Determination of Pesticide Residues in Tomatoes Sold in Open Markets in Plateau State, North Central Nigeria

Indiscriminate use of synthetic pesticides in Nigerian smallholder agriculture raises consumer safety concerns, particularly for fresh produce sold in unregulated open markets. This study determines the residue levels of organophosphate and pyrethroid pesticides in tomato samples purchased from five major markets in Plateau State, North Central Nigeria. Tomato samples are collected weekly over an eight-week period during the dry season farming cycle and analysed using gas chromatography coupled with electron capture detection following standard QuEChERS extraction and cleanup procedures. Target analytes include chlorpyrifos, malathion, cypermethrin, and lambda-cyhalothrin, representing the most commonly applied pesticides among vegetable farmers in the region. Results are compared against maximum residue limits established by the Codex Alimentarius Commission and the Nigerian Agricultural Quarantine Service. The study also administers structured questionnaires to selected traders and farmers to document pesticide application practices and pre-harvest intervals. Dietary exposure estimates are calculated using standard daily intake models for an adult Nigerian consumer. It is anticipated that a proportion of samples will contain pesticide residues above permissible limits, reflecting insufficient pre-harvest intervals. Findings inform regulatory bodies and support public health advocacy for stricter enforcement of pesticide use guidelines in smallholder vegetable production in the North Central zone. Keywords: pesticide residues, tomatoes, organophosphates, Plateau State, food safety