Health risk assessment of natural radionuclide and heavy metals in commonly consumed medicinal plants in south-west Nigeria

Abstract

The natural radionuclide and heavy metal contents of five commonly consumed medicinal plants in southwestern Nigeria were determined using gamma spectrometry with high purity germanium detector and flame atomic absorption spectrophotometer. The activity concentration of ⁴⁰K ranged from 315.65±39.17 to 892.04±63.09 Bqkg^-1. ²³⁸U ranged from 1.73±1.95 - 5.41±2.39 Bqkg^-1 and ²³²Th ranged from 1.22±1.75 Bqkg^-1 to 8.49±2.69 Bqkg^-1 in zobo. The mean annual effective dose was found to be lower than the standard proposed by United Nation Scientific Committee on Energy and Atomic Research. Fatal cancer risk and hereditary cancer risk from ingestion of the plants lie within the safe limit as recommended by United State Environmental Protection Authority and World Health Organization. The mean concentrations of the heavy metals in the samples were compared with the permissible limit in literature and were found to be within the safe limit. The estimated annual daily doses are lower than the recommended daily intake except Zn which is higher. The estimated fractional hazard quotient of the metals is lower than or equal to 1 except for Zinc in garlic and ginger. Total hazard index obtained for all the samples are higher than 1.0 but lower than 3.0. This implies that there is no probable hazard from the consumption of these plants

Keywords: Radionuclide, Heavy metal, Fractional hazard quotient, Average daily doses, Effective dose