Bioaccumulation of six heavy metals (Mn, Fe, Co, Ni, Cu, Zn) in the muscle of highly consumed fish species (Mastacembelus armatus) were measured using atomic absorption spectrometer. Fe (213.29 mg/kg dry weight) concentration was the most, followed by Zn (186.19 mg/kg dry weight), Ni (58.98 mg/kg dry weight), Cu (41.36 mg/kg dry weight), Co (9.06 mg/kg dry weight) and Mn (9.03 mg/kg dry weight). Estimated daily intake of heavy metals was calculated by mean fish consumption rate 19.5 × 10−3 kg/day, on the basis of a calculation of the amount of fish consumed by adult individuals (male and female). The studied fish species pose non carcinogenic risk for Co and Ni [target hazard quotient (THQ) > 1] only. Hazard index (HI) was high. Carcinogenic risk (TR) posed by this fish for male and female was 3.43 × 10−3 and 3.91 × 10−3, respectively for Ni (the carcinogenic potency slope factor was available for Ni only). The study is an alert indicating that inhabitants who consume these fishes (particularly females) were at risk of Co and Ni toxicity. In India recommended guidelines have yet not been established for these heavy metals, which is essential for setting of toxicological standards.

The present study was conducted to examine the contamination of rivulet situated at Kasimpur, Aligarh (27.218° N; 79.378° E). It receives the wastewater of Harduaganj Thermal Power Plant (HTPS) containing fly ash and heavy metals. Among the heavy metals estimated in the rivulet water, Fe (8.71 mgL-1) was present in the highest concentration followed by Cu (0.86 mgL-1), Zn (0.30 mgL-1) Mn (0.21 mgL-1), Ni (0.12 mgL-1), Co (0.11 mgL-1) and Cr (0.10 mgL-1). The values for the heavy metals such as Fe, Ni and Mn were beyond the limits set by UNEPGEMS. Bioaccumulation of these heavy metals was detected in tissues such as gills, liver, kidney, muscle and integument of the fish Mastacembelus armatus. Accumulation of Fe (213.29 – 2601.49 mgkg-1.dw) was highest in all the organs. Liver was the most influenced organ and integument had the least metal load. The accumulation of Fe, Zn, Cu and Mn, observed in the tissues were above the values recommended by FAO/WHO. Biochemical estimation related to blood glucose, liver and muscle glycogen conducted showed significant (p < 0.01) elevation in blood glucose content over control (17.73%), whereas liver glycogen dropped significantly (p < 0.01) over control (−89.83%), and similarly muscle glycogen also decreased significantly (p < 0.05) over control (−71.95%), suggesting enhanced glycolytic capacity to fuel hepatic metabolism. Histopathological alterations were also observed in selected organs (gills, liver and kidney) of Mastacembelus armatus.

The present study was conducted to assess the toxicity of thermal power plant effluent containing heavy metals (Fe > Cu > Zn > Mn > Ni > Co > Cr) on haematological indices, micronuclei, lobed nuclei and activity of pathological marker enzymes [alkaline phosphatase (ALP), aspartate transferase (AST), alanine transferase (ALT) and creatine kinase (CK)] in Channa punctatus. Total erythrocyte count (−54.52 %), hemoglobin (−36.98 %), packed cell volume (−36.25 %), mean corpuscular hemoglobin concentration (−1.41 %) and oxygen (O2) carrying capacity (−37.04 %) declined significantly over reference fish, however total leukocyte count (+25.43 %), mean corpuscular hemoglobin (+33.52 %) and mean corpuscular volume (+35.49 %) showed elevation. High frequency of micronuclei (1133.3 %) and lobed nuclei (150 %) were observed in exposed fish which may indicate mutagenesis. Activities of pathological marker enzymes ALP, AST, ALT and CK increased significantly in serum of exposed fish. The ratio of ALT: AST in exposed fish was beyond 1 which indicates manifestation of pathological processes. These biomarkers show that fish have macrocytic hypochromic anemia. Leukocytosis showed general defence response against heavy metal toxicity and marker enzymes showed tissue degeneration. In conclusion, thermal power plant effluent has strong potential to induce micronuclei, tissue pathology, making the fish anemic, weak, stressed and vulnerable to diseases.