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Heavy metal contamination in aquatic environment is a serious concern throughout the world. Metal contamination are responsible for the accumulation of metals within the fish body. And, consumption of these contaminated fish possess serious threat to the associated consumers. In this current study, five commonly cultured freshwater fishes (rui, Labeo rohita; mrigal, Cirrhinus mrigala; silver carp, Hypophthalmicthys molitrix; bata, Labeo bata, and sarpunti, Puntius sarana) were collected from a commercial fish farm of Natore district, Bangladesh to analyze metals levels in edible portion (flesh), and to assess the associated human health risk. Several heavy metals such as zinc (Zn); cadmium (Cd); chromium (Cr); arsenic (As); lead (Pb); and nickel (Ni) were analyzed by a flame atomic absorption spectrophotometer. Besides, the target hazard quotient (THQ), hazard index (HI) and lifetime cancer risk (TR) were also estimated for assessing the associated human health risk. In this study, concentrations of Zn, Cd, Cr, As, Pb and Ni in different fish species were found 6.36 ± 1.48 to 13.31 ± 1.33; 0.017 ± 0.01 to 0.049 ± 0.02; 0.654 ± 0.04; 0.015 ± 0.01 to 0.033 ± 0.01; 0.534 ± 0.11 and 0.08 ± 0.05, respectively. All the analyzed values were within the recommended level except Cr in C. mrigala. The THQ, HI and TR values of all the analyzed metals in the fishes indicated that no associated cancer risk resulting from the consumption of those fishes. Therefore, the current study revealed that fishes of the target area might be free from associated metals contamination and hence, might be safe for human consumption.

Pesticides are from the potent chemical contaminants in aquatic environment. These chemicals are routed into the aquatic environment through several natural and anthropogenic activities. Pesticides toxicity adversely affect growth, physiology, reproduction, immunity, hemato-biochemical profile and induce serious histopathological alterations of several tissues of aquatic organisms including fish. From the aforementioned effects, histopathological and hemato-biochemical parameters serve as important biomarkers of aquatic contamination resulted from pesticides. Pesticides are major concern around the world as they can bioaccumulate into different fish tissues which will consequently result in serious health concern for the consumers. Therefore, searching out of ecofriendly, effective, and suitable alternatives of pesticides is important to protect the aquatic ecosystems as well as health status of several aquatic living organisms especially fish. In this context, the present review depicts several histopathological and hemato-biochemical alterations resulted from pesticide toxicity. It also highlights the possible methods for diminishing the negative effects of pesticides on fish to ensure healthy aquatic environment for fish farming.

Water pollution is a threat to aquatic organisms, including fish, and is a global concern for aquatic biodiversity and ecosystem integrity. This study evaluates the effect of waterborne pollutants on Gangetic Mystus (Mystus cavasius) collected from the Surma River, Bangladesh between April 2018 to March 2019. Histomorphological studies of liver and kidney were carried out on 10 individual species collected at each of four sampling sites and one control site. Water quality parameters were also recorded at each site. We observed several histological alterations in the liver, including hemorrhage, pyknosis, necrosis, vacuolation, lipid droplet, nuclear alterations, and hepatocyte hypertrophy. In the kidney, the histopathological alterations included vacuolation, necrosis, hemorrhage, degeneration of glomerular tubule, dilation of Bowman's space and blood congestion. Temperature fluctuated between 19.7 ± 1.57 °C and 32.3 ± 1.74 °C, dissolved oxygen at the surface ranged from 4.15 ± 0.31 to 5.15 ± 0.35 ppm, pH ranged from 7.42 ± 0.33 to 6.50 ± 0.12, nitrite ranged from 0.022 ± 0.21 to 0.817 ± 0.02 mg/l, ammonia ranged from 0.70 ± 0.11 to 0.16 ± 0.19 mg/l and alkalinity ranged from 109.41 ± 0.02 to 14.32 ± 0.20 mg/l during the time frame of the study. Water quality parameters could not found the suitable range from November to February. The main aim of the present investigation revealed that histopathological changes of liver and kidney of Gangetic Mystus appeared to be a useful biomarker to assess the impact of toxicity of water pollution.