Assessment of groundwater quality and associated health risks in Khagaria district, Bihar, India

Groundwater arsenic (As) contamination is a pressing public health concern in alluvial floodplain areas worldwide, including India. This study aimed to investigate As and other trace elements, along with relevant physicochemical parameters, in household drinking water wells and assess both point and probabilistic health risks associated with As exposure in Khagaria district situated in the Koshi–Ganga Floodplain, Bihar, India. The mean concentration of As (51.65 µg/L) in the groundwater samples collected from 38 wells far exceeded the WHO-recommended limit (10 µg/L). Elevated levels of iron (Fe) and manganese (Mn) suggest reductive dissolution of their oxyhydroxides, whereas high bicarbonate and sulfate levels, along with low nitrate concentrations, primarily indicate mixed aquifer systems and microbial activity contributing to As mobilization. Correlation and principal component analysis (PCA) suggested geogenic and anthropogenic contributions to different contaminants. The cancer risk (CR) and total hazard quotient (THQ) was found to be higher than the acceptable range (between 0.0001 and 0.000001) and > 1, respectively, from both point and probabilistic health risk assessments, indicating high cancer and adverse non-cancer-related health risks from drinking contaminated water. These findings emphasize the need for large-scale As monitoring and appropriate mitigation measures to minimize adverse health outcomes in the As-contaminated areas.