Assessment of Pesticide Use Patterns and Chemical Residue Risks in Vegetable Farming Around Kano City

Vegetable farming in peri-urban areas surrounding Kano City, North West Nigeria, relies heavily on synthetic pesticide application to achieve commercially viable yields, creating potential for chemical residue accumulation in edible produce and risks to farmer health and environmental quality. This study assessed pesticide use patterns, adherence to recommended pre-harvest intervals, and residue levels in vegetables farmed in three irrigation districts around Kano City. Structured interviews with 120 vegetable farmers were conducted to document pesticide types, application frequencies, dosages, and safety practices. Vegetable samples of tomato, pepper, cabbage, and lettuce were collected at harvest and analysed for organophosphate, carbamate, and pyrethroid residues by gas chromatography. Chlorpyrifos was the most frequently used pesticide, applied by 84 percent of farmers. Pre-harvest intervals were not followed by 73 percent of farmers, many of whom harvested within 24 hours of application. None of the farmers used calibrated spraying equipment. Chlorpyrifos residues in lettuce samples were the highest at concentrations up to 0.86 mg/kg, exceeding the Codex MRL of 0.01 mg/kg. Permethrin and cypermethrin were found in 65 percent of tomato samples. Combined exposure estimates for consumers eating typical Kano vegetable servings suggested moderate exceedance of acute dietary reference doses for young children. These findings call for comprehensive extension service training on integrated pest management, pre-harvest interval compliance, and pesticide residue monitoring programmes coordinated through the Kano State Agricultural Development Authority.

Keywords: pesticide residues, vegetable farming, Kano City, pre-harvest interval, maximum residue limits