Analysis of heavy metals in some commercially important fishes of Kathmandu Valley, Nepal.
Since the most of the fish consumed in the Kathmandu Valley are brought from commercial farms in the Terai region of Nepal and some from India, the quality characteristics of such fishes are foremost importance. Therefore, this study was carried out to provide the information on heavy metal concentrations in the muscles of nine commercial fish species available in the markets of Kathmandu Valley and to make people aware of the possible health risk associated with their consumption. The concentrations of Lead (Pb), Arsenic (As), Cadmium (Cd), Zinc (Zn), Manganese (Mn) and Chromium (Cr) were determined in the muscles of Catla catla, Pampus species, Puntius chola, Eutropiichthys vacha, Pampus chinensis, Clarias batrachus, Labeo bata, Labeo rohita and Mystus tengara. The levels of heavy metals were measured by atomic absorption spectrophotometry after digestion of the samples using the heating digester. There were significant variations among heavy metal levels in the muscles of the nine fish species, and no fish types had the highest levels of more than two metals. First, three maximum mean concentrations of potentially toxic elements were found 16.75 μg/g in Puntius chola, 12.13 μg/g in Eutropiichthys vacha, 11.63 μg/g in Catla catla for lead; 1.45 μg/g in Puntius chola, 1.35 μg/g in Pampus species and 1.15 μg/g in Mystus tengara for cadmium; and 1.01 μg/g in Eutropiichthys vacha, 0.76 μg/g in Pampus species, 0.65 μg/g in Pampus chinensis for arsenic. Similarly, first three maximum mean concentrations of essential elements were found 9.88 μg/g in Puntius chola, 7.63 μg/g in Clarias batrachus, 5.75 μg/g in Catla catla for manganese; 89.75 μg/g in Clarias batrachus, 68.37 μg/g in Catla catla, 65.38 μg/g in Puntius chola for zinc; and 14.63 μg/g in Clarias batrachus, 13.13 μg/g in Pampus species, 10.50 μg/g in Labeo rohita for chromium. The results showed that the heavy metals were found to be higher mean concentrations in the sample of Puntius chola, then in Catla catla, Pampus species and Clarias batrachus respectively; whereas they were found to be lower mean concentration in Eutropiichthys vacha, Pampus chinensis, Labeo bata, Labeo rohita and Mystus tengara correspondingly. The total mean concentration of manganese, lead and chromium in all fish samples was found to be higher than the limits permitted by the Food and Agriculture Organization (FAO) of the United Nations/World Health Organization (WHO) whereas the mean concentration of zinc and cadmium was found lower than the permissible level of FAO/WHO, National Health and Medical Research Council (NHMRC) and Malaysian Food and Regulations (MFR) guidelines. Similarly, the total mean concentration of cadmium was also found to be lower than the permissible level of Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Boletin Oficial del Estado (BOE), NHMRC, European Community Regulation (EU) and MRF in all fish samples. The total mean level of lead was found lower than BOE guidelines. Likewise, the total mean level of chromium was found slightly exceeded over limits suggested by the European Economic Community (EEC). This study showed that all the fish samples examined were found to contain some heavy metals above the FAO/WHO standard levels which may cause problems on the human health. At last, this research work suggests that fish consumers should always bear in mind that standards cannot provide a margin of safety when they are not enforced locally.