Natural radioactivity hazards of building bricks fabricated from clay soil of Bomet District, Bomet County, Kenya

Abstract

Primordial radionuclides in building materials are one of the major sources of radiation hazard in dwellings. Clay bricks are mainly used for the construction of dwellings in Bomet district, Bomet County, Kenya. Therefore, knowledge of the presence of natural radioactivity in these materials is of great importance in order to assess the radiological hazards associated with them. In this context, specific activities of 226Ra, 232Th and 40K were measured in brick samples collected from different localities of the district using NaI(Tl) gamma-ray spectrometer. The average measured activities for 226Ra, 232Th and 40K in the brick samples were 47 ± 5, 62 ± 11 and 714 ± 54 Bqkg−1 respectively. Radium equivalent activity was also calculated and was found to be 190 ± 18 Bqkg−1 for brick samples. The average absorbed dose rate was found to be 168± 15 nGyh-1. The annual average effective doses from these samples were 0.82 ± 0.07 mSv. External, internal and other representative hazard indices measured for all the samples studied were less than the internationally accepted upper limit for building materials of a unity. The results of this study showed that the building bricks have low background radiation levels and as such no significant hazard is expected of them. To estimate the potential radiological health risk in clay bricks, the dose rate associated to radon gas should also be investigated well. A further study on the epidemiology on the cause of cancer in the studied area is also recommended