Revisiting the influence of the equilibrium factor and the contribution of Rn, Tn and their progeny in dose assessment
摘要
This study is a comparative analysis of the methodology for estimating the total effective inhalation dose of radon (Rn), thoron (Tn) and their decay products. In particular, it considers the influence of the equilibrium factor and the contribution of Rn, Tn and their decay products in dose estimation. Radon and thoron concentrations and their progeny were measured using two types of passive integrated discriminative radon-thoron detectors commercially known as RADUET and DRPS/DTPS. The concentration of Rn ranged from 33 to 75 Bq m−3, with a mean value of 49 Bq m−3. The concentration of Tn ranged from 11 to 742 Bq m−3, with a mean value of 203 Bq m−3. It was determined that 93% of dwellings exhibited EERC values below the global mean of 15 Bq m−3, with the EETC mean value being 22 times greater than the global average value of 0.5 Bq m−3. The research provides substantial contributions for the implementation of the national radon plan in Cameroon. The equilibrium factor for radon (FRn) was found to be 60% higher than the UNSCEAR average value of 0.4. The study underscores the limitation in the application of the UNSCEAR equilibrium factor in assessment of total effective inhalation dose, as it could potentially lead to an underestimation of the risk of public exposure to thoron and radon in many regions worldwide. The annual effective inhalation dose was estimated directly, with radon, thoron, EERC, and EETC contributing to the total effective inhalation dose at 2% (0.04 mSv), 5% (0.11 mSv), 38% (0.93 mSv), and 55% (1.34 mSv), respectively. These results highlight the importance of direct measurements of the progeny concentrations either for radon and thoron for accurately estimation of the effective inhalation dose.