Quantification of pesticide residues in cucumbers and watermelons from Dar es Salaam city markets and assessment of associated non-carcinogenic dietary health risks

The application of pesticides improves crop productivity and quality by controlling insect pests. However, their excessive use negatively affects human health. The present study quantified pesticide residues in cucumber ( n = 25) and watermelon ( n = 25) from five Dar es Salaam city markets using the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) multi-residue extraction method coupled with Liquid Chromatography—Tandem Mass Spectrometry (LC-MS/MS) and assessed associated dietary health risks. Twenty-three pesticides were detected; MRL exceedances occurred in 70% of cucumber samples and 85% of watermelon samples, with carbendazim and hexaconazole being the most prevalent. The World Health Organisation classified 78% of detected pesticides as moderately to severely hazardous (Classes Ib, II, and III). Whilst adult hazard index (HI) values were below 100% (acceptable risk), children exhibited critical HI exceedances: lufenuron (682.1%) and carbendazim (137.4%) in cucumber, and acetamiprid (158.2%) in watermelon. The cumulative hazard index (HI) for cucumber samples was 1,419.8% and 401.2% for children and adults, respectively; for watermelon samples, the cumulative HI was 672.7% for children and 150.3% for adults. These findings highlight urgent gaps in pesticide regulation, enforcement, and farm-level practices in Tanzania that warrant immediate attention from policymakers and stakeholders to inform effective interventions and safeguard public health.