From Radon and Thoron Measurements, Inhalation Dose Assessment to National Regulation and Radon Action Plan in Cameroon

다국어 초록 (Multilingual Abstract)

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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