Assessment of pesticide residues from herbal medicines sold in selected markets in Kampala District, Uganda

Abstract

The growing reliance on herbal medicines in Uganda, especially in Kampala District's urban areas, has raised safety concerns due to potential pesticide contamination. This study evaluated pesticide residue levels in herbal medicines sold in four major markets (Kalerwe, Usafi, Owino, and Nakasero) in Kampala District and evaluated the associated health risks through consumption of pesticide-contaminated herbal medicines. A total of 64 herbal medicine samples (48 liquid and 16 solid formulations) were analysed. Samples were extracted using solvent-based techniques (acetonitrile for liquids and a mixture of n-hexane/dichloromethane for solids), cleaned with Florisil-packed columns, and analyzed using gas chromatography-mass spectrometry (GC-MS) for 31 pesticides of various chemical groups (organochlorines, OCPs; organophosphates, OPPs; herbicides; other pesticides, namely cypermethrin, quinoxyfen, and cybutryne). Pesticide levels in liquid samples ranged from 1.20 to 306.07µg kg⁻¹ f.w., with the total mean of 96.89 µg kg⁻¹ f.w. OCPs were the most predominant pesticides (45.1% of the total pesticides), followed by others (23.2%). For solid samples, pesticide concentrations varied from 0.36 to 307.34 µg kg⁻¹ d.w., with the total mean of 162.11 µg kg⁻¹ d.w. The herbal medicines from Nakasero market had the highest total mean concentrations (148.9 µg kg⁻¹), followed by Owino (112.60 µg kg⁻¹). Endrin-aldehyde was the most frequently detected pesticide (98.4% of the samples), while hexachlorobenzene was the least detected (14.1%). In general, the pesticide levels were below the limits set by the World Health Organization (WHO), Food and Agriculture Organization (FAO), and Codex Alimentarius Commission for herbal products. Most of the samples had HQ and HI values