Cabbage or ‘pesticide’ on the platter? Chemical analysis reveals multiple and excessive residues in african vegetable markets

Overuse of pesticides in vegetables and related fresh products raises serious public health concerns. However, the recognition and assessment of the magnitude of public health risk remains a low priority in low income African communities. Brassicas are a cosmopolitan crop in African horticulture, and equally so, is the major economic pest, the diamondback moth, Plutella xylostella (L.). In consequence, insecticide use on P. xylostella in brassica production systems presents persistent pesticide overuse on produce directly destined for public consumption. Using the quick easy cheap effective rugged and safe (QuEChERS) multi-residue analysis method, followed by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS), we investigated the occurrence and magnitude of pesticide residues at three vegetable market levels (farmgates, vendors and supermarkets) in Botswana. We detected pesticide residues in 74.1% of the samples while 33.4% had multiple compounds. Farmgates recorded higher pesticide residues than other markets. We multi-detected 10 low-highly hazardous pesticides [World Health Organisation (WHO)] (classes 1B & II), that included Organophosphates, Pyrethroids, Neonicotinoids and Carbamates. Fifty percent of the detected pesticides from farms and supermarkets had residue quantities exceeding the Codex Maximum Residue Limit thresholds; although estimated daily per capita consumption was lower than the WHO Average Daily Intake (ADI) and Acute Reference Doses (ARfDs). These results indicate presence of multiple and excessive pesticide residues in routinely consumed vegetables on the markets, and points to an imminent public health hazard. Urgent attention is needed to develop and enforce effective policies and regulations on pesticide use practices and investment in non-chemical pest management alternatives.