Heavy metals in water, sediment and fish species of the Bhairab River in southwest Bangladesh and their health implications

• Fe, Mn, and Zn content were exceeded the threshold limit for drinking water standard. • CF and Igeo < 1 indicate sediment suitability for crop cultivation during winter. • HMs in water, sediment, and fish samples were lower in monsoon than winter season. • HMs in the studied fish species did not exceed the tolerable limit except Cr. • THQ and HI < 1 indicate no potential health risk due to consumption of the studied fish. • Cr was associated with the possibility for cancer due to life time exposure of studied fish. Rapid industrialization in southwestern Bangladesh has led to significant accumulation of heavy metals (HMs) in riverine ecosystem. However, the extent of HMs accumulation in the Bhairab River and its potential risk still remain unknown. The current study quantified HMs in water, sediment, and different fish species of Bhairab River to evaluate the ecological and human health risk. Water, sediment, and fish samples were collected during two seasons (monsoon and winter) from three locations and measured for HMs (Pb, Cd, Cr, Fe, Mn, Zn) using flame atomic absorption spectrophotometer (F-AAS, Model: Shimadzu AA-7000, Japan). HMs in water and sediment were found in the order of Cd < Pb < Cr < Zn < Mn < Fe. The Fe, Mn, and Zn exceeded the threshold limit for drinking standard as per WHO (2004) and USEPA (1999). The contamination factor and geo-accumulation index were < 1, indicating that river bank sediment is suitable for crop cultivation during winter. HMs in water, sediment, and fish were lower during the monsoon compared to winter, due to dilution effects. According to WHO (2004), FAO (1983), and MOFL (2014), HMs in fish did not exceed the tolerable limit except for Cr. According to WHO (2004) guidlines, the daily intake of HMs was less than reference dose. For non-carcinogenic risk, THQ and HI < 1, indicating no potential health risk for Khulna urban inhabitants due to consumption of the studied fish. Cr posed a potential carcinogenic risk from lifelong consumption of these fish. These findings may support national policy-making and riverine ecosystem management in achieving the Sustainable Development Goals (SDGs).