Assessment of radiobiological and chemical contamination in water systems and food products in Nigeria and their implications for public health and environmental safety

Abstract

Environmental contamination of water systems and food products by radionuclides, heavy metals, and pathogenic microorganisms poses significant public health and environmental challenges in Nigeria. However, comprehensive evidence integrating these contaminants across water and food systems remains limited. This study systematically reviewed the occurrence, distribution, and health implications of radiological, chemical, and microbiological contaminants in Nigerian water systems and food products. A systematic review was conducted following PRISMA 2020 guidelines. Literature searches covering 2000–2025 identified 2,483 records from major databases. After duplicate removal and screening, 238 full-text articles were assessed, and 72 studies were included in the final synthesis, comprising radiological (n = 21), chemical (n = 27), food microbiology (n = 20), and water microbiology (n = 24) investigations. Annual effective doses from drinking water generally ranged from 0.02 to 0.09 mSv/year and remained below the WHO reference level of 0.1 mSv/year, although localized studies reported doses of 2.48–6.01 mSv/year and infant exposures of approximately 4.63 mSv/year. Radionuclide concentrations ranged from 0.41 to 8.78 Bq/L for ²³²Th and 4.29–376 Bq/L for ⁴⁰K. Heavy metal studies reported Pb concentrations of 0.021–0.145 mg/L and Cd concentrations of 0.002–0.008 mg/L, with hazard indices frequently exceeding unity and lifetime cancer risks ranging from 2.1 × 10⁻⁴ to 4.7 × 10⁻³. Microbiological contamination was widespread, with bacterial loads reaching 10⁶ CFU/mL in water and 1.06 × 10⁷ CFU/g in food products. Escherichia coli concentrations reached 98–106 CFU/100 mL, while total coliform prevalence and E. coli prevalence were 53.3% and 12.4%, respectively. Multidrug-resistant bacteria were reported in 94–99% of isolates from ready-to-eat foods. Radiological contamination in Nigeria is generally localized and mostly within international safety limits, whereas heavy metal and microbiological contamination represent persistent and widespread public health hazards. The findings highlight the need for integrated environmental surveillance, strengthened regulatory enforcement, routine monitoring of food and water systems, and implementation of One Health strategies to reduce environmental exposure and associated health risks. Not applicable.