Erickson (2003) suggested that field kits used to measure As in the regions’ groundwater are unreliable and that many wells in Bangladesh have been labeled incorrectly. To assess the magnitude of As contamination, the World Bank, UNICEF, WHO and several other international aid agencies made a joint decision 1997 to test all hand pumped tubewells using colorimetric field kits. After that more than million of wells were tested in Bangladesh and labeled with red (>0.05 mg L-1) and green (