Pesticide residues and potential health risk through the consumption of fish from Ibadan, Oyo state, Nigeria

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June, 2015.
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This study was conducted to determine the concentration of organochlorine, organophosphorus and pyrethroid pesticide residues present in some selected fish species (Oreochromis niloticus, Clarias gariepinus, Trachurus trachurus, Sardinella madenrensis and Scomber japonicus) from markets in Ibadan, Oyo state, Nigeria. Further studies were carried out to determine the health risk posed on the human population from the consumption of the selected fish species. The extraction procedure and clean-up was done using Hexane/Acetone solvent system. The five fish species were analyzed for pesticide residues by gas chromatography equipped with electron capture detector. Nine (9) organophosphorus pesticides (Methamidopho, Phorate, Fonofos, Primiphos-methyl, Chlorpyrifos, Malathion, Fenithrothion, Parathion-ethyl and Profenofos), nine (9) pyrethroid pesticides (Allenthrin, Bifenthrin, Fenpropathrin, Lambda-cyhalothrin, Cyfluthrin, Cypermethrin, Fenvalerate, Delta-methrin and Permethrin) and thirteen (13) organochlorine pesticides (β-HCH, δ-HCH, Heptachlor, γ-Chlordane, α-endosulfan, β-endosulfan, p,p’-DDE, Dieldrin, Endrin, p,p’-DDD, p,p’-DDT, Methoxychlor and Aldrin) were detected. The mean concentrations detected for organophosphorus pesticides ranged from 0.0024±0.0002 µg/g to 0.0076±0.0031 µg/g, pyrethroids ranged from 0.2154±0.0066 µg/g to 7.6504±0.0259 µg/g and organochlorine pesticides ranged from 0.1048±0.0079 µg/g to 3.2062±0.0348 µg/g. The health risk assessment analysis performed on the samples had health index of less than 1 (HI<1) for pyrethroids and organophosphorus pesticides in all fish species analyzed, indicating that their intake through fish consumption may pose no danger or harm to its consumers. On the other hand, health index was less than 1 (HI<1) for most organochlorines, with the exception of heptachlor, dieldrin and aldrin which had HI greater than 1 (HI>1) in some fish species, indicating that there may be harm in continuous consumption of such fish which could result in detrimental chronic effects on the consumer.
A thesis submitted to the Department of Chemistry, in partial fulfillment of the requirements for the award of the degree of Master of Philosophy (M.Phil.) In Environmental Chemistry, 2015