Natural background dose measurements in south Cameroon.

The natural background doses due to (40)K, (226)Ra and (232)Th have been measured in soil samples collected from various sampling sites in the locality of Lolodorf, Cameroon. For data acquisition and analysis, a high-purity germanium detector and a PC-based MCA were used. The mean activity concentrations of (40)K, (226)Ra and (232)Th were measured to be 2001 +/- 521, 329 +/- 491 and 414 +/- 309 Bq kg(-1), respectively, in rock samples, while in soil samples the activity concentrations were found to be 1482 +/- 280 Bq kg(-1) for (40)K, 134 +/- 64 Bq kg(-1) for (226)Ra and 177 +/- 102 Bq kg(-1) for (232)Th. The average outdoor absorbed dose rates in air, 1 m above the ground surface due to soil samples, were estimated to be 218 +/- 61 and 250 +/- 97 nGy h(-1) in the locations of Ngombas and Bikoue, respectively. The corresponding annual effective dose rates in air were determined to be 0.267 mSv y(-1) in Ngombas and 0.307 mSv y(-1) in Bikoue. The level of radioactivity in the studied area is relatively high.