Preliminary assessment of organochlorine pesticide residues and associated health risks in locally processed rice after Nigeria’s 2022 importation ban

Abstract

Rice is a staple food consumed globally. In Nigeria, a ban on rice importation was implemented in 2022 to reduce overdependence on foreign rice and boost local production. This policy shift led to increased cultivation of local rice and the introduction of new products into the Nigerian markets. However, despite this increase, the availability of a variety of locally processed rice products in Bayelsa State remains limited, posing a challenge for comprehensive sampling. Hence, this preliminary study - based on five rice products purchased from Swali Market, Bayelsa State - assessed the level of organochlorine pesticide (OCP) residues and associated health risks. Sixteen target OCPs were analyzed, and the detected concentration ranged from 2.11-4.78 µg·kg^-1, with the average levels following the order: endrin > endrin aldehyde > heptachlor epoxide > dieldrin > β-HCH > aldrin. β-HCH was the only detected hexachlorocyclohexane, while dichlorodiphenyltrichloroethane (DDT) and its degradation products were not detected. All detected OCPs were within their respective maximum residue limits (MRLs) for cereals. Deterministic health risk assessments revealed that non-cancer risks were negligible (HQ and HI < 1), and total cancer risk values were within the acceptable range (10^-6-10^-4). The Monte Carlo simulation showed that simulated exposures were within the recommended safety thresholds. Although the findings suggest that locally processed rice is relatively safe regarding OCP contamination, the small sample size limits the generalization of the results. Future large-scale studies are recommended to provide a more comprehensive evaluation. Additionally, promoting non-chemical pest control methods, such as biological control and organic farming, can help reduce reliance on synthetic pesticides and further enhance food safety.

Keywords

Organochlorine pesticides / maximum residue limit / food safety / dietary exposure / health risk assessment

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