Evaluation of Some Heavy Metals in Selected Sea Foods Directly from the Creeks in Rivers State, Nigeria

To assess and compare the levels of arsenic, cadmium, mercury and lead, in common seafoods (mudskippers, periwinkle and Shrimp) consumed in Rivers state obtained from different creeks of Rivers State Nigeria.

Study Design: Commonly consumed seafoods in Rivers State: Periopthalmus barbarous (mudskipper), Pandalus borealis (shrimp) and Tympanotonus fucatus (periwinkle) were collected at 5 different occasions from each of the study location (creek): Eagle Island, Iwofe, Bodo and Borokiri creeks in Rivers State. Eagle Island and Iwofe creeks are in Obio/Apkor and Degema LGA respectively, Borokiri Creek is in Port Harcourt LGA while Bodo creek is located in Gokana LGA.

Study Area: The study was carried out in the Department of Medical Laboratory Science, Rivers State University between the periods of June, 2018 – March, 2019. Samples of seafoods were collected from Bodo, Eagle Island, Borokiri and Iwofe creeks of Rivers State for 5 times at interval of 30 days between the periods of June, 2018 – October, 2018 during the wet season.

Methodology: Periopthalmus barbarous, Pandalus borealis, and Tympanotonus fucatus were collected from Eagle Island, Iwofe, Bodo and Borokiri creeks. The samples were correctly labeled, dried in an oven at 80°C, ground to powdered form then sieved to attain homogenous particles. Each sample was weighed, recorded and the concentrations of metals in the samples were determined. Two (2) grams each of the ground samples were weighed and put into a beaker with 6mls of nitric acid (HNO3) which was added as oxidizing acid to break the sample matrix and 2ml of perchloric acid as a reagent with 2 mls of de-ionized water was added to blend it. The sample was place on a heating mantle at 105°C until the sample volume reduced to two third of its original volume, the sample color clear and turns yellowish and its entire component was digested. The concentration of HMs: lead, arsenic, cadmium and mercury in the digested seafood samples were analysed using Atomic absorption spectrophotometer (AAS). The concentration of HMs from the sample were determined from the absorbance calibration in parts per million (ppm) or mg/kg dw.

Results: The bio-concentration mercury and arsenic in the selected seafoods from the creeks were below the World Health Organization permissible limits while levels of cadmium and lead in the seafoods in the order of periwinkle>mudskipper>shrimp collected from these creeks were above the FAO/WHO permissible limits of 0.5 1.0 mg/kg dw and 2.0 mg/kg dw respectively.

Conclusion: Mudskipper, periwinkle and shrimp were observed to bio-accumulate HMs beyond FAO/WHO permissible limits. Toxicities of these HMs in humans could induce several clinical derangements and eventually death if drastic measures are not put in place to stop or limit these anthropogenic activities.