Characteristic of thoron ( 220 Rn) in environment

Hosoda, Masahiro; Kudo, Hiromi; Iwaoka, Kazuki; Yamada, Ryohei; Suzuki, Takahito; Tamakuma, Yuki; Tokonami, Shinji

doi:10.1016/j.apradiso.2016.11.014

Cited by 35 publications

(22 citation statements)

References 25 publications

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“…Recent studies have shown that, the contribution of thoron to the internal exposure of the public is not always negligible compared to radon. In some places, this contribution may be greater than that of radon (4,5,(7)(8)(9)(10)(11). The objective of the current study is to show the importance of direct progeny measurements for correct estimation of effective dose.…”

Section: Introductionmentioning

confidence: 95%

“…Among the errors that are desirable to avoid nowadays in radioprotection, there is that of wanting to evaluate the risk of internal exposure of the public on the basis of the indirect determination of thoron effective dose from its equilibrium factor. Literature shows that there is no real correlation between the concentration of thoron gas and that of solid progeny in a dwelling (4). Thoron concentration in a dwelling depends on the distance from the source and the measurement result depends on the detector position in relation to the source.…”

Section: Introductionmentioning

confidence: 99%

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The Importance of Direct Progeny Measurements for Correct Estimation of Effective Dose Due to Radon and Thoron

Bineng

Saïdou

Tokonami

et al. 2020

Front. Public Health

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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.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

The Importance of Direct Progeny Measurements for Correct Estimation of Effective Dose Due to Radon and Thoron

Bineng

Saïdou

Tokonami

et al. 2020

Front. Public Health

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“…The exhalation and diffusion of thoron is approximately described as a one-dimensional phenomenon. When the exhalation rate of thoron from the wall is considered, for instance, the indoor thoron concentration (C Tn (x) [Bq m −3 ]) at distance x from the wall can be expressed by the Equation (3) [10,11]:…”

Section: Physical Property and Behaviormentioning

confidence: 99%

Characteristics of Thoron (220Rn) and Its Progeny in the Indoor Environment

Tokonami

2020

IJERPH

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The present paper outlines characteristics of thoron and its progeny in the indoor environment. Since the half-life of thoron (220Rn) is very short (55.6 s), its behavior is quite different from the isotope radon (222Rn, half-life 3.8 days) in the environment. Analyses of radon and lung cancer risk have revealed a clearly positive relationship in epidemiological studies among miners and residents. However, there is no epidemiological evidence for thoron exposure causing lung cancer risk. In contrast to this, a dosimetric approach has been approved in the International Commission on Radiological Protection (ICRP) Publication 137, from which new dose conversion factors for radon and thoron progenies can be obtained. They are given as 16.8 and 107 nSv (Bq m−3 h)−1, respectively. It implies that even a small quantity of thoron progeny will induce higher radiation exposure compared to radon. Thus, an interest in thoron exposure is increasing among the relevant scientific communities. As measurement technologies for thoron and its progeny have been developed, they are now readily available. This paper reviews measurement technologies, activity levels, dosimetry and resulting doses. Although thoron has been underestimated in the past, recent findings have revealed that reassessment of risks due to radon exposure may need to take the presence of thoron and its progeny into account.

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“…The indoor thoron concentrations were also obtained in this radon survey. However, it is difficult to obtain a representative indoor/outdoor thoron concentration because the monitors used for the survey were installed at different distances from the wall surface [15,42,43]. Therefore, it should be noted that the main purpose of a radon-thoron discriminative monitor like the RADUET is to reduce the influence of thoron on the radon measurements.…”

Section: Lessons Learned On Radon and Thoron Measurement By The Raduetmentioning

confidence: 99%

Importance of Discriminative Measurement for Radon Isotopes and Its Utilization in the Environment and Lessons Learned from Using the RADUET Monitor

Kranrod

Tamakuma

Hosoda

et al. 2020

IJERPH

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Radon (222Rn) and thoron (220Rn), sources of natural background radiation, have been the subjects of long-standing studies, including research into radon and thoron as major causes of lung cancer at domestic and international levels. In this regard, radon and thoron measurement studies have been widely conducted all over the world. Generally, the techniques used relate to passive nuclear track detectors. Some surveys have shown that passive monitors for radon are sensitive to thoron, and hence some measured results have probably overestimated radon concentrations. This study investigated radon and thoron measurements in domestic and international surveys using the passive radon–thoron discriminative monitor, commercially named RADUET. This paper attempts to provide an understanding of discriminative measurements of radon isotopes and to present an evidence-based roadmap.

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Characteristic of thoron ( 220 Rn) in environment

Cited by 35 publications

References 25 publications

The Importance of Direct Progeny Measurements for Correct Estimation of Effective Dose Due to Radon and Thoron

The Importance of Direct Progeny Measurements for Correct Estimation of Effective Dose Due to Radon and Thoron

Characteristics of Thoron (220Rn) and Its Progeny in the Indoor Environment

Importance of Discriminative Measurement for Radon Isotopes and Its Utilization in the Environment and Lessons Learned from Using the RADUET Monitor

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