OMONIYI TEMITOPE GRACE

Pesticide contamination in aquatic organisms poses a growing concern for both food safety and environmental health. This study evaluated the effect of boiling on the residual levels of organochlorine and organophosphate pesticides in the African freshwater prawn (Macrobrachium vollenhovenii) obtained from markets in Benin City, Edo State, Nigeria. Prawn samples were collected from Uselu and Oba markets in August 2025. Pesticide residues were extracted and analysed using Gas Chromatography–Mass Spectrometry (GC–MS). Results showed that twenty (20) organochlorine and fourteen (14) organophosphate pesticide residues were detected in both raw and boiled prawn samples. The total concentration of organochlorines decreased from 28.42 ppb in raw samples to 23.845 ppb after boiling, indicating a slight reduction following heat treatment. Conversely, organophosphate pesticide levels increased from 8.595ppb in raw prawns to11.405ppb in boiled samples. Among organochlorines, α-HCH, β-HCH, PP‘-DDT were eliminated after boiling while Gamma-Chlordane, Alpha chlordane, PP‘-DDD, Methoxy For organophosphates, Chlorpyrifos (2.405 ppb) and Phosalone (1.58 ppb) showed notably higher levels of post-boiling, whereas Isazophos and Pyrazophos were completely degraded. For both pesticide groups, the estimated daily intake (EDI) for local consumers, based on an average prawn consumption rate of 0.33 kg/day and a 60 kg adult body weight for both the raw and boiled samples, were below the acceptable daily intake (ADI), indicating minimal potential health risks. Similarly, the hazard quotient (HQ) and hazard index (HI) values for both pesticide groups were less than one (<1) for both the raw and boiled samples, implying low non￾carcinogenic and carcinogenic risk to consumers. When compared with the FAO/WHO Codex and EU maximum residue limit (0.01 mg/kg for seafood), the total concentrations of organochlorine pesticides (0.028 mg/kg) exceeded the acceptable limit, indicating potential xiii xiv contamination risks. These findings suggest that while boiling can reduce certain persistent organochlorine residues, it may also increase the apparent concentration of some organophosphate pesticides. Continuous monitoring and further investigation into the effects of cooking methods on pesticide dynamics are recommended to safeguard consumer health.