Radon Exposure Research Articles

DNA methylome profiling in occupational radon exposure miners using an Illumina Infinium Methylation EPIC BeadChip.

A causal relationship between occupational radon exposure in underground miners and lung cancer risk has been demonstrated through large cohort epidemiological studies. However, the mechanisms by which radon exposure causes adverse effects on lung tissue remain unclear. Epigenetic alterations such as DNA methylation may provide new insights into interactions at molecular levels induced by prolonged radon exposure. We used the Illumina Infinium Human Methylation 850K BeadChip to detect and compare genome-wide DNA methylation profiles in peripheral blood samples from underground miners (n=14) and aboveground workers (n=9). The average concentration of radon in underground workplaces was significantly higher than that of aboveground places (1,198Bq·m-3 vs 58Bq·m-3, p<0.001). A total of 191 differentially methylated positions (DMPs) corresponding to 104 hub genes were identified when |Δβ|≥0.1 and p<0.05, with 107 hypermethylated sites and 84 hypomethylated sites. GO and KEGG analysis revealed that differentially methylated genes between underground miners and aboveground workers were prominently enriched in pathways/networks involved in neurotransmitter regulation, immunomodulatory effects and cell adhesion ability. Furthermore, methylation changes of selected genes FERMT1, ALCAM, HLA-DPA1, PON1 and OR2L13 were validated by pyrosequencing, which may play vital roles in these biological processes induced by radon. In summary, the DNA methylation pattern of the underground miners exposed to radon was distinct from that of the aboveground workers. Such abnormalities in the genomic DNA methylation profile associated with prolonged radon exposure are worth studying in terms of neuro- and immune-system regulation, as well as cell adhesion ability in the future.

Preliminary study of chromosome aberrations using Giemsa, two-colour fish, and micronucleus assays in lymphocytes of individuals living in elevated radon concentration areas.

The frequencies of unstable and stable chromosome aberrations and micronuclei were examined in peripheral blood samples from 10 individuals living in elevated radon concentration areas (Takandeang Village, Mamuju, Indonesia). Blood samples from 10 people living in Topoyo Village were used as a control group. For unstable chromosome aberration analysis, a dicentric chromosome assay was conducted using conventional Giemsa staining. Chromosomal painting of chromosomes 1 and 4 using the fluorescence in situ hybridisation technique was also applied to four subjects to assess the stable chromosome aberration. Our study showed no significant increases across all groups in dicentric and other unstable chromosome aberrations, such as rings and acentric fragments. Translocations were found in one person from Takandeang Village and two Topoyo Village inhabitants. The translocations found in the subjects from Takandeang Village were due more to aging factors than to radon exposure. The number of micronuclei per 1000 binucleus cells in Takandeang Village inhabitants was not significantly different than that in the control group (p=0.943). A more comprehensive analysis should be conducted in a subsequent study by increasing the number of study donors and the number of metaphases to be analysed in both dicentric chromosome assay and fluorescence in situ hybridisation assays. Such research could provide valid information on the cytogenetic effects of elevated indoor radon exposure.

Radon Activity Concentration Measurements in the Water Collected from the Lower Zab River in the Kurdistan Region of Iraq

This study aims to assess radon levels in the water of the Lower Zab River. Knowing the radon concentrations is crucial for understanding the potential risks to human health and implementing protective measures. ARAD7-H2O detector has been used to measure the radon concentration in 28 water samples from the Lower Zab River in the Kurdistan Region of Iraq. Results show that the radon activity concentrations ranged from 0.5 to 4 Bq.L−1, with an average of 0.61 Bq.L−1, and the resulting annual effective dose (AED) varied from 0.137 to 60.06 Sv.y−1, with an average of 12.08 Sv.y−1. The average radon concentration and AED in the measured samples are below the reference levels recommended by the ICRP and the World Health Organization. Consequently, the LZR water is suitable for human consumption and use and does not present any health hazards related to radon exposure.

Survival of bronchopulmonary cancers according to radon exposure

Survival of bronchopulmonary cancers according to radon exposure

Risk Assessment of Lung Cancer Caused by Indoor Radon Exposure in China during 2006–2016: A Multicity, Longitudinal Analysis

Indoor radon is a well-documented environmental factor as a second cause of lung cancer. Based on the chronological data on indoor radon concentration, lung cancer incidence, and the distribution of sex-age-specific population, the risk of lung cancer caused by indoor radon exposure in a total of 15 cities in China was assessed by using the risk model developed by the U.S. Environmental Protection Agency (EPA) in this study. The estimate revealed that both the excess relative risk (ERR) and lifetime relative risk (LRR) have obviously increased after 2010. The population attributable risk (PAR) in 2016 was estimated in a range from 6.66% to 22.42%, with a median of 15.33% for the 15 cities. The lung cancer incidence attributed to indoor radon in 2016 ranged from 3.96 to 15.07 per 10,000 population in males and 1.21 to 8.27 per 10,000 population in females. Across age and sex, the risk of lung cancer caused by indoor radon was found more pronounced in males and 40-45 age groups. The chronological variation of radon concentrations was considered in this study; the estimate of lung cancer caused by indoor radon in China is considered more reasonable than ever before.

Updated risk models for lung cancer due to radon exposure in the German Wismut cohort of uranium miners, 1946-2018.

UNSCEAR recently recommended that future research on the lung cancer risk at low radon exposures or exposure rates should focus on more contemporary uranium miners. For this purpose, risk models in the German Wismut cohort of uranium miners were updated extending the follow-up period by 5years to 1946-2018. The full cohort (n = 58,972) and specifically the 1960 + sub-cohort of miners first hired in 1960 or later (n = 26,764) were analyzed. The 1960 + sub-cohort is characterized by low protracted radon exposure of high quality of measurements. Internal Poisson regression was used to estimate the excess relative risk (ERR) for lung cancer per cumulative radon exposure in Working Level Months (WLM). Applying the BEIR VI exposure-age-concentration model, the ERR/100WLM was 2.50 (95% confidence interval (CI) 0.81; 4.18) and 6.92 (95% CI < 0; 16.59) among miners with attained age < 55years, time since exposure 5-14years, and annual exposure rates < 0.5WL in the full (n = 4329 lung cancer deaths) and in the 1960 + sub-cohort (n = 663 lung cancer deaths), respectively. Both ERR/WLM decreased with older attained ages, increasing time since exposure, and higher exposure rates. Findings of the 1960 + sub-cohort are in line with those from large pooled studies, and ERR/WLM are about two times higher than in the full Wismut cohort. Notably, 20-30years after closure of the Wismut mines in 1990, the estimated fraction of lung cancer deaths attributable to occupational radon exposure is still 26% in the full Wismut cohort and 19% in the 1960 + sub-cohort, respectively. This demonstrates the need for radiation protection against radon.

Development and a feasibility study using Gafchromic XRQA2 film as a novel passive radon measurement technique

In the present paper, a novel passive-type radon measurement technique based on Gafchromic XRQA2 film was developed. A Gafchromic XRQA2 film was modified by peeling off a polyester layer to enhance the film sensitivity to alpha particles, which were mainly emitted from radon and its progeny, and the response of the modified Gafchromic XRQA2 film to alpha particles was investigated. The results indicated that, with the increase in time-integrated alpha activity, the darkness of the exposed modified Gafchromic film increased, and only a small alpha energy dependence with less than 2% relative difference in the film response was observed. Next, the modified Gafchromic XRQA2 film was deployed with a RADUET container for radon measurement to evaluate application feasibility, and the radon response of the modified Gafchromic XRQA2 film was compared with the traditional one of a RADUET with CR-39 detector. The radon calibration was investigated using the radon exposure chamber. The obtained calibration functions showed that the net optical density of modified Gafchromic XRQA2 film was directly proportional to the accumulated radon concentration over the exposure period. From the calibration, the minimum and maximum detectable radon concentrations for a three-month measurement period were estimated to be about 390 Bq m−3 and 15,000 Bq m−3, respectively. Moreover, this technique enables to minimize the effect of thoron interference by the RADUET container design. These results suggest that this technique can be used for measuring radon, particularly in areas with potentially high radon concentrations, for example, underground mines and caves.

Applying machine learning to model radon using topsoil geochemistry

Radon is classified as a Class 1 carcinogen, being the leading cause of lung cancer in non-smokers. Understanding the prominent sources of radon helps to mitigate against the adverse effects of radon exposure. Considering soil-gas radon is the main contributor to indoor radon, it is possible that soil geochemistry can be used as a proxy for the soil radon emanation potential or geogenic radon classes for a particular location. This paper investigates the relationship between soil geochemistry and geogenic radon. A large area of 17,983 km2 from the West, Midlands and East of Ireland was selected to represent a range of geology types and radon categories. A rigorous assessment is presented to investigate the relationship of geogenic radon and topsoil geochemistry; using univariate processes (i.e. r2, Pearson r and heatmaps) and multivariate techniques (i.e. principle component analysis (PCA) and machine learning (ML) algorithms including Gaussian process regression, logistic regression and random forest). Here, PCA and ML techniques were used to test the utility of soil geochemistry to predict geogenic radon classes. Gaussian Process Regression yielded the highest accuracy (74%) and f1-score (0.74) of all models. The feature importance (i.e. highest ranking elements for predicting geogenic radon class) from the ML models outputs elements including [Y, Tl, Mn, Cr, Co, Be, Sc and Rb]. The PCA biplot demonstrates that these elements cluster in conjunction with higher geogenic radon categories. Multivariate data analysis reveals that certain elements important for predicting higher geogenic radon classes, also covary together within topsoil samples; here these are termed “radon-prone elements”. Spatial covariance of radon-prone elements permits soil geochemistry to be used as a tool for understanding the distribution of geogenic radon. The methodology presented in this paper provides a comprehensive geo-statistical approach to investigate the relation between topsoil geochemistry and geogenic radon. This approach could be applied as a diagnostic tool to assist radon mitigation measures, hence adding value to legacy soil geochemistry datasets.

Indoor radon monitoring for occupational health reinforcement in Portugal: compliance, prevention, and technological advancements

This article highlights the relevance of indoor radon monitoring for occupational health protection, disease prevention, and compliance with safety regulations. Radon, a colorless, odorless, and tasteless radioactive gas, is a leading cause of lung cancer after tobacco smoking, and therefore in situ monitoring is fundamental to identify areas with high radon levels so that remediation measures must be implemented to reduce indoor exposure. The article gives an overview of the regulations in force in Portugal for indoor radon monitoring and identifies the responsibilities of different authorities and organizations in ensuring compliance with radiological protection requirements. It also outlines the legal framework for radon protection in Portugal, including the identification of reference levels for radon concentration in workplaces and dwellings, and the need to implement measures concerning indoor radon exposure reduction. Additionally, it is detailed the process of monitoring radon in indoor environments, including the selection of an appropriate measurement device and the necessary measurement time, and the need to inform and train workers about the risks associated with radon exposure. In short, this review provides information on the importance of radon monitoring and the measures required to ensure public safety.

Radiometric analysis of Brazilian commercial ornamental stones

The term “commercial ornamental stones” comprises different natural stones with different mineralogical components and the distribution and amount of natural radionuclides depended on the mineralogy. Few studies on natural radioactivity in ornamental stones carried out in Rio de Janeiro (Brazil) and the present work were carried out in order to analyze the distribution of activity concentration in these materials. The activity concentration of 238U, 235U, 226Ra, 232Th and 40K in Ornamental Stones measured using γ-ray spectrometry to estimate the radiation hazard as well as establishing a database for radioactivity levels. Samples were collected in stores in Rio de Janeiro, carefully transported, weighed, packed with PVC film and left to rest for at least 45 days to reach secular equilibrium. Samples analyzed by gamma spectrometry using a hyper pure germanium detector (HPGE). Detection efficiency for each sample was obtained using LabSOCS software. The activity concentrations for samples were within the ranges (0.83 ± 0.15 to 39.96 ± 1.19, 8.04 ± 2.54 to 111.36 ± 13.33, 0.43 ± 0.03 to 264.58 ± 0.98, BDL to 8.17± 0.65 and 1.30 ± 0.57 to 1567.01 ± 65.08) Bq⋅kg−1 for 238U, 226Ra, 232Th, 235U and 40K, respectively. The world average for building materials is 50 Bq⋅kg−1 for 238U, 50 Bq.kg−1 for 232Th and 500 Bq⋅kg−1 for 40K. In the present work, the average for granite was 19.43 ± 0.39 Bq⋅kg−1 for 238U, 56.70 ± 1.13 Bq⋅kg−1 for 232Th and 1113.28 ± 20.27 Bq⋅kg−1 for 40K, thus the values for 232Th and 238U are above the world average. Analyzing for the granite that showed the highest concentrations of activity the average values of Transport Rate was 3.12 ± 0.04 Bq⋅m−2⋅s−1, Emanation Rate was 0.16 ± 0.00 Bq⋅kg−1⋅s−1, Exhalation Flow was 530.26 ± 6.05 Bq⋅m−3, Effective Equivalent Dose Due to Radon Exposure was 0.78 ± 0.01 WLM⋅year−1 and Annual Effective Dose Due to Radon and Thoron was 7.02 ± 0.10 mSv⋅year−1. Annual Effective Dose Due to Radon and Thoron it is above the annual limit for public individuals which is 1 mSv⋅year−1 and below the occupationally exposed individual, which is 20 mSv⋅year−1 in an average of 5 years, it does not exceed the maximum level recommended by ICRP-60.

Characterizing human health damage from ionizing radiation in life cycle assessment

PurposeAlthough a wide number of industrial processes routinely release radionuclides into the environment, the resulting potential impacts on human health have been largely overlooked in life cycle assessment (LCA). As part of the Life Cycle Initiative project on Global Guidance for Life Cycle Impact Assessment Indicators and Methods (GLAM), we aim to develop a consensus-based source-to-damage framework and factors for characterizing human health damage from ionizing radiation in LCA.MethodsOur framework comprises four modules. The fate and exposure modules are based on UCrad, an earlier developed compartment-based environmental model for radionuclides. The focus of the present work is on the dose response and severity modules, which are based on most recent data from the International Committee on Radiological Protection and the Global Burden of Disease project series. The characterization factors are expressed in terms of DALY per kBq released.Results and discussionsWe obtain characterization factors for 115 radionuclides and 8 environmental compartments. To evaluate our approach, we compare both effect factors (combining dose response and severity) and characterization factors with those proposed in earlier studies. Our analysis demonstrates that differences are explicable by the different approaches used in the fate and exposure modelling. We also test the sensitivity of our factors to different approaches for filling data gaps, suggesting that our factors are robust. Finally, we apply our factors in an illustrative case study on rice production and consumption under various scenarios to identify dominant radionuclides and how these differ when other approaches are used.ConclusionsOur framework is aligned with widely adopted methodologies for human health impact assessment, thus enabling robust comparisons, and covers nearly all radionuclides released by anthropogenic activities, including those that may arise from disposal of nuclear waste. Our factors are readily applicable for assessing radionuclide emissions in LCA. As next step we recommend (i) incorporating decay products into the fate model and (ii) integrating a model for indoor emissions of radon and indoor exposure to naturally occurring radionuclides (NORM).

Technical Report Evaluation and study of radon occupational exposure levels in dams: a case study of the Gallery of Medau Zirimilis Dam (Sardinia, Italy)

Protection of people from radon exposure in workplaces is an important factor in decreasing lung cancer risk. International authorities have set ‘reference levels’ to control enhanced radon exposure. Radiometric investigations, including in-situ radon measurements and laboratory gamma-spectroscopy, were carried out to monitor the radon exposure and define the radon transfer model in the workplaces of Medau-Zirimilis Dam in Sardinia. It was found that a shale formation is the main source of radon accumulated in the gallery of this dam. The water passing through the bedrock transports a considerable amount of sediments containing uranium-bearing minerals. Outgassing of radon from water flowing in the drainage canal and its accumulation due to poor ventilation could be the main reasons for the enhanced indoor radon level. The methodology introduced here can be adopted in underground workplaces like mines and tunnels to understand the natural radiation hazard and the effectiveness of the possible mitigation strategies.

Geology and climate: a novel method to estimate indoor radon exposure risk in South Africa

ABSTRACT The severe health risk associated with elevated levels of indoor radon gas is well known and widely reported. Measuring residential indoor radon-in-air levels is expensive, labour- and time-intensive. Two of the most important estimators of high levels of indoor radon gas are the underlying geology of an area and the climatic conditions, especially temperature and wind. While varying geology leads to different exhalation rates of radon gas, the climate can mitigate or enhance indoor radon gas levels. The research in this study developed and tested a novel approach to rapidly identify the most probable areas of high indoor radon levels, potential targets for indoor radon measurements. The study utilizes GIS tools to superimpose overlays of geology, climate, and wind to identify possible radon hotspots. South Africa was selected as a study site due to its varying climatic conditions and unique geology which have large areas of underlaying uranium-bearing rock units. Several of the identified hotspots were compared to actual indoor radon measurements, and a good similarity between actual and estimated indoor radon levels was found. This method can easily be applied to other sites or regions, giving it both practical and theoretical values.

Assessment of annual effective dose and health risk due to radon exposure in nurseries in the city of Poznań, Poland

The results of the scientific work presented in the World Health Organisation (WHO) report indicate that exposure to radon increases the risk of lung cancer in humans. In the past, radon concentrations of 400 Bq/m3 were considered dangerous, but today the level that poses a threat has been lowered to 100 Bq/m3. Children are particularly vulnerable to the effects of ionising radiation. In the article, the exposure of children to the effects of radon was evaluated on the basis of measurements in nurseries taken in the course of several months. A pulsed ionisation chamber with a passive diffusion sampling method was used for the measurements. The effective dose was assumed as the evaluation criterion. The research was carried out in selected rooms of two nurseries located in the city of Poznań in Poland. Similar profiles of variability in radon concentration (r = 0.88, p < 0.001) were observed in two different nurseries. The higher values of radon concentration in the rooms were found to be influenced by the low value of the wind speed. The experimental studies were supplemented with questionnaire studies, which showed that the average person's awareness of radioactivity is at a low level. The results of the effective dose level can be used to optimise future radon testing in buildings intended for various purposes.

Mapping in a radon-prone area in Adamawa region, Cameroon, by measurement of radon activity concentration in soil.

The radon-prone area of the Adamawa region in Cameroon is characterized by high natural radiation background resulting from the high concentrations of radium-226, thorium-232, and indoor radon. To produce a radon-risk map, radon measurements in soil were carried out in the city of Ngaoundere. The radon activity concentration in soil gas ranged from 256 to 166kBqm-3 with a mean of 80kBqm-3 and a standard deviation of 38kBqm-3. The area is mostly classified as high risk (80%) according to the Swedish classification, and 20% as medium risk. A low-risk area was not observed. Granite-like geology sites were characterized by higher radon concentration. A ratio of about 295:1 was obtained for soil radon gas to indoor radon concentrations, with a positive correlation (R = 0.40), and a transfer factor of 3 per mil. These results demonstrate that in situ measurements of radon concentration in soil can provide accurate information on the level of indoor radon concentrations. Geostatistical and deterministic interpolation techniques have been used to obtain a radon map by comparing the suitability of ordinary kriging and inverse-distance-weighted (IDW) interpolation methods. It turned out that there is not much difference in the prediction errors of the two techniques (Root Mean Square Error = 34.4 for ordinary kriging and 34.3 for IDW). It is concluded that both methods give acceptable results. In situ measurements and geostatistical analysis allow assessment of expected indoor radon exposure in a given area at reduced costs and time required. However, for the investigated area, more research is needed to produce reliable radon-risk maps.

Indoor radon exposure and living conditions in patients with advanced lung cancer in Lublin region, Poland.

Radon (Rn-222) is a noble gas formed in the uranium path (U-238) as a decay product of radium (Ra-226). It is estimated to cause between 3% to 14% of all lung cancers, depending on the national average radon level and smoking prevalence. Radon molecules emit alpha radiation, which is characterized by low permeability through tissues, but due to its remarkably high energy, it has a high potential for DNA damage. The aim of our research was to assess the radon concentration inside the houses of patients with advanced lung cancer and to analyze their socio-economics status. The measurements of radon concentration were performed in 102 patients with stage 3B or higher lung cancer in the region of Lublin, Poland. One month of radon exposure measurement was performed with alpha-track detectors. In addition, patients filled in a detailed survey about factors that might influence the concentration of radon inside their houses. The average concentration of radon during the exposure of the detector in the residential premises of the respondents was at the level of 69.0 Bq/m3 [37.0-117.0]. A few significant correlations were discovered, e.g., higher levels of radon in countryside houses or in houses equipped with air conditioning. As radon exposure is a modifiable risk factor for lung cancer, it is extremely important to find factors that may reduce its concentration in dwelling places. Since our research was performed in houses of people with lung cancer, taking corrective actions based on our findings could prevent new lung cancer incidence in patients' flatmates.

A Genome-Wide Association Study of Small Cell Lung Cancer

IntroductionSmall cell lung cancer (SCLC) comprises 10–15% of all lung cancer cases and is the most aggressive histological type. Survival is poor and the molecular landscape of this disease is extraordinarily complex. The objective of this paper was to perform a Genome-Wide Association Study (GWAS) of this disease using a case–control study specifically designed for small cell lung cancer (SCLC). MethodsIncident cases were consecutively recruited from 8 hospitals from different regions of Spain. Controls were recruited from the same hospitals using a frequency sampling based on age and sex distribution of cases. Biological samples were obtained along with detailed information on cases and controls lifestyle, including tobacco and radon exposure. ResultsWe included 271 SCLC cases and 557 controls. We found evidence (p-values<10−5) of an association in the complete dataset for several loci, while MAP4 showed a significant association in the gene-based analysis. Pathway analysis suggested that ATR, ATRIP, MCM4, MCM5, ORC4, RPA3 and CDC25A genes have a role on the onset of SCLC. ConclusionThis study provides biological evidence for pathways related to SCLC, offering novel loci for further research.

Outdoor Radon and Its Progeny in Relation to the Particulate Matter during Different Polluted Weather in Beijing

This study aimed to investigate the differences in the relationship between radon and its progeny concentrations and particulate matter concentrations under varying pollution weather conditions. Outdoor radon and its progeny concentrations were measured by a radon/thoron- and radon/thoron progeny monitor (ERS-RDM-2S) during haze and dust storm weather in Beijing. Particulate matter concentrations and meteorological data were simultaneously recorded. Results showed that radon and its progeny concentrations exhibited a diurnal variation pattern, with a minimum in the late afternoon and a maximum in the early morning. The average radon concentrations were similar under both pollution weather conditions, but significantly higher than the reported average for Beijing. The equilibrium equivalent radon concentration during haze was about two times that during a dust storm. PM10 concentrations were similar in both pollution weather conditions, but PM2.5 concentrations during haze were approximately 2.6 times higher than that during dust storms. A positive correlation was observed between radon and its progeny concentrations and particulate matter concentrations, but the correlation was significantly higher during haze than during dust storms. The higher PM2.5 concentration during haze significantly increased the correlation between radon and its progeny concentrations and particulate matter concentrations. We recommended protecting against radon exposure during pollutant weather, especially haze.

The Relationship between Radon and Geology: Sources, Transport and Indoor Accumulation

This review study examines the relationship between radon and geology, including its origins, transmission, and accumulation, as well as its impact on human health and mitigation strategies. The decay of uranium and thorium produces radon, a radioactive gas. Its concentration in the environment fluctuates based on local geology, soil permeability, climate, and terrain, as well as regional, seasonal, and daily meteorological conditions. Exposure to radon indoors is associated with an increased risk of lung cancer, making it a significant public health concern. Measuring radon concentrations in indoor environments is essential for identifying high-risk areas and devising effective mitigation strategies, such as ventilation, fissure sealing, and exhaust installation. The need for greater knowledge of regional and seasonal fluctuations in radon concentration, as well as the development of more effective and cost-effective measuring and mitigation strategies, has implications for future research. To influence public health policies and practices, more research on the long-term health effects of radon exposure is required. The focus of public health policy should be on increasing awareness of the dangers associated with radon exposure, supporting regular measurement and monitoring of radon concentrations in indoor areas, and encouraging the adoption of effective mitigation techniques. When selecting construction sites, urban planning regulations and building codes should consider the local geology and radon levels in the soil.

Using information provision and interactive risk maps to motivate testing for radon

Radon exposure in homes is a leading cause of lung cancer, but the rate at which householders test for this environmental risk is low. In a pre-registered experiment with a nationally representative sample of adults (N = 1700), we used psychological theory to design information interventions to influence perceptions of risk from radon and motivate testing. Results show that information about radon increased belief that exposure would lead to negative consequences, but not perceived likelihood of exposure. Interactive maps depicting the geographical distribution of radon risk increased perceived likelihood of exposure, general worry and willingness to test for radon, but the effects depended on the map's attributes. Maps communicating risk using numeric frequencies of the number of homes in an area likely to be affected by radon (e.g., 1 in 5 homes) were more effective than ones that used simple statements (e.g., your home is at high risk). Adding an intermediate “moderate” risk category increased perceived risk compared to a binary high/low classification system among those in the moderate risk area, without altering perceptions of those at high risk. Other map features (colour and search functionality) had little impact. The best performing map led to 72% more people being willing to test for radon, compared to the map in use by the national Environmental Protection Agency at the time of the study. The results have implications for theories of risk perception and show the potential for techniques from psychological science to help mitigate a real-world environmental risk.