A nation-wide survey on indoor radon from 2007 to 2010 in Japan

Comparing the risks of environmental carcinogenic chemicals in Japan using the loss of happy life expectancy indicator

In this study, we aimed to use the loss of happy life expectancy (LHpLE), an indicator that enables risk assessment considering wellbeing, to compare the risks of environmental carcinogenic chemicals in Japan. First, we surveyed Japanese people to determine their emotional happiness by age and sex and evaluated whether cancer incidence reduced emotional happiness. Questionnaires were administered to a general population panel and a panel of patients with cancer in 2022, recruiting a predetermined number of responses of 5000 and 850, respectively. Second, using the survey data, LHpLE was calculated for radon, arsenic, and fine particulate matter (aerodynamic diameter <2.5 μm; PM2.5) and compared to psychological distress, considering increased mortality and decreased emotional happiness due to these risks. We discovered no significant decrease in emotional happiness due to cancer incidence and no significant associations between emotional happiness and cancer type, history, or stage. LHpLE was calculated to be 6.4 × 10-3 years for radon, 2.6 × 10-3 years for arsenic, 1.1 × 10-2 years (2012 exposure) and 8.6 × 10-4 years (2020 exposure) for PM2.5, and 9.7 × 10-1 years for psychological distress. The fraction of losses caused by these carcinogenic chemicals to HpLE exceeded 10-5, suggesting that risk reduction for these chemicals is important in environmental policies. The LHpLE indicator allows for comparing different types of risks, such as environmental chemicals and psychological distress. This is the first study to compare chemical risks using the LHpLE indicator.

Assessment of indoor radon exposure in South Korea

The objective of this study is to update the national and regional indoor radon concentrations in South Korea and assess indoor radon exposure. Based on the previously published survey results and the collected measurement data of surveys conducted since 2011, a total of 9271 indoor radon measurement data covering 17 administrative divisions are finally used for analysis. The annual effective dose from the indoor radon exposure is calculated using dose coefficients recommended by the International Commission on Radiological Protection. The population-weighted average indoor radon concentration was estimated to be a geometric mean of 46 Bq m^-3(GSD = 1.2) with 3.9% of all samples showing values exceeding 300 Bq m^-3. The regional average indoor radon concentration ranged from 34 to 73 Bq m^-3. The radon concentrations in detached houses were relatively higher than those in public buildings and multi-family houses. The annual effective doses to the Korean population due to indoor radon exposure were estimated to be 2.18 mSv. The updated values in this study might better represent the national indoor radon exposure level in South Korea because they contain more samples and cover a wider range of geographical areas than previous studies.

Lung cancer as adverse health effect by indoor radon exposure in China from 2000 to 2020: A systematic review and meta-analysis

Indoor radon exposure is thought to be associated with adverse health effect as lung cancer. Lung cancer incidences in China have been the highest worldwide during the past two decades. It is important to quantitively address indoor radon exposure and its health effect, especially in countries like China. In this paper, we have conducted a meta-analysis based on indoor radon and its health effect studies from a systematic review between 2000 and 2020. A total of 8 studies were included for lung cancer. We found that the relative risk (RR) was 1.01 (95% CI: 1.01-1.02) per 10 Bq/m³ increase of indoor radon for lung cancer in China. The subgroup analysis found no significant difference between the conclusions from the studies from China and other regions. The health effect of indoor radon exposure is relatively consistent for the low-exposure and high-exposure groups in the subgroup analysis. With a better understanding of exposure level of indoor radon, the outcomes and conclusions of this study will provide supports for next phase of researches on estimation of environmental burden of disease by indoor radon exposures in countries like China.

Radiation exposure due to 222Rn, 220Rn and their progenies in three metropolises in China and Japan with different air quality levels

Radiation exposure due to radon contributes most of the ionizing radiation exposure to people among natural radiation sources. This research measured the ²²²Rn, ²²⁰Rn by the RADUET and their progeny concentrations by the improved deposition based ²²²Rn and ²²⁰Rn progeny monitor, and the contribution of outdoor PM_2.5 concentrations to indoors by a modified steady-state mass balance model in Beijing, Changchun, China and Aomori, Japan. Based on these results, we preliminarily explored the relevance between the city level outdoor PM_2.5 exposure and indoor ²²²Rn, ²²⁰Rn inhalation exposure in these three metropolises with different air quality levels. The average equilibrium equivalent radon concentration (EERC) and equilibirum equivalent thoron concentration (EETC) indoor were 17.2 and 1.1 Bq m^-3 in Beijing, 19.4 and 1.3 Bq m^-3 in Changchun, and 10.8 and 0.9 Bq m^-3 in Aomori, respectively. The indoor EERC and EETC in Beijing showed 1.4 and 2.2 times as high as that measured in 2006. The indoor radiation dose due to inhalation presented in a descending order as Changchun, Beijing and Aomori, which were in accordance with their outdoor ²²²Rn concentrations. The indoor radiation doses due to ²²⁰Rn contributed 30% of the total dose in the three cities, indicating that ²²⁰Rn cannot be neglected when evaluating indoor radiation dose. It should be noted that, the indoor PM_2.5 concentrations of outdoor origin presented strong correlation (r = 0.772) with indoor EETC and moderate correlation (r = 0.663) with indoor EERC, indicating that the PM_2.5 of outdoor origin can break the concentration balance of the indoor PM_2.5, then affect the indoor ²²²Rn and ²²⁰Rn behaviors, and further affect the inhalation exposure of radon.

Indoor exposure levels of radon in dwellings, schools, and offices in China from 2000 to 2020: A systematic review

After decades of development, the indoor environment in China has changed. A systematic review was conducted from peer-reviewed scientific papers with field test data of indoor radon in China from 2000 to 2020 for three types of buildings. The mean concentrations of indoor radon for dwellings, school buildings, and office buildings are 54.6, 56.1, and 54.9 Bq/m³ . The indoor radon concentration was related to seasons, climate regions, ventilation, decoration, and other factors such as soil and outdoor air. Colder seasons, especially in severe colder areas of China, newer decorated buildings, closed windows, and doors were all associated with higher indoor radon concentrations. Variables like climate region and ventilation showed statistical significance in the correlation analysis. Regarding the increasing trend of indoor radon concentration in China during the last two decades, further study of indoor radon is necessary especially for school buildings and office buildings, and will help access its environmental burden of disease in China more accurately.

Study of CMOS Sensing System for Radon and Alpha Radiation

This study focuses on a CMOS sensing system for Radon and alpha radiation, which is based on a semiconductor device that is integrated monolithically on a single chip with the Readout Circuitry, thus allowing fabrication of a low-power and low-cost sensing system. The new sensor is based on a new mosaic design of an array of Floating Gate non-volatile memory-like transistors, which are implemented in a standard CMOS technology, with a single polysilicon layer. The transistors are electrically combined in parallel and are operated at subthreshold, thus achieving very high sensitivity and reduced noise. The sensing system’s architecture and design is presented, along with key operation concepts, characterization, and analysis results. Alpha and radon exposure results are compared to commercial radon detectors. The new sensor, dubbed TODOS-Radon sensor, measures continuously, is battery operated and insensitive to humidity.

Estimating population lung cancer risk from radon using a resource efficient stratified population weighted sample survey protocol - Lessons and results from Ireland

A 2018 estimate indicates that there were 226,057 radon-attributable lung cancer deaths in 66 countries that had representative radon surveys. This is a shocking figure, and as it comes from only 66 countries it underestimates the worldwide death toll. Any research that enables countries to conduct representative radon surveys and to understand better the risk to citizens from radon is surely welcome. We hope this paper provides a useful methodology for estimating population risk. The estimation of population weighted average indoor radon levels requires statistically valid sampling methodologies that use a representative sample of occupied homes throughout the country. A literature review indicates that in many population weighted surveys, the sampling methodology may not have been designed to do this. This paper describes a simple, resource efficient methodology which produces statistically valid and reliable estimates based on a small scale sample that is representative of the population distribution. The resource efficient design of this study enables it to be repeated at frequent intervals providing for a longitudinal analysis of the population risk from indoor radon. This survey was conducted in Ireland using 653 measurements and a representative sampling strategy to provide a baseline population weighted radon exposure for future comparisons. This study estimates the average population weighted indoor radon concentration in Ireland to be 97.83 Bq m^-3 (95% Confidence Interval 90.69 Bq m^-3 to 105.53 Bq m^-3), and that there are an estimated 350 lung cancer cases and 255 deaths per year due to radon exposure. The mortality rate of 5.3 per 100,000 due to indoor radon, demonstrates that radon remains one of the highest preventable causes of death in Ireland.

Investigation of the indoor 222Rn and 220Rn levels in the residential environment and estimation of the annual effective radiation dose for ordinary residents

To evaluate the health risk of radon and its progeny, a large amount of accurate monitoring data is needed according to the theory and practice of health risk assessment. However, the indoor radon levels in different regions in China and worldwide reveal temporal and spatial variations. In addition, the residents living in different areas follow distinct living modes. Therefore, it is recommended and accepted by many researchers to detect the radon level in local areas and subsequently conduct health risk assessments based on local detection data. In this study, 21 bedrooms of households in Weifang city were selected, and the indoor 222Rn and 220Rn levels were detected with RAD7 radon detector in winter, while the annual effective radiation dose was calculated for ordinary residents in Weifang city. Our investigation showed that the 24- and 12-hour average levels of 222Rn were 35.7±15.2 Bq/m3 and 36.2±15.8 Bq/m3, respectively. The 24- and 12-hour average levels of 220Rn were 30.4±12.3 Bq/m3 and 22.4±11.6 Bq/m3, respectively. There were significant differences in the average levels of 222Rn and 220Rn between floors. The estimated annual effective radiation dose received by ordinary residents in Weifang city was 1.7193 mSv, of which 0.9479 mSv originated from 222Rn and its progeny and 0.7714 mSv originated from 220Rn and its progeny, accounting for 55.1% and 44.9%, respectively, of the total dose. Our findings suggest that 220Rn should not be ignored by local residents in Weifang city, and more attention should be paid to 220Rn in future research.

Japanese population dose from natural radiation

The radiation doses from natural radiation sources in Japan are reviewed using the latest knowledge. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the Nuclear Safety Research Association report the annual effective doses from cosmic rays, terrestrial radiation, inhalation, and ingestion as natural sources. In this paper, the total annual effective dose from cosmic-ray exposure is evaluated as 0.29 mSv. The arithmetic mean of the annual effective dose from external exposure to terrestrial radiation is 0.33 mSv for the Japanese population using the data of nationwide surveys by the National Institute of Radiological Sciences. Previously in Japan, although three different groups have conducted nationwide indoor radon surveys using passive-type radon monitors, to date only the Japan Chemical Analysis Center (JCAC) has performed a nationwide radon survey using a unified method for radon measurements conducted indoor, outdoor, and in the workplace. Consequently, the JCAC results are used for the annual effective dose from radon and that for radon inhalation is estimated as 0.50 mSv using a current dose conversion factor. In this paper, UNSCEAR values are used for the mean indoor and outdoor thoron-progeny concentrations, and the annual effective dose from thoron is reported as 0.09 mSv. Thus, the annual effective dose from radon and thoron inhalation is 0.59 mSv. From a JCAC large-scale survey of foodstuffs, the committed effective dose from the main radionuclides in dietary intake is 0.99 mSv. Finally, the Japanese population dose from natural radiation is given as 2.2 mSv, which is similar to the reported global average of 2.4 mSv.

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

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.

Variable Strength in Thoron Interference for a Diffusion-Type Radon Monitor Depending on Ventilation of the Outer Air

Thoron interference in radon measurements using passive diffusion radon detectors/monitors is a crucial problem when it comes to assessing the internal exposure to radon precisely. The present study reported, as one of the potential factors, the effects of air flow conditions on changes in thoron interference. Rates of thoron infiltration (as thoron interference) into the diffusion chamber of the monitor were evaluated. The temporal variation was obtained based on measurements of the underfloor space of a Japanese wooden dwelling using a diffusion-type radon monitor, a reference radon monitor which was not affected by thoron interference, and a thoron monitor. The thoron infiltration rate for the diffusion-type monitor varied from 0% to 20%. In particular, it appeared to increase when ventilation of the underfloor space air was forced. The variable thoron infiltration rate, with respect to ventilation strength, implied that not only a diffusive process, but also an advective process, played a major role in air exchange between the diffusion chamber of the monitor and the outer air. When an exposure room is characterized by the frequent variation in air ventilation, a variable thoron response is considered to occur in radon–thoron discriminative detectors, in which only diffusive entry is employed as a mechanism for the discrimination of radon and thoron.

First indoor radon mapping and assessment excess lifetime cancer risk in Iran

Radon (222Rn) is believed to be the main contributor to lung cancer second to smoking. The first national indoor radon map derived from some scattered regional radon surveys in Iran. The arithmetic mean of indoor radon concentration was calculated to 117.4 ± 97.7 Bq/m3. The mean excess life time cancer risk (ELCR) values were found to be in the range of 0.1%-4.26%, with an overall average value of 1.01%. The mean radon-induced lung cancer risk was 46.8 per million persons. Absence of sufficient indoor radon data showed that national wide monitoring programs should be activated in uncovered areas. Meanwhile, in order to provide further baseline values for radon mapping, we attempted to survey the radon levels inside 50 dwellings of Shabestar County in northwest of Iran. The investigation was also focused on the effects of some buildings related variables. The radon levels recorded varied from 3.92 to 520.12 Bq/m3, with a mean value of 56.19 ± 45.96 Bq/m3. In 9% of dwellings radon concentration exceeded 100 Bq/m3, the limit recommended by the World Health Organization. The average annual effective dose received by the residents of studied area was calculated to be 1.4 mSv. The ELCR was estimated to be 0.54%.

Numerical modeling of the sources and behaviors of 222Rn, 220Rn and their progenies in the indoor environment-A review

²²²Rn, ²²⁰Rn and their short-lived progenies are well known radioactive indoor pollutants, identified as the leading environmental cause of lung cancer next to smoking. Apart from the conventional measurement methods, numerical modeling methods are developed to simulate their physical and decay processes in ²²²Rn and ²²⁰Rn's life cycle, estimate their levels, concentration distributions, as well as effects of control strategies in the indoor environment. In this article, we summarized the numerical models used to illustrate the physical processes of each source of ²²²Rn and ²²⁰Rn entry into the indoor environment, and the application of Jacobi room models and CFD (Computational Fluid Dynamic) models used to present the behaviors of indoor ²²²Rn, ²²⁰Rn and their progenies. Furthermore, we consider that the development of numerical modeling of ²²²Rn and ²²⁰Rn would have a bright prospect in the directions of stochastic methods based on a steady-state model, the fine simulation of the time-dependent model as well as the multi-dimension model.

Machine learning methods as a tool to analyse incomplete or irregularly sampled radon time series data

Machine learning is a class of statistical techniques which has proven to be a powerful tool for modelling the behaviour of complex systems, in which response quantities depend on assumed controls or predictors in a complicated way. In this paper, as our first purpose, we propose the application of machine learning to reconstruct incomplete or irregularly sampled data of time series indoor radon (²²²Rn). The physical assumption underlying the modelling is that Rn concentration in the air is controlled by environmental variables such as air temperature and pressure. The algorithms "learn" from complete sections of multivariate series, derive a dependence model and apply it to sections where the controls are available, but not the response (Rn), and in this way complete the Rn series. Three machine learning techniques are applied in this study, namely random forest, its extension called the gradient boosting machine and deep learning. For a comparison, we apply the classical multiple regression in a generalized linear model version. Performance of the models is evaluated through different metrics. The performance of the gradient boosting machine is found to be superior to that of the other techniques. By applying learning machines, we show, as our second purpose, that missing data or periods of Rn series data can be reconstructed and resampled on a regular grid reasonably, if data of appropriate physical controls are available. The techniques also identify to which degree the assumed controls contribute to imputing missing Rn values. Our third purpose, though no less important from the viewpoint of physics, is identifying to which degree physical, in this case environmental variables, are relevant as Rn predictors, or in other words, which predictors explain most of the temporal variability of Rn. We show that variables which contribute most to the Rn series reconstruction, are temperature, relative humidity and day of the year. The first two are physical predictors, while "day of the year" is a statistical proxy or surrogate for missing or unknown predictors.

Investigation of Natural Radioactivity in a Monazite Processing Plant in Japan

Monazite is a naturally occurring radioactive material that is processed for use in a variety of domestic applications. At present, there is little information available on potential radiation doses experienced by people working with monazite. The ambient dose rate and activity concentration of natural radionuclides in raw materials, products, and dust in work sites as well as the Rn and Rn concentrations in work sites were measured in a monazite processing plant in Japan. Dose estimations for plant workers were also conducted. The activity concentration of the U series in raw materials and products for the monazite processing plant was found to be higher than the relevant values described in the International Atomic Energy Agency Safety Standards. The ambient dose rates in the raw material yard were higher than those in other work sites. Moreover, the activity concentrations of dust in the milling site were higher than those in other work sites. The Rn concentrations in all work sites were almost the same as those in regular indoor environments in Japan. The Rn concentrations in all work sites were much higher than those in regular indoor environments in Japan. The maximum value of the effective dose for workers was 0.62 mSv y, which is lower than the reference level range (1-20 mSv y) for abnormally high levels of natural background radiation published in the International Commission of Radiological Protection Publication 103.

STUDY ON RADON CONCENTRATION AT THE WORK PLACES OF MYSURU, BENGALURU AND KOLAR DISTRICTS OF KARNATAKA STATE, SOUTH INDIA

Concentrations of radon, thoron and their progeny inside the working place depend on the activity of radionuclides in the soil, building materials, atmospheric conditions, construction of the building, type of work and ventilation condition. Radon is a radioactive noble gas, and it is emanated from ²²⁶Ra present in earth crest and building material. Based on the type of work, construction of the building and ventilation condition, concentrations of radon, thoron and their progeny have been measured in 60 workplaces at 10 locations of Mysuru, Bengaluru and Kolar districts of Karnataka state using Solid-State Nuclear Track Detector technique. From the study, variations of radon, thoron and their progeny have been observed with the nature of work.

A comparison of the dose from natural radionuclides and artificial radionuclides after the Fukushima nuclear accident

Due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the evacuees from Namie Town still cannot reside in the town, and some continue to live in temporary housing units. In this study, the radon activity concentrations were measured at temporary housing facilities, apartments and detached houses in Fukushima Prefecture in order to estimate the annual internal exposure dose of residents. A passive radon-thoron monitor (using a CR-39) and a pulse-type ionization chamber were used to evaluate the radon activity concentration. The average radon activity concentrations at temporary housing units, including a medical clinic, apartments and detached houses, were 5, 7 and 9 Bq m(-3), respectively. Assuming the residents lived in these facilities for one year, the average annual effective doses due to indoor radon in each housing type were evaluated as 0.18, 0.22 and 0.29 mSv, respectively. The average effective doses to all residents in Fukushima Prefecture due to natural and artificial sources were estimated using the results of the indoor radon measurements and published data. The average effective dose due to natural sources for the evacuees from Namie Town was estimated to be 1.9 mSv. In comparison, for the first year after the FDNPP accident, the average effective dose for the evacuees due to artificial sources from the accident was 5.0 mSv. Although residents' internal and external exposures due to natural radionuclides cannot be avoided, it might be possible to lower external exposure due to the artificial radionuclides by changing some behaviors of residents.

Characteristics of indoor radon and its progeny in a Japanese dwelling while using air appliances

Characteristics of radon and its progeny were investigated in different air conditions by turning four types of indoor air appliances on and off in a two-story concrete Japanese dwelling. The four appliances were air conditioner, air cleaner, gas heater and cooker hood. The measurements were done using two devices: (1) a Si-based semiconductor detector for continuous measurement of indoor radon concentration and (2) a ZnS(Ag) scintillation counting system for equilibrium-equivalent radon concentration. Throughout the entire experiment, the cooker hood was the most effective in decreasing indoor radon concentration over a long period of time and the less effective was the air conditioner, while the air cleaner and gas heater did not affect the concentration of radon. However, the results measured in each air condition will differ according to the lifestyles and activities of the inhabitants. In this study, indoor radon and its progeny in a Japanese dwelling will be characterised by the different air conditions.

Occupational exposure to natural radiation in zirconium refractory plants in Japan

The authors measured the ambient dose rate and activity concentration of natural radionuclides in raw materials, products, and aerosols on worksites, as well as the (222)Rn and (220)Rn concentrations in an unshaped refractory, a shaped refractory, and an electrocast refractory plant processing zirconium ore in Japan. Estimations were made of the effective doses to plant workers. The activity concentration of the (238)U series in raw materials and products in the refractory plants was higher than the critical values (10 Bq g(-1) for (40)K and 1 Bq g(-1) for all other radionuclides of natural origin) specified in the International Atomic Energy Agency Safety Guide. The ambient dose rate in the raw material warehouse of the electrocast refractory plant was 0.75 μSv h(-1), which was the highest among all the worksites at all the refractory plants studied. The activity concentrations of aerosols in the product-output site of the unshaped refractory plant was 0.0015 Bq m for U and 0.00078 Bq m(-3) for (232)Th, which were the highest of all the worksites for all refractory plants. The indoor (222)Rn and (220)Rn concentrations in all worksites of all the refractory plants were almost the same levels as those in everyday indoor places in Japan. The maximum value of the effective dose to workers was 430 μSv y(-1), which was lower than the intervention exemption level (1,000 μSv y(-1)) specified in ICRP Publication 82.

Measurement of radon/thoron exhalation rates and gamma-ray dose rate in granite areas in Japan

Radon and thoron exhalation rates and gamma-ray dose rate in different places in Hiroshima Prefecture were measured. Exhalation rates were measured using an accumulation chamber method. The radon exhalation rate was found to vary from 3 to 37 mBq m(-2) s(-1), while the thoron exhalation rate ranged from 40 to 3330 mBq m(-2) s(-1). The highest radon exhalation rate (37 mBq m(-2) s(-1)) and gamma-ray dose rate (92 nGy h(-1)) were found in the same city (Kure City). In Kure City, indoor radon and thoron concentrations were previously measured at nine selected houses using a radon-thoron discriminative detector (Raduet). The indoor radon concentrations varied from 16 to 78 Bq m(-3), which was higher than the average value in Japan (15.5 Bq m(-3)). The indoor thoron concentration ranged from ND (not detected: below a detection limit of approximately 10 Bq m(-3)) to 314 Bq m(-3). The results suggest that radon exhalation rate from the ground is an influential factor for indoor radon concentration.