Assessment of Persistent Organochlorine Pesticide Residues in Commercially Important Fin and Shell Fishes of River Majidun, Lagos, Nigeria

Aim: The pesticide pollution of aquatic ecosystems has developed serious environmental anxiety, provoking a necessity for continuous evaluation of harmful constituents.

Study Design: A quantitative cum descriptive experimental design was used to evaluate the occurrence and concentration of Persistent Organochlorine Pesticides (POPs) in water, sediment, fish (Tilapia zilli and Chrysichthys nigrodigitatus) and shell fishes (Macrobrachium vollenhovenii, Littorina littorea and Callinectes pallidus) of River Majidun, Lagos, Nigeria.

Place and Duration of Study: Nigerian Institute of Oceanography and Marine Research (NIOMR) between June and December, 2019.

Methodology: Sediment samples were collected by the Rigosha grab sampler and fish samples were purchased from commercial fishermen. Sample preparation was done according to the Environmental Protection Agency (US EPA) 3570 method. POPs were evaluated using Hewlett Packard 5890 series II gas chromatography with electron capture detector.

Results: Twenty-one organochlorine residues were identified including p’p’DDT, Lindane (γ-HCH), Dieldrin, Heptachlor, Aldrin, Chlordane, Endrin aldehyde, Endrin ketone, Methoxichlor and Endosulphan. Concentrations in water ranged between 0.03 µg l-1 (Endrin ketone) and 1.97 µg l-1 (Methoxychlor). In sediment, it is between 4.55 µg kg-1 (β-HCH) and 128.25 µg kg-1 (Methoxychlor). In Macrobrachium vollenhovenii, Methoxychlor was 123.83 µg kg-1 and Lindane ((γ)- HCH) was highest here (39.35 µg kg-1). Callinectes pallidus had a high concentration of Endrin ketone (133.13 µg kg-1). The Tilapia zilli highest concentration was 110.35 µg kg-1 (endrin ketone) and it had the highest pp’DDT which was 41.40 µg kg-1.

Conclusion: Evidently, there was sequestration of POPs from water into sediment and bioaccumulation in the organisms, due to exposure. The level of POPs in all samples were below the limits of 200 µg kg-1 fresh weight in fish and sea food set by Codex Alimentarius Commission by FAO/WHO. The attendant environmental/human menace cum inherent danger of the raised levels of POPs, calls for continuous monitoring of River Majidun.