Radon

Groundwater radon data were recorded at monthly intervals from two selected monitoring sites of the northern extension of the Dead Sea Fault System in western Syria during 1993 and 1994. This set of data was utilized to estimate the basic radon background content and the range of its normal variations in groundwater along the fault zone. The results suggest that the establishment of such range is important when attempting to separate the usual groundwater radon fluctuations from other anomalous or earthquake related values. In addition, the seismic activity in the study region was statistically analyzed, and the completeness of the earthquake catalogue during the given time-window was estimated to be at magnitude M > 3.5.

53 ból kiindulva. Az ivóvízellátás céljára csak az ásványvíz termelõ kutakat (8 db, összesen 24.915 m 3 /d), háztartási víz céljára pedig csak a fõváros fürdõinek medencetöltõ kútjait (16 db, összesen 42.759 m 3 /d) vettük számításba. Kimaradtak tehát a fürdõk forrásai, és más források, az ipari célra használt fúrt és ásott kutak, valamint a ma is nagy számban fellelhetõ egyéni felhasználású ásott kutak. A vízhozamokat annak fényében vizsgáltuk, hogy minõsített idõszakban elõírás szerint 3 l/d/fõ ivóvízmennyiséget, valamint 30 l/d/fõ háztartási vizet kell biztosítani. Számításaink szerint 14,7 l/d/fõ ásványvíz áll rendelkezésre, vagyis mintegy 5 Budapestnyi lakosság kiszolgálására elegendõ, a medencetöltõ vízbõl a fõváros lakosságának 84 %-a látható el. Ha pedig beszámítjuk ide az ivóvízellátás hatalmas fölöslegét, a háztartási víz igény is 100 %-ban kielégíthetõ.

Radon is a radioactive gas that is formed naturally by the breakdown of uranium in soil, rock and water. Recent epidemiological findings from residential studies demonstrate a statistically significant increase of lung cancer risk from prolonged exposure to indoor radon. The new requirements of ICRP and WHO include the control of indoor exposure due radon and establishment of a reference level for the annual average activity concentration up to 300 Bq/m 3 for existing dwellings and public buildings. In this paper the results of indoor radon survey in Plovdiv city are presented. Radon measurements were made in 44 dwellings and 91 kindergartens by using CR-39 nuclear track detectors. The detectors in dwellings were exposed for 6 months from The average annual indoor radon concentration (GM) for dwelling was found to be 100 Bq/m 3 and for kindergartens 230 Bq/m 3. The maximum measurement value of radon concentration in dwellings was 930 Bq/m 3 and for kindergartens 1094 Bq/m 3. The radon concentrations in dwellings were compared with that in kindergartens and the results show that kindergartens have a high indoor radon concentration than dwellings. A detailed statistical analysis of the building factors was presented as well as the risk from radon exposure was assessed.

Resumo O radônio é um elemento químico da família dos gases nobres, de número atômico 86, que apresenta-se na forma de um gás insípido, inodoro, incolor e o mais importante, radioativo. É o responsável pela maior parte da dose de radioatividade natural que uma pessoa recebe durante sua vida. Neste trabalho será descrito como ocorre a formação desse gás, quais os seus riscos para a saúde e como mitigar a exposição ao mesmo. RADON FROM NATURAL RADIOACTIVITY 1 Abstract Radon is a chemical element in the family of noble gases, atomic number 86, in the form of an odorless, odorless, colorless gas and, most importantly, radioactive. It is the responsible for most of the dose of natural radioactivity that a person receives during their lifetime. This work will describe how the formation of this gas occurs, what its health risks are and how to mitigate the exposure to it.

The estimated incidence of acute promyelocytic leukemia (APL) is approximately 6 cases per 10 million people per year with no apparent differences between sexes. The age of APL cases is younger than that of other acute myeloid leukemias (AML). Spatial and temporal clusters of APL have been reported. These observations suggest a possible selective role for environmental and/or occupational factors in APL development. A multicenter case-control study was carried out on risk factors for acute leukemias and preleukemias. In this report data related to APL are selectively analyzed from the larger study to identify specific risk factors. The case-control study on 38 cases of APL showed a strong association with shoemaking (odds ration 6.3, 95% confidence interval 1.3-31.1). A moderate leukemogenic effect from living in houses built with tuff, a polous building material containing gamma-emitting radionuclides and having a high radon concentration, and from using hair dyes was also suggeste...

Radon is a natural, inert, invisible, odorless and chemically inactive radioactive gas emitted from the earth. It is produced by the decay of uranium ore, such as radium, actinium, or thorium. Because inhaling radon and its radioactive decay products causes irradiation of lung tissue, prolonged exposure to high concentrations of radon significantly increases the risk of developing cancer. Various types of equipment and components have been proposed to date for radon detection. In this paper, a radon counter using arduino MCU module is implemented. To demonstrate the practical significance of the results, some simulation and experimental results are presented.

Radionuclides are naturally present throughout all environments, in varying amounts in air, water, plants, soil, rocks and etc. Naturally – occurring radionuclide’s are mainly derived from three separate decay chains (238U, 235U, and 232Th), and singly occurring 40K. These radionuclides may enter the human body from eating, drinking, external exposure or by inhaling. Then they penetrate into tissue and its cells, which causes ionization effects to its basic matter "cytoplasm".
222Rn is a colorless, odorless, tasteless, radioactive noble gas, which arises from the radioactive decay of 226Ra (itself a decay product of 238U). It is present in almost all rock, soil, and water, and typically moves up through the ground to the air above and into buildings through cracks and other holes in the underlying foundation. 222Rn is one of the most significant of the avoidable hazards in the environment, typically accounting for more than 50% of the dose to an average population.
Measurements of natural radioactivity and radon levels in water samples from Qena governorate, Egypt, and their human impact are outlined in this thesis. This was performed by collecting two hundred twenty water samples (ground, drinking tap and mineral water) from different sites in Qena, and employing Alpha GUARD monitoring system to determine the activity concentrations of 222Rn, also gamma spectrometry "NaI(Tl)" was used to determine the activity concentrations of 222Rn, 226Ra, 232Th and 40K in ground water.
In ground water samples 222Rn activity concentrations were fluctuated between 0.04±0.025 and 10.07±0.219 Bq/l, with an average value of 3.57±0.077 Bq/l.
In order to check the obtained results, two radon measuring techniques (Alpha GUARD and gamma spectrometry) were applied for measure some ground water samples from all sites, and the obtained results show that the two radon measuring techniques results are in a good agreement.
In the measuring ground water samples, the obtained measuring results for 226Ra, 232Th and 40K activity concentrations were fluctuated between (0.126±0.007 and 1.93±0.117), (0.037±0.003 and 0.899±0.077) and (3.18±0.273 and 7±0.602), with averages values of 0.54±0.029, 0.4±0.027 and 5.10±0.44 Bq/l, for 226Ra, 232Th and 40K, respectively.
In the investigated drinking tap water samples, the obtained results for 222Rn activity concentrations show that, the activity concentrations were ranged between 0.006±0.0005 and 0.117±0.0027 Bq/l, with an average value of 0.049±0.003 Bq/l.
The obtained results for 222Rn activity concentrations in the investigated mineral water samples show that, the activity concentrations were fluctuated between 0.014±0.003 and 0.237±0.005 Bq/l, with an average value of 0.077±0.002 Bq/l.
The impacts of geochemical parameters of water such as PH, conductivity and TDS on the natural radionuclides activity concentration were studied, a reasonable correlation between pH and the 222Rn, 226Ra and 232Th activity concentrations were found, in which the activity concentrations decreased with increasing PH, whereas no general trend was observed that related the radionuclides activity concentrations with conductivity and TDS.
Health aspects are discussed, based on calculation of the annual effective doses for different age groups, which found in values lower than the reference level.

Understanding soil gas radon spatial variations can allow the constructor of a new house to prevent radon gas flowing from the ground. Indoor radon concentration distribution depends on many parameters and it is difficult to use its spatial variation to assess radon potential. Many scientists use to measure outdoor soil gas radon concentrations to assess the radon potential. Geostatistical methods provide us a valuable tool to study spatial structure of radon concentration and mapping. To explore the structure of soil gas radon concentration within an area in south Italy and choice a kriging algorithm, we compared the prediction performances of four different kriging algorithms: ordinary kriging, lognormal kriging, ordinary multi-Gaussian kriging, and ordinary indicator cokriging. Their results were compared using an independent validation data set. The comparison of predictions was based on three measures of accuracy: (1) the mean absolute error, (2) the mean-squared error of prediction; (3) the mean relative error, and a measure of effectiveness: the goodness-of-prediction estimate. The results obtained in this case study showed that the multi-Gaussian kriging was the most accurate approach among those considered. Comparing radon anomalies with lithology and fault locations, no evidence of a strict correlation between type of outcropping terrain and radon anomalies was found, except in the western sector where there were granitic and gneissic terrain. Moreover, there was a clear correlation between radon anomalies and fault systems.

Measurement of 222 Rn is an important research concern because of the highenergy alpha emission of its 218 Po and 214 Po progeny. The LR-115 passive detector is the basis of a solid-state nuclear track detector (SSNTD) whose use for radon measurements has been well established. The usage of the SSNTD technique requires calibration by comparison. The aim of this work is to evaluate the efficiency calibration parameters for the radon measurement system that three steps: (1) irradiation conditions, (2) etching conditions, and (3) track counting. The following parameters were evaluated: breakdown and counting voltages for the spark counter, detector thickness, etching time, temperature and NaOH concentration as etching conditions for the LR-115 detector. Calibrating factors of 0.035 and 0.028 tracks cm Ϫ2 Bq Ϫ1 m 3 d Ϫ1 for the open-and closed-chamber radon monitors, respectively, were determined considering the best efficiency calibration parameter values. Health Phys. 98(Supplement 2):S63-S68; 2010

D R varies (80-258 nGy h −1 ), no correlation between acidity and radon concentration. 222 Rn in soil (143 kBq m −3 ) high considering than in typical soil 40 kBq m −3 . 222 Rn in surface air varied within EPA and ICRP. All sites exhibited larger D R compared with the world of 84 nGy h −1 except for two sites. A statistically significant correlation between 222 Rn s -220 Rn.

This paper presents information on various radon elimination techniques and presents knowledge on anticipated elimination performances following literature. The technologies assessed in this review comprise different aeration techniques and granular activated carbon (GAC) as tools to eliminate and decrease radon in potable water. Because radon does not bound to water molecules, it is not dissolved. Radon's low solubility and its elevated vapor pressure imply that it strongly partitions into the air through diffusion. For the reason that it readily diffuses from water to air, radon is scarcely observed in surface waters and is firstly trouble in groundwater and radon is easily removed through aeration processes. Aeration transmits the radon pollution from water to air, so precautions should be taken to avoid such air contamination hazards. Aeration is not sufficient for removing radon from drinking water; it should be supported by adsorption method. Air is mainly composed of nitrogen (N 2(gas) , ~80%) and oxygen (O 2(g) , ~20%). N 2 is hydrophilic and O 2 is hydrophobic. Injecting pure O 2 into water would be more efficient than air (i.e., N 2 + O 2) in removing radon from water, thanks to its hydrophobicity. At the opposite extreme, injecting pure N 2 would be less performant, due to its hydrophilicity. Research should be made on this direction.

initiated a programme on the evaluation of the carcinogenic risk of chemicals to humans involving the production of critically evaluated monographs on individual chemicals. The programme was subsequently expanded to include evaluations of carcinogenic risks associated with exposures to complex mixtures, life-style factors and biological and physical agents, as well as those in specific occupations.

Radon and its radioactive progenies in indoor places are recognized as the main sources of public exposure from the natural radioactive sources. Exposure to radon occurs when breathing airborne radon while using water: showering, washing dishes, cooking and drinking water that contain radon. In the present research, number of (197) drinking water samples were collected from various places and supplies of public water used in Kassala State, Eastern Sudan, which has about 2 million population. Then radon concentration has been measured by using passive integrated solid-state nuclear track devices containing allyl diglycol carbonate plastic detectors. Results show that about 82.74% of water samples exceeded EPA (Environmental Protection Agency) recommendation for maximum contaminant level (MCL) for radon in drinking water of 11.1 Bq/l and have radon concentration gathered than 10 Bq/L, which advised EPA as a normal level. According to measurements data, the arithmetic mean of radon concentration for all samples was 15.94 ± 4.03 Bq/L. Similarly, the annual effective dose in stomach and lung per person has been evaluated in this research. According to the advice of WHO and EU Council, the total annual effective dose lowers than 0.1 mSv/y.

Apart from the linear monitoring studies concerning the relationship between radon and earthquake, an artificial neural networks (ANNs) model approach is presented starting out from non-linear changes of the eight different parameters during the earthquake occurrence. A three-layer Levenberg-Marquardt feedforward learning algorithm is used to model the earthquake prediction process in the East Anatolian Fault System (EAFS). The proposed ANN system employs individual training strategy with fixed-weight and supervised models leading to estimations. The average relative error between the magnitudes of the earthquakes acquired by ANN and measured data is about 2.3%. The relative error between the test and earthquake data varies between 0% and 12%. In addition, the factor analysis was applied on all data and the model output values to see the statistical variation. The total variance of 80.18% was explained with four factors by this analysis. Consequently, it can be concluded that ANN approach is a potential alternative to other models with complex mathematical operations.

Groundwater is an important source of water supply for
the various uses and its increasing demands in agricultural,
industrial and domestic sectors necessitates proper water
resources assessment and management strategies. Improper
management of groundwater resources can lead to various
troubles such as higher pumping cost, reduction in yield,
failure of wells, sea water intrusion to fresh water aquifers
in coastal regions, sub marine groundwater discharge (SGD)
and land subsidence. For proper assessment of groundwater
resources and groundwater budgeting we need to investigate
hydro-geological parameters and aquifer characteristics
more precisely.

Natural radiation is the major source of human exposure to ionising radiation, and its largest contributing component to effective dose arises from inhalation of (222)Rn and its radioactive progeny. However, despite extensive knowledge of radiation risks gained through epidemiologic investigations and mechanistic considerations, the health effects of chronic low-level radiation exposure are still poorly understood. The present paper reviews the possible contribution of studies of populations living in high natural background radiation (HNBR) areas (Guarapari, Brazil; Kerala, India; Ramsar, Iran; Yangjiang, China), including radon-prone areas, to low dose risk estimation. Much of the direct information about risk related to HNBR comes from case-control studies of radon and lung cancer, which provide convincing evidence of an association between long-term protracted radiation exposures in the general population and disease incidence. The success of these studies is mainly due to the c...

Radon is an invisible, odorless and chemically inactive radioactive gas that is produced by the decay of uranium ore. Various types of equipment and components have been proposed to date for radon detection. In this paper, a radon counter using PIN photodiode radon sensor module is implemented. Through experimental studies, we found that the PIN photodiode sensor module could be used for a radon counter.

Background: Case-control studies conducted in North America, Europe, and Asia provided evidence of increased lung cancer risk due to radon in homes. Here, the association between residential radon and lung cancer mortality was examined in a large-scale cohort study. Methods: Nearly 1.2 million Cancer Prevention Study-II participants were recruited in 1982. Mean countylevel residential radon concentrations were linked to study participants according to ZIP code information at enrollment [mean (SD) ¼ 53.5 Bq/m 3 (38.0)]. Cox proportional hazards regression models were used to obtain adjusted HR and 95% CI for lung cancer mortality associated with radon. Potential effect modification by cigarette smoking, ambient sulfate concentrations, and other risk factors was assessed on both the additive and multiplicative scales. Results: Through 1988, 3,493 lung cancer deaths were observed among 811,961 participants included in the analysis. A significant positive linear trend was observed between categories of radon concentrations and lung cancer mortality (P ¼ 0.02). A 15% (95% CI, 1-31) increase in the risk of lung cancer mortality was observed per 100 Bq/m 3 increase in radon. Participants with mean radon concentrations above the EPA guideline value (148 Bq/m 3) experienced a 34% (95% CI, 7-68) increase in risk for lung cancer mortality relative to those below the guideline value. Conclusions: This large prospective study showed positive associations between ecological indicators of residential radon and lung cancer. Impact: These results further support efforts to reduce radon concentrations in homes to the lowest possible level. Cancer Epidemiol Biomarkers Prev; 20(3); 438-48. Ó2011 AACR.

Radon is a radioactive gas that is colorless, odorless, and tasteless and is impossible to detect without the use of sensitive test equipment. Various types of equipment and components have been proposed to date for radon detection. In this paper, the calibrations of PIN photodiode radon counters are performed using an ion chamber type radon counter. Through some experimental studies, we found that the performances of PIN photodiode radon counters were improved by virtue of a linear regression analysis technique.

Coal and its by products often contain significant amounts of radionuclides, including uranium which is the ultimate source of the radioactive gas radon. Burning of coal and the subsequent emission to the atmosphere cause the re-distribution of toxic trace elements in the environment. Due to considerable economic and environmental importance and diverse uses, the collected fly ash has become a subject of worldwide interest in recent years. In the present study, radon exhalation rate and the activity concentration of 238 U, 232 Th and 40 K radionuclides in fly ash samples from Durgapur thermal power plant (WB) have been measured by ''Sealed Can technique'' using LR-115 type II detectors and a low level NaI (Tl) based gamma ray spectrometer, respectively. Radon exhalation rate varied from 360.0 to 470.0 mBq m À2 h À1 with an average value of 406.8 mBq m À2 h À1 . Activity concentrations of 238 U ranged from 84.8 to 126.4 Bq kg À1 with an average value of 99.3 Bq kg À1 , 232 Th ranged from 98.1 to 140.5 Bq kg À1 with an average value of 112.9 Bq kg À1 and 40 K ranged from 267.1 to 364.9 Bq kg À1 with an average value of 308.9 Bq kg À1 . Radium equivalent activity obtained from activity concentrations is found to vary from 256.5 to 352.8 Bq kg À1 with an average value of 282.5 Bq kg À1 . Absorbed gamma dose rates due to the presence of 238 U, 232 Th and 40 K in fly ash samples vary in the range 115.3-158.5 nGy h À1 with an average value of 126.4 nGy h À1 . While the external annual effective dose rate varies from 0.14 to 0.19 mSv y À1 with an average value of 0.15 mSv y À1 , effective dose equivalent estimated from exhalation rate varies from 42.5 to 55.2 mSv y À1 with an average value of 47.8 mSv y À1 . Values of external hazard index H ex for the fly ash samples studied in this work range from 0.69 to 0.96 with a mean value of 0.77.

Background: Radon is a high impact environmental pollutant and is the second leading cause of lung cancer in Canada. Despite the gravity of the health risk, residents have inadequate awareness and have taken minimum preventive actions. The success of any population-level health awareness program is contingent on the views and actions of key decision makers at the household level. People's perceptions of the risk should inform health communication messaging that aims to motivate them to take preventive measures. The objective of this study was to measure the quantifiable associations and predictions between perceptions of radon health risk and their preventive actions; to explore and examines the social determinants that enable and hinder the adoption of preventive measures. Additionally, the best effective radon control systems for both the new and existing houses and relevant policy implications have been examined. Methods: A mixed methods study consisting of surveys (n=557) and qualitative interviews (n=35) was conducted with both homeowners and tenants of Ottawa-Gatineau areas. Descriptive, correlation and regression analyses addressed the quantitative research questions. Thematic, inductive analysis identified themes in the qualitative data. A mixed methods analysis triangulate both results. A registered systematic review of radon interventions around the world was conducted and radon policy analysis was done by applying interdisciplinary frameworks. Results: Residents’ perceptions of radon health risk, smoking at home, social influence, and care for family significantly correlated with their intention to test for radon; the same variables predicted their protection behaviours. Residents obtained information on radon from the media, individual search, workplace and social networks. Residents who had dual - cognitive and emotional awareness of the risk, were motivated enough to take action. Having an understanding of the risk, caring for family, knowing others who contracted lung cancer and being financially capable were enablers for action. Obstacles included lack of awareness, cost of mitigation, lack of home ownership and potential stigma in selling the house. Residents attributed primary responsibility to public agencies for disseminating information and suggested incentivizing and mandating actions to promote preventive measures. Indoor radon is best controlled by installing an active SSDS with additional measures to seal any entry points in the foundation. The policy analysis generated a list of recommendations that can be implemented through multisectoral systems level actions to address the social determinants of risk distribution. Conclusions: Residents do not get the crucial information on radon health risk and report barriers in testing and engaging in protective action. Risk perceptions are subjective and influenced by micro and macro level factors. Inducing protective action to reduce risk requires comprehensive interventions taking into account dual perceptions of the threat. Future research can explore the dual aspects of risk perception and examine the contents of the risk communication message. Policy should address the shared responsibility of both governments and residents in tackling the issue with reasonable incentives and mandatory regulations.

A representative national survey on population exposure to radon in Italian dwellings was carried out from 1989 to 1994, with the co-operation of the National Health Service. The measurements were performed by 19 Regional Laboratories, all using the same techniques and protocols. A stratified, two-stage sampling procedure was used to sample families. The sampled families were approached door-to-door to maximize response. To optimize the quality of the measurements, two dosimeters, each containing two alpha track detectors, were placed together in one room (typically the bedroom) for two consecutive 6-mo periods. The distribution of annual radon concentration was derived from measurements in 4,866 dwellings. The average value is 75 Bq m-' and the fractions of dwellings above the reference levels of 150,200,400, and 600 Bq m-' are 8.7%, 4.7%, 1.09' 0, and 0.2%, respectively. The geometric mean is 57 Bq m-3 while the geometric standard deviation is 2.0. The average values in the Italian Regions fall within the 20-120 Bq m-3 range. When the average radon concentration is examined vs. story, building materials seem to play a significant role. The average lifetime risk of lung cancer for chronic radon exposure of Italian population at home would be about 5 X using the risk factor proposed by the ICRP in 1993.

Two examples of industrial by-products having a slightly elevated content of radionuclides are considered: coal fly ash and phosphogypsum. The properties of both are reviewed and the advantages of their re-using in construction are shown, as well as the problems caused by elevated content of chemical/radioactive contaminants. The problem of utilizing such byproducts in construction is discussed. Radiological aspects and legislation issues are analyzed. The tendency to develop stricter environmental norms observed in ...

In this paper, forty samples of building materials collected from local market in Dakahlia Governorate, Egypt. The radon concentration in these samples were measured using solid state nuclear track detector. Solid state nuclear track detectors have become an important tool in every investigation of the radon levels in the surrounding environment. The obtained results have shown that the highest average of radon concentration in granite samples and the average value is 845.43 Bqm-3, while the lowest average value is white cement 68.42 Bqm-3. The present work is important to detect any harmful radiation in our houses that affect human and to establish a data base for building materials which, used in a local market. The obtained results show that the radon concentrations of the most samples are below the allowed limit of ICRP.

Due to a recent upward trend in the price of uranium and subsequent increased interest in uranium mining, accurate modeling of baseline dose from environmental sources of radioactivity is of increasing interest. Residual radioactivity model and code (RESRAD) is a program used to model environmental movement and calculate the dose due to the inhalation, ingestion, and exposure to radioactive materials following a placement. This paper presents a novel use of RESRAD for the calculation of dose from non-enhanced, or ancient, naturally occurring radioactive material (NORM). In order to use RESRAD to calculate the total effective dose (TED) due to ancient NORM, a procedural adaptation was developed to negate the effects of time progressive distribution of radioactive materials. A dose due to United States' average concentrations of uranium, actinium, and thorium series radionuclides was then calculated. For adults exposed in a residential setting and assumed to eat significant amounts of food grown in NORM concentrated areas, the annual dose due to national average NORM concentrations was 0.935 mSv y ؊1 . A set of environmental dose factors were calculated for simple estimation of dose from uranium, thorium, and actinium series radionuclides for various age groups and exposure scenarios as a function of elemental uranium and thorium activity concentrations in groundwater and soil. The values of these factors for uranium were lowest for an adult exposed in an industrial setting: 0.00476 Sv kg Bq ؊1 y ؊1 for soil and 0.00596 Sv m 3 Bq ؊1 y ؊1 for water (assuming a 1:1 234 U: 238 U activity ratio in water). The uranium factors were highest for infants exposed in a residential setting and assumed to ingest food grown onsite: 34.8 Sv kg Bq ؊1 y ؊1 in soil and 13.0 Sv m 3 Bq ؊1 y ؊1 in water. Health Phys. 97(1):50 -67; 2009

Exposing the Raduet Rn -Tn solid-state nuclear track detectors, radon (Rn: 222 Rn) and thoron (Tn: 220 Rn) activity concentrations have been measured in 7 kindergartens and 18 elementary schools in Slovenia. Diurnal variations of both gases were monitored using a Rad7 device. The Rn concentration was in the range from 145 to 794 Bq m -3 in kindergartens and from 70 to 770 Bq m -3 in schools, and the Tn concentration was in the range from 21 to 73 Bq m -3 in kindergartens and from 4 to 91 Bq m -3 in schools. The Tn versus Rn concentration ratio varied from 0.02 to 0.83. Monthly effective doses due to radon and its decay products ranged from 109 to 600 mSv month -1 in kindergartens and from 21 to 232 mSv month -1 in schools, and those due to thoron and its decay products ranged from 3.8 to 13.3 mSv month -1 in kindergartens and from 0.29 to 6.62 mSv month -1 in schools. The contribution of thoron to the total effective dose was from 1.3 to 11 % in kindergartens and from 0.4 to 17 % in schools.