NATURAL RADIOACTIVITY IN SOME BUILDING-MATERIALS IN KENYA AND THE CONTRIBUTIONS TO THE INDOOR EXTERNAL DOSES

Against a background of growing concern over the health risks associat ed with exposure to natural sources of radiation, a study has been car ried out in Kenya in which the activity concentrations of the major ra dionuclides in some natural building materials are determined. Differe nt types of rock and soil samples were analysed with a gamma ray spect rometer. Typical activities, so far encountered, are in the ranges: 50 to 1500 Bq.kg(-1) for K-40; 5 to 200 Bq.kg(-1) for Ra-226; and 5 to 3 00 Bq.kg(-1) for Th-232. Th, external gamma ray absorbed doses in indo or air, and the corresponding effective dose equivalents in a typical dwelling are presented. The need for further studies is also discussed .