Comprehensive analysis of toxic metals and their sources accumulated by cultured Oreochromis niloticus in Pagla Sewage Treatment Plant, Narayanganj, Dhaka, Bangladesh

Toxic metals are discharged into water bodies from geologic and human-induced sources and easily absorbed in aquatic organisms through water and sediments. To assess the level of toxic metal contamination from lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg) of the most consumed fish Oreochromis niloticus , their sources, and the health risk for inhabitants surrounding the area, a study was undertaken. Results indicated that Pb concentration in water in all the treatments was mild and does usually not exceed the permissible limits given by the WHO ( 2004 ), ECR ( 1997 ), and USEPA ( 1999 ), which are 10μg/L, 50 μg/L, and 15 μg/L, respectively. While the concentration of other selected toxic metals were within the tolerable limits. In sediment, maximum concentration of Pb was found in T5 (394±8.7 mg/kg) whereas minimum concentration in T3 (283±4.3 mg/kg). This result exceeds the limit of the FAO ( 1985 ), USEPA ( 1999 ), and EPA ( 2002 ). The concentration of Cr is also above the limit of FAO ( 1985 ), USEPA ( 1999 ), and EPA ( 2002 ). In case of fish of two groups, the concentration of Pb and Cd is above the detection limit with comparison with other international guidelines. For ecological risk assessment, contamination factor, and ecological risk factor were calculated. And for the health risk assessment, target hazard quotient (THQ), hazard index (HI), estimated daily intake (EDI), and carcinogenic risk (CR) were observed simultaneously. The ecological risk (Eri) for sediments showed considerable ecological risk (80≤Eri