Update of Ireland's national average indoor radon concentration - Application of a new survey protocol

A psycho-social-environmental lens on radon air pollutant: authorities', mitigation contractors', and residents' perceptions of barriers and facilitators to domestic radon mitigation

Introduction

Radon is a major indoor air pollutant that poses a significant risk of lung cancer to those exposed in their homes. While mitigation of high radon levels in homes has been shown to be effective, home mitigation rates remain low. This study examines the barriers and facilitators to radon mitigation in homes from the perspectives of authorities responsible for radon risk management, the mitigation industry (contractors), and residents in four European countries (Belgium, Ireland, Slovenia, and the UK) with high radon risks and low mitigation rates.

Methods

A multi-method approach was used to gather data from various stakeholders, including online surveys, content analysis of legal documents, group interviews, workshops, and focus groups.

Results

Authorities, contractors, and residents identified various facilitators to radon mitigation, including legal requirements for mitigation, awareness campaigns, low mitigation costs, availability of financial support, accreditation of mitigation contractors, and a perception of radon as a health threat. However, barriers to mitigation were also identified, such as a lack of awareness, fragmented mitigation processes, and inadequate communication between stakeholders.

Discussion

The study highlights the complexity of the radon mitigation process and suggests that interventions aimed at increasing mitigation rates should target stakeholders beyond just residents, such as constructors, health professionals, and policy makers. An integrated approach to radon mitigation, from policy to provision, is necessary to effectively lower levels of this indoor air pollutant.

Assessment of indoor radon exposure in South Korea

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

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

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

National Radon Action Plans in Europe and Need of Effectiveness Indicators: An Overview of HERCA Activities

Protection of the population and of workers from exposure to radon is a unique challenge in radiation protection. Many coordinated actions and a variety of expertise are needed. Initially, a National Radon Action Plan (NRAP) has been developed and implemented by some countries, while it is currently recommended by international organizations (e.g., World Health Organization) and required by international regulations, such as the European Council Directive 2013/59/Euratom and the International Basic Safety Standards on Radiation Protection and Safety of Radiation Sources, cosponsored by eight international organizations. Within this framework, the Heads of the European Radiological Protection Competent Authorities (HERCA) have organized activities aimed at sharing experiences to contribute toward the development and implementation of effective NRAPs. Two workshops were held in 2014 and 2015, the latter on radon in workplaces. As a follow-up to these, an online event took place in March 2021, and a second specific workshop on NRAP is planned for June 2022. These workshops were attended by experts from the competent authorities of European countries, relevant national and international organizations. The experience of several countries and the outcomes from these workshops have highlighted the need for adequate indicators of the effectiveness and progress of the actions of NRAPs, which could also be useful to implement the principle of optimization and the graded approach in NRAPs. In this paper, the activities of HERCA to support the development and implementation of effective NRAPs are described and some examples of effectiveness indicators are reported, including those already included in the NRAP of some European countries.

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

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

Evaluation of citizen science contributions to radon research

In order to reduce lung cancer due to radon exposure situations, not only authorities and organisations but also citizens may meaningfully contribute to radon mitigation actions. Citizen science (CS) initiatives are recognised for their scientific, societal and policy value related to environmental issues. The purpose of this paper is to identify which CS initiatives in the field of radon exist and evaluate to what extent these CS initiatives contribute to radon research and/or radiation protection from radon. We conducted a systematic review of internet pages and scientific literature (September-December 2020) as well as expert consultation to help us identify and assess CS initiatives on radon (September 2020-February 2021). The ten principles of the European Citizen Science Association have been used as a starting point to develop indicators for the analysis of CS contributions to radon research. The results show that there are at least eight CS initiatives in the world contributing to radon related research which comply, to some degree, with each of the ten principles. In all these initiatives citizens contributed or are contributing meaningfully to radon testing and measurements. However, most of them apply the simplest form of participation (crowdsourcing) and only one focuses on radon mitigation. Moreover, unlike CS initiatives in other environmental areas, those focusing on radon are always led by the authorities and/or universities, in a top-down manner. Yet, results confirm that both the experts in radon-related fields and the citizen scientists from radon prone areas benefit from taking part in radon CS initiatives. Experiences and lessons learned in radon related to CS initiatives are identified and discussed in order to inspire future CS initiatives potentially contributing to reducing exposure to radon as well as to the implementation of national radon action plans.

Designing an Indoor Radon Risk Exposure Indicator (IRREI): An Evaluation Tool for Risk Management and Communication in the IoT Age

The explosive data growth in the current information age requires consistent new methodologies harmonized with the new IoT era for data analysis in a space-time context. Moreover, intuitive data visualization is a central feature in exploring, interpreting, and extracting specific insights for subsequent numerical data representation. This integrated process is normally based on the definition of relevant metrics and specific performance indicators, both computed upon continuous real-time data, considering the specificities of a particular application case for data validation. This article presents an IoT-oriented evaluation tool for Radon Risk Management (RRM), based on the design of a simple and intuitive Indoor Radon Risk Exposure Indicator (IRREI), specifically tailored to be used as a decision-making aid tool for building owners, building designers, and buildings managers, or simply as an alert flag for the problem awareness of ordinary citizens. The proposed methodology was designed for graphic representation aligned with the requirements of the current IoT age, i.e., the methodology is robust enough for continuous data collection with specific Spatio-temporal attributes and, therefore, a set of adequate Radon risk-related metrics can be extracted and proposed. Metrics are summarized considering the application case, taken as a case study for data validation, by including relevant variables to frame the study, such as the regulatory International Commission on Radiological Protection (ICRP) dosimetric limits, building occupancy (spatial dimension), and occupants' exposure periods (temporal dimension). This work has the following main contributions: (1) providing a historical perspective regarding RRM indicator evolution along time; (2) outlining both the formulation and the validation of the proposed IRREI indicator; (3) implementing an IoT-oriented methodology for an RRM indicator; and (4) a discussion on Radon risk public perception, undertaken based on the results obtained after assessment of the IRREI indicator by applying a screening questionnaire with a total of 873 valid answers.

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

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

A New Methodology for Defining Radon Priority Areas in Spain

One of the requirements of EU-BSS (European Basic Safety Standards) is the design and implementation of a National Radon Action Plan in the member states. This should define, as accurately as possible, areas of risk for the presence of radon gas (222Rn) in homes and workplaces. The concept used by the Spanish Nuclear Safety Council (CSN), the body responsible for nuclear safety and radiation protection in Spain, to identify "radon priority areas" is that of radon potential. This paper establishes a different methodology from that used by the CSN, using the same study variables (indoor radon measurements, gamma radiation exposure data, and geological information) to prepare a radon potential map that improves the definition of the areas potentially exposed to radon in Spain. The main advantage of this methodology is that by using simple data processing the definition of these areas is improved. In addition, the application of this methodology can improve the delimitation of radon priority areas and can be applied within the cartographic system used by the European Commission-Joint Research Center (EC-JRC) in the representation of different environmental parameters.

A unique high natural background radiation area - Dose assessment and perspectives

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h^-1 and 1109 nGy h^-1. Indoor radon concentrations ranged from 124 Bq m^-3 to 1015 Bq m^-3. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m^-3 recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

Japanese population dose from natural radiation

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

Passive-Type Radon Monitor Constructed Using a Small Container for Personal Dosimetry

The International Commission on Radiological Protection (ICRP) recently recommended a new dose conversion factor for radon based on the latest epidemiological studies and dosimetric model. It is important to evaluate an inhalation dose from radon and its progeny. In the present study, a passive radon personal monitor was designed using a small container for storing contact lenses and its performance was evaluated. The conversion factor for radon (²²²Rn), the effect of thoron (²²⁰Rn) concentration and the air exchange rate were evaluated using the calibration chamber at Hirosaki University. The minimum and maximum detectable radon concentrations were calculated. The conversion factor was evaluated as 2.0 ± 0.3 tracks cm⁻² per kBq h m⁻³; statistical analyses of results showed no significant effect from thoron concentration. The minimum and maximum detectable radon concentrations were 92 Bq m⁻³ and 231 kBq m⁻³ for a measurement period of three months, respectively. The air exchange rate was estimated to be 0.26 ± 0.16 h⁻¹, whose effect on the measured time-integrated radon concentration was small. These results indicate that the monitor could be used as a wearable monitor for radon measurements, especially in places where radon concentrations may be relatively high, such as mines and caves.

Review of recent radon research in Ireland, OPTI-SDS project and its impact on the National Radon Control Strategy

Radon is a radioactive gas originating from uranium, present in all rocks and soils in the Earth's Crust; emanating from the ground, radon can be released into the atmosphere. It is the greatest source of natural radioactivity exposure for the population and, as declared by the World Health Organization (WHO), the leading cause of lung cancer only after smoking. Although radon is a natural gas, its accumulation provoking elevated indoor radon levels is a result from building practices and thus, not natural. In Ireland, exposure to radon is estimated to be responsible for approximately 14% of all lung cancers, which is equivalent to around 300 lung cancers annually. In 2011, an interagency group was established in Ireland to develop a strategy to address indoor radon exposure, considered a significant public health concern. In 2014 a National Radon Control Strategy (NRCS) for Ireland was first published, giving a list of recommendations to be accomplished in a 4-year period Phase 1. A series of research actions to achieve the effective implementation of the strategy were conducted, including the development of a research project (OPTI-SDS) on the optimum specifications for radon mitigation by soil depressurisation systems. An overview of Phase 1 of the NRCS is presented, including outcomes from the research work carried out.

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

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

An Investigation into Indoor Radon Concentrations in Certified Passive House Homes

The Energy Performance of Buildings Directive (EPBD) has introduced the concept of Nearly Zero Energy Buildings (NZEB) specifying that by 31 December 2020 all new buildings must meet the nearly zero- energy standard, the Passive House standard has emerged as a key enabler for the Nearly Zero Energy Building standard. The combination of Passive House with renewables represents a suitable solution to move to low/zero carbon. The hypothesis in this study is that a certified passive house building with high levels of airtightness with a balanced mechanical ventilation with heat recovery (MVHR) should yield lower indoor radon concentrations. This article presents results and analysis of measured radon levels in a total of 97 certified passive house dwellings using CR-39³ alpha track diffusion radon gas detectors. The results support the hypothesis that certified passive house buildings present lower radon levels. A striking observation to emerge from the data shows a difference in radon distribution between upstairs and downstairs when compared against regular housing. The study is a first for Ireland and the United Kingdom and it has relevance to a much wider context with the significant growth of the passive house standard globally.

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

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

Qualitative overview of indoor radon surveys in Europe

The revised European Directive from 2013 regarding basic safety standard oblige EU Member States to establish a national action plan regarding the exposure to radon. At the same time, International Atomic Energy Agency started technical projects in order to assist countries to establish and implement national radon action. As a consequence, in recent years, in numerous countries national radon surveys were conducted and action plans established, which were not performed before. In this paper, a qualitative overview of radon surveys performed in Europe is given with a special attention to the qualitative and conceptual description of surveys, representativeness and QA/QC (quality assurance/quality control).

Analysis of the spatial variation of indoor radon concentrations (national survey in Bulgaria)

This paper presents the methodology and results of the national radon survey in Bulgaria and its spatial variability. The measurements were carried out in 2778 dwellings using CR-39 track detectors over two successive 9 and 3-month periods from April 2015 to March 2016. The arithmetic (AM) and geometric (GM) means of annual indoor radon concentration were 111 ± 105 Bq/m³ and 81 Bq/m³ (GSD = 2.15), respectively. The distribution of data has been accepted to be log-normal. Two hypotheses have been investigated in the paper. The first one was a spatial variation of indoor radon concentration and the second was spatiality of the factor that influences radon variation. The indoor radon concentrations in the 28 districts have been significantly different, which prove the first hypothesis. The influence of the factors, geology (geotectonic unit, type of rock, and faults distance of the measuring site), type of the region, and the presence of the basement in the building on radon spatial variation, was examined. The analyses have been shown that they significantly affect radon variations but with a relatively small contribution in comparison to the radon variation between district. Furthermore, the significance and contribution of the investigated factors were different in each district, which confirmed the second hypothesis for their spatiality.

Radon survey in Montenegro - A base to set national radon reference and "urgent action" level

The first nationwide indoor radon survey in Montenegro started in 2002 and year-long radon measurements with CR-39 track-etch detectors, within the national grid of 5 km × 5 km and local grids in urban areas of 0.5 km × 0.5 km, were performed in homes in half of the country's territory. The survey continued in 2014 and measurements in the rest of the country were completed at the end of 2015. The 953 valid results, obtained in the national radon survey, give an average radon activity concentration in Montenegrin homes of 110 Bq/m³. Assuming a log-normal distribution of the experimental results, geometric mean GM = 58.3 Bq/m³ and geometric standard deviation GSD = 2.91 are calculated. However, normality tests show that the experimental data are not log-normal, and that they become closest to a log-normal distribution after subtracting from them radon concentration in the outdoor air of 7 Bq/m³, which is theoretically calculated. Such a transformed distribution has GM_tr = 46.7 Bq/m³ and GSD_tr = 3.54. The estimations derived from positing a priory that the experimental results conform to a log-normal distribution underestimate the percentage of homes with radon concentrations at the thresholds of 300 Bq/m³ and above, which is better estimated by using GM_tr and GSD_tr. Based on the results of radon survey, a new national radon reference level of 300 Bq/m³ and an "urgent action level" of 1000 Bq/m³ are suggested, with estimated fractions of the national dwelling stock above these levels of 7.4% and 0.8% respectively. Fractions of homes with radon concentrations above the suggested levels are also estimated for each of the 23 municipalities in Montenegro, using appropriate GM_tr and GSD_tr. The six municipalities which have more than 10% of homes with radon concentration above 300 Bq/m³ are recommended as radon priority areas.

REVIEW OF INDOOR RADON CONCENTRATIONS IN SCHOOLS AND KINDERGARTENS

Analysis includes review of 63 national and regional indoor radon surveys in kindergartens and schools. Preliminary assessment of the worldwide population weighted characteristics of radon concentration in children's institutions is: arithmetic mean = 59 and geometric mean = 36 Bq/m3. Higher indoor radon concentrations in children's institutions in comparison with the dwellings can be explained by characteristics of ventilation, attendance regime and construction features. Special protocol of measurements in the kindergartens and schools is required.

Performance of radon monitors in a purpose-built radon chamber

The purpose of this paper is to benchmark several different radon monitors, by quantifying their accuracy and response time. Radon monitors with different characteristics were tested in a purpose-built radon chamber under reference conditions. The radon concentration in the chamber was controlled and maintained at a stable radon concentration of (2648 ± 85) Bq m^-3 to evaluate the accuracy and precision of these monitors. The response time of the monitors was analysed for two time intervals. To assess the response time of the monitors, radon concentration was varied from a theoretical value of 0-6441 Bq m^-3 and then from 6441 to 2648 Bq m^-3. The results from this study show that general purpose radon monitors are less accurate than those used by radon testing service providers and the research community. All monitors tested reported a mean radon concentration within the ±10% of the reference detector value at the radon equilibrium concentration. Different response time analysis methods were proposed and discussed, and for the particular time intervals analysed, response time was found to be slower for those radon monitors intended for general purpose applications.

High Radon Areas and lung cancer prevalence: Evidence from Ireland

This paper examined the relationship between radon risk and lung cancer prevalence using a novel dataset combining spatially-coded survey data with a radon risk map. A logit model was employed to test for significant associations between a high risk of indoor radon and lung cancer prevalence using data on 5590 people aged 50+ from The Irish Longitudinal Study on Ageing (TILDA) and radon risk data from Ireland's Environmental Protection Agency (EPA). The use of data at the individual level allowed a wide range of potentially confounding factors (such as smoking) to be included. Results indicate that those who lived in an area in which 10%-20% of households were above the national reference level (200 Bq/m³) were 2.9-3.1 times more likely to report a lung cancer diagnosis relative to those who lived in areas in which less than 1% of households were above the national reference level.

Logistic regression model for detecting radon prone areas in Ireland

A new high spatial resolution radon risk map of Ireland has been developed, based on a combination of indoor radon measurements (n=31,910) and relevant geological information (i.e. Bedrock Geology, Quaternary Geology, soil permeability and aquifer type). Logistic regression was used to predict the probability of having an indoor radon concentration above the national reference level of 200Bqm^-3 in Ireland. The four geological datasets evaluated were found to be statistically significant, and, based on combinations of these four variables, the predicted probabilities ranged from 0.57% to 75.5%. Results show that the Republic of Ireland may be divided in three main radon risk categories: High (HR), Medium (MR) and Low (LR). The probability of having an indoor radon concentration above 200Bqm^-3 in each area was found to be 19%, 8% and 3%; respectively. In the Republic of Ireland, the population affected by radon concentrations above 200Bqm^-3 is estimated at ca. 460k (about 10% of the total population). Of these, 57% (265k), 35% (160k) and 8% (35k) are in High, Medium and Low Risk Areas, respectively. Our results provide a high spatial resolution utility which permit customised radon-awareness information to be targeted at specific geographic areas.