Incidence of aflatoxins, heavy metals and pesticide residues contamination in imported and locally grown white rice in Uganda

Abstract

There is increased global interest in the safety of rice because rice is a staple food for half of the world’s population and its safety influences consumers’ health. This study aimed at assessing the levels of aflatoxins (B1, B2, G1, and G2), heavy metals (Arsenic, Lead, and Cadmium), and organochlorine pesticide residues (OCPs) in imported and local rice in Uganda so as to compare their incidence and level of contamination. Rice (n = 305 samples) was collected from 4 major rice-producing districts and 4 rice entry points in Uganda from January 2018 to December 2019. Thin-layer chromatography was used to analyze samples for aflatoxins, atomic absorption spectrophotometry for heavy metals, and gas chromatography for organochlorine pesticide residues. The mean total aflatoxin contamination in imported rice (2.14±3.73 μg/kg) was higher than (0.01±0.09μg/kg) reported in local rice; with 14 (11.9%) samples above the Ugandan standard specification of 10 µg/Kg. The mean cadmium and lead levels (0.52±1.15mg/kg and 0.79±1.27mg/kg) exceeded the Ugandan Standard (US 738: 2019) and Codex Standard (CXS 193-1995) specifications of 0.1 mg/kg and 0.2mg/kg, respectively. OCPs including Aldrin, Endosulfan sulphate, 4, 4-DDE detected in imported rice were higher than the maximum residual limit (MRL) of Codex Alimentarius Commission. Heavy metal and OCP contamination of imported rice in Uganda may predispose rice consumers to toxicological risks. Handling and transit conditions for imported rice should be improved to reduce on aflatoxin contamination. Contamination of low land rice with heavy metals can be managed through enforcement of environmental laws that control wetland pollution. Continuous monitoring of heavy metals and OCPs in both local and imported rice is proposed to promote food safety and protect human health.