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Saïdou,Shinji Tokonami,Masahiro Hosoda,Augustin Simo,Joseph Victor Hell,Olga German,Esmel Gislere Oscar Meless 대한방사선방어학회 2022 방사선방어학회지 Vol.47 No.4
Background : The current study reports measurements of activity concentrations of radon (222Rn) and thoron (220Rn) in dwellings , followed by inhalation dose assessment of the public , and then by the development of regulation and the national radon action plan (NRAP) in Cameroon . Materials and Methods : Radon , thoron , and thoron progeny measurements were carried out from 2014 to 2017 using radon-thoron discriminative detectors (commercially RADUET) in 450 dwellings and thoron progeny monitors in 350 dwellings . From 2019 to 2020 , radon track detectors (commercially RADTRAK) were deployed in 1 , 400 dwellings . It was found that activ- ity concentrations of radon range in 1 , 850 houses from 10 to 2 , 620 Bq/m3 with a geometric mean of 76 Bq/m3 . Results and Discussion : Activity concentrations of thoron range from 20 to 700 Bq/m3 with a geometric mean of 107 Bq/m3 . Thoron equilibrium factor ranges from 0 . 01 to 0 . 6 , with an arithmetic mean of 0 . 09 that is higher than the default value of 0 . 02 given by UNSCEAR . On average , 49% , 9% , and 2% of all surveyed houses have radon concentrations above 100 , 200 , and 300 Bq/m3 , respectively. The average contribution of thoron to the inhalation dose due to radon and thoron exposure is about 40% . Thus , thoron cannot be neglected in dose assessment to avoid biased results in radio-epidemiological studies . Only radon was considered in the drafted regulation and in the NRAP adopted in October 2020 . Reference levels of 300 Bq/m3 and 1 , 000 Bq/m3 were recommended for dwellings and workplaces . Conclusion : Priority actions for the coming years include the following : radon risk mapping , promotion of a protection policy against radon in buildings , integration of the radon prevention and mitigation into the training of construction specialists , mitigation of dwellings and workplaces with high radon levels , increased public awareness of the health risks associated with radon , and development of programs on the scientific and technical aspects .
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Nkoulou II Joseph Emmanuel Ndjana,Engola Louis Ngoa,Dallou Guy Blanchard,Saïdou,Bongue Daniel,Hosoda Masahiro,Njock Moïse Godefroy Kwato,Tokonami Shinji 대한방사선방어학회 2023 방사선방어학회지 Vol.48 No.2
Background : This study aims to reevaluate natural radiation exposure , following up on our previous study conducted in 2019 , and to assess the associated risk of lung cancer to the public residing in the gold mining areas of Betare-Oya , east Cameroon , and its vicinity. Materials and Methods : Gamma-ray spectra collected using a 7 . 62 cm × 7 . 62 cm in NaI(Tl) scintillation spectrometer during a car-borne survey, in situ measurements and laboratory mea- surements performed in previous studies were used to determine the outdoor absorbed dose rate in air to evaluate the annual external dose inhaled by the public . For determining internal exposure , radon gas concentrations were measured and used to estimate the inhalation dose while considering the inhalation of radon and its decay products . Results and Discussion : The mean value of the laboratory-measured outdoor gamma dose rate was 47 nGy/hr, which agrees with our previous results (44 nGy/hr) recorded through direct mea- surements (in situ and car-borne survey) . The resulting annual external dose (0 . 29 ± 0 . 09 mSv/yr) obtained is similar to that of the previous study (0 . 33 ± 0 . 03 mSv/yr) . The total inhalation dose resulting from radon isotopes and their decay products ranged between 1 . 96 and 9 . 63 mSv/yr with an arithmetic mean of 3 . 95 ± 1 . 65 mSv/yr. The resulting excess lung cancer risk was esti- mated ; it ranged from 62 to 216 excess deaths per million persons per year (MPY) , 81 to 243 ex- cess deaths per MPY, or 135 excess deaths per MPY, based on whether risk factors reported by the U. S . Environmental Protection Agency, United Nations Scientific Committee on the effects of Atomic Radiation , or International Commission on Radiological Protection were used , re- spectively. These values are more than double the world average values reported by the same agencies . Conclusion : There is an elevated level of risk of lung cancer from indoor radon in locations close to the Betare-Oya gold mining region in east Cameroon . Therefore , educating the public on the harmful effects of radon exposure and considering some remedial actions for protection against radon and its progenies is necessary.
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