Residential Radon Concentrations Research Articles

The study on the residential radon concentration in the rooms in the areas of the Republic of Moldova

Natural radioactivity is still a topic addressed at the international level with multiple segments interspersed in the upward pace of technological and economic development at the local level. The intensity of concerns in the aspect of radioprotection starts from a series of factors that condition the level and doses of exposure of the population to sources of ionizing radiation, thus determining the medical, social, economic and demographic effects in the characteristic of a medico-social problem. Radon, through its contribution to the creation of the natural radioactive background, has a crucial role in the etiology of oncological diseases of broncho-pulmonary origin, leukemias and other pathologies. Long-term exposure to increased concentrations of radon and the association of other risk factors, such as tobacco consumption, causes the alteration of cellular metabolism processes, the damage of DNA and RNA nucleic acids, the formation of free radicals and the appearance of mutations that can constantly trigger lung cancer. The continuous monitoring of residential radon concentrations is a primary objective within the strategy to control and reduce the long-term negative effects of radon, being a main element of the action plan of the EURATOM Directive 59/2013.

Impact of indoor air pollution on the lung cancer – literature review

Introduction: Lung cancer is the most diagnosed type of cancer and the leading cause of death around the world. The most important risk factor for lung cancer is tobacco smoking. However, there are a lot of other lung cancer risk factors, which include: second-hand smoke exposure, environmental exposures (indoor and outdoor air pollution), occupational exposures, genetic predisposition, and previous lung disease. In this study, we would like to present the actual state of knowledge about the influence of radon as well as other indoor air pollutants on the prevalence of lung cancer.
 State of knowledge: We analyzed nineteen studies in terms of the impact of indoor air pollution on morbidity and mortality caused by lung cancer. The authors of the included studies agree that both radon and other household air pollution (HAP) increase risk of the lung cancer. HAPs are formed during the combustion of solid fuels (i.e. charcoal, wood). Indoor air pollution can cause in the lungs chronic inflammation, cells damage and their proliferation, depletion of antioxidants, impairment of defense mechanisms, production of reactive oxygen species as well as genetic mutations. Radon, on the other hand, emits alpha radiation, which can affect the respiratory epithelium and produce various cytotoxic and genotoxic effects, which promote carcinogenesis. The risk of lung cancer rises by approximately 6-16% per 100 Bq/m3 increase in long-time average residential radon concentration. 
 Conclusions: Radon and other indoor air pollutants are crucial lung cancer risk factors. It is essential to reduce HAPs production, especially in rural areas, where many people still use coal, wood, or straw for household heating and cooking. Moreover, there are regions where is a need to improve ventilation as well as to switch to clean fuel sources, such as gas and electricity. These activities will contribute to reducing the concentration of HAPs in buildings and decreasing the risk of lung cancer.

Radon - occurrence and impact on the health.

Radon is noble, monatomic, radioactive, heavier than the air gas. It is colorless, odorless, tasteless. It exists in natural environment as a result of the decay of radium, and emits mainly alpha radiation and less beta radiation. Residential radon concentrations vary widely by geographic area. The higher concentration of radon is expected globally in the grounds where uranium, radium and thoron are present. Radon may gather in caves, tunnels, mines as well as in other lowestlying spaces, such as basements, and cellars. In accordance with Atomic Law (2000), the reference level for the average annual concentration of radioactive radon in rooms intended for human habitation is 300 Bq/m3. The most dangerous damages caused by ionizing radiation i.e. radon and its derivatives are changes to DNA, which may disturb the functions of cells and in the consequence lead to induction of cancer of respiratory tract, mainly of lungs and also leukaemia. So, the main consequence of exposure to high amount of radon are cancers of respiratory system. Radon enters the human organism mainly through inhaled atmospheric air. Moreover, radon significantly increased a risk of induction cancer in smokers and vice versa, smoking promotes the development of lung cancer after the exposure to radon and its derivatives. Radon may also have beneficial effect on the human body. Therefore it is used in medicine; mainly in radonbalneotherapy i.e. bath treatments, rinsing the mouth and inhalation. Beneficial effects of radon confirms the validity of the theory of radiation hormesis, which assumes that low doses of radiation may stimulate the repair of DNA damage by activation of protective mechanisms, which neutralize free radicals.

Residential radon and characteristics of chronic obstructive pulmonary disease

It is not known whether residential radon exposure may be linked to the development of chronic obstructive pulmonary disease (COPD) and/or have an influence on the functional characteristics or exacerbations of COPD. The aim of this study was therefore to ascertain whether there might be an association between residential radon concentrations and certain characteristics of COPD. We analyzed COPD cases drawn from a case–control study conducted in an area of high radon exposure. Data were collected on spirometric pulmonary function variables, hospital admissions, and smoking. Radon measurements were taken using alpha-track-type CR-39 detectors individually placed in patients’ homes. All statistical analyses were performed using the IBM SPSS v22 computer software program. The study included 189 COPD cases (79.4% men; median age 64 years). The median radon concentration was 157 Bq/m3. No differences were found between radon concentration and sex, age or severity of breathing obstruction as measured by FEV1%. It should be noted, however, that 48.1% of patients with FEV1% < 50 had radon concentrations below 100 Bq/m3, as compared to 35.6% with the same severity of obstruction who had over 300 Bq/m3. COPD cases with radon concentrations higher than > 600 Bq/m3 exhibited no different characteristics in lung function. Exposure to radon does not appear to have an influence on the clinical characteristics of smokers and ex-smokers with COPD. As exposure to residential radon increases, there is no trend towards a worsening of FEV1%. Further studies are thus needed to analyze this possible association in never-smokers with COPD.

Indoor Radon Exposure and COPD, Synergic Association? A Multicentric, Hospital-Based Case–Control Study in a Radon-Prone Area

BackgroundCOPD is a multifactorial disease which causes considerable mortality and morbidity worldwide. Previous studies assessing the possible relationship between indoor radon exposure and COPD have shown inconclusive results. MethodsA multicentric, hospital-based, case-control study was conducted in a Spanish radon-prone area. COPD cases were confirmed by spirometry and controls were selected due to trivial surgery or procedures not related to tobacco consumption. All participants had to have lived for at least 15 years in the same dwelling. Radon measurements were conducted individually in dwellings using alpha-track detectors. Results were obtained using multivariate logistic regression. Results189 cases and 747 controls took part. There was no significant association between residential radon concentrations and COPD onset with a OR of 1.12 (95%CI 0.41–3.06) for individuals exposed to more than 200Bq/m3 compared to those exposed to less than 50Bq/m3. Heavy smokers seem to increase their COPD risk if exposed to higher radon concentrations vs those exposed to lower concentrations. There was a statistically significant synergy index between radon exposure and tobacco consumption, S-index 11.60 (95%CI 3.71–36.26). Indoor radon concentration was higher in never/light smokers with COPD compared to controls. ConclusionsNo association between indoor radon and COPD has been observed. However, there might be some effect modification on the COPD risk in heavy smokers when high radon exposure is present. This is supported by the additive synergy observed. Also, a possible association between indoor radon and COPD onset in never and light smokers needs to be further studied.

P661 Radon exposure and inflammatory bowel disease in a radon prone area

Abstract Background Inflammatory Bowel Disease (IBD) is a multifactorial pathology with an increasing incidence. There are environmental factors, many unknown, that participate in its development. There is no study having assessed a possible relationship with residential radon exposure, which is very high in the study area. The aim of this study was to analyze if residential radon concentration measured at a municipal level is associated with a higher incidence of IBD and its characteristics (clinical or demographic). Methods We performed an ecological study where we included all incident cases of IBD in the area of Santiago de Compostela between January and December 2017 in order to estimate municipal incidence rates. Radon levels at a municipal level were obtained from the Galician Radon Map and correlated with demographic factors and type of IBD. We used the Spearman’s correlation coefficient to test the existence of any association. Results 96 patients were included, 63 (65.6%) with Ulcerative Colitis, 29 (30.25) with Crohn’s Disease and 4 (4.2%) with indeterminate colitis. Median age was 41 (IQR: 33.5 to 56 years), and 50.0% were women. The incidence rate per 100.000 inhabitants-year in the study area was 21.6 cases. The median radon concentration was 104.9Bq/m3 (IQR: 91.0 to 154.6), without statistically significant differences in function of the location of the house (rural vs. urban) nor the type of edification (flat vs house), p &amp;gt;0.05. There were no statistically significant differences on the type of IBD developed (ulcerative colitis, Crohn’s disease or indeterminate colitis) regarding radon levels either (p&amp;gt;0.05). There were no statistically significant differences (p&amp;gt;0.05) between radon and sex of IBD cases. No correlation between radon levels and age of the individuals was observed (Spearman’s rho = -0.13, p-value 0.2), nor radon levels variation by age groups (p&amp;gt;0.05). There was no correlation between radon concentration and cumulative incidence of IBD at municipal level (Spearman’s rho = 0.13, p-value 0.5), as it is shown in figure 1. Conclusion In the area of Santiago de Compostela there is a higher incidence of IBD in comparison with previous studies taking western countries as reference. It is possible that some environmental risk factors, could be responsible of this difference. In this study we have not found any correlation with municipal average radon concentration and incidence of IBD or any of its types.

Residencial radon and small cell lung cancer: A case control study.

e20566 Background: Residential radon is the second most important risk factor for lung cancer. We aim to asses the effect of residential radon exposure on the risk of SCLC in general population. Methods: A multicentric hospital-based case-control study was designed including 10 hospitals from Spain and Portugal. Incident cases with pathological diagnosis of SCLC were prospectively recruited. Controls consisted in patients undergoing non-complex surgery unrelated to tobacco consumption. All study participants were sent a radon detector. Results: A total of 375 cases and 902 controls were recruited. 24.5% of cases were women. The median age at diagnosis was 66 for cases. 6.4% of the cases were younger than 50 years. Tobacco consumption was higher in cases compared to controls. Residential radon concentrations were higher than 147 Bq/m3 in 161 SCLC cases (42.9%). Median residential radon concentration was also higher in SCLC cases compared to controls (152.5 Bq/m3 vs 142 Bq/m3). Those people exposed to more than 147 Bq/m3 and heavy smokers showed an OR of 72,62 (95%CI 17.95 - 499.41) compared to never-smokers with less than 50 Bq/m3. Conclusions: radon exposure seems to increase the risk of small cell lung cancer. There is a significant lung cancer risk departing from 148 Bq/m3 and there is also a linear dose-response pattern. Tobacco consumption may also produce an important effect modification for radon exposure. Those individuals exposed to high radon concentrations and heavy smokers can have a very high risk of this cancer type compared with their low exposed and never-smoking counterparts. It is necessary to increase radon awareness among citizens and administrations in order they can establish the necessary protective and mitigation measures against residential radon. Effect modification between residential radon exposure and tobacco consumption on the risk of small cell lung cancer.[Table: see text]

Small-cell lung cancer in never-smokers

BackgroundLung cancer is a public health problem worldwide. Small-cell lung cancer (SCLC) is the most aggressive histologic type, with a 5-year survival <10%. SCLC is closely associated with tobacco consumption and infrequent in never-smokers. We aim to describe SCLC characteristics in never-smokers recruited in a radon-prone area.Patients and methodsWe designed a multicentric case series where SCLC cases were recruited consecutively following histologic confirmation. Detailed information was obtained for indoor radon exposure, occupation and environmental tobacco smoke. We also collected different clinical characteristics such as extended or limited disease at diagnosis.ResultsWe recruited 32 never-smoking SCLC cases. Median age was 75 years and 87.5% were women; 47% had extended disease. Median radon concentration was 182 Bq/m3. There were no statistically significant differences in residential radon concentration neither regarding age at diagnosis nor regarding sex. The most frequent symptoms were constitutional syndrome (23.1%) and coughing (23.1%). As much as 63% of cases had an Eastern Cooperative Oncology Group Study (ECOG) status of 0-2. The 1- and 2-year survival rates were 34.4% and 21.9%, respectively. The 2-year survival rate with a localized tumor was 26.7%, compared with 18.8% for extended disease.ConclusionsThese results show, for the first time, that indoor radon might not be associated with SCLC characteristics at diagnosis in never-smokers, and also confirms the low survival of this aggressive type of lung cancer also for never-smokers.

Radon exposure and inflammatory bowel disease in a radon prone area.

inflammatory bowel disease (IBD) is a multifactorial pathology with an increasing incidence. There is no study that has assessed a possible relationship with very high residential radon exposure in the study area. The aim of the study was to analyze if residential radon concentration is associated with a higher incidence of IBD. an ecological study was performed. All incident cases of inflammatory bowel disease in the area of Santiago de Compostela were included between January and December 2017. Radon levels at a municipal level were correlated with demographic factors and type of IBD. ninety-six patients were included, 63 (65.6 %) with ulcerative colitis, 29 (30.25) with Crohn's disease and four (4.2 %) with indeterminate colitis. The incidence rate per 100,000 inhabitants-year was 21.6 cases. There were no statistically significant differences in the type of disease developed regarding radon levels (p > 0.05). No correlation between radon levels and the cumulative incidence of inflammatory bowel disease at the municipal level was observed (Spearman's rho = 0.13, p-value 0.5). in the area of Santiago de Compostela, there is a higher incidence of IBD in comparison with previous studies using western countries as reference. However, there was no correlation with the municipal average radon concentration and incidence of IBD or any of its types in this study.

Indoor Radon Exposure and COPD, Synergic Association? A Multicentric, Hospital-Based Case–Control Study in a Radon-Prone Area

BackgroundCOPD is a multifactorial disease which causes considerable mortality and morbidity worldwide. Previous studies assessing the possible relationship between indoor radon exposure and COPD have shown inconclusive results. MethodsA multicentric, hospital-based, case-control study was conducted in a Spanish radon-prone area. COPD cases were confirmed by spirometry and controls were selected due to trivial surgery or procedures not related to tobacco consumption. All participants had to have lived for at least 15 years in the same dwelling. Radon measurements were conducted individually in dwellings using alpha-track detectors. Results were obtained using multivariate logistic regression. Results189 cases and 747 controls took part. There was no significant association between residential radon concentrations and COPD onset with a OR of 1.12 (95%CI 0.41–3.06) for individuals exposed to more than 200Bq/m3 compared to those exposed to less than 50Bq/m3. Heavy smokers seem to increase their COPD risk if exposed to higher radon concentrations vs those exposed to lower concentrations. There was a statistically significant synergy index between radon exposure and tobacco consumption, S-index 11.60 (95%CI 3.71–36.26). Indoor radon concentration was higher in never/light smokers with COPD compared to controls. ConclusionsNo association between indoor radon and COPD has been observed. However, there might be some effect modification on the COPD risk in heavy smokers when high radon exposure is present. This is supported by the additive synergy observed. Also, a possible association between indoor radon and COPD onset in never and light smokers needs to be further studied.

Reanalysis of residential radon surveys in China from 1980 to 2019

A study on the published historic data of the residential radon concentration was carried out in order to provide a systematic retrospect and the confluent analysis of the investigations from 1980 to 2019 in China. A new database was established by collecting the results of nearly all radon surveys reported in China. A total of 129 surveys on residential radon, covering 147 cities with the sampling size of 72,295 were collected into the data pool for secondary analysis. The results from different decades confirmed the rapid increase trend of residential radon concentration in China. The geographical coverage, the sampling density and the geographic distribution of sampling sites of these surveys were discussed. The analysis on the local data sequences indicated the average increasing rate of residential radon concentration for 28 Chinese cities was estimated to be 0.80 Bq·m−3·a−1 in last 40 years. The results in this study provided the overall expression of the radon investigations in China and were expected to be benefit to the radon-related studies in the future.

Model selection in radon data fusion

Abstract Fitting parametric models or the use of the empirical cumulative distribution function are problematic when it comes to the estimation of tail probabilities from small samples. A possible remedy is to fuse or combine the small samples with additional data from external sources and base the inference on the so called density ratio model with variable tilt functions, which widens the support of the estimated distribution of interest. This approach is illustrated using residential radon concentration data collected from western Pennsylvania.

Estimation of residential radon concentration in Pennsylvania counties by data fusion

A data fusion method for the estimation of residential radon level distribution in any Pennsylvania county is proposed. The method is based on a multisample density ratio model with variable tilts and is applied to combined radon data from a reference county of interest and its neighboring counties. Beaver county and its four immediate neighbors are taken as a case in point. The distribution of radon concentration is estimated in each of six periods, and then the analysis is repeated combining the data from all the periods to obtain estimates of Beaver threshold probabilities and the corresponding confidence intervals.

Predicting residential radon concentrations in Finland: Model development, validation, and application to childhood leukemia.

Objectives Inhaled radon gas is a known alpha-emitting carcinogen linked especially to lung cancer. Studies on higher concentrations of indoor radon and childhood leukemia have conflicting but largely negative results. In this study, we aimed to create a sophisticated statistical model to predict indoor radon concentrations and apply it to a Finnish childhood leukemia case-control dataset. Methods Prediction was based on ~80 000 indoor radon measurements, which were linked to national registries for potential indoor radon predictors based on the literature. In modelling, we used classical methods, random forests and deep neural networks. We had 1093 cases and 3279 controls from a nationwide case-control study. We estimated odds ratio (OR) for childhood leukemia using conditional logistic regression adjusted for potential confounders. Results The r 2of the final log-linear model was 0.21 for houses and 0.20 for apartments. Using random forest method, we were able to obtain slightly better fit for both houses (r 2= 0.28) and apartments (r 2= 0.23). In a risk analysis based on the case-control data with log-linear model, we observed a non-significant (P=0.54) increase with predicted radon concentrations [OR for the 2 ndquartile 1.08, 95% confidence interval (CI) 0.77-1.50, OR 1.10 with 95% CI 0.79-1.53 for the 3 rd, and 1.29 with 95% CI 0.93-1.77 for the highest quartile]. Conclusions Our modelling and the previously published models performed similarly but involves major uncertainties, and the results should be interpreted with caution. We observed a slight non-significant increase in risk of childhood leukemia related to higher average indoor radon concentrations.

Effect modification of ambient particle mortality by radon: A time series analysis in 108 U.S. cities

ABSTRACTNumerous studies have reported a positive association between ambient fine particles and daily mortality, but little is known about the particle properties or environmental factors that may contribute to these effects. This study assessed potential modification of radon on PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm)-associated daily mortality in 108 U.S. cities using a two-stage statistical approach. First, city- and season-specific PM2.5 mortality risks were estimated using over-dispersed Poisson regression models. These PM2.5 effect estimates were then regressed against mean city-level residential radon concentrations to estimate overall PM2.5 effects and potential modification by radon. Radon exposure estimates based on measured short-term basement concentrations and modeled long-term living-area concentrations were both assessed. Exposure to PM2.5 was associated with total, cardiovascular, and respiratory mortality in both the spring and the fall. In addition, higher mean city-level radon concentrations increased PM2.5-associated mortality in the spring and fall. For example, a 10 µg/m3 increase in PM2.5 in the spring at the 10th percentile of city-averaged short-term radon concentrations (21.1 Bq/m3) was associated with a 1.92% increase in total mortality (95% CI: 1.29, 2.55), whereas the same PM2.5 exposure at the 90th radon percentile (234.2 Bq/m3) was associated with a 3.73% increase in total mortality (95% CI: 2.87, 4.59). Results were robust to adjustment for spatial confounders, including average planetary boundary height, population age, percent poverty and tobacco use. While additional research is necessary, this study suggests that radon enhances PM2.5 mortality. This is of significant regulatory importance, as effective regulation should consider the increased risk for particle mortality in cities with higher radon levels.Implications: In this large national study, city-averaged indoor radon concentration was a significant effect modifier of PM2.5-associated total, cardiovascular, and respiratory mortality risk in the spring and fall. These results suggest that radon may enhance PM2.5-associated mortality. In addition, local radon concentrations partially explain the significant variability in PM2.5 effect estimates across U.S. cities, noted in this and previous studies. Although the concept of PM as a vector for radon progeny is feasible, additional research is needed on the noncancer health effects of radon and its potential interaction with PM. Future air quality regulations may need to consider the increased risk for particle mortality in cities with higher radon levels.

Indoor radon concentration in Korearesidential environments.

The purpose of this study is to provide basic data for the evaluation and management of health effects with respect to exposure to radon within residential environments in South Korea. It is part of a case-control study to develop a management plan based on indoor radon exposure levels and assess their impact on health. To investigate the long-term cumulative concentration levels of radon, 599 patients who have respiratory diseases were recruited in South Korea, and alpha track detectors were installed in their residences for a period of 3months from mid-2015 to late 2016. A survey was then conducted to determine the factors affecting the radon concentration. The radon concentration levels were analyzed in conjunction with the survey results. The results show that the arithmetic mean of the radon concentrations in domestic residences was in the range of 70.8 ± 65.2Bq/m3. An analysis of covariance (ANCOVA) was performed to identify the environmental factors affecting the radon concentration and contributing to variations in the residential radon concentration based on the height of the residence. The results show that the contribution of the local environmental factor to the variation in radon concentration (p < 0.05) was greater than that of other environmental factors. Although no statistically significant difference was found with regard to the construction year of the building before the control (p > 0.05), the same was found with regard to the construction year after the control (p < 0.05).

Small Cell Lung Cancer. Methodology and Preliminary Results of the SMALL CELL Study

IntroductionSmall cell lung cancer (SCLC) is the most aggressive histologic type of lung cancer, and accounts for approximately 10%–15% of all cases. Few studies have analyzed the effect of residential radon. Our aim is to determine the risk factors of SCLC. MethodsWe designed a multicenter, hospital-based case-control study with the participation of 11 hospitals in 4 autonomous communities. ResultsResults of the first 113 cases have been analyzed, 63 of which included residential radon measurements. Median age at diagnosis was 63 years; 11% of cases were younger than 50 years of age; 22% were women; 57% had extended disease; and 95% were smokers or former smokers. Median residential radon concentration was 128Bq/m3. Concentrations higher than 400Bq/m3 were found in 8% of cases. The only remarkable difference by gender was the percentage of never smokers, which was higher in women compared to men (P<.001). Radon concentration was higher in patients with stage IV disease (non-significant difference) and in individuals diagnosed at 63 years of age or older (P=.032). ConclusionsA high percentage of SCLC cases are diagnosed early and there is a predominance of disseminated disease at diagnosis. Residential radon seems to play an important role on the onset of this disease, with some cases having very high indoor radon concentrations.

Residential radon in Galicia: a cross-sectional study in a radon-prone area

Residential radon exposure is a major public health problem. It is the second greatest cause of lung cancer, after smoking, and the greatest in never-smokers. This study shows the indoor radon exposure distribution in Galicia and estimates the percentage of dwellings exceeding reference levels. It is based on 3245 residential radon measurements obtained from the Galician Radon Map project and from controls of two previous case-control studies on residential radon and lung cancer. Results show a high median residential radon concentration in Galicia (99 Bq m−3), with 49.3% of dwellings having a radon concentration above 100 Bq m−3 and 11.1% having a concentration above 300 Bq m−3. Ourense and Pontevedra, located in South Galicia, are the provinces with the highest median indoor radon concentrations (137 Bq m−3 and 123.5 Bq m−3, respectively). Results also show lower radon levels in progressively higher building storeys. These high residential radon concentrations confirm Galicia as a radon-prone area. A policy on radon should be developed and implemented in Galicia to minimize the residential radon exposure of the population.

Cáncer de pulmón microcítico. Metodología y resultados preliminares del estudio SMALL CELL

IntroductionSmall cell lung cancer (SCLC) is the most aggressive histologic type of lung cancer, and accounts for approximately 10%-15% of all cases. Few studies have analyzed the effect of residential radon. Our aim is to determine the risk factors of SCLC. MethodsWe designed a multicenter, hospital-based case-control study with the participation of 11 hospitals in 4 autonomous communities. ResultsResults of the first 113 cases have been analyzed, 63 of which included residential radon measurements. Median age at diagnosis was 63 years; 11% of cases were younger than 50 years of age; 22% were women; 57% had extended disease; and 95% were smokers or former smokers. Median residential radon concentration was 128Bq/m3. Concentrations higher than 400Bq/m3 were found in 8% of cases. The only remarkable difference by gender was the percentage of never smokers, which was higher in women compared to men (P<.001). Radon concentration was higher in patients with stageIV disease (non-significant difference) and in individuals diagnosed at 63 years of age or older (P=.032). ConclusionsA high percentage of SCLC cases are diagnosed early and there is a predominance of disseminated disease at diagnosis. Residential radon seems to play an important role on the onset of this disease, with some cases having very high indoor radon concentrations.

Long-term measurements of residential radon, thoron, and thoron progeny concentrations around the Chhatrapur placer deposit, a high background radiation area in Odisha, India

The Chhatrapur placer deposit is found in a high background radiation area which has been recently identified on the southeastern coast of India. Previously, some geochemical studies of this area were carried out to assess external dose from radionuclides-bearing heavy mineral sands. In this study, radon, thoron and thoron progeny concentrations were measured in about 100 dwellings during three seasons (autumn-winter, summer, and rainy) in a 10- to 12-month period and annual doses due to inhalation of them were evaluated. The measurements were made by passive-type radon-thoron discriminative detectors and thoron progeny detectors in which solid state nuclear track detectors were deployed. The results show that radon and thoron concentrations differ by one order of magnitude depending on exposure periods, while thoron progeny concentration is nearly constant throughout the year. Since thorium-rich sand is distributed in the studied area, exposure to thoron is equal to, or exceeds, exposure to radon and is not negligible for dose evaluation. Based on the measurements, doses due to inhalation of radon and thoron are evaluated as 0.1–1.6 mSv y−1 and 0.2–3.8 mSv y−1, respectively. The total dose is 0.8–4.6 mSv y−1, which is the same order of magnitude as the worldwide value.