Bangladesh is among the countries that are on the track to fulfill Millennium Development Goal for child mortality. An important factor behind this is the change of water sources from ponds and canals to groundwater. Unfortunately it was found that a large fraction of the wells drilled contained toxic levels of arsenic. Effects of chronic exposure with the levels found in Bangladesh and adjoining West Bengal in India show up only after 10-15 years which means that millions of wells were drilled before this problem was discovered. Remedies have been tested, such as filters which do function technically but not socially as the handling of water is mainly a task for women and they cannot find time for using and caring of filters. In the last few years local drillers have found that they can use the color of sediments to find a groundwater low in iron. As in this case arsenic levels are closely related to iron contents in the water these sediments also often provide low arsenic water. Research has shown that this simple strategy is likely to be sustainable with a low risk for cross-contamination from over- and underlying sediments with arseniferous groundwater (Robinson et al. 2011).
However, the low iron and arsenic groundwater may contain elevated concentrations of manganese. Manganese in drinking water has been considered as a technical problem, dis-coloring water with manganese precipitates during distribution. However, recent epidemiological investigations have shown that manganese in drinking water may lower the intellectual capacity of children (Bouchard et al. 2011). Manganese is an essential element and the human body can efficiently regulate the uptake of it from food – but not from drinking water. This probably reflects that the use of groundwater from deeper strata containing dissolved manganese is a rather new phenomenon in the history of mankind. In Bangladesh this is still another factor to consider. It seems that the driller´s strategy is still possible to use even when taking into account that manganese levels should not be excessive. The findings regarding the effect of manganese in drinking water will have global implications, as todays permissible limits set by WHO and in different countries including Sweden do not take into consideration the health aspects.
Bouchard et al. (2011) Environmental Health Perspectives 119: 138-143.
Robinson et al. (2011) Applied Geochemistry 26: 624-635.