Bioaccumulation of Heavy Metals with Increasing Fish Size in Rawal Lake Islamabad, Pakistan

Fish is a good source of essential nutrients for human health. However, as a result of consuming and dwelling in aquatic ecosystems such as lakes, potentially harmful heavy metals are absorbed into the biological tissues of fish. When humans eat the contaminated fish, they absorb the heavy metals. In the present study, the bioaccumulation of heavy metals  Aluminum (Al), Arsenic (As), Boron  (B),  Cadmium (Cd),  Chromium (Cr),  Copper (Cu),  Cobalt (Co), Iron (Fe),  Mercury (Hg), Manganese (Mn), Nickel (Ni), Lead (Pb), Selenium (Se) and Zinc (Zn) in six fish species namely Ctenopharyngodon idella (GrassCarp), Catla catla (Thala),Cyprinus carpio (Gulfam), Labeo rohita (Rahu), Hypophthalmichthys molitrix (Silver carp), Channa punctata (Dolla)of Rawal Lake (Islamabad) Pakistan was determined with increasing fish size under natural conditions. Rawal Lake is the main source of water supply for the twin cities of Rawalpindi and Islamabad. Contaminants from poultry farms, sewage drains and landfill sites, sewage and industrial effluent has seriously affected the quality of surface water which is affecting food chain of the lake.  The sampling of the six edible fish species of different sizes from Rawal Lake was carried out monthly from September 2013 to December 2013 for metal analysis. Pb and Co were measured by Polarograph Computrace VA-83 and Al, As, B, Cd, Cr, Cu,  Fe, Hg, Mn, Ni, Se, Zn by Inductively Coupled Plasma Spectroscopy (ICP-OES). As, Co, Hg and Se were found below detection limit in all the fish samples. Concentration of all other metals increased with increasing length of the fish. Pb, Cu, Cd, Cr, Fe, Mn, Ni and Zn content in all the fish samples ranged from 0.98 µg/g to 0.2 µg/g, 1.05 to 6.62 µg/g, 0.2 to 1.68 µg/, 0.5 to 13.48 µg/g, 22.13 to 376.56 µg/g, 1.1 to 5.07 µg/g, 0.31 to 12.98 µg/g and 15.03 to 72.39 µg/g respectively .Cd and Fe concentration were within permissible limits except two and three samples respectively. Pb, Cu, Ni and Zn concentration in all the fish species were below permissible limit.  Cr in most and Mn in all fish samples were above permissible limit set by WHO/ FAO. Consequently, it is unfit for human consumption and poses a public health risk.