In this neighborhood-scale study and in 2 national-scale studies of drinking water tubewells in Bangladesh, As, Mn, U, Pb, Ni, Cr, B, Ba, and Mo were found above WHO health-based guidelines (Table 1; BGS/DPHE 2001; Frisbie et al. 2002). In this study, 96% of the tubewells exceeded WHO health-based guidelines for at least 1 of these toxic elements. The single greatest risk to public health is from As in drinking water.
Of the 67% of tubewells that had As concentrations below the WHO drinking water guideline, 87% had unsafe levels of Mn and 64% had unsafe levels of U (Table 5). Thus, testing for As alone is not sufficient to ensure safe drinking water. To address the threats to public health posed by the prevalence of multiple toxic elements, we have proposed a 3-step drinking water testing program.
Of the 33% of tubewells that had As concentrations above the WHO drinking water guideline, 59% also had unsafe levels of Mn, 14% had unsafe levels of U, 5% had unsafe levels of Pb, 5% had unsafe levels of Ni, and 5% had unsafe levels of Cr (Table 3). Thus, water treatment systems that have been designed solely for As removal may not provide safe drinking water and should be further evaluated for the removal of Mn, U, Pb, Ni, Cr, B, Ba, and Mo.
