Assessment of natural radioactivity and associated radiation hazards in some Cameroonian building materials

Abstract The concentration of 238 U, 232 Th and 40 K in 13 building materials obtained from factories and collected in field in Cameroon were investigated by γ -ray spectrometry. The activity ranged from 1.76 to 49.84 Bq kg - 1 , 0.32 to 147 Bq kg - 1 and 18 to 1226 Bq kg - 1 for 238 U, 232 Th and 40 K, respectively. The highest 238 U activity was found in compressed red soil brick type I ( 49.6 ± 0.3 Bq kg - 1 ) produced by a local manufacturer while the highest 232 Th ( 139 ± 13 Bq kg - 1 ) and 40 K ( 1162 ± 108 Bq kg - 1 ) activities were found in gravel collected from an exploitation site in Logbadjeck. The activities are compared with available data from other investigations and with the world average value for soils. The radium equivalent activity Ra eq , the external hazard index H ex , the indoor absorbed dose rate D ˙ in air and the annual effective dose equivalent E ˙ were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. All building materials have shown Ra eq (range from 10 to 313 Bq kg - 1 ) lower than the limit of 370 Bq kg - 1 set in the Organization for Economic Cooperation and Development [OECD, 1979. Exposure to radiation from the natural radioactivity in building materials. OECD, Paris] report which is equivalent to a γ -dose of 1.5 mSv yr - 1 . Except for the gravel from Logbadjeck, all the materials examined are acceptable for use as building materials as defined by the OECD criterion.