Natural radioactivity in building materials, indoor radon measurements, and assessment of the associated risk indicators in some localities of the Centre Region, Cameroon.

The objective of the current study is to investigate the natural radioactivity of some building materials, the resulting long-term external and internal effective dose equivalents (EEDE and IEDE) analysis followed by indoor radon measurements, and the assessment of some radiological risk indicators associated with radon exposure. A total of 37 samples of building materials were analyzed with a sodium iodide detector (NaI (Tl)), and the computer code RESRAD-BUILD was used for the analysis of the EEDE and IEDE of the structural elements of the houses (walls and floor). For indoor radon measurements, 140 houses were selected, and in each of them was placed 01 RADTRAK dosimeter. Inhalation dose, total dose, and some radiological risk indicators were calculated. The specific activities of 226Ra, 232Th, and 40K for the overall sampled building materials were found to vary between 10 ± 2-52 ± 7, 10 ± 1-95 ± 10, and 31 ± 1-673 ± 20 Bq kg-1, respectively. The dwelling types with bare brick walls, cement mortar plastered walls, and concrete floors show EEDE and IEDE values well below the recommended limits. The corresponding dwelling type contributions to the measured average indoor radon concentration (42 ± 12 Bq m-3) are 22%, 13%, and 16%, respectively. Inhalation dose resulting from the measured indoor radon concentrations varies from 0.35 to 3.24 mSv y-1 with a mean value of 0.96 ± 0.55 mSv y-1, which represents about 65% of the total dose simulated (1.49 ± 0.88 mSv y-1) by the RESRAD-BUILD code. The overall analysis of indoor radon-related radiological risk indicators shows low levels of risk relative to permissible limits.

SIMULTANEOUS INDOOR RADON, THORON AND THORON PROGENY MEASUREMENTS IN BETARE-OYA GOLD MINING AREAS, EASTERN CAMEROON.

Indoor radon (Rn), thoron (Tn) and thoron progeny (TnP) were simultaneously measured in the gold mining areas of Betare-Oya using RADUET detectors and TnP monitors. Rn and Tn concentrations range between 88-282 and 4-383 Bq m-3, respectively, with the arithmetic means of 133 ± 39 and 93 ± 76 Bq m-3. The 76% of houses for Rn and 25% for Tn exceed the WHO reference level of 100 Bq m-3 and 3% of the houses exceed the ICRP threshold of 300 Bq m-3. The equilibrium equivalent thoron concentration ranges between 1 and 19 Bq m-3 with a mean value of 6 ± 4 Bq m-3. The thoron equilibrium factor ranges between 0.01 and 0.55 with arithmetic mean of 0.11, higher than the world average value of 0.02 given by UNSCEAR. The total inhalation dose due to Rn, Tn and their progeny ranges between 1.8 and 6.2 mSv y-1 with the arithmetic mean of 3.8 ± 1.1 mSv y-1.