia coli), engineered to bioluminesce on induction by arsenic ions. The team has developed specific protocols for overcoming interference from iron and has now confirmed the viability of the test against results obtained using atomic absorption spectroscopy. Pham Thi Kim Trang, Pham Hung Viet, and Nguyen Van Mui of Hanoi University of Science and Michael Berg of the Swiss Federal Institute of Aquatic Science and Technology and Jan Roelof van der Meer of the University of Lausanne analysed almost 200 groundwater samples from the Red River and Mekong River Delta regions of Vietnam, which are among those areas of the world presenting an insidious health threat to those who rely on these water sources. The team analyzed the samples both by AAS and by their arsenic bioreporter protocol. They found that the bacterial reporters performed well at concentration levels of above 7 micrograms per litre. Indeed, they found an almost linear increase in bioluminescence correlating with concentrations from 10 to 100 ug/l. When the team compared these results with the AAS data, they saw an overall average of about one in twelve false negatives and 2.4% false positives at the recommended safety limit for arsenic concentration (10 ug/l) as determined by the World Health Organisation. This, say Trang and colleagues, is a great improvement on standard chemical field test kits for arsenic contamination. The researchers point out that the bacterial assay is much easier to carry out than standard analytical tests and moreover is less expensive. As such, the researchers believe the test could find wide use across Asia where arsenic contamination is a major problem from Vietnam and the Gulf of Thailand to the Himalaya.
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Michael Berg
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