Search

To assess public exposure to radon, thoron, and their progeny, measurements were conducted in 50 dwellings within the bauxite-rich area of Fongo-Tongo in western Cameroon. Passive integrating radon-thoron discriminative detectors (specifically RADUET) were employed for radon and thoron measurements. Additionally, concentrations of short-lived radon and thoron progeny were estimated using Direct Radon Progeny Sensors (DRPSs) and Direct Thoron Progeny Sensors (DTPSs) based on LR-115 detectors. The findings revealed indoor radon concentrations ranging from 31 to 123 Bq m -3 with a geometric mean (GM) of 62 Bq m -3 , and indoor thoron concentrations ranging from 36 to 688 Bq m -3 with a GM of 242 Bq m -3 . The Equilibrium Equivalent Radon Concentration (EERC) ranged from 3 to 86 Bq m -3 with a GM of 25 Bq m -3 , while the Equilibrium Equivalent Thoron Concentration (EETC) ranged from 1.2 to 12.5 Bq m -3 with a GM of 7.6 Bq m -3 . Notably, all dwellings recorded radon concentrations below 100 Bq m -3 . Arithmetic means of radon and thoron equilibrium factors were calculated as 0.47 and 0.04, respectively. To assess annual effective doses from radon and thoron inhalation, equilibrium factors were used along with direct measurements of EERC and EETC. The differences observed in annual effective doses were 4.5% for radon and 42.5% for thoron. Furthermore, the contribution of thoron and its decay products to the annual effective dose from radon, thoron, and their progeny ranged from 12 to 94%, with an average contribution of 58%. Thus, this study found that the effective dose due to thoron inhalation in the study area exceeded that due to radon inhalation. It is concluded that, when evaluating radiation doses and health risks, it is crucial to consider both thoron and its progeny alongside radon and its progeny. This underscores the importance of considering direct measurements for accurately estimating radiation doses., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Breeding in oil palm aims mainly at improving palm oil yield. Short palms are also desired because they are easy to harvest and increase the economic life of the plantation. A total of 23 progenies from Deli × La Mé and Deli × PO 1097 P (Yangambi) crosses were field tested at La Dibamba Oil Palm Research Centre in Cameroon from 1988 to 1998. Oil yield components were measured on per palm basis from 3 to 9 years after planting, and the vertical growth at 6 years after planting. The mean oil yield of the trial was average, representing 102% of the control (3.515 t/ha), and the mean height 6 years after planting was 101% that of the control (88.0 cm). The analysis of variance detected differences among progenies for various yield parameters and vertical growth. The comparison of means showed clear separation of groups of progenies for oil yield at the juvenile period (3–5 years after planting). At maturity (6–9 years after planting), the groups of progenies were overlapping indicating that progenies were comparable each other. However, four precocious progenies and high oil yielding at maturity (119–122% of the control) in absolute values can be released to planters. Though their vertical growth represented 116–127% of that of the control, short pisifera palm are expected from parental selfs or crosses given the intrinsic heterozygosity of oil palm. [ABSTRACT FROM AUTHOR]

Radon (Rn), thoron (Tn), and thoron progeny (TnP) were measured in seven inhabited areas of the uranium and thorium bearing region of Lolodorf, located in southwestern Cameroon. Then the equilibrium factor (F Tn ) between thoron and its progeny was determined in order to show the importance of direct progeny measurements for correct estimation of effective dose due to radon, thoron and their progenies. A total of 220 RADUET detectors were used to measure indoor radon and thoron and 130 TnP monitors for thoron progeny indoors. The arithmetic and geometric mean concentrations of Rn, Tn, and TnP were 103 and 89 Bq m -3 , 173, and 118 Bq m -3 , 10.7, and 7.4 Bq m -3 , respectively. Total effective dose determined from radon, thoron, and their progenies was estimated at 4.2 ± 0.5 mSv y -1 . Thoron equilibrium factor varied according to seasons, the type of dwelling, building materials and localities. Thoron (Tn and TnP) contribution to effective dose ranged between 3 and 80% with the average value of 53%. Total effective dose estimated from the world average equilibrium factor of 0.02 given by UNSCEAR was 2.7 ± 0.2 mSv y -1 . The effective dose due to thoron varied greatly according to the different values taken by F Tn and was different from that determined directly using TnP concentrations. Thus, effective dose due to thoron determined from the equilibrium factor is unreliable. Therefore, the risk of public exposure due to thoron (Tn and TnP) may therefore be higher than that of radon (Rn and RnP) in many parts of the world if F Tn is no longer used in estimating total effective dose. This is not in contradiction with the UNSCEAR conclusions. It is therefore important to directly measure the radon and thoron progeny for a correct estimate of effective dose., (Copyright © 2020 Bineng, Saïdou, Tokonami, Hosoda, Tchuente Siaka, Issa, Suzuki, Kudo and Bouba.)