Ingestion exposure of natural radionuclide and toxic heavy metallic origin in samples of local staple food

Abstract

In this study, measurements were made of the concentration of metals of heavy origin (Cd, Cr, Cu and Zn) and activity-characterized concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in ten samples of local staple food (amala) that are accessible in Abraka by means of Atomic Absorption Spectrometry technique and Gamma ray spectrometry, respectively. Assessment was also made of possible carcinogenic risk for children and adults. Based on carcinogenic risk evaluation of the metals, the mean values of total average daily intake in mg/kg-day were 7.51984E-08 for Cd, 6.64596E-08 for Cr, 7.52187E-08 for Cu and 8.3785E-08 for Zn for children, while these values were 3.60862E-08 for Cd, 1.64861E-09 for Cr, 2.15744E-09 for Cu and 1.33517E-07 for Zn for adults. The average hazard quotients were 1.82202E-05 for Cd, 9.2564E-06 for Cr, 1.58334E-05 for Cu and 1.58604E-05 for Zn for children while these values were found to be 3.61706E-05 for Cd, 3.1181E-08 for Cr, 5.39351E-08 for Cu and 4.45056E-07 for Zn for adults. The average total hazard index were 5.46605E-05 for Cd, 2.77692E-05 for Cr, 4.75001E-05 for Cu and 4.75811E-05 for Zn for children and 2.96873E-05 for Cd, 1.50881E-05 for Cr, 2.57992E-05 for Cu and 2.58431E-05 for Zn for adults. The average cancer risk were 8.09253E-07 for Cd and 5.34189E-07 for Cr for children and 4.38597E-07 for Cd and 2.89519E-07 for Cr for adults. For Cu and Zn, no cancer risk was detected, for both children and adults.

The estimated radioactivity concentration for K-40, Ra-226 and Th-232 varied from 97.60 $\pm$ 1.88 to 302.25$\pm$ 0.43 Bqkg⁻¹ with a mean value of 236.67 $\pm$ 1.07 and 15.18$\pm$ 0.21 to 89.50$\pm$ 1.83 Bqkg⁻¹ with a mean value of 42.89 $\pm$ 1.10 as well as 39.40$\pm$ 0.94 to 92.12$\pm$ 0.94 Bqkg⁻¹ with a mean value of 65.45 $\pm$ 1.71, respectively. The radioactivity levels of ⁴⁰K were found to be higher than those of ²²⁶Ra and ²³²Th for all samples. The calculated radium equivalent activities ranged from 103.09Bqkg⁻¹ to 235.22 Bqkg⁻¹ with an average value of 154.70 Bqkg⁻¹ and were found to be lower than the recommended value of 370 Bqkg⁻¹ by UNSCEAR. The absorbed possible dose rates were estimated to vary from the value of 46.70 nGyh⁻¹ to the value of 104.36 nGyh⁻¹ with an average value of 69.22 nGyh⁻¹. The mean absorbed dose rates of the samples of amala in this study were also higher than the recommended average value of 55nGyh⁻¹ by UNSCEAR.

The variation in activity concentration identified in the different samples of amala could be as a result of differences in the chemical composition of the various samples of soils where the raw materials were planted. The implication of the results suggested that the consumption of amala by the people living around the study area poses no significant health risk to their daily living. In addition, this study will be of great benefit to food safety policy makers using radionuclide and toxic heavy metallic parameters.