Bioaccumulation of organochlorine pesticide residues in fish and invertebrates of Lagos Lagoon, Nigeria

The rate at which organochlorine pesticides (OCs) are being used in Nigeria is becoming a matter of concern considering the heavy negative health effects associated with these chemicals. OCs are very persistent, bioaccumulative and toxic, and they can easily find their way into an adjacent water course such as the Lagos Lagoon via soil run-off and leaching. The levels of OCs were therefore assessed in water, sediment, invertebrates (crayfish shrimps and crabs) and twelve species of fish, including commercially important fish sold to local markets. Samples were collected and analyzed using Gas chromatography/ Mass selective Detector (GC/MSD). The most bioaccumulated OCs in the fish were beta-HCH (22.72-0.90ng/g d. w.) and p,p’DDE (16.040.44ng/g d. w.). The most bioaccumulative OCs in the invertebrates were still beta-HCH (24.5016.10ng/g d. w.) and p,p’DDE (22.20-1.85ng/g d. w.). The sum OCs of 55.22 ng/g d. w. in crab eggs, 63.90ng/g d. w. in agaza (Caranx hippos), and 69.40ng/g d. w. in young blue crabs (Callinectus amnicola) revealed these biota as the most contaminated. Spatial patterns of contaminant accumulation were contrasted between environmental media and biological samples and a risk model for human exposures of organochlorine pesticides due to consumption of contaminated fish and invertebrates is presented.