The U.S. Environmental Protection Agency's assessment of risks from indoor radon

Lung cancer mortality attributable to residential radon: a systematic scoping review

After smoking, residential radon is the second risk factor of lung cancer in general population and the first in never-smokers. Previous studies have analyzed radon attributable lung cancer mortality for some countries. We aim to identify, summarize, and critically analyze the available data regarding the mortality burden of lung cancer due to radon, performing a quality assessment of the papers included, and comparing the results from different countries. We performed a systematic scoping review using the main biomedical databases. We included original studies with attributable mortality data related to radon exposure. We selected studies according to specific inclusion and exclusion criteria. PRISMA 2020 methodology and PRISMA Extension for Scoping Reviews requirements were followed. Data were abstracted using a standardized data sheet and a tailored scale was used to assess quality. We selected 24 studies describing radon attributable mortality derived from 14 different countries. Overall, 13 studies used risk models based on cohorts of miners, 8 used risks from residential radon case-control studies and 3 used both risk model options. Radon geometric mean concentration ranged from 11 to 83 Becquerels per cubic meter (Bq/m3) and the population attributable fraction (PAF) ranged from 0.2 to 26%. Studies performed in radon prone areas obtained the highest attributable mortality. High-quality publications reported PAF ranging from 3 to 12% for residential risk sources and from 7 to 25% for miner risk sources. Radon PAF for lung cancer mortality varies widely between studies. A large part of the variation is due to differences in the risk source used and the conceptual description of radon exposure assumed. A common methodology should be described and used from now on to improve the communication of these results.

The Influence of Adopting New Reference Breathing Parameters on ICRP66 Model on the Regional Deposition of the Inhaled Attached Radon-222 Daughters Within the Human Airways

The radiation dose from internal radiation exposure is difficult to measure directly and hence different lung models were developed. The dose on the lung is the result of the regional deposition of aerosols carrying radon daughters in the respiratory tract. Deposition of aerosols can be take place during inhalation and exhalation in the 5 regions of the respiratory tract due to variation of aerosol sizes and other biological factors such as breathing rate. In this paper, a modified breathing rate is instead applied on the assumptions developed by the ICRP66 model to analyze the regional deposition of radioactive aerosols and a comparison has been made with the result of ICRP66 model deposition. According to the result, as the diameter of aerosols increases from 1 to 10 μm, the percentage deposition fraction in extrathoracic regions, in ET1 region increases from 6.53% to 48.43% and in ET2 region increases from 7.3% to 50.33%. The aerodynamic deposition of the attached fraction of radon aerosols along the bronchial regions (bronchi (BB), and bronchiolar (bb) region) is found small and almost constant. For 1 μm diameter aerosols, the percentage deposition is found 0.82%, for 5 μm diameter aerosols, the deposition is predicted 2.56% and at 10 μm the deposition is predicted about 1.93% in bronchi (BB) region. In the bronchiolar region (bb) for 1 μm aerosols, the deposition predicted is 1.5% and at 10 μm about 0.88% is predicted. The deposition of small size attached fraction of radon aerosols is found maximum in the alveolar region as compared to other regions of the respiratory tract and the deposition becomes almost negligible for large size aerosols in this region.

High-efficiency radon adsorption by nickel nanoparticles supported on activated carbon

Nickel nanoparticles supported on AC (Ni/AC) composites, combining abundant micropores with open metal sites, are rationally designed for adsorbing Rn.

Indoor radon measurement in buildings of a university campus in central Iran and estimation of its effective dose and health risk assessment

Indoor radon is a serious health concern and contributes about 10% of deaths from lung cancer in the USA and Europe. In this study, radon and thoron levels of 20 multi-floor buildings on the campus of Isfahan University of Medical Sciences were measured in cold and hot seasons of a year. SARAD- RTM1688 radon and thoron monitor was used for measurement. The annual effective dose of radon exposure was also estimated for residences on the campus. The results showed that radon concentration was below the WHO guideline (100 Bq m- 3) in most of the buildings. The ranges of radon were from 3 ± 10% to 322 ± 15% Bq m- 3 in winter and from below the detectable level to 145 ± 8% Bq m- 3 in summer. Mostly, the radon concentration in the basement or ground floors was higher than upper floors, however, exceptions were observed in some locations. For thoron, no special trends were observed, and in the majority of buildings, its concentration was below the detectable level. However, in a few locations besides radon, thoron was also measured at a high level during both seasons. The average annual effective dose via radon exposure was estimated to be 0.261 ± 0.339 mSv y- 1. The mean excess lung cancer risk (ELCR) was estimated to be 0.10%. It was concluded that indoor air ventilation, buildings' flooring and construction materials, along with the geological structure of the ground could be the factors influencing the radon concentration inside the buildings. Thus, some applicable radon prevention and mitigation techniques were suggested.

Radiometric evaluation of indoor radon levels with influence of building characteristics in residential homes from southwestern Nigeria

Indoor radon (²²²Rn) measurements were carried out using solid state nuclear track detectors (SSNTD) in some dwellings from southwestern Nigeria. This was aimed at statistically assessing influence of building characteristics on the measured radon and estimating excess lifetime cancer risks (ELCR). The measured radon concentrations followed lognormal distribution and were significantly influenced by some building properties. The arithmetic mean (1.60 mSv) of annual effective doses (AEDs) due to indoor radon was observed to be higher than the world average level (1.15 mSv) but less than lower limit (3 mSv) of International Commission on Radiological Protection (ICRP). The evaluated excess lifetime cancer risk ranged from 1.5 to 28.1 (MPy)^-1 with an average value of 6.3 (MPy)^-1, indicating that after exposure to indoor radon for 70 years, 6 people in every 1000 are likely to suffer the risk of developing lung cancer. Adequate ventilation systems were recommended for houses with high level of radon to avoid unnecessary exposure to radon. However, the investigated data would form important component of the database required to set up guidelines and policy of controlling radon at home.

Challenging the concept of de novo acute myeloid leukemia: Environmental and occupational leukemogens hiding in our midst

Myeloid neoplasms like acute myeloid leukemia (AML) originate from genomic disruption, usually in a multi-step fashion. Hematopoietic stem/progenitor cell acquisition of abnormalities in vital cellular processes, when coupled with intrinsic factors such as germline predisposition or extrinsic factors such as the marrow microenvironment or environmental agents, can lead to requisite pre-leukemic clonal selection, expansion and evolution. Several of these entities have been invoked as "leukemogens." The known leukemogens are numerous and are found in the therapeutic, occupational and ambient environments, however they are often difficult to implicate for individual patients. Patients treated with particular chemotherapeutic agents or radiotherapy accept a calculated risk of therapy-related AML. Occupational exposures to benzene, dioxins, formaldehyde, electromagnetic and particle radiation have been associated with an increased risk of AML. Although regulatory agencies have established acceptable exposure limits in the workplace, accidental exposures and even ambient exposures to leukemogens are possible. It is plausible that inescapable exposure to non-anthropogenic ambient leukemogens may be responsible for many cases of non-inherited de novo AML. In this review, we discuss the current understanding of leukemogens as they relate to AML, assess to what extent the term "de novo" leukemia is meaningful, and describe the potential to identify and characterize new leukemogens.

Low-Dose CT Screening for Lung Cancer: Evidence from 2 Decades of Study

Lung cancer remains the overwhelmingly greatest cause of cancer death in the United States, accounting for more annual deaths than breast, prostate, and colon cancer combined. Accumulated evidence since the mid to late 1990s, however, indicates that low-dose CT screening of high-risk patients enables detection of lung cancer at an early stage and can reduce the risk of dying from lung cancer. CT screening is now a recommended clinical service in the United States, subject to guidelines and reimbursement requirements intended to standardize practice and optimize the balance of benefits and risks. In this review, the evidence on the effectiveness of CT screening will be summarized and the current guidelines and standards will be described in the context of knowledge gained from lung cancer screening studies. In addition, an overview of the potential advances that may improve CT screening will be presented, and the need to better understand the performance in clinical practice outside of the research trial setting will be discussed. © RSNA, 2020.

Evaluation of radon exposure risk and lung cancer incidence/mortality in South-eastern Italy

INTRODUCTION

Radon and its decay products may cause substantial health damage after long-term exposure. The aim of the study was to perform a spatial analysis of radon concentration in the Salento peninsula, province of Lecce (South-eastern Italy) in order to better characterize possible risk for human health, with specific focus on lung cancer.

METHODS

Based on previous radon monitoring campaigns carried out in 2006 on behalf of the Local Health Authority (ASL Lecce) involving 419 schools and through the application of kriging estimation method, a radon risk map was obtained for the province of Lecce, in order to determine if areas with higher radon concentrations were overlapping with those characterized by the highest pulmonary cancer incidence and mortality rates.

RESULTS

According to our data, areas at higher radon concentrations seem to overlap with those characterized by the highest pulmonary cancer mortality and incidence rates, thus indicating that human exposure to radon could possibly enhance other individual or environmental pro-carcinogenic risk factors (i.e. cigarette smoking, air pollution and other exposures).

CONCLUSIONS

The radon risk should be further assessed in the evaluation of the causes resulting in higher mortality and incidence rates for pulmonary cancer in Salento area vs Italian average national data. For these reasons, ASL Lecce in cooperation with ARPA Puglia and CNR-IFC has included the monitoring of individual indoor radon concentrations in the protocol of PROTOS case-control Study, aimed at investigating the role of different personal and environmental risk factors for lung cancer in Salento.

Residential Radon and Histological Types of Lung Cancer: A Meta-Analysis of Case‒Control Studies

Epidemiological studies on residential radon exposure and the risk of histological types of lung cancer have yielded inconsistent results. We conducted a meta-analysis on this topic and updated previous related meta-analyses. We searched the databases of Cochrane Library, Embase, PubMed, Web of Science and Chinese National Knowledge Infrastructure for papers published up to 13 November 2018. The pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using fixed and random effects models. Subgroup and dose‒response analyses were also conducted. This study was registered with PROSPERO (No. CRD42019127761). A total of 28 studies, which included 13,748 lung cancer cases and 23,112 controls, were used for this meta-analysis. The pooled OR indicated that the highest residential radon exposure was significantly associated with an increased risk of lung cancer (OR = 1.48, 95% CI = 1.26–1.73). All histological types of lung cancer were associated with residential radon. Strongest association with small-cell lung carcinoma (OR = 2.03, 95% CI = 1.52–2.71) was found, followed by adenocarcinoma (OR = 1.58, 95% CI = 1.31–1.91), other histological types (OR = 1.54, 95% CI = 1.11–2.15) and squamous cell carcinoma (OR = 1.43, 95% CI = 1.18–1.74). With increasing residential radon levels per 100 Bq/m³, the risk of lung cancer, small-cell lung carcinoma and adenocarcinoma increased by 11%, 19% and 13%, respectively. This meta-analysis provides new evidence for a potential relationship between residential radon and all histological types of lung cancer.

Natural radioactivity in Brazil: a systematic review

Natural radioactivity is a public health concern worldwide. Its deleterious effects are largely associated with emitting ionizing particles which generate innumerable toxicological consequences to human being. The present study aimed to describe the research state of the art on natural radioactivity in Brazil through a systematic review limited to articles published in the twenty-first century in the PubMed, SciELO, Lilacs, and Google Scholar databases. A total of 55 research articles were considered for this purpose. Based on the collected sample types, the radiation analysis in most of the scientific reports was performed on solid samples (soil/sediment/rocks), followed by water and air. In fact, most of the available information came from geological studies. A wide range of concentrations and a variety of radionuclides have been assessed, with radium being the most cited. Most of the studies described radiation levels above the international guidelines, and consider the Brazilian territory as a high natural background radiation region (HNBR). In comparison with other HNBR areas, the scientific information about the related risks to human health is still scarce. There is uncertainty about the real impact of natural radioactivity on human health, as there is a lack of scientific information for most of the country about this issue. The analysis and comparison of the available information highlights the potential risks linked to natural radioactivity and the need to incorporate suitable environmental management policies about this issue.

Indoor Radon in EGFR- and BRAF-Mutated and ALK-Rearranged Non-Small-Cell Lung Cancer Patients

BACKGROUND

Radon gas is the leading cause of lung cancer in the nonsmoking population. The World Health Organization (WHO) recommends indoor concentrations of < 100 Bq/m³. Several molecular alterations have been described in non-small-cell lung cancer (NSCLC), mainly in nonsmokers, with no risk factors identified. We studied the role of indoor radon in NSCLC patients harboring specific driver alterations.

PATIENTS AND METHODS

We assessed the radon concentration from EGFR-, BRAF-mutated (m), and ALK-rearranged (r) NSCLC patients measured by an alpha-track detector placed in their homes between September 2014 and August 2015. Clinical characteristics were collected prospectively, and pathologic samples were reviewed retrospectively.

RESULTS

Forty-eight patients were included (36 EGFRm, 10 ALKr, 2 BRAFm). Median radon concentration was 104 Bq/m³ (IQR 69-160) overall, and was 96 Bq/m³ (42-915) for EGFRm, 116 (64-852) for ALKr, and 125 for BRAFm, with no significant differences. Twenty-seven patients (56%) had indoor radon above WHO recommendations, 8 (80%) of 10 ALKr, 2 (100%) of 2 BRAFm, and 17 (47%) of 36 EGFRm.

CONCLUSION

The median indoor radon concentration was above the WHO recommendations, with no differences between EGFR, ALK, and BRAF patients. Concentrations above the WHO recommendations were most common with ALKr and BRAFm. These findings should be validated in larger studies.

The Disease Burden of Lung Cancer Attributable to Residential Radon Exposure in Korean Homes

BACKGROUND

Residential radon exposure is known to be an important risk factor for the development of lung cancer. The objective of this study was to calculate the disease burden of lung cancer attributable to residential radon exposure in Korea.

METHODS

We calculated the national exposure level using Korean national radon survey data from 2011 to 2014, and house structure distribution data from each administrative region. Using the exposure-risk function, the population attributable fraction (PAF) was calculated and applied to calculate the disease burden for lung cancer attributable to residential radon exposure.

RESULTS

Residential radon exposure levels were the highest, at 116.4 ± 50.4 Bq/m³ (annual mean radon concentration ± standard deviation) in detached houses, followed by 74.1 ± 30.0 Bq/m³ in the multi-family dwellings, and 55.9 ± 21.1 Bq/m³ in apartments. The PAF for lung cancer, due to long-term radon exposure in Korean homes, was 6.6% and 4.7% in men and women, respectively. The total disease burden of lung cancer attributable to residential radon exposure was 14,866 years of life lost (YLL) and 1,586 years lost due to disability (YLD) in 2013. Overall, 1,039 deaths occurred due to residential radon exposure, of which 828 were in men and 211 in women.

CONCLUSION

The smoking rate of men in Korea exceeded 70% in the 1990s, and is still near 40%. Although the size of the effect varies depending on the estimation method, it is a critical aspect as a risk factor of lung cancer because of the synergistic relationship between smoking and radon exposure. Because the Korean society is rapidly aging, population who were formerly heavy-smokers are entering a high-risk age of lung cancer. Therefore, it is necessary to inform the public about the health benefits of reduced radon exposure and to strengthen the risk communication.

Epidemiology of Lung Cancer

Lung cancer has been transformed from a rare disease into a global problem and public health issue. The etiologic factors of lung cancer become more complex along with industrialization, urbanization, and environmental pollution around the world. Currently, the control of lung cancer has attracted worldwide attention. Studies on the epidemiologic characteristics of lung cancer and its relative risk factors have played an important role in the tertiary prevention of lung cancer and in exploring new ways of diagnosis and treatment. This article reviews the current evolution of the epidemiology of lung cancer.

Radon emissions from natural gas power plants at The Pennsylvania State University

Burning natural gas in power plants may emit radon (²²²Rn) into the atmosphere. On the University Park campus of The Pennsylvania State University, atmospheric radon enhancements were measured and modeled in the vicinity of their two power plants. The three-part study first involved measuring ambient outdoor radon concentrations from August 2014 through January 2015 at four sites upwind and downwind of the power plants at distances ranging from 80 m to 310 m. For each plant, one site served as a background site, while three other sites measured radon concentration enhancements downwind. Second, the radon content of natural gas flowing into the power plant was measured, and third, a plume dispersion model was used to predict the radon concentrations downwind of the power plants. These predictions are compared to the measured downwind enhancements in radon to determine whether the observed radon concentration enhancements could be attributed to the power plants' emissions. Atmospheric radon concentrations were consistently low as compared to the EPA action level of 148 Bq m^-3, averaging 34.5 ± 2.7 Bq m^-3 around the East Campus Steam Plant (ECSP) and 31.6 ± 2.7 Bq m^-3 around the West Campus Steam Plant (WCSP). Significant concentrations of radon, ranging from 516 to 1,240 Bq m^-3, were detected in the natural gas. The measured enhancements downwind of the ECSP averaged 6.2 Bq m^-3 compared to modeled enhancements of 0.08 Bq m^-3. Measured enhancements around the WCSP averaged -0.2 Bq m^-3 compared to the modeled enhancements of 0.05 Bq m^-3, which were not significant compared to observational error. The comparison of the measured to modeled downwind radon enhancements shows no correlation over time. The measurements of radon levels in the vicinity of the power plants appear to be unaffected by the emissions from the power plants.

IMPLICATIONS

Radon measurements at sites surrounding power plants that utilize natural gas did not indicate that the radon concentrations originated from the plants' emissions. There were elevated radon concentrations in the natural gas supply flowing into the power plants, but combustion dilution puts the concentration below EPA action levels coming out of the stack, so no hazardous levels were expected downwind. Power plant combustion of natural gas is not likely to pose a radiation health hazard unless very different gas radon concentrations or combustion dilution ratios are encountered.

Predictors of Indoor Radon Concentrations in Pennsylvania, 1989-2013

BACKGROUND

Radon is the second-leading cause of lung cancer worldwide. Most indoor exposure occurs by diffusion of soil gas. Radon is also found in well water, natural gas, and ambient air. Pennsylvania has high indoor radon concentrations; buildings are often tested during real estate transactions, with results reported to the Department of Environmental Protection (PADEP).

OBJECTIVES

We evaluated predictors of indoor radon concentrations.

METHODS

Using first-floor and basement indoor radon results reported to the PADEP between 1987 and 2013, we evaluated associations of radon concentrations (natural log transformed) with geology, water source, building characteristics, season, weather, community socioeconomic status, community type, and unconventional natural gas development measures based on drilled and producing wells.

RESULTS

Primary analysis included 866,735 first measurements by building, with the large majority from homes. The geologic rock layer on which the building sat was strongly associated with radon concentration (e.g., Axemann Formation, median = 365 Bq/m3, IQR = 167-679 vs. Stockton Formation, median = 93 Bq/m3, IQR = 52-178). In adjusted analysis, buildings using well water had 21% higher concentrations (β = 0.191, 95% CI: 0.184, 0.198). Buildings in cities (vs. townships) had lower concentrations (β = -0.323, 95% CI: -0.333, -0.314). When we included multiple tests per building, concentrations declined with repeated measurements over time. Between 2005 and 2013, 7,469 unconventional wells were drilled in Pennsylvania. Basement radon concentrations fluctuated between 1987 and 2003, but began an upward trend from 2004 to 2012 in all county categories (p < 0.001), with higher levels in counties having ≥ 100 drilled wells versus counties with none, and with highest levels in the Reading Prong.

CONCLUSIONS

Geologic unit, well water, community, weather, and unconventional natural gas development were associated with indoor radon concentrations. Future studies should include direct environmental measurement of radon, as well as building features unavailable for this analysis.

CITATION

Casey JA, Ogburn EL, Rasmussen SG, Irving JK, Pollak J, Locke PA, Schwartz BS. 2015. Predictors of indoor radon concentrations in Pennsylvania, 1989-2013. Environ Health Perspect 123:1130-1137; http://dx.doi.org/10.1289/ehp.1409014.

Radon decay products in realistic living rooms and their activity distributions in human respiratory system

In this study, the individual activity concentrations of attached short-lived radon decay products ((218)Po, (214)Pb and (214)Po) in aerosol particles were measured in ten poorly ventilated realistic living rooms. Using standard methodologies, the samples were collected using a filter holder technique connected with alpha-spectrometric. The mean value of air activity concentration of these radionuclides was found to be 5.3±0.8, 4.5±0.5 and 3.9±0.4 Bq m(-3), respectively. Based on the physical properties of the attached decay products and physiological parameters of light work activity for an adult human male recommended by ICRP 66 and considering the parameters of activity size distribution (AMD = 0.25 μm and σ(g) = 2.5) given by NRC, the total and regional deposition fractions in each airway generation could be evaluated. Moreover, the total and regional equivalent doses in the human respiratory tract could be estimated. In addition, the surface activity distribution per generation is calculated for the bronchial region (BB) and the bronchiolar region (bb) of the respiratory system. The maximum values of these activities were found in the upper bronchial airway generations.

Risk-reduction strategies to expand radon care planning with vulnerable groups

OBJECTIVES

Radon is the second leading cause of lung cancer in the United States and the leading cause of lung cancer among nonsmokers. Residential radon is the cause of approximately 21,000 U.S. lung cancer deaths each year. Dangerous levels of radon are just as likely to be found in low-rise apartments and townhomes as single-family homes in the same area. The preferred radon mitigation strategy can be expensive and requires structural modifications to the home. The public health nurse (PHN) needs a collection of low-cost alternatives when working with low-income families or families who rent their homes.

METHOD

A review of the literature was performed to identify evidence-based methods to reduce radon risk with vulnerable populations.

RESULTS

Fourteen recommendations for radon risk reduction were categorized into four strategies. Nine additional activities for raising awareness and increasing testing were also included.

DISCUSSION

The results pair the PHN with practical interventions and the underlying rationale to develop radon careplans with vulnerable families across housing types. The PHN has both the competence and the access to help families reduce their exposure to this potent carcinogen.

Radiation-exposed populations: who, why, and how to study

Everyone is exposed to natural and manmade ionizing radiation that can originate from sources in the environment and in medical and occupational settings. There is notable variation, however, among individuals and across populations in the types of sources of radiation and in the frequency, level, and duration of exposure. Adverse health effects associated with radiation exposure have been known for decades, and ionizing radiation exposure has been linked with a broad range of different types of cancer and benign neoplasms as well as birth defects, reproductive effects, and diseases of the circulatory, hematologic, and neurologic systems. Our present understanding of radiation-related health risks derives primarily from multidisciplinary health risk (epidemiologic) studies that provide the key information on radiation-associated health outcomes, quantify radiation-related disease risks, and enhance understanding of mechanisms of radiation-related disease pathogenesis. Such information is central to quantifying risks in relation to benefits; addressing public concerns, including societal and clinical needs in relation to radiation exposure; and providing the database needed for establishing recommendations for radiation protection. Because of the importance of determining risks compared to benefits for all situations where exposure to ionizing radiation might result, it is useful for planning new health risks studies to categorize exposed populations according to the sources and types of radiation. This paper describes a wide range of populations exposed to radiation and the motivation and key methodological criteria that drive the rationale and priority of studying such populations. Also, discussed are alternative methods for evaluating radiation-related health risks in these populations, with a major focus on epidemiologic approaches. This paper concludes with a short summary of major highlights from radiation epidemiologic research and important unanswered questions.Introduction of Exposed Populations (Video 1:29, http://links.lww.com/HP/A22).

Epidemiology of lung cancer

Incidence and mortality attributed to lung cancer has risen steadily since the 1930s. Efforts to improve outcomes have not only led to a greater understanding of the etiology of lung cancer, but also the histologic and molecular characteristics of individual lung tumors. This article describes this evolution by discussing the extent of the current lung cancer epidemic including contemporary incidence and mortality trends, the risk factors for development of lung cancer, and details of promising molecular targets for treatment.

Radon, smoking, and lung cancer: the need to refocus radon control policy

Exposure to radon is the second leading cause of lung cancer, and the risk is significantly higher for smokers than for nonsmokers. More than 85% of radon-induced lung cancer deaths are among smokers. The most powerful approach for reducing the public health burden of radon is shaped by 2 overarching principles: public communication efforts that promote residential radon testing and remediation will be the most cost effective if they are primarily directed at current and former smokers; and focusing on smoking prevention and cessation is the optimal strategy for reducing radon-induced lung cancer in terms of both public health gains and economic efficiency. Tobacco control policy is the most promising route to the public health goals of radon control policy.

The effectiveness of mitigation for reducing radon risk in single-family Minnesota homes

Increased lung cancer incidence has been linked with long-term exposure to elevated residential radon. Experimental studies have shown that soil ventilation can be effective in reducing radon concentrations in single-family homes. Most radon mitigation systems in the U.S. are installed by private contractors. The long-term effectiveness of these systems is not well known, since few state radon programs regulate or independently confirm post-mitigation radon concentrations. The effectiveness of soil ventilation systems in Minnesota was measured for 140 randomly selected clients of six professional mitigators. Homeowners reported pre-mitigation radon screening concentrations that averaged 380 Bq m (10.3 pCi L). Long term post-mitigation radon measurements on the two lowest floors show that, even years after mitigation, 97% of these homes have concentrations below the 150 Bq m U.S. Environmental Protection Agency action level. The average post-mitigation radon in the houses was 30 Bq m, an average observed reduction of >90%. If that reduction was maintained over the lifetime of the 1.2 million Minnesotans who currently reside in single-family homes with living space radon above the EPA action level, approximately 50,000 lives could be extended for nearly two decades by preventing radon-related lung cancers.

Modeling joint exposures and health outcomes for cumulative risk assessment: the case of radon and smoking

Community-based cumulative risk assessment requires characterization of exposures to multiple chemical and non-chemical stressors, with consideration of how the non-chemical stressors may influence risks from chemical stressors. Residential radon provides an interesting case example, given its large attributable risk, effect modification due to smoking, and significant variability in radon concentrations and smoking patterns. In spite of this fact, no study to date has estimated geographic and sociodemographic patterns of both radon and smoking in a manner that would allow for inclusion of radon in community-based cumulative risk assessment. In this study, we apply multi-level regression models to explain variability in radon based on housing characteristics and geological variables, and construct a regression model predicting housing characteristics using U.S. Census data. Multi-level regression models of smoking based on predictors common to the housing model allow us to link the exposures. We estimate county-average lifetime lung cancer risks from radon ranging from 0.15 to 1.8 in 100, with high-risk clusters in areas and for subpopulations with high predicted radon and smoking rates. Our findings demonstrate the viability of screening-level assessment to characterize patterns of lung cancer risk from radon, with an approach that can be generalized to multiple chemical and non-chemical stressors.

Measurement of radon and xenon binding to a cryptophane molecular host

Xenon and radon have many similar properties, a difference being that all 35 isotopes of radon ((195)Rn-(229)Rn) are radioactive. Radon is a pervasive indoor air pollutant believed to cause significant incidence of lung cancer in many geographic regions, yet radon affinity for a discrete molecular species has never been determined. By comparison, the chemistry of xenon has been widely studied and applied in science and technology. Here, both noble gases were found to bind with exceptional affinity to tris-(triazole ethylamine) cryptophane, a previously unsynthesized water-soluble organic host molecule. The cryptophane-xenon association constant, K(a)=42,000 ± 2,000 M(-1) at 293 K, was determined by isothermal titration calorimetry. This value represents the highest measured xenon affinity for a host molecule. The partitioning of radon between air and aqueous cryptophane solutions of varying concentration was determined radiometrically to give the cryptophane-radon association constant K(a)=49,000 ± 12,000 M(-1) at 293 K.

A brief review of radiation hormesis

This paper reviews physical, experimental and epidemiological evidence for and against radiation hormesis and discusses implications with regards to radiation protection. The scientific community is still divided on the premise of radiation hormesis, with new literature published on a regular basis. The International Commission on Radiological Protection (ICRP) recommends the use of the Linear No Threshold (LNT) model, for planning radiation protection. This model states that the probability of induced cancer and hereditary effects increases with dose in a linear fashion. As a consequence, all radiation exposures must be justified and have a sufficient protection standard in place so that exposures are kept below certain dose limitations. The LNT model has sufficient evidence at high doses but has been extrapolated in a linear fashion to low dose regions with much less scientific evidence. Much experimentation has suggested discrepancies of this extrapolation at low doses. The hypothesis of radiation hormesis suggests low dose radiation is beneficial to the irradiated cell and organism. There is definite standing ground for the hormesis hypothesis both evolutionarily and biophysically, but experimental evidence is yet to change official policies on this matter. Application of the LNT model has important radiation protection and general human health ramifications, and thus it is important that the matter be resolved.

Work to save dose: contrasting effective dose rates from radon exposure in workplaces and residences against the backdrop of public and occupational regulatory limits

Office workers are exposed to radon while at work and at home. Though there are a multitude of studies reporting radon concentrations and potential lung and effective doses associated with radon progeny exposure in homes, similar studies in non-mine workplaces are lacking. Additionally, there are few, if any, comparative analyses of radon exposures at more "typical" workplace with residential exposures within the same county. The purposes of this study were to measure radon concentrations in office and residential spaces in the same county and explore the radiation dose implications. Sixty-five track-etch detectors were deployed for 3-mo sampling periods in office spaces and 47 were deployed in residences, all within Los Alamos County, New Mexico. The measured concentrations were used to calculate and compare effective dose rates resulting from exposure while at work and at home. Results showed that full-time office workers receive on average about 8 times greater exposure at home than while in the office (2.3 mSv y-1 vs. 0.3 mSv y-1). The estimated effective dose rate for a more homebound person was about 3 mSv y-1. Estimating effective doses from background radon exposure in the same county as Los Alamos National Laboratory, with thousands of "radiological workers," highlights interesting contrasts in radiation protection standards that span public and occupational settings. For example, the effective dose rate from background radon exposure in unregulated office spaces ranged up to 1.1 mSv y-1, which is similar to the 1 mSv y-1 threshold for regulation of a "radiological worker," as defined in the Department of Energy regulations for occupational exposure. Additionally, the estimated average effective dose total of >3 mSv y-1 from radon background exposure in homes stands in contrast to the 0.1 mSv y-1 air pathway effective public dose limit regulated by the Environmental Protection Agency for radioactive air emissions, and both these are substantially lower than effective doses associated with priority radon levels in homes of "tens of pCi L-1 and greater" (>370 Bq m-3), as suggested by the Health Physics Society.

A study of residential radon in Sweden using multi-level analysis

A Swedish radon data set, consisting of more than 8,000 measurements of residential radon levels in about 50% of the Swedish municipalities, was analyzed using a multi-level approach. The results were compared with those of a single-level analysis. We found that there was a significant variability between municipalities. The point estimates of the population mean radon levels were similar (geometric mean 60 Bq m-3 and arithmetic mean 106 Bq m-3). The analysis shows the advantages of multi-level modeling compared with a single-level ordinary least squares (OLS) model. A single-level model results in too optimistic standard errors, about 25% of those of the multi-level model, which can lead to erroneous conclusions. In a multi-level model including house type as a fixed effect (single-family house, row house, or apartment in multi-family house), the estimates of the fixed effect of house type were similar for the single-level and the multi-level models.

Examination of underground miner data for radon progeny size reduction as cause of high radon "inverse" dose rate effect

Radon progeny measurements of particle size distributions show that at high radon levels the distributions decrease in arithmetic mean diameters (AMD)--apparently due to increased neutralization rates affected by high radon concentrations. The radon concentration threshold for this diameter decrease effect (enhanced deposition effect, EDE), decreases with increased humidity. From graded screen array measurements, in a test chamber the AMD's are known vs. radon concentration. Knowing all the necessary parameters and using the ICRP 66 human respiratory tract model, the reduction in human lung dose rate per unit radon concentration was computed to be a factor of 2.5 in the test chamber. Supported by other work, this implies that the underground miners must experience a similar lung dose reduction. A prior estimate of a factor of 4 was obtained for the miners, but with only an estimate of the crucially important mine humidity distributions. Here a re-evaluation, using more realistic values for a representative mine work area surface to volume ratio and using in-mine measured humidity data at 108 mine work locations in 15 different mines, the re-computed estimate for the EDE miner lung dose rate reduction was 4.3. Analyzing separately in-mine data in unventilated locations finds a greater transition rate of the EDE lung dose reduction. These results are affirmed by measured mine progeny to radon concentration ratios, mine deposition rates and miners' individual work shift exposures at the North Alice, Utah mine. In comparing our data with other radon "inverse" dose rate effect (IDRE) data, a significant portion of the IDRE must be from reduction in lung dose from this EDE and not from decreased lung cancer incidence per progeny lung dose. We offer the only currently plausible answer for IDRE. This does not negate any bystander effects at the very low radon concentrations where other data are least accurate.

Radioactive materials in biosolids: dose modeling

The Interagency Steering Committee on Radiation Standards (ISCORS) has recently completed a study of the occurrence within the United States of radioactive materials in sewage sludge and sewage incineration ash. One component of that effort was an examination of the possible transport of radioactivity from sludge into the local environment and the subsequent exposure of humans. A stochastic environmental pathway model was applied separately to seven hypothetical, generic sludge-release scenarios, leading to the creation of seven tables of Dose-to-Source Ratios (DSR), which can be used in translating from specific activity in sludge into dose to an individual. These DSR values were then combined with the results of an ISCORS survey of sludge and ash at more than 300 publicly owned treatment works, to explore the potential for radiation exposure of sludge workers and members of the public. This paper provides a brief overview of the pathway modeling methodology employed in the exposure and dose assessments and discusses technical aspects of the results obtained.

Public Education and Cancer Control

OBJECTIVES

To provide an overview of public education efforts in tobacco, obesity, environmental health, and cancer screening.

DATA SOURCES

Cochrane, AHRQ, the CDC's Guide to Community Preventive Services, and other reviews.

CONCLUSION

Major changes in rates of smoking and cancer screening attest to the effectiveness of public education efforts. Diet and physical activity have more resistant behaviors. Communication technologies offer possibilities for connecting people with the education they need.

IMPLICATIONS FOR NURSING PRACTICE

Nurses can play important roles in public education by helping to overcome people's misperceptions and biases related to cancer. There also may be an important role for nurses as information brokers.