Arsenic mitigation in Bangladesh: national screening data and case studies in three upazilas.

Since 2000, nearly 5 million wells in Bangladesh have been tested for arsenic. Results of this survey are presented, and it is estimated that approximately 20% of tube wells nationwide contain arsenic above the drinking water limit of 50 parts per billion, with approximately 20 million people at risk of consuming water above this limit. Three case studies in arsenic mitigation are presented, which indicate that substantial progress has been made in raising awareness about arsenic. Substantial differences were found in tubewell surveys made in 2001 and 2005, with 17% of tubewells painted green in 2001 showing arsenic above 50 ppb in 2005, and 12% of tubewells painted red in 2001 showing 50 ppb arsenic or less in 2005. In 38% of households having red tubewells, household water was found to contain 50 ppb arsenic or less, indicating substantial behaviour change. In two upazilas where safe alternatives (primarily safe shallow tubewells and newly installed deep tubewells) are available, 52% and 75% of people at risk were found to have arsenic-safe water in the household, indicating that they have changed their drinking water sources. In a third upazila where safe alternatives are scarce, less than 10% of people at risk were found to have safe water in the home. The greatest challenges remain in areas where contamination is high but installation of new safe water points is constrained for technical reasons (e.g. unsuitability of the deep aquifer).