Assessment of Levels of Natural Radioactivity in Sand Samples Collected from Ekalakala in Machakos County, Kenya.

Construction sand is naturally polluted with radionuclides of terrestrial origin. In this study, specific activities of U, Th, and K in 30 sand samples collected along the Ekalakala River, Machakos County, Kenya, were measured using a high-purity germanium -ray spectrometer. The specific activities ranged between 9.7 Bqkg and 24.0 Bqkg, 11.5 Bqkg and 26.2 Bqkg, and 820 Bqkg and 1850 Bqkg for U, Th, and K, respectively. While the mean specific activities for U and Th were less than half of the world average values of 33 Bqkg and 45 Bqkg, respectively, the average specific activity of K was significant since it was three times the global mean value of 420 Bqkg. A calculated absorbed radiation dose rate for the sand varied between 46.8 nGyh and 94.2 nGyh with a mean of 68.5 ± 13.3 nGyh. This is not significantly different from the world average dose rate of 60 nGyh for geological samples. The AEDR and H had maximum values of 0.29 mSvy and 0.52, respectively, both within the recommended limits of radiation exposure for members of the general public. Based on these results, the sand from Ekalakala River does not pose significant health implication to the sand harvesters as well as the inhabitants of the houses constructed using this sand.