Pesticide Residues in Mangoes from Makueni County, Kenya: Multi-Analytical Characterization, Post-Harvest Reduction, and Farmer Practice Implications for Food Safety

Abstract The aim of this study was to evaluate pesticide residue levels in mangoes from Makueni County, Kenya, using multi-analytical characterization and to assess farmers' pesticide-handling practices for food-safety risk mitigation. Seventy-five samples across 25 farms in Nzaui Ward were categorized into unwashed peels, washed peels, and washed pulp. Residues of nine pesticides were quantified via QuEChERS extraction followed by LC–MS, while FTIR, XRD, and SEM characterized peel chemistry and morphology. Structured questionnaires captured farmer knowledge and practices. FTIR spectra confirmed cuticular wax involvement in residue retention through hydroxyl, carbonyl, and carbohydrate functional groups, while XRD patterns revealed semi-crystalline cellulose structures that may trap pesticides. SEM micrographs showed rough, wax-aggregated surfaces in unwashed peels that become disrupted after washing, explaining incomplete residue removal. LC–MS detected carbaryl (0.736 ppb), ethoprophos (0.406 ppb), and monocrotophos (0.292 ppb) as predominant residues in unwashed peels. Washing reduced carbaryl by 56% and azinphos-methyl by 63%, but ethoprophos persisted (− 3%), reflecting its lipophilicity. Peeling further lowered pulp concentrations by 49–79%, though ethoprophos (0.206 ppb) and carbaryl (0.184 ppb) remained detectable. All residues were below WHO and PCPB maximum residue limits, but co-occurrence of organophosphates warrants cumulative risk assessment. Over 57% of farmers reported limited pesticide-use knowledge, correlating with potential non-compliance in pre-harvest intervals. Integrated characterization alongside practice assessment provides a robust food-safety evaluation framework. Strengthened extension services, routine market surveillance, promotion of integrated pest management, consumer peeling advisories, and regulatory enforcement on pesticide registration are recommended to safeguard public health and support sustainable mango production in semi-arid Kenya.