Domestic radon exposure and risk of childhood leukemia: A meta-analysis

PURPOSE

This meta-analysis evaluated the potential influence of environmental radon exposure on childhood leukemia.

METHODS

We searched comprehensive electronic databases from PubMed, EMBASE, and Cochrane Library to identify studies evaluating the association between radon and leukemia.

RESULTS

Ten eligible studies published from 1995 to 2014 were enrolled. Of these 10 studies, 8 were case-control studies (involving 10803 cases and 16202 controls) and 2 were cohort studies (involving 1,428 cases). Overall results as odds ratio (OR) with the corresponding 95% confidence intervals (95%CI) for case-control studies and fully adjusted hazard ratio (HR) with corresponding 95%CI for cohort studies were identified. A positive but weak association was found between radon exposure and childhood leukemia in case-control studies (summary OR 1.22, 95%CI 1.01-1.42) rather than cohort studies (summary HR 0.97, 95%CI 0.81-1.15). Heterogeneity or publication bias was not observed. Moreover, overall ORs were not changed by removing any single study, suggesting the stability and reliability of conclusions.

CONCLUSIONS

Future prospective studies with well-controlled confounders are needed to verify the conclusion.

Radon, an invisible killer in Canadian homes: perceptions of Ottawa-Gatineau residents

OBJECTIVES

Canadians have reason to care about indoor air quality as they spend over 90% of the time indoors. Although indoor radon causes more deaths than any other environmental hazard, only 55% of Canadians have heard of it, and of these, 6% have taken action. The gap between residents' risk awareness and adoption of actual protective behaviour presents a challenge to public health practitioners. Residents' perception of the risk should inform health communication that targets motivation for action. In Canada, research about the public perception of radon health risk is lacking. The aim of this study was to describe residents' perceptions of radon health risks and, applying a theoretical lens, evaluate how perceptions correlate with protection behaviours.

METHODS

We conducted a mixed online and face-to-face survey (N = 557) with both homeowners and tenants in Ottawa-Gatineau census metropolitan area. Descriptive, correlation, and regression analyses addressed the research questions.

RESULTS

Compared to the gravity of the risk, public perception remained low. While 32% of residents expressed some concern about radon health risk, 12% of them tested and only 3% mitigated their homes for radon. Residents' perceptions of the probability and severity of the risk, social influence, care for children, and smoking in home correlated significantly with their intention to test; these factors also predicted their behaviours for testing and mitigation.

CONCLUSION

Health risk communication programs need to consider the affective aspects of risk perception in addition to rational cognition to improve protection behaviours. A qualitative study can explore the reasons behind the gap between testing and mitigation.

Indoor Radon and Lung Cancer: Estimation of Attributable Risk, Disease Burden, and Effects of Mitigation

PURPOSE

Exposure to indoor radon is associated with lung cancer. This study aimed to estimate the number of lung cancer deaths attributable to indoor radon exposure, its burden of disease, and the effects of radon mitigation in Korea in 2010.

MATERIALS AND METHODS

Lung cancer deaths due to indoor radon exposure were estimated using exposure-response relations reported in previous studies. Years of life lost (YLLs) were calculated to quantify disease burden in relation to premature deaths. Mitigation effects were examined under scenarios in which all homes with indoor radon concentrations above a specified level were remediated below the level.

RESULTS

The estimated number of lung cancer deaths attributable to indoor radon exposure ranged from 1946 to 3863, accounting for 12.5-24.7% of 15623 total lung cancer deaths in 2010. YLLs due to premature deaths were estimated at 43140-101855 years (90-212 years per 100000 population). If all homes with radon levels above 148 Bq/m³ are effectively remediated, 502-732 lung cancer deaths and 10972-18479 YLLs could be prevented.

CONCLUSION

These findings suggest that indoor radon exposure contributes considerably to lung cancer, and that reducing indoor radon concentration would be helpful for decreasing the disease burden from lung cancer deaths.

Residential radon and small cell lung cancer. A systematic review

Residential radon exposure is considered the second cause of lung cancer and the first in never smokers. Nevertheless, the association between the different histological types of lung cancer and radon is not completely clear, and radon effect on small cell lung cancer is not completely understood. We aim to asses the effect of residential radon exposure on the risk of small cell lung cancer (SCLC) in general population and miners through a systematic review applying predefined inclusion and exclusion criteria. 16 studies were included. Most of them point to a relationship between indoor radon and SCLC, though some investigations show no association. When comparing the risk of SCLC due to radon exposure with NSCLC, it can be observed that an increased risk for SCLC is present. Small cell lung cancer seems to be the histological type of lung cancer most tightly related with residential radon.

Geographic variation in radon and associated lung cancer risk in Canada

OBJECTIVE

Radon is an important risk factor for lung cancer. Here we use maps of the geographic variation in radon to estimate the lung cancer risk associated with living in high radon areas of Canada.

METHODS

Geographic variation in radon was estimated using two mapping methods. The first used a Health Canada survey of 14,000 residential radon measurements aggregated to health regions, and the second, radon risk areas previously estimated from geology, sediment geochemistry and aerial gamma-ray spectrometry. Lung cancer risk associated with living in these radon areas was examined using a population-based case-control study of 2,390 lung cancer cases and 3,507 controls collected from 1994-1997 in eight Canadian provinces. Residential histories over a 20-year period were used in combination with the two mapping methods to estimate ecological radon exposures. Hierarchical logistic regression analyses were used to estimate odds ratios for lung cancer incidence, after adjusting for a comprehensive set of individual and geographic covariates.

RESULTS

Across health regions in Canada, significant variation in average residential radon concentrations (range: 16-386 Bq/m3) and in high geological-based radon areas (range: 0-100%) is present. In multivariate models, a 50 Bq/m3 increase in average health region radon was associated with a 7% (95% CI: -6-21%) increase in the odds of lung cancer. For every 10 years that individuals lived in high radon geological areas, the odds of lung cancer increased by 11% (95% CI: 1-23%).

CONCLUSIONS

These findings provide further evidence that radon is an important risk factor for lung cancer and that risks are unevenly distributed across Canada.

Dual home screening and tailored environmental feedback to reduce radon and secondhand smoke: an exploratory study

Combined exposure to secondhand smoke (SHS) and radon increases lung cancer risk 10-fold. The authors assessed the feasibility and impact of a brief home screening and environmental feedback intervention to reduce radon and SHS (Freedom from Radon and Smoking in the Home [FRESH]) and measured perceived risk of lung cancer and synergistic risk perception (SHS x radon). Participants (N = 50) received home radon and SHS kits and completed baseline surveys. Test results were shared using an intervention guided by the Teachable Moment Model. Half of the participants completed online surveys two months later. Most (76%) returned the radon test kits; 48% returned SHS kits. Of the returned radon test kits, 26% were >4.0 pCi/L. Of the returned SHS kits, 38% had nicotine > .1 microg/m3. Of those with high radon, more than half had contacted a mitigation specialist or planned contact. Of those with positive air nicotine, 75% had adopted smoke-free homes. A significant increase occurred in perceived risk for lung cancer and synergistic risk perception after FRESH.

Incidence of non-lung solid cancers in Czech uranium miners: a case-cohort study

OBJECTIVES

Uranium miners are chronically exposed to radon and its progeny, which are known to cause lung cancer and may be associated with leukemia. This study was undertaken to evaluate risk of non-lung solid cancers among uranium miners in Příbram region, Czech Republic.

METHODS

A retrospective stratified case-cohort study in a cohort of 22,816 underground miners who were employed between 1949 and 1975. All incident non-lung solid cancers were ascertained among miners who worked underground for at least 12 months (n=1020). A subcohort of 1707 subjects was randomly drawn from the same population by random sampling stratified on age. The follow-up period lasted from 1977 to 1996.

RESULTS

Relative risks comparing 180 WLM (90th percentile) of cumulative lifetime radon exposure to 3 WLM (10th percentile) were 0.88 for all non-lung solid cancers combined (95% CI 0.73-1.04, n=1020), 0.87 for all digestive cancers (95% CI 0.69-1.09, n=561), 2.39 for gallbladder cancer (95% CI 0.52-10.98, n=13), 0.79 for larynx cancer (95% CI 0.38-1.64, n=62), 2.92 for malignant melanoma (95% CI 0.91-9.42, n=23), 0.84 for bladder cancer (95% CI 0.43-1.65, n=73), and 1.13 for kidney cancer (95% CI 0.62-2.04, n=66). No cancer type was significantly associated with radon exposure; only malignant melanoma and gallbladder cancer showed elevated but non-significant association with radon.

CONCLUSIONS

Radon was not significantly associated with incidence of any cancer of interest, although a positive association of radon with malignant melanoma and gallbladder cancer cannot be entirely ruled out.

A hybrid model for reducing ecological bias

A major drawback of epidemiological ecological studies, in which the association between area-level summaries of risk and exposure is used to make inference about individual risk, is the difficulty in characterizing within-area variability in exposure and confounder variables. To avoid ecological bias, samples of individual exposure/confounder data within each area are required. Unfortunately, these may be difficult or expensive to obtain, particularly if large samples are required. In this paper, we propose a new approach suitable for use with small samples. We combine a Bayesian nonparametric Dirichlet process prior with an estimating functions' approach and show that this model gives a compromise between 2 previously described methods. The method is investigated using simulated data, and a practical illustration is provided through an analysis of lung cancer mortality and residential radon exposure in counties of Minnesota. We conclude that we require good quality prior information about the exposure/confounder distributions and a large between- to within-area variability ratio for an ecological study to be feasible using only small samples of individual data.

Environments, indoor air quality, and children

This article addresses air-quality science in the indoor environments in which children and adolescents find themselves, including the home, the school, and other environments such as work and recreational situations. The home arena is covered extensively, presenting an analysis of the usual exposures such as environmental tobacco smoke and bioaerosols and also touching on discrete issues such as sudden infant death syndrome, carbon monoxide, and public housing. Recreation and work environments are covered as well.

Toxin or Medicine? Explanatory Models of Radon in Montana Health Mines

Environmental protection and public health agencies in the United States and elsewhere label radioactive radon gas a toxic environmental hazard and a major cause of lung cancer. Paradoxically, in Europe and Japan radon gas is also used as an analgesic and anti-inflammatory, as one choice in the spectrum of conventional medical care. Although it is possible to find radon therapy in the United States, it exists only as an unconventional practice in Montana "radon health mines." In this article, I examine the use of radon therapy by Americans despite intensive public health education media campaigns. Using the notion of explanatory models as an analytical framework, I argue that American health mine clients adjust or replace "toxic models" of radon with new kinds of explanatory models that allow radon to be redefined as a healing substance. The manner of this adjustment varies according to peoples' individual needs, their own preexisting cultural models and experiences, and their individual personalities; the source of authoritative knowledge accepted by each person is a strong influence. Through these altered explanatory models, mine clients are able to view their use of radon therapy as a rational course of action.

Examining the relationship between lung cancer and radon in small areas across Scotland

Numerous studies have suggested that long-term exposure to radon gas may be an important cause of lung cancer, yet the precise effects are still not fully understood, especially in residential settings. This paper considers whether there is a relationship between the distribution of naturally occurring radon gas and lung cancer incidence in Scotland, for the period 1988-1991. We use regression analysis to test whether exposure to radon was a significant cause of lung cancer in Scotland, once smoking and other possible confounding factors were controlled for. The results demonstrate that for the population aged over 54, there was no significant relationship between radon exposure and lung cancer incidence. However, for those aged less than 55, lung cancer rates were significantly higher in places expected to have the highest levels of radon. These results suggest that more research is needed into the relationship between exposure to naturally occurring radon gas and lung cancer in Scotland, particularly among younger age groups.

Residential radon exposure, diet and lung cancer: a case-control study in a Mediterranean region

We performed a case-control study in Lazio, a region in central Italy characterized by high levels of indoor radon, Mediterranean climate and diet. Cases (384) and controls (404) aged 35-90 years were recruited in the hospital. Detailed information regarding smoking, diet and other risk factors were collected by direct interview. Residential history during the 30-year period ending 5 years before enrollment was ascertained. In each dwelling, radon detectors were placed in both the main bedroom and the living room for 2 consecutive 6-month periods. We computed odds ratios (ORs) and 95% confidence intervals (CIs) for time-weighted radon concentrations using both categorical and continuous unconditional logistic regression analysis and adjusting for smoking, diet and other variables. Radon measurements were available from 89% and 91% of the time period for cases and controls, respectively. The adjusted ORs were 1.30 (1.03-1.64), 1.48 (1.08-2.02), 1.49 (0.82-2.71) and 2.89 (0.45-18.6) for 50-99, 100-199, 200-399 and 400+ Bq/m(3), respectively, compared with 0-49 Bq/m(3) (OR = 1; 0.56-1.79). The excess odds ratio (EOR) per 100 Bq/m(3) was 0.14 (-0.11, 0.46) for all subjects, 0.24 (-0.09, 0.70) for subjects with complete radon measurements and 0.30 (-0.08, 0.82) for subjects who had lived in 1 or 2 dwellings. There was a tendency of higher risk estimates among subjects with low-medium consumption of dietary antioxidants (EOR = 0.32; -0.19, 1.16) and for adenocarcinoma, small cell and epidermoid cancers. This study indicates an association, although generally not statistically significant, between residential radon and lung cancer with both categorical and continuous analyses. Subjects with presumably lower uncertainty in the exposure assessment showed a higher risk. Dietary antioxidants may act as an effect modifier.

Residential radon and risk of lung cancer: a combined analysis of 7 North American case-control studies

BACKGROUND

Underground miners exposed to high levels of radon have an excess risk of lung cancer. Residential exposure to radon is at much lower levels, and the risk of lung cancer with residential exposure is less clear. We conducted a systematic analysis of pooled data from all North American residential radon studies.

METHODS

The pooling project included original data from 7 North American case-control studies, all of which used long-term alpha-track detectors to assess residential radon concentrations. A total of 3662 cases and 4966 controls were retained for the analysis. We used conditional likelihood regression to estimate the excess risk of lung cancer.

RESULTS

Odds ratios (ORs) for lung cancer increased with residential radon concentration. The estimated OR after exposure to radon at a concentration of 100 Bq/m3 in the exposure time window 5 to 30 years before the index date was 1.11 (95% confidence interval = 1.00-1.28). This estimate is compatible with the estimate of 1.12 (1.02-1.25) predicted by downward extrapolation of the miner data. There was no evidence of heterogeneity of radon effects across studies. There was no apparent heterogeneity in the association by sex, educational level, type of respondent (proxy or self), or cigarette smoking, although there was some evidence of a decreasing radon-associated lung cancer risk with age. Analyses restricted to subsets of the data with presumed more accurate radon dosimetry resulted in increased estimates of risk.

CONCLUSIONS

These results provide direct evidence of an association between residential radon and lung cancer risk, a finding predicted using miner data and consistent with results from animal and in vitro studies.

The potential risk from 222radon posed to archaeologists and earth scientists: reconnaissance study of radon concentrations, excavations, and archaeological shelters in the Great Cave of Niah, Sarawak, Malaysia

This reconnaissance study of radon concentrations in the Great Cave of Niah in Sarawak shows that in relatively deep pits and trenches in surficial deposits largely covered by protective shelters with poor ventilation, excavators are working in a micro-environment in which radon concentrations at the ground surface can exceed those of the surrounding area by a factor of > x 2. Although radon concentrations in this famous cave are low by world standards (alpha track-etch results ranging from 100 to 3075 Bq m(-3)), they still may pose a health risk to both excavators (personal dosemeter readings varied from 0.368 to 0.857 mSv for 60 days of work) and cave occupants (1 yr exposure at 15 h per day with an average radon level of 608 Bq m(-3) giving a dose of 26.42 mSv). The data here presented also demonstrate that there is considerable local variation in radon levels in such environments as these.

Analysis of the individual health benefits accruing from a domestic radon remediation programme

Although radon can be present within buildings at sufficient levels to pose a health risk, levels can be reduced relatively easily. Recent studies on a group of radon-remediated homes, based on assessment of collective population-average risk coefficients, have estimated the benefits and cost effectiveness accruing from remediation and have confirmed that domestic remediation in UK radon Affected Areas would result in significantly reduced cancer risks to the population in those areas. Although the population-average approach used hitherto has applied occupancy and lung-cancer risk factors, these are potentially misleading in assessing discrete populations. The study reported here uses the recently developed European Community Radon Software (ECRS) to quantify individual risks in a sample of householders who remediated their homes following indications that radon levels exceeded the action level. The study proceeds from population-averaged to 'individual risk' evaluation, successfully comparing individual and collective risk assessments, and demonstrates that those who remediate are not representative of the general population. Health benefits accruing from remediation are three times lower than expected, largely because remediators are older, live in smaller households, and smoke less than the population average, leading to the conclusion that the current strategy employed in the UK is failing to target those most at risk.

Comparative study on Tp53 gene mutations in lung tumors from rats exposed to 239Pu, 237Np and 222Rn

The tumor suppressor gene Tp53 was analyzed by polymerase chain reaction-amplification of genomic DNA extracted from paraffin-embedded tissue sections of rat lung tumors to compare mutations that occurred after inhalation exposures to plutonium dioxide, neptunium dioxide, or radon and radon progenies. Exons 5 to 8 of the gene were amplified in 16 plutonium-, 23 neptunium- and 15 radon-induced lung tumors, and their polymerase chain reaction products were examined for mutations by single strand conformational polymorphism analysis and direct sequencing method. Two point mutations were detected in the plutonium-induced tumors, i.e., a guanine to adenine transition at codon 219 of exon 6 and a cytosine to thymine transition at codon 266 of exon 8. Although only one point mutation was found at codon 175 of exon 5 (cytosine to thymine transition) from neptunium-induced tumors, no mutations were detectable from radon-induced tumors. These results indicate that the abnormalities of the Tp53 gene might not be so critical for the pulmonary carcinogenesis after the inhalation of different alpha emitters, even though the presence and frequencies of the Tp53 gene mutations were different.

Residential radon and risk of lung cancer in Eastern Germany

BACKGROUND

There is suggestive evidence that residential radon increases lung cancer risk. To elucidate this association further, we conducted a case-control study in Thuringia and Saxony in Eastern Germany during 1990-1997.

METHODS

Histologically confirmed lung cancer patients from hospitals and a random sample of population controls matched on age, sex and geographical area were personally interviewed with respect to residential history, smoking, and other risk factors. One-year radon measurements were performed in houses occupied during the 5-35 years prior to the interview. The final analysis included a total of 1,192 cases and 1,640 controls. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by logistic regression.

RESULTS

Measurements covered on average 72% of the exposure time window, with mean radon concentrations of 76 Bq/m3 among the cases and 74 Bq/m3 among the controls. The smoking- and asbestos-adjusted ORs for categories of radon (50-80, 80-140 and >140 Bq/m*3, compared with 0-50 Bq/m3) were 0.95 (CI = 0.77 to 1.18), 1.13 (CI = 0.86 to1.50) and 1.30 (CI = 0.88 to 1.93). The excess relative risk per 100 Bq/mł was 0.08 (CI = -0.03 to 0.20) for all subjects and 0.09 (CI = -0.06 to 0.27) for subjects with complete measurements for all 30 years.

CONCLUSIONS

Our data indicate a small increase in lung cancer risk as a result of residential radon that is consistent with the findings of previous indoor radon and miner studies.

Preliminary indoor radon risk assessment at the Poços de Caldas Plateau, MG-Brazil

This paper aims to present an assessment of the environmental radiological exposure at a Brazilian area of high natural radiation and discusses the indoor radon exposure risk. A survey of inhabitant exposures arising from the inhalation of radon progeny and external gamma exposure was conducted in urban and rural areas of the Poços de Caldas Plateau, which is recognized worldwide as a high natural radiation region. The results of this survey indicated that highest radiation exposure was restricted to the rural area of Poços de Caldas. The radiation exposure in urban locations was quite similar to the values observed in normal background areas in some Brazilian counties. By the application of a constant relative risk model, an additional 20% in the lifetime risk of lung cancer mortality due to the exposure to radon progeny was estimated at Poços de Caldas. It was also estimated that 16% of all lung cancer deaths at Poços de Caldas county could be attributable to radon exposure.

Cancer incidence among workers exposed to radon and thoron daughters at a niobium mine

The aim of this study was to investigate the incidence of cancer among 318 male employees of a niobium mining company which was only operated between 1951 and 1965. Many of the workers, especially underground miners, were exposed to the daughters of radon and thoron and also to thorium. The accumulated doses to the workers from short-lived radon and thoron daughters in the mine atmosphere were assessed to be relatively low; up to 300 working-level months. During the follow-up period 1953-1981, 24 new cases of cancer were observed compared to an expected number of 22.8. Twelve cases of lung cancer had occurred versus 3.0 expected. Among the 77 miners, 9 cases of lung cancer were observed against 0.8 expected. Associations between the occurrence of lung cancer and exposure to alpha radiation and smoking were found. For the radon and thoron daughter exposure, about 50 excess cases per million person-years at risk per working-level month were observed.