Assessment of Insecticide Residues in Maize Grains from Major Markets in Ogbomoso, Nigeria. Nigerian Journal of Post-Harvest Research, 3(2), 65-72.

Maize (Zea mays L.) is a staple cereal crop of significant economic and nutritional importance worldwide. However, its production and postharvest storage are frequently compromised by infestations of insect pests, leading to yield and quality losses. The predominant method of pest control in maize storage involves the application of synthetic insecticides. This study evaluated the concentration of insecticide residues in maize grains sourced from major markets in Ogbomoso, Nigeria. Snowballing sampling technique was used to randomly select maize marketers from three markets: Odo-Oba, Iluju, and New Waso. Ten maize stores were sampled in each market. Composite samples representative of each market were prepared by combining 100 g subsamples from each store, with three replicates per market. Samples were transported to the laboratory, milled, and analyzed for pesticide residues using the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction method, followed by gas chromatography – mass spectrometry (GC-MS) analysis on a Varian 3800/4000 instrument. Descriptive statistics and one-way analysis of variance (ANOVA) were performed using SAS version 9.2, with mean comparisons conducted using Duncan's Multiple Range Test at p < 0.05. Dichlorvos (2,2-dichlorovinyl dimethyl phosphate) was detected in all maize samples from three markets, ranging from 144.1 to 269.7 mg/kg, vastly exceeding the EU-MRL of 0.01 mg/kg. Such high residues pose severe health risks, including genotoxic, neurotoxic, reproductive, carcinogenic, respiratory, and dermal effects, potentially causing systemic toxicity or death. Urgent measures are needed to mitigate contamination and protect public health.