Arsenic in geoenvironments of Nicaragua: Exposure, health effects, mitigation and future needs.

In contrast to other Latin American countries, where the presence of arsenic (As) in drinking water sources and related adverse human health impacts are well-known, little is internationally known from Nicaragua. However, the As problem is of high relevance as numerous assessments by national research, governmental and non-governmental institutions have proven. To assess for the first time and globally disseminate this predominantly nationally originated information is the aim of this review. In Nicaragua, >1000 water samples have been analyzed for total As from 1991 to 2017. By today, 144 communities distributed within 12 departments and one autonomous region (RACCS) are impacted with As. At least 55,700 people are exposed to drinking water with As (n = 173; range: 10-1320 μg/L, mean: 48.30 μg/L; 21.95%). Arsenic in surface water ranged from 0.99 to 2650 μg/L (n = 124, mean: 65.62 μg/L, 62.9% < 10 μg/L); and in groundwater from 0.10 to 1320 μg/L [n = 624, mean: 20.86 μg/L (70.7% < 10 μg/L)]. The highest As concentration was recorded from a well of the El Zapote community in 1996 (1320 μg/L), alerting national authorities and academic's to research As in water sources and health risks. Since then, 10 μg As/L has been the national regulatory limit for drinking water supplies. Occurrence of high As levels is linked to three geoenvironments: (i) Paleocene-Mesozoic metamorphic rocks (Northern Highlands) where As is present in epithermal veins, (ii) Tertiary volcanic rocks (Central Plateau) where As is related to fossil hydrothermal/volcanic systems, (iii) Quaternary rocks (Nicaragua Depression) where As is caused by active geothermal/volcanic activities. No mitigation measures have been implemented. Incipient water treatment efforts (Kanchan filters activated carbon) have failed because they were not socially accepted. More integrated, cross-sectorial research on genesis, health impacts and problem mitigation is needed. Provision of water treatment units for As removal on a single-household and community scale is needed, calling for the cooperation of national entities with communities in problem detection and solving.