Short-lived Progeny Research Articles

Abstract SY39-01: Stem cells in squamous cell carcinomas: Their biology, heterogeneity, and resistance to therapy

Abstract Tissue stem cells self-renew long term and differentiate into one or more tissues. Many stem cells are used sparingly to replenish cells during normal homeostasis. However, even stem cells that are quiescent must be able to respond quickly to injury in order to fuel rapid tissue regeneration. How stem cells govern tissue growth is of fundamental importance to our understanding of normal tissue maintenance and wound repair. Increasing evidence suggests that the regulatory circuitry governing the balancing act between quiescence and proliferation is often at the root of cancers. The hair follicle is an ideal model for dissecting how stem cells remain quiescent during times of minimal wear and tear, how these cells become mobilized during the cyclical bouts of hair growth and wound repair, and how the normal process of stem cell activation goes awry in cancer. We have identified and characterized at a molecular level an important stem cell niche within the hair follicle. We have mapped the chromatin landscape of these stem cells while they reside quiescently in this niche, and elucidated how this changes when the stem cells become activated to proliferate and progress along their lineage to generate short-lived progeny. We have also shown that when these stem cells exit their niche during wound repair, they undergo marked chromatin remodeling, a change functionally required to enable stem cells to survive in a stressful tissue environment. We have begun to uncover the underlying mechanisms by which stem cells receive these external signals from the wound microenvironment and transmit them to the nucleus to elicit chromatin remodeling. Intriguingly in cancer, the initial steps of wound repair are recapitulated, but the off signals that prompt stem cells to return to quiescence following repair are no longer operative. Our in vivo chromatin analyses have yielded important insights into the underlying mechanisms. These epithelial stem cells are known to be a source of squamous cell carcinomas (SCCs), which, as a class, are one of the most common and life-threatening cancers worldwide. Using mice as our model, we have applied our knowledge of normal skin stem cells to explore the tumor-initiating "stem cells" of SCCs. Remarkably, within the SSC, these tumor-initiating cells reside at the tumor-stroma interface, where they exist in two distinct states. The slower-cycling state occurs in stem cells close to the perivasculature, rich in TGF-β. These stem cells undergo SMAD2-signaling, express EMT markers, break down the basement membrane, and invade. They are also resistant to cisplatin chemotherapy. By contrast, the stem cells that do not receive the TGFβ signal proliferate faster but apoptose upon cisplatin treatment. Thus, within the developing SCC, heterogeneity due to an ever-changing tumor microenvironment elicits distinct behaviors in its stem cells, both of which contribute to tumor growth and malignancy. In the past year, we have continued to make inroads into understanding how tumor stem cells receive signals from their microenvironment that lead to changes in their behavior but also in their resistance to therapy. I will discuss our most recent discoveries, including transcriptional and translational remodeling in response to tumor stressful environments. Together, our multipronged approaches should be useful in our ever-growing endeavors to understand the underlying basis for squamous cell carcinomas, which are not only one of the most common but also one of the most life-threatening cancers worldwide. Citation Format: Elaine Fuchs. Stem cells in squamous cell carcinomas: Their biology, heterogeneity, and resistance to therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr SY39-01.

Establishment of detailed respiratory tract model and Monte Carlo simulation of radon progeny caused dose

As radon is one of the most important natural radiation sources, its radiation hazard has always been a concern. α and β particles emitted by short-lived radioactive radon progeny nuclides could result in a high local dose and induce radiation damage to the respiratory tract. A detailed respiratory tract model needs to be built and dose distribution in the respiratory tract should be studied to reflect the characteristics of energy deposition caused by radon and its progeny. Therefore, in the present work, a dosimetric study was conducted on the respiratory tract and non-uniform dose distribution in the bronchial region was studied. First, a detailed voxel respiratory tract model was established based on the anatomic bronchial parameters of an adult Chinese male. The dimensional parameters of the tracheo-bronchial tree of an adult male adopted in ICRP Publication 66 (ICRP Human Respiratory Tract Model for Radiological Protection ICRP Publication 66 (Oxford: Pergamon)), featured by consecutive 16 generations of bronchi structures to express the irregular structure of the respiratory tract and the radiosensitive tissues in the bronchial region, were also built for dosimetric study. Then the deposition and clearance models recommended by ICRP were used to analyse the regional deposition and transfer in the respiratory tract, and a fluid dynamic simulation was used to obtain 3D distribution of radon progeny aerosol particles in the bronchial region. The result showed that the highest deposition fraction density occurs at the first and second generations of bronchi. Furthermore, the detailed voxel respiratory tract model along with the Monte Carlo method were used to obtain dose distribution in the BB region. It was found that the dose distribution in the respiratory tract is very non-uniform and the maximum voxel dose is about 30 times higher than the average voxel dose. The dose conversion factor (DCF) for lung in the home environment derived with the dosimetry method in the present work is 9.86 mSv·WLM−1. Sensitivity analysis was performed for the parameters involved in the DCF calculation and it was found that the unattached fraction and breathing rate influence the DCF the most.

High time-resolved radon progeny measurements in the Arctic region (Svalbard islands, Norway): results and potentialities

Abstract. The estimation of radon progeny in the Arctic region represents a scientific challenge due to the required low limit of detection in consideration of the limited radon emanation associated with permafrost dynamics. This preliminary study highlighted, for the first time above 70∘ N, the possibility to monitor radon progeny in the Arctic region with a higher time resolution. The composition of the radon progeny offered the opportunity to identify air masses dominated by long-range transport, in presence or absence of near-constant radon progeny instead of long- and short-lived progenies. Furthermore, the different ratio between radon and thoron progenies evidenced the contributions of local emissions and atmospheric stability. Two different emanation periods were defined in accordance with the permafrost dynamics at the ground and several accumulation windows were recognized coherently to the meteo-climatic conditions occurring at the study site.

Dosimetry is Key to Good Epidemiology: Workers at Mallinckrodt Chemical Works had Seven Different Source Exposures.

Mallinckrodt Chemical Works was the earliest uranium processing facility in the Manhattan Project, beginning in 1942. Even then, concern existed about possible health effects resulting from exposure to radiation and pitchblende dust. This concern was well founded as the facility processed Belgian Congo pitchblende ore that was up to 60% pure uranium with high U content and up to 100 mg of radium per ton. Workers were exposed to external gamma radiation plus internal radiation from inhalation and ingestion of pitchblende dust (uranium, radium, and silica). Multiple sources of exposure were available for organ dose reconstruction to a degree unique for an epidemiologic study. Personal film badge measures available from 1945 captured external exposures. Additional external exposure included 15,518 occupational medical x-rays and 210 radiation exposure records from other facilities outside of Mallinckrodt employment. Organ dose calculations considered organ-specific coefficients that account for photon energy and job-specific orientation of workers to the radiation source during processing. Intakes of uranium and radium were based on 39,451 uranium urine bioassays and 2,341 breath radon measurements, and International Commission on Radiological Protection (ICRP) Publication 68 biokinetic models were used to estimate organ-specific radiation absorbed dose. Estimates of exposure to airborne radon and its short-lived progeny were based on radon measurements in work areas where radium-containing materials were handled or stored, together with estimated exposure times in these areas based on job titles. Dose estimates for radon and its short-lived progeny were based on models and methods recently recommended in ICRP Publication 137. This comprehensive dosimetric approach follows methods outlined by the National Council on Radiation Protection Scientific Committee 6-9 for the Million Worker Study. Annual doses were calculated for six organs: lung, brain, heart, kidney, colon and red bone marrow. Evaluation and adjustment for individual cumulative measures of pitchblende dust inhalation were made for lung and kidney diseases.

DETERMINATION OF EQUILIBRIUM EQUIVALENT OF THORON AND RADON CONCENTRATION IN SCHOOLS OF THE CITY OF BANJA LUKA

The paper analyzes the relationship of short-lived progenies of radon and thoron decay. Concentration of progenies is expressed as equilibrium equivalent concentration of EETC (equilibrium equivalent concentration of thoron) and EERC (equilibrium equivalent concentration of radon) abbreviated (EEТC/ EERC). Мeasuring of radon and thoron progenies was carried out in 25 schools in the territory of the City of Banja Luka using CR -39 (RADUET) detectors. Detectors were exposed for six months and were set in the staff room at the height of 30 cm from the ceiling in internal wall. The relationship is determined (EEТC/ EERC) and comparison carried out of obtained results with the world standards, and then the correlation coefficient between radon and thoron was determined.

Estimation of indoor radon and thoron in dwellings of Palakkad, Kerala, India using solid state nuclear track detectors

Radon, thoron and their short lived progenies have a significant contribution to natural background radiation. Long term exposure of such radiation increases the probability of occurrence of cancer at low to moderate levels. The present study covers 25 dwellings in Pirayiri region of the Palakkad district, Kerala, India, using twin cup based dosimeter. The data analysis shows that geometric mean of radon gas concentration (25.52 Bqm−3) and thoron concentration (14.58 Bqm−3) are slightly higher than the nation wide average value. However, the radon gas concentration range is within the limit of UNSCEAR East Asian values. Annual Effective Inhalation Dose limit is less than the action level limit (3 mSv/y), recommended by International Commission on Radiological Protection (ICRP).

Modeling of indoor 222Rn distribution in ventilated room and resulting radiation doses measured in the respiratory tract

Most of radiation hazard of indoor radon is largely due to the radon progenies, which are inhaled and deposited in the human respiratory tract. It is therefore important to understanding the distribution of radon and their progeny in indoor environment helps in calculating the inhalation doses due to them. This paper focuses on effects of exhalation from different sources (wall, floor and ceiling) and the ventilation profile on distribution of the concentrations of radon and their progeny indoor. The radon exhalation rate from walls, floor and ceiling, and ventilation rate were measured as a part of this study and are used as input in Finite Volume Method (FVM) simulation. The findings show that the radon concentration which is distributed in a non-homogeneous way in the room is due to the difference in the radon concentration of different sources (wall, floor and ceiling). Moreover, the radon concentration is much larger near walls, and decreases in the middle of the room because of the effect of air velocity. It has also been found that the distributions of unattached and attached fraction of 218Po, 214Pb and 214Po radionuclides are similar to that of 222Rn. In addition, equilibrium fraction F and the unattached fraction ( fj) of 218Po, 214Pb and 214Po radionuclides for different values of the attachment rate were evaluated. The committed equivalent doses due to 218Po and 214Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of workers from the inhalation of indoor air.

Study of <formula> <tex>$^{222}$</tex> </formula>Rn Absorption and Detection Properties of EJ-212 and BC-400 Plastic Scintillators

This paper presents a study of the 222Rn absorption properties of EJ-212 and BC-400 plastic scintillators (PSs). The diffusion length and the partition coefficient of 222Rn from air are determined at $T=21^{\circ }\text{C}$ , which fully characterize the radon absorption properties of these PS at this temperature. The pulse-shape discrimination (PSD) properties of the PS and their energy resolution are studied experimentally. It is found that PSD is applicable to discriminate between the $\alpha $ - and $\beta $ -pulses of the 222Rn and its short-lived progeny absorbed in the volume of the PS and that the $\alpha $ -peaks energy resolution of PS is the same as that of a liquid scintillation cocktail. The steady-state 222Rn diffusion in plate-parallel PS is studied and the transient time needed to reach it is estimated. Examples of steady-state distributions of the 222Rn activity concentration in the volume of PS are presented and discussed. The results of this study have two applications: for the measurement of 222Rn in air by absorption in EJ-212 or BC-400 PSs and for the estimation of the contribution of 222Rn to the background signal when the PSs are used for other measurements like low-background measurements and portal monitoring.

Daily variation of radon gas and its short-lived progeny concentration near ground level and estimation of aerosol residence time**Project supported by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah (Grant No. 291/965/1434).

Atmospheric concentrations of radon (222Rn) gas and its short-lived progenies 218Po, 214Pb, and 214Po were continuously monitored every four hours at the ground level in Jeddah city, Kingdom of Saudi Arabia. The measurements were performed three times every week, starting from November 2014 to October 2015. A method of electrostatic precipitation of positively charged 218Po and 214Po by a positive voltage was applied for determining 222Rn gas concentration. The short-lived 222Rn progeny concentration was determined by using a filter holder connected with the alpha-spectrometric technique. The meteorological parameters (relative air humidity, air temperature, and wind speed) were determined during the measurements of 222Rn and its progeny concentrations. 222Rn gas as well as its short-lived progeny concentration display a daily and seasonal variation with high values in the night and early morning hours as compared to low values at noon and in the afternoon. The observed monthly atmospheric concentrations showed a seasonal trend with the highest values in the autumn/winter season and the lowest values in the spring/summer season. Moreover, and in parallel with alpha-spectrometric measurements, a single filter-holder was used to collect air samples. The deposited activities of 214Pb and the long-lived 222Rn daughter 210Pb on the filter were measured with the gamma spectrometric technique. The measured activity concentrations of 214Pb by both techniques were found to be relatively equal largely. The highest mean seasonally activity concentrations of 210Pb were observed in the autumn/winter season while the lowest mean were observed in the spring/summer season. The mean residence time (MRT) of aerosol particles in the atmospheric air could be estimated from the activity ratios of 210Pb/214Pb.

Optimization of the Timepix chip to measurement of radon, thoron and their progenies

Radon and thoron as well as their short-lived progenies are decay products of the radium and thorium series decays. They are the most important radionuclide elements with respect to public exposure. To utilize the semiconductor pixel radiation Timepix chip for the measurement of active and real-time alpha particles from radon, thoron and their progenies, it is necessary to check the registration and visualization of the chip.An energy check for radon, thoron and their progenies, as well as for 241Am and210Po sources, was performed using the radon and thoron chambers at NIRS (National Institute of Radiological Sciences). The check found an energy resolution of 200 keV with a 14% efficiency as well as a linear dependency between the channel number (cluster volume) and the energy. The coefficient of determination r2 of 0.99 for the range of 5 to 9 MeV was calculated. In addition, an offset for specific Timepix configurations between pre-calibration for low energy from 6 to 60 keV, and the actual calibration for alpha particles with energies from 4000 to 9000 keV, was detected.

Impact of haze-fog days to radon progeny equilibrium factor and discussion of related factors

The equilibrium factor F between radon and its short-lived progenies is an important parameter to estimate radon exposure of humans. Therefore, indoor and outdoor concentrations of radon and its short-lived radon progeny were measured in Beijing area using a continuously measuring device, in an effort to obtain information on the F value. The results showed that the mean values of F were 0.58 ± 0.13 (0.25-0.95, n = 305) and 0.52 ± 0.12 (0.31-0.91, n = 64) for indoor and outdoor, respectively. The indoor F value during haze-fog days was higher than the typical value of 0.4 recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation, and it was also higher than the values of 0.47 and 0.49 reported in the literature. A positive correlation was observed between indoor F values and PM2.5 concentrations (R (2) = 0.71). Since 2013, owing to frequent heavy haze-fog events in Beijing and surrounding areas, the number of the days with severe pollution remains at a high level. Future studies on the impact of the ambient fine particulate matter on indoor radon progeny equilibrium factor F could be important.

Radon and Thoron Measured in Petrol and Gas-oil Exhaust Fumes by Using CR-39 and LR-115 II Nuclear Track Detectors: Radiation Doses to the Respiratory Tract of Mechanic Workers.

Mechanic workers are exposed to exhaust fumes when controlling vehicle engines in motion inside repair shops. To assess radiation doses due to radon short-lived progeny from the inhalation of exhaust fumes by mechanic workers, concentrations of these radionuclides were measured in petrol (gasoline) and gas-oil exhaust fumes by evaluating mean critical angles of etching of the CR-39 and LR-115 type II SSNTDs for alpha particles emitted by the radon and thoron decay series. Committed effective doses due to ²¹⁸Po and ²¹⁴Po short-lived radon decay products from the inhalation of petrol and gas-oil exhaust fumes by workers were evaluated. A maximum value of 1.35 mSv y⁻¹ due to radon short-lived decay products from the inhalation of gas-oil exhaust fumes by mechanic workers was found, which is lower than the (3-10 mSv y⁻¹) dose limit interval for workers.

Radon sources and associated risk in terms of exposure and dose.

Radon concerns the international scientific community from the early twentieth century, initially as radium emanation and nearly the second half of the century as a significant hazard to human health. The initial brilliant period of its use as medicine was followed by a period of intense concern for its health effects. Miners in Europe and later in the U.S were the primary target groups surveyed. Nowadays, there is a concrete evidence that radon and its progeny can cause lung cancer (1). Human activities may create or modify pathways increasing indoor radon concentration compared to outdoor background. These pathways can be controlled by preventive and corrective actions (2). Indoor radon and its short-lived progeny either attached on aerosol particles or free, compose an air mixture that carries a significant energy amount [Potential Alpha-Energy Concentration (PAEC)]. Prior research at that topic focused on the exposure on PAEC and the dose delivered by the human body or tissues. Special mention was made to the case of water workers due to inadequate data. Furthermore, radon risk assessment and relevant legislation for the dose delivered by man from radon and its progeny has been also reviewed.

Estimating dosimetric quantities of radon progeny using human CT scan data and small tissue volume analysis with Geant4 code system

Estimating the health effects of radon exposure is of great interest because radon is considered the second leading cause of lung cancer after smoking. The dose-response curve is not well understood at low-dose levels where radon exposure is estimated. Therefore, the health mechanisms of radiation due to radon progeny at the cellular and molecular levels are of interest for providing an indication of a possible threshold value above which the exposure may indicate cancer formation. In this paper we present a macroscopic and cellular level numerical analysis of the radon-induced dose estimates based on the Geant4 code system. Macroscopic estimates are assessed based on patient-specific computer tomography scans that provide geometries easily applicable to modeling radiation effects of the radon progeny sources. A small tissue volumes analysis based on the Geant4 code system is developed so as to provide information about the interactions and particle track structures at the microscopic (cellular) levels producing the dosimetric effects of radon short-lived progenies. The results presented in this paper also call attention to the capabilities of Geant4 to provide radon-related dosimetric parameters of large and small-scale biological systems.

Radon, Thoron and Progeny Measured in Urban Health Centres and the Resulting Radiation Doses to Doctors, Nurses and Patients from the Inhalation of Air

Doctors and nurses spent about 8 hours a day inside urban health centres examining a large number of patients. To assess radiation dose due to the attached and unattached fractions of the short-lived alpha-emitting radon decay products from the inhalation of air by working personnel and patients, concentrations of these radionuclides as well as those of radon and thoron gases were measured in indoor air of different health centres in the city of Marrakech (Morocco) by means of CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). Committed equivalent doses per hour of exposure due to the attached and unattached fractions of 218Po and 214Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of individuals from the inhalation of air inside the studied health centres. The influence of the activity of the attached and unattached fractions of 218Po and 214Po and mass of the tissue on the committed equivalent doses per hour of exposure was investigated. Annual committed effective doses due to the attached and unattached fractions of218Po and 214Po radon short-lived progeny from the inhalation of air by doctors, nurses and patients inside the studied hospitals were determined. A maximum value of 7.1 mSv y-1 was found for doctors working 40 hours per week.

Activity determination of 227Ac and 223Ra by means of liquid scintillation counting and determination of nuclear decay data

The activity concentrations of solutions containing 227Ac and 223Ra in equilibrium with their progenies, respectively, were measured by means of liquid scintillation counting. The counting efficiencies were determined with the aid of a free parameter model. The corresponding calculations comprise the computation of several alpha, beta and beta/gamma branches. For short-lived progenies like 215Po the counting efficiency depends on the counter dead time. Measurements were made in custom-built triple-to-double coincidence ratio (TDCR) systems and various dead-time adjustments were used. In addition, two commercial counters were used to apply the CIEMAT/NIST efficiency tracing technique using 3H as a tracer.For the 227Ac solution, the overall relative standard uncertainty of the activity concentration was found to be 0.93%. The dominant uncertainty components are assigned to the efficiency computation of the low-energy beta transitions of 227Ac. We have identified a need for improved 227Ac decay data to achieve a significant reduction in the overall uncertainty.In the case of 223Ra, the activity concentrations were determined with relative standard uncertainties below 0.3%. Hence, PTB is prepared to provide calibration services for 223Ra, which is an isotope of increasing interest in nuclear medicine.The TDCR measurements were also used to determine the half-life of 223Ra. The decay was followed for about 58 days and a half-life T1/2=11.4362(50)d was obtained.

Evaluation of occupational radiological exposures associated with a low ore grade underground uranium mine of Bagjata, India

In an underground uranium mine, workers are mainly exposed to radon and its short-lived progenies and to external gamma radiation during their work. Assessment of radon and gamma radiation levels were carried out in Bagjata underground uranium mine to estimate the radiation dose to the miners and to adopt necessary control measures to minimize the radiation dose, accordingly. Scintillation cell technique and radiation survey meter were used to measure radon and gamma radiation levels in the mine workings, respectively. The values for radon concentrations in the mine were found to vary from 0.08 to 1.92 kBq m−3 with geometric mean (GM) of 0.23 kBq m−3. Further, gamma absorbed dose rates were found to oscillate between 0.09 and 6.93 μGy h−1, with GM of 0.86 μGy h−1. The total mean annual effective dose received by the members of radiation workers of Bagjata mine from internal and external exposure was estimated to be 3.2 mSv year−1 which is about 16 % of the prescribed dose limit of 20 mSv year−1, averaged over defined periods of 5 years.

Attached and unattached fractions of short-lived radon decay products in outdoor environments: effect on the human respiratory system

The authors developed a model for determining the alpha- and beta-activities per unit volume of air due to radon ((222)Rn), thoron ((220)Rn) and their decay products attached and unattached to the aerosol in the outdoor air at the workplace in natural conditions at different locations in Morocco by using both CR-39 and LR-115 type II solid-state nuclear track detectors. In addition, the percentage of (218)Po, (214)Pb and (214)Po radionuclides attached to the aerosols and the unattached fraction f(j) for different values of the attachment rate were evaluated. Radon and thoron concentrations in outdoor air of the studied different locations were found to vary from 9.20±0.8 to 16.30±1.50 Bq m(-3) and 0.22±0.02 to 1.80±0.20 Bq m(-3), respectively. The committed equivalent doses due to the radon short-lived progeny (218)Po and (214)Po attached and unattached to the aerosol air were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of outdoor air.

Response of CR-39 Polymer Radon-Sensors via Monte-Carlo Modelling and Measurements

International studies of radon indoors and in workplaces have shown significant radiation dose burden of the general population due to inhalation of radon (222Rn) and its short-lived progeny (218Po,214Pb, 214Bi, 214Po). As far as atmospheric radon concerns, 222Rn, is not necessarily in equilibrium with its short-lived progeny. For this reason, radon’s equilibrium factor F was solved graphically as a function of the track density ratio R=TB/TR, namely of the ratio between the recordings of cup-type and bare CR-39 detectors. TB was computed through special Monte-Carlo codes which were implemented for the calculation of the efficiency of bare CR-39 polymers, regarding their ability in sensing the alpha particles emitted by the decay of radon and its short-lived progeny. For a realistic approach, Monte-Carlo inputs were adjusted according to actual experimental concentration measurements of radon, decay products and F of Greek apartment dwellings. Concentration measurements were further utilized for the calculation of the unattached fraction, fp, in terms of Potential Alpha Energy Concentration (PAEC, defined as the sum of the initial - per volume - energies of all alpha particles emitted due to the decay of radon and its short-lived progeny that are present within a certain amount of air). This was employed for the calculation of F in terms of ratio (A4/A0), where Ai represents the activity concentration of radon (i=0) and 214Po (i=4) respectively. Measured and calculated values of F were plotted versus R. The results were fitted and checked with model’s predictions.

Assessment of the radiological impact of gamma and radon dose rates at former U mining sites in Tajikistan

An assessment of the radiological situation due to exposure to gamma radiation, radon (222Rn) and thoron (220Rn) was carried out at former uranium (U) mining and processing sites in Taboshar and at Digmai in Tajikistan. Gamma dose rate measurements were made using various field instruments. 222Rn/220Rn measurements were carried out with field instruments for instantaneous measurements and then discriminative 222Rn/220Rn solid state nuclear track detectors (SSNTD) were used for longer representative measurements. The detectors were exposed for an extended period of time in different outdoor and indoor public and residential environments at the selected U legacy sites. The results showed that gamma, 222Rn and 220Rn doses were in general low, which consequently implies a low to relatively low radiological risk. The radiation doses deriving from external radiation (gamma dose rate), indoor 222Rn and 220Rn with their short-lived progenies did not exceed national or international standards. At none of the sites investigated did the average individual annual effective doses exceed 10 mSv, the recommended threshold value for the general public. A radiation hazard could be associated with exceptional situations, such as elevated exposures to ionizing radiation at the Digmai tailings site and/or in industrial facilities, where gamma and 222Rn/220Rn dose rates could reach values of several 10 mSv/a. Current doses of ionizing radiation do not represent a hazard to the health of the resident public, with the exception of some specific situations. These issues should be adequately addressed to further reduce needless exposure of the resident public to ionizing radiation.