Health Risk Assessment of Natural Radioactivity in Wasteland Soils in Okakarara, Namibia..

Abstract

Human activities such as waste disposal tend to impact negatively on the environment. Some waste products are associated with elevated levels of natural radioactivity. It was therefore, the aim of the study to investigate the health risk associated with natural radioactivity from Okakarara municipal waste dumpsite. In this study, gamma spectrometric analysis was used to determine the activity concentrations of 226Ra, 232Th and 40K in 18 soil samples. From these activity concentrations, some radiological parameters were calculated. The average activity concentrations of 226Ra, 232Th and 40K in (Bq.kg-1) were 15.45±0.47, 18.00±0.55, and 215.73±4.29, respectively. The average Raeq value was 57.80±0.98 Bq.kg-1. In all the samples, Raeq values were found to be lower than the worldwide value of 370 Bq.kg-1. The absorbed dose rate was found to be 27.00±0.44 nGy.h-1, whereas an average value of 0.03 mSv.y-1 for AEDE is noted, which is less than 0.48 mSv, the worldwide average. The Annual Gonadal Dose Equivalent (AGDE) was 190.89 μSv.y-1, a value less than the world average of 298 μSv.y-1. The average values of the Representative Level Index (RLI) and the External Hazard Index (Hex) was found to be 0.43 and 0.16., respectively. These indices were less than unity. The average value of the excess lifetime cancer risk (ECLR) was 1.16 x 10-4. This value was lower than the internationally acceptable limit of 2.9 x 10-4. From these results it can be concluded that natural radioactivity from the wasteland area of Okakarara was not an issue of health concern.