Evaluation of non-cancer risk owing to groundwater fluoride and iron in a semi-arid region near the Indo-Bangladesh international frontier

Groundwater quality in Hili, a semi-arid border region at Indo-Bangladesh border, was investigated in the post-monsoon season of 2021, succeeded by assessment of probabilistic health risk arising from fluoride (F⁻) and iron (Fe) intake, with the hypothesis that groundwater quality of the region was not satisfactory for human consumption and health, considering earlier reports on high groundwater F⁻ and Fe in few of the neighboring districts. All water samples were found to be potable in terms of Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻ and NO₃^−, , but F⁻ and Fe exceeded prescribed safe limits for drinking water in about 48% and 7% samples. Almost all water samples were found to be good for irrigation in terms of sodium adsorption ratio (SAR), soluble sodium percentage (SSP), Kelly’s index (KI), %Na and magnesium ratio (MR). The principal component analysis (PCA) identified three major factors influencing groundwater quality, explaining about 71.8% of total variance and indicated that groundwater quality was primarily influenced by geochemical factors. Carbonate and silicate weathering were mainly responsible for dissolution of minerals in groundwater. Non-carcinogenic risk due to cumulative impact of F⁻and Fe intake was in the order of THI_Children > THI_Infant > THI_Adult. As per Monte Carlo simulation run with 5000 trials to ascertain the order of probabilistic health risk, the most dominant governing factors behind non-carcinogenic risk caused by F⁻and Fe intake were their concentration (Ci) followed by ingestion rate (IR), and exposure duration (ED).