Contamination of heavy metals in sediment is regarded as a global crisis with a large share in developing countries like Bangladesh. Four heavy metals such as arsenic (As), chromium (Cr), cadmium (Cd) and lead (Pb) in sediments and water were investigated from Karnaphuli River in Bangladesh. The decreasing trend of metals were observed in water as Cr>As>Pb>Cd and in sediment Cr>Pb>As>Cd. The ranges of heavy metals in water were 13.31–53.87, 46.09–112.43, 2.54–18.34 and 5.29–27.45μg/L and in sediments were 11.56–35.48, 37.23–160.32, 0.63–3.56 and 21.98–73.42mg/kg for As, Cr, Cd and Pb. The level of studied metals in water samples exceeded the safe limits of drinking water, indicated that water from this river is not safe for drinking and/or cooking. Contamination factor (CF) confirmed that the sediment samples were moderate to high contamination by As, Cd and Pb. The pollution load index (PLI) values were above one (>1) indicates advanced decline of the sediment quality. This study recommended that continuous monitoring of As, Cd and Pb in water; sediment and other aquatic biota of Karnaphuli River should be directed to assess the risk of these vital metals to safe the ecology in the vicinity of this river

Heavy metals contamination is a serious threat for the toxicity and bioaccumulation in food chain. Aquatic environment contamination has become a global concern because they have toxic effects on fishes. The concentration of heavy metals like arsenic (As), chromium (Cr), cadmium (Cd) and lead (Pb) in commercially fishes (Tenualosa ilisha, Gudusia chapra, Otolithoides pama, Setipinna phasa, Harpadon nehereus, Polynemus paradiseus, Sillaginopsis panijus and Pampus chinensis) collected from Karnaphuli River in Bangladesh were (fish muscles) assessed with health risk during summer and winter season. These heavy metals are toxic in nature and can come to human food chain through fish consumption. The mean concentration of As, Cr, Cd and Pb was found 1.59, 0.73, 0.41 and 1.13 mg/kg in summer and 1.81, 0.92, 0.52 and 1.45 mg/kg in winter, respectively. Cr and Pb concentration of all fish species were found to be higher than Food and Agriculture Organization (FAO)/(WHO) tolerable concentration assuming these metal pose risk to human. The hazard quotients value of heavy metals in Harpadon nehereus was found higher than one resulting non-carcinogenic risk for consumption of this fishes. Carcinogenic risk value for As and Pb were remaining 10⁻⁶ to 10⁻⁴ indicating continuously consumption of studied fish samples may cause cancer risk.