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<160). The ecological risk factor of Pb, Cr, Hg, and As are 24.5, 1.2, 27.2, and 3, respectively. The result showed that water and sediment quality of the ponds are contaminated due to atmospheric deposition, anthropogenic activities (rock weathering, manufacture of metal goods and batteries, wood treatment, tanning, plating, use of fertilizers, etc.), industrial effluents, and domestic sewage from the adjacent areas discharged into it. This research will be helpful for the proper management and monitoring of this treatment plant and surrounding inhabitants.

有毒金属从地质和人为来源排放到水体中，并且很容易通过水和沉积物被水生生物吸收。评估消费最多的尼罗罗非鱼的铅 (Pb)、镉 (Cd)、铬 (Cr)、砷 (As) 和汞 (Hg) 的有毒金属污染水平、它们的来源以及该地区周围居民的健康风险，进行了一项研究。结果表明，所有处理的水中铅浓度均较温和，通常不超过 WHO（2004）、ECR（1997）和 USEPA（1999）给出的允许限值，分别为 10μg/L、50μg/L和 15 μg/L。而其他选定的有毒金属的浓度在可容忍的范围内。在沉积物中，Pb 的最大浓度出现在 T5 (394±8.7 mg/kg) 而最低浓度在 T3 (283±4.3 mg/kg)。这一结果超过了FAO（1985）、USEPA（1999）和EPA（2002）的限制。Cr 的浓度也高于 FAO (1985)、USEPA (1999) 和 EPA (2002) 的限值。如果是两组鱼，与其他国际指南相比，Pb 和 Cd 的浓度高于检测限。对于生态风险评估，计算污染因子和生态风险因子。对于健康风险评估，同时观察目标危害商数（THQ）、危害指数（HI）、估计每日摄入量（EDI）和致癌风险（CR）。沉积物的生态风险（Eri）表现出相当大的生态风险（80≤Eri<160）。Pb、Cr、Hg 和 As 的生态风险因子分别为 24.5、1.2、27.2 和 3。结果表明，由于大气沉降、人为活动（岩石风化、金属制品和电池制造、木材处理、鞣革、电镀、使用化肥等）、工业废水、及周边地区生活污水排入。这项研究将有助于对该处理厂和周围居民的适当管理和监测。