Determination of Heavy Metals in Fish (Clarias gariepinus) Organs from Asaba Major Markets, Delta State, Nigeria

Aim: To determine and compare the bioaccumulation of selected heavy metals- zinc, lead, cadmium, copper, mercury, and cobalt in organs of Clarias gariepinus obtained from fish sellers in the three major markets in Asaba.

Place and Duration of Study: Department of Chemistry Education Laboratory, Federal College of Education (Technical), Asaba between June and August 2013.

Methodology: Catfish, Clarias gariepinus sold commercially, were bought in replicates from three major markets in Asaba. The samples were dissected and the various organs dried separately at 110ºC to constant weight. The ground samples were digested with aqua regia solution and the heavy metals concentrations determined by AAS machine.

Results: The result revealed that the gills contained the highest total concentration (11.363 ppm)representing 27.70% of the detected heavy metals followed by the liver (11.267 ppm) representing 27.46% followed by the heart (10.303 ppm) representing 25.11% while the muscle had the lowest concentration (8.095) representing 19.73%. The difference in the bioaccumulation in the various organs however, did not differ significantly (P = 0.990). The overall accumulation pattern for the three markets was: Ogbeogonogo - Zn > Hg > Cu >Pb> Cd > Co; Cable - Zn > Cu > Hg >Pb> Co > Cd; and Abraka - Zn > Cu > Hg > Cd > Co >Pb. Zn mean concentration differs significantly (P =.000) from those of other metals. Mean concentrations of Pb, Cd, and Co were significantly the same but differ from those of Cu and Hg whose mean concentrations were statistically the same. The total concentrations in ppm of Zn (35.995, 32.336, and 36.292); Cu (1.587, 4.189, and 3.496) and Co (0.016, 0.070, and 0.088) in the three markets were below the permissible limits of 150 ppm, 10 ppm, and 0.15 – 1.0 ppm respectively stipulated by FAO/WHO. Also, the concentrations of Pb, 0.139 in Cable and 0.000 in Abraka; and Cd, 0.042 in Ogbeogonogo and 0.031 in Cable were below the permissible limits 0.5 ppm for Pb and 0.05 ppm for Cd. However, the concentrations in ppm of Pb, 0.949 in Ogbeogonogo, Cd, 0.673 in Abraka, and Hg in all three markets were above the permissible limits of 0.5 ppm, 0.05 ppm and 0.5 ppm in fish and food substances.

Conclusion: The consumption of Clarias gariepinus sold in these markets poses serious health threat to humans especially pregnant women.