Status of Water Quality for Human Consumption in High-Andean Rural Communities: Discrepancies between Techniques for Identifying Trace Metals

Access to safe water is essential for people’s lives and health. However, little information is available about the quality of water consumed in rural communities in the Andes of Peru. The difficulties of accessing communities, and the lack of nearby laboratories, raise the question of which techniques are being used or could be used to monitor water quality (and specifically, for trace metal content determination), as discrepancies between different techniques have been reported. This work focuses on water characterization of (i) physicochemical, microbiological, and parasitological parameters; and (ii) the presence of trace metals in a specific Andean region involving five communities, determined by two different techniques: inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS). AAS was performed at local laboratories in the province capital located within a 4-h travel distance from sampling points, and ICP-MS was performed in a certified lab in Lima at a 24-h bus travel distance (on average) from sampling points. The physicochemical characterization shows non-compliance with regulations of 16.4% of reservoirs and 23.1% of households. Further, standards for microbiological and parasitological parameters were not met by 14.5% of spring water points, 18.8% of water reservoirs, and 14.3% of households. These results are in agreement with the Peruvian government´s general figures regarding water quality in rural areas. While ICP-MS and AAS gave equivalent results for most pairs of sample metals tested, differences were found for Mo, Mn, Al, Zn, Cd, and Cu concentrations (with larger differences for Mo, Cd, and Cu). Differences in Al and Mo affect the comparison with water quality standards and generate uncertainty in terms of acceptability for human consumption.