HEAVY METALS IN WATER: A GLOBAL SURVEY TO CHARACTERIZE UNTREATED DRINKING SOURCES

Contamination of drinking water sources with dissolved heavy metals is a growing concern in the United States, globally, and particularly in the developing world where untreated sources are common. As part of a global reconnaissance survey, our research group has investigated 114 untreated drinking water sources in 23 countries for the presence of dissolved metal contamination. Analytes included As, Ba, Cd, Cr, Cu, Mn, Ni, Pb, Sb, Se, and Zn. Metal-chelating polyurethane foam blocks were used to sequester metals from source water samples, following a standardized field protocol employed at all sampling sites. Foams were processed at Hope College and rinsates were analyzed by ICP-OES techniques consistent with EPA method 200.7. Raw data were processed through a statistical comparison routine and reverse protocol calculator to estimate metal concentrations in field drinking water sources. Results were compiled for each analyte into a 3-category dashboard for every site. These categories were: non-detect/not significant (ND/NS), present (P), and present with recommendation for re-testing (P_rt). ND indicated that analyte concentrations were below the method detection limit (MDL). NS indicated the analyte concentrations were statistically indistinguishable from the composition of control chelating foam rinsates. P indicated that concentrations were above the MDL but below the limit of quantification (LOQ). P_rt indicated that the metal concentrations were quantifiable and above the World Health Organization guideline for the contaminant. Of the 114 water sources sampled and analyzed via the foams, all sites contained at least one metal contaminant. 48% of the sites contained at least two metals and 52% contained more than two metals. Approximately 48% of the sites contained metals above the World Health Organization guidelines. The most common of these was As, while the other common non-compliant element was Cu. Overall the most abundant metal found in the drinking water sources was Mn. Further data analysis is underway to investigate potential metadatic geographical relationships and to identify sources requiring direct water sample analysis.