Evaluating the geochemistry of groundwater contamination with iron and manganese and probabilistic human health risk assessment in endemic areas of the world’s largest River Island, India

[Display omitted] •The Fe and Mn content varied from 0.1 to 9.04 mg L−1 and 0.03 to 4.48 mg L−1, respectively.•A total of 88.37 % and 74.41 % samples for Fe and Mn exceeded the WHO standards.•The exposure doses were greater than the reference dose for Fe and Mn.•The non-cancerous risk was higher in children and adults due to Fe and Mn ingestion.•Reducing condition in the soil and aquifer induced by flooding may be responsible for high Fe and Mn concentration in the groundwater. Iron (Fe) and manganese (Mn) are harmful for human health, if present in a higher concentration, particularly in groundwater. The results of the study revealed that the concentration of Fe and Mn exceeded the WHO guideline for safe drinking water in 88 % and 74 % of groundwater samples, respectively. The non-carcinogenic health risk as assessed through computation of hazard quotient (HQ) due to intake of Fe and Mn contaminated groundwater was found much higher for children and adults. The values of HQ were recorded up to 1.96 for children and 1.52 for adult in case of Fe; and up to 2.13 for children and 1.61 for adult associated with Mn. On the basis of occurrence and spatial distribution of Fe and Mn in groundwater, the study area was delineated under high, elevated and low risk zone for priority attention.