Nitrate in drinking water in rural communities in Goiás, Brazil

Abstract

Access to safe drinking water is a fundamental human right, yet rural communities often face challenges related to nitrate contamination, posing risks to public health. This study assessed the presence of nitrate and health risks in 24 rural communities in the state of Goiás, Brazil. A total of 158 water samples from surface and groundwater sources were analyzed to determine nitrate concentrations, Hazard Quotient (HQ), and Hazard Index (HI). Nitrate was detected in 60.1% of the samples, with concentrations ranging from non-detectable to 11.6 mg/L, with the highest levels having being observed in shallow wells. Although mean HQ and HI values remained below 1.0, maximum values exceeding this threshold were recorded in hand-dug and shallow tube wells, indicating increased health risk. Communities relying on individual water supply solutions and characterized by inadequate sanitation infrastructure exhibited the poorest indices. Rudimentary pit latrines were present in 70.8% of the communities, and 29.2% had distances shorter than 45 m between latrines and water abstraction points, increasing the potential for cross-contamination. Animal excreta in household yards were identified in 16 communities, further exacerbating water vulnerability. The poorest results were associated with the use of wells as the primary water source, with a predominance of shallow hand-dug wells in Lageado (11 of 13 samples) and shallow tube wells in Olhos d’Água. Overall, the findings indicate a higher risk of nitrate contamination in individual water supply systems, particularly in rural settlements and where pit latrines are located near abstraction points. In contrast, surface water sources and collective supply systems showed lower nitrate concentrations, below health risk thresholds, underscoring the need for continuous monitoring — especially in communities with HI>1.0 — and for the implementation of preventive and educational measures.