Residential radon exposure and lung cancer in Sweden

Human Health Impacts of Residential Radon Exposure: Updated Systematic Review and Meta-Analysis of Case-Control Studies

This study investigated the impact of residential radon exposure on human cancers (i.e., lung cancer and childhood leukemia) through a systematic review and meta-analysis of case−control studies. A total of 9724 articles obtained from electronic databases were assessed; however, only 55 case−control studies were eligible after manually screening and eliminating unnecessary studies. The causal associations were addressed by determining the meta-analysis’s estimated size effects (i.e., ORs/RRs) of the meta-analysis. Residential radon was revealed to significantly increase the incidence of lung cancer and childhood leukemia with pooled ORs of 1.38 [1.19; 1.60] (I2 = 90%; p < 0.00001) and 1.43 [1.19; 1.72] (I2 = 0% and p = 0.51), respectively. In addition, subgroup analyses were performed to reduce the heterogeneity of the initial meta-analyses. The results provided strong evidence that inhaling radon in the indoor environments is closely associated with the development of lung cancer and childhood leukemia in patients living in Europe and areas with high radon levels (≥100 Bq/m3).

Indoor radon exposure and its correlation with the radiometric map of uranium in Sweden

Indoor radon concentrations are controlled by both human factors and geological factors. It is important to separate the anthropogenic and geogenic contributions. We show that there is a positive correlation between the radiometric map of uranium in the ground and the measured radon in the household in Sweden. A map of gamma radiation is used to obtain an equivalent uranium concentration (ppm eU) for each postcode area. The aggregated uranium content is compared to the yearly average indoor radon concentration for different types of houses. Interestingly, modern households show reduced radon concentrations even in postcode areas with high average uranium concentrations. This shows that modern construction is effective at reducing the correlation with background uranium concentrations and minimizing the health risk associated with radon exposure. These correlations and predictive housing parameters could assist in monitoring higher risk areas.

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.

Rising Canadian and falling Swedish radon gas exposure as a consequence of 20th to 21st century residential build practices

Radioactive radon gas inhalation is a major cause of lung cancer worldwide and is a consequence of the built environment. The average radon level of properties built in a given period (their 'innate radon risk') varies over time and by region, although the underlying reasons for these differences are unclear. To investigate this, we analyzed long term radon tests and buildings from 25,489 Canadian to 38,596 Swedish residential properties constructed after 1945. While Canadian and Swedish properties built from 1970 to 1980s are comparable (96-103 Bq/m3), innate radon risks subsequently diverge, rising in Canada and falling in Sweden such that Canadian houses built in the 2010-2020s have 467% greater radon (131 Bq/m3) versus Swedish equivalents (28 Bq/m3). These trends are consistent across distinct building types, and regional subdivisions. The introduction of energy efficiency measures (such as heat recovery ventilation) within each nation's build codes are independent of radon fluctuations over time. Deep learning-based models forecast that (without intervention) the average Canadian residential radon level will increase to 176 Bq/m3 by 2050. Provisions in the 2010 Canada Build Code have not significantly reduced innate radon risks, highlighting the urgency of novel code interventions to achieve systemic radon reduction and cancer prevention in Canada.

The shared genetic architecture between epidemiological and behavioral traits with lung cancer

The complex polygenic nature of lung cancer is not fully characterized. Our study seeks to identify novel phenotypes associated with lung cancer using cross-trait linkage disequilibrium score regression (LDSR). We measured pairwise genetic correlation (rg) and SNP heritability (h2) between 347 traits and lung cancer risk using genome-wide association study summary statistics from the UKBB and OncoArray consortium. Further, we conducted analysis after removing genomic regions previously associated with smoking behaviors to mitigate potential confounding effects. We found significant negative genetic correlations between lung cancer risk and dietary behaviors, fitness metrics, educational attainment, and other psychosocial traits. Alcohol taken with meals (rg = - 0.41, h2 = 0.10, p = 1.33 × 10-16), increased fluid intelligence scores (rg = - 0.25, h2 = 0.22, p = 4.54 × 10-8), and the age at which full time education was completed (rg = - 0.45, h2 = 0.11, p = 1.24 × 10-20) demonstrated negative genetic correlation with lung cancer susceptibility. The body mass index was positively correlated with lung cancer risk (rg = 0.20, h2 = 0.25, p = 2.61 × 10-9). This analysis reveals shared genetic architecture between several traits and lung cancer predisposition. Future work should test for causal relationships and investigate common underlying genetic mechanisms across these genetically correlated traits.

Systematic review and meta-analysis of residential radon and lung cancer in never-smokers

Background

Globally, radon is the leading risk factor for lung cancer in never-smokers (LCINS). In this study, we systematically reviewed and meta-analysed the evidence of the risk of LCINS associated with residential radon exposure.

Methods

Medline and Embase databases were searched using predefined inclusion and exclusion criteria to identify relevant studies published from 1 January 1990 to 5 March 2020 focused on never-smokers. We identified four pooled collaborative studies (incorporating data from 24 case–control studies), one case–control study and one cohort study for systematic review. Meta-analysis was performed on the results of the four pooled studies due to different measures of effect and outcome reported in the cohort study and insufficient information reported for the case–control study. In a post hoc analysis, the corresponding risk for ever-smokers was also examined.

Results

Risk estimates of lung cancer from residential radon exposure were pooled in the meta-analysis for 2341 never-smoker cases, 8967 never-smoker controls, 9937 ever-smoker cases and 12 463 ever-smoker controls. Adjusted excess relative risks (aERRs) per 100 Bq·m⁻³ of radon level were 0.15 (95% CI 0.06–0.25) for never-smokers and 0.09 (95% CI 0.03–0.16) for ever-smokers, and the difference between them was statistically insignificant (p=0.32). The aERR per 100 Bq·m⁻³was higher for men (0.46; 95% CI 0.15–0.76) than for women (0.09; 95% CI −0.02–0.20) among never-smokers (p=0.027).

Conclusion

This study provided quantified risk estimates for lung cancer from residential radon exposure among both never-smokers and ever-smokers. Among never-smokers in radon-prone areas, men were at higher risk of lung cancer than women.

Globally, radon is the leading cause of lung cancer in never-smokers. Yet its quantified link with lung cancer risk among never-smokers is not known. This study computes the risk estimate of lung cancer from residential radon exposure among never-smokers.https://bit.ly/32frCbq

A 10-year follow-up study of yearly indoor radon measurements in homes, review of other studies and implications on lung cancer risk estimates

Uncertainty on long-term average radon concentration has a large impact on lung cancer risk assessment in epidemiological studies. The uncertainty can be estimated by year-to-year radon concentration variability, however few data are available. In Italy a study has been planned and conducted to evaluate year-to-year radon variability over several years in normally inhabited dwellings, mainly located in Rome. This is the longest study of this kind in Europe; repeat radon measurements are carried out for 10 years using LR-115 radon detectors in the same home in consecutive years. The study includes 84 dwellings with long-term average radon concentration ranging from 28 to 636 Bq/m³. The result shows that year-to-year variability of repeated measurements made in the same home in different years is low, with an overall coefficient of variation of 17%. This is smaller than most of those observed in studies from other European countries and USA, ranging from 15% to 62%. Influencing factors that may explain the differences between this study and other studies have been discussed. Due to the low yearly variability estimated in the present 10-year study, a negligible impact on lung cancer risk estimate for the Italian epidemiological study is expected.

Residential Radon and Small Cell Lung Cancer. Final Results of the Small Cell Study

INTRODUCTION

Residential radon is considered the second cause of lung cancer and the first in never smokers. Nevertheless, there is little information regarding the association between elevated radon levels and small cell lung cancer (SCLC). We aimed to assess the effect of residential radon exposure on the risk of SCLC in general population through a multicentric case-control study.

METHODS

A multicentric hospital-based case-control study was designed including 9 hospitals from Spain and Portugal, mostly including radon-prone areas. Indoor radon was measured using Solid State Nuclear Track Detectors at the Galician Radon Laboratory.

RESULTS

A total of 375 cases and 902 controls were included, with 24.5% of cases being women. The median number of years living in the measured dwelling was higher than 25 years for both cases and controls. There was a statistically significant association for those exposed to concentrations higher than the EPA action level of 148Bq/m3, with an Odds Ratio of 2.08 (95%CI: 1.03-4.39) compared to those exposed to concentrations lower than 50Bq/m3. When using a dose-response model with 100Bq/m3 as a reference, it can be observed a linear effect for small cell lung cancer risk. Smokers exposed to higher radon concentrations pose a much higher risk of SCLC compared to smokers exposed to lower indoor radon concentrations.

CONCLUSIONS

Radon exposure seems to increase the risk of small cell lung cancer with a linear dose-response pattern. Tobacco consumption may also produce an important effect modification for radon exposure.

Radon-The Element of Risk. The Impact of Radon Exposure on Human Health

Lung cancer is a heterogeneous group of diseases with multifactorial aetiology. Smoking has been undeniably recognized as the main aetiological factor in lung cancer, but it should be emphasized that it is not the only factor. It is worth noting that a number of nonsmokers also develop this disease. Radon exposure is the second greatest risk factor for lung cancer among smokers-after smoking-and the first one for nonsmokers. The knowledge about this element amongst specialist oncologists and pulmonologists seems to be very superficial. We discuss the impact of radon on human health, with particular emphasis on respiratory diseases, including lung cancer. A better understanding of the problem will increase the chance of reducing the impact of radon exposure on public health and may contribute to more effective prevention of a number of lung diseases.

Lung cancer risk and residential radon exposure: A pooling of case-control studies in northwestern Spain

BACKGROUND

Through a pooled case-control study design, we have assessed the relationship between residential radon exposure and lung cancer risk. Other objectives of the study were to evaluate the different risk estimates for the non-small cell lung cancer histological types and to assess the effect modification of the radon exposure on lung cancer risk by tobacco consumption.

METHODS

We collected individual data from various case-control studies performed in northwest Spain that investigated residential radon and lung cancer. Cases had a confirmed anatomopathological diagnosis of primary lung cancer and controls were selected because they were undergoing ambulatory evaluation or surgical procedures that were unrelated to tobacco use. Residential radon was measured using alpha track detectors. Results were analyzed using logistic regression.

RESULTS

3704 participants were enrrolled, 1842 cases and 1862 controls. Data show that lung cancer risk increases with radon exposure, finding a significant association of radon exposure with lung cancer at radon exposures above 50 Bq/m³. The estimated adjusted OR for individuals exposed to concentrations >200 Bq/m³ was 2.06 (95% CI: 1.61-2.64) compared with those exposed to ≤50 Bq/m³. Within a smoking category, lung cancer risk increases markedly as radon concentration increases, reaching an OR of 29.3 (95% CI: 15.4-55.7) for heavy smokers exposed to more than 200 Bq/m.³ CONCLUSIONS: This study confirms that residential radon exposure is a risk factor for lung cancer well below action levels established by international organizations. As expected, there is also an effect modification between radon exposure and tobacco consumption.

Comparison of antioxidative effects between radon and thoron inhalation in mouse organs

Radon therapy has been traditionally performed globally for oxidative stress-related diseases. Many researchers have studied the beneficial effects of radon exposure in living organisms. However, the effects of thoron, a radioisotope of radon, have not been fully examined. In this study, we aimed to compare the biological effects of radon and thoron inhalation on mouse organs with a focus on oxidative stress. Male BALB/c mice were randomly divided into 15 groups: sham inhalation, radon inhalation at a dose of 500 Bq/m³ or 2000 Bq/m³, and thoron inhalation at a dose of 500 Bq/m³ or 2000 Bq/m³ were carried out. Immediately after inhalation, mouse tissues were excised for biochemical assays. The results showed a significant increase in superoxide dismutase and total glutathione, and a significant decrease in lipid peroxide following thoron inhalation under several conditions. Additionally, similar effects were observed for different doses and inhalation times between radon and thoron. Our results suggest that thoron inhalation also exerts antioxidative effects against oxidative stress in organs. However, the inhalation conditions should be carefully analyzed because of the differences in physical characteristics between radon and thoron.

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.

Lung cancer progression using fast switching multiple ion beam radiation and countermeasure prevention

Most of the research in understanding space radiation-induced cancer progression and risk assessment has been performed using mono-energetic single-ion beams. However, the space radiation environment consists of a wide variety of ion species with a various range of energies. Using the fast beam switching technology developed at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL), ion species can be switched rapidly allowing investigators to use multiple ions with different energies to simulate more closely the radiation environment found in space. Here, we exposed a lung cancer susceptible mouse model (K-ras^LA-1) to three sequential ion beams: Proton (H) (120 MeV/n) 20 cGy, Helium (He) (250 MeV/n) 5.0 cGy, and Silicon (Si) (300 MeV/n) 5.0 cGy with a dose rate of 0.5 cGy/min. Using three ion beams we performed whole body irradiation with a total dose of 30 cGy in two different orders: 3B-1 (H→He→Si) and 3B-2 (Si→He→H) and used 30 cGy H single-ion beam as a reference. In this study we show that whole-body irradiation with H→He→Si increases the incidence of premalignant lesions and systemic oxidative stress in mice 100 days post-irradiation more than (Si→He→H) and H only irradiation. Additionally, we observed an increase in adenomas with atypia and adenocarcinomas in H→He→Si irradiated mice but not in (Si→He→H) or H (30 cGy) only irradiated mice. When we used the H→He→Si irradiation sequence but skipped a day before exposing the mice to Si, we did not observe the increased incidence of cancer initiation and progression. We also found that a non-toxic anti-inflammatory, anti-oxidative radioprotector (CDDO-EA) reduced H→He→Si induced oxidative stress and cancer initiation almost back to baseline. Thus, exposure to H→He→Si elicits significant changes in lung cancer initiation that can be mitigated using CDDO-EA.

MEASUREMENT OF RADON SOIL GAS IN AND AROUND BHARATHINAGARA, MANDYA DISTRICT

Radon activity concentration in soil gas has been studied in and around Bharathinagara, Mandya district (12° 13|| N and 77° 20|| E) using Solid State Nuclear Track Detectors with Twin cup dosimeter. The activity concentration of 222Rn in soil gas was studied at two depths. Radon in soil gas was found to increase with depth and decrease with increase in moisture content of the soil. Radon in soil gas was found to be higher in winter season which varies from 0.22 ± 0.01 to 1.31 ± 0.01 kBq/m3 with a Geometric mean value of 0.56 ± 0.01 kBq/m3 in 1 m depth and lower radon soil gas was found to be 0.16 ± 0.01 to 0.60 ± 0.01 kBq/m3 with a Geometric mean value of 0.30 ± 0.01 kBq/m3 in 0.5 m depth during summer season. The activity concentrations of radon soil gas from in and around Bharathinagara are lower compared to those in other parts of the world.

Lifetime Smoking History and Risk of Lung Cancer: Results From the Framingham Heart Study

Background

The relative risk of lung cancer decreases with years since quitting (YSQ) smoking, but risk beyond 25 YSQ remains unclear. Current lung cancer screening guidelines, which exclude smokers with more than 15 YSQ, may not detect lung cancers in this population.

Methods

We analyzed data from Framingham Heart Study Original (n = 3905) and Offspring cohort (n = 5002) participants for lifetime smoking and lung cancer incidence from 1954 to 1958 (Exam 4) and 1971 to 1975 (Exam 1), respectively, through 2013. We used multivariable-adjusted Cox proportional hazards regression models to compare current, former, and never smokers and lung cancer risk. Smoking status and covariates were time-updated every two years (Original) or four years (Offspring). Primary analyses were restricted to heavy ever smokers with more than 21.3 pack-years; additional analyses included all ever smokers.

Results

On follow-up (median = 28.7 years), 284 lung cancers were detected: incidence rates/1000 person-years in current, former, and never smokers were 1.97 (95% confidence interval [CI] = 1.66 to 2.33), 1.61 (95% CI = 1.34 to 1.93), and 0.26 (95% CI = 0.17 to 0.39), respectively. Heavy former (vs never) smokers had elevated lung cancer risk at all YSQ (<5: hazard ratio [HR] = 12.12, 95% CI = 6.94 to 21.17; 5-9: HR = 11.77, 95% CI = 6.78 to 20.45; 10-14: HR = 7.81, 95% CI = 3.98 to 15.33; 15-24: HR = 5.88, 95% CI = 3.19-10.83; ≥25: HR = 3.85, 95% CI = 1.80 to 8.26). Heavy former (vs current) smokers had 39.1% lower lung cancer risk within five YSQ. Among all former smokers, 40.8% of lung cancers occurred after more than 15 YSQ.

Conclusions

Among heavy former smokers, lung cancer risk drops within five YSQ relative to continuing smokers, yet it remains more than threefold higher than never smokers after 25 YSQ. Four of ten lung cancers occurred in former smokers with more 15 YSQ, beyond the screening window of the current guideline.

Combined effect of alpha particles and cigarette smoke on human lung epithelial cells in vitro

Purpose: The combined toxicity of alpha particles and cigarette smoke to the critical cells in the lungs was investigated to assess the risk of smoking workers who handle naturally occurring radioactive materials. Materials and methods: The toxicity of alpha particles and cigarette smoke extract (CSE) was evaluated in terms of DNA double-strand break (DSB) induction and clonogenic cell death of human lung epithelial cells in vitro. The cells were exposed to alpha particles at doses of up to 0.25 Gy for gamma-H2AX assay and from 1.25 Gy to 5 Gy for clonogenic assay. CSE exposure of the cells was facilitated in the culture medium at CSE concentrations ranging from 1% to 12%. Additional experiments were performed using mouse endothelial cells for comparison. Results: The increases in the levels of DNA DSBs were linearly dependent on radiation dose and CSE concentration. The CSE-treated cells also responded with a linearly increasing number of DNA DSBs to the radiation dose. Both human lung epithelial cells and mouse endothelial cells showed exponential decreases in clonogenic surviving fraction as the dose from alpha particle exposure increased. Both cells responded with the clonogenic surviving fractions decreasing in a linear proportion to the CSE concentration in the culture medium. Conclusion: In our experimental in vitro setup, CSE treatment and alpha particle exposure affected the cells in an additive manner either for DNA DSB production or for clonogenic cell death induction.

Lung cancer and residential radon in never-smokers: A pooling study in the Northwest of Spain

BACKGROUND

Using a pooled case-control study design, including only never-smokers, we have assessed the association of residential radon exposure with the subsequent occurrence of lung cancer. We also investigated whether residential radon poses a different risk specifically for adenocarcinoma.

METHODS

We pooled individual data from different case-control studies conducted in recent years in Northwestern Spain which investigated residential radon and lung cancer. All participants were never-smokers. Cases had a confirmed biopsy of primary lung cancer. Hospital controls were selected at pre-surgery units, presenting for non-complex surgical procedures. They were interviewed using a standardized instrument. Residential radon was measured using alpha track detectors at the Galician Radon Laboratory at the University of Santiago de Compostela.

RESULTS

A total of 1415 individuals, 523 cases and 892 controls were included. We observed an odds ratio of 1.73 (95%CI: 1.27-2.35) for individuals exposed to ≥ 200 Bq/m³ compared with those exposed to ≤100 Bq/m³. Lung cancer risk for adenocarcinoma was 1.52 (95%CI: 1.14-2.02) using the same categories for radon exposure.

CONCLUSIONS

Residential radon is a clear risk factor for lung cancer in never-smokers. Our data suggest that radon exposure is associated with all histological types of lung cancer and also with adenocarcinoma, which is currently the most frequent histological type for this disease.

Meta-analysis of case-control studies on the relationship between lung cancer and indoor radon exposure

Indoor exposure to natural radon is a factor that influences lung cancer risk worldwide. The present study includes a meta-analysis of epidemiological data on the relationship between lung cancer and indoor radon. Altogether, 31 case-control studies with 20,703 cases, 34,518 controls and 140 individual odds ratio (OR) estimates are included in the meta-analysis. Weighted median OR was calculated for five radon intervals. The following parameters were used for the weighting: standard error of OR, duration of radon concentration measurement, and relative number of controls in reference intervals. The dependence of the weighted median OR on the radon concentration was estimated applying linear non-threshold and threshold models. The results obtained suggest a significant linear no-threshold exposure-effect relationship for radon concentrations above 100 Bq/m³, with a slope of 0.14 (95% confidence interval 0.08-0.21) per 100 Bq/m³.

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.

Meta-analysis of thirty-two case-control and two ecological radon studies of lung cancer

A re-analysis has been carried out of thirty-two case-control and two ecological studies concerning the influence of radon, a radioactive gas, on the risk of lung cancer. Three mathematically simplest dose-response relationships (models) were tested: constant (zero health effect), linear, and parabolic (linear-quadratic). Health effect end-points reported in the analysed studies are odds ratios or relative risk ratios, related either to morbidity or mortality. In our preliminary analysis, we show that the results of dose-response fitting are qualitatively (within uncertainties, given as error bars) the same, whichever of these health effect end-points are applied. Therefore, we deemed it reasonable to aggregate all response data into the so-called Relative Health Factor and jointly analysed such mixed data, to obtain better statistical power. In the second part of our analysis, robust Bayesian and classical methods of analysis were applied to this combined dataset. In this part of our analysis, we selected different subranges of radon concentrations. In view of substantial differences between the methodology used by the authors of case-control and ecological studies, the mathematical relationships (models) were applied mainly to the thirty-two case-control studies. The degree to which the two ecological studies, analysed separately, affect the overall results when combined with the thirty-two case-control studies, has also been evaluated. In all, as a result of our meta-analysis of the combined cohort, we conclude that the analysed data concerning radon concentrations below ~1000 Bq/m3 (~20 mSv/year of effective dose to the whole body) do not support the thesis that radon may be a cause of any statistically significant increase in lung cancer incidence.

Occupational exposure to diesel motor exhaust and risk of lung cancer by histological subtype: a population-based case-control study in Swedish men

We investigated occupational exposure to diesel motor exhaust (DME) and the risk of lung cancer by histological subtype among men, using elemental carbon (EC) as a marker of DME exposure. 993 cases and 2359 controls frequency-matched on age and year of study inclusion were analyzed by unconditional logistic regression in this Swedish case-control study. Work and smoking histories were collected by a questionnaire and telephone interviews. DME was assessed by a job-exposure matrix. We adjusted for age, year of study inclusion, smoking, occupational exposure to asbestos and combustion products (other than motor exhaust), residential exposure to radon and exposure to air pollution from road traffic. The OR for lung cancer for ever vs. never exposure to DME was 1.15 (95% CI 0.94-1.41). The risk was higher for squamous and large cell, anaplastic or mixed cell carcinoma than for alveolar cell cancer, adenocarcinoma and small cell carcinoma. The OR in the highest quartile of exposure duration (≥34 years) vs. never exposed was 1.66 (95% CI 1.08-2.56; p for trend over all quartiles: 0.027) for lung cancer overall, 1.73 (95% CI 1.00-3.00; p: 0.040) for squamous cell carcinoma and 2.89 (95% CI 1.37-6.11; p: 0.005) for the group of undifferentiated, large cell, anaplastic and mixed cell carcinomas. We found no convincing association between exposure intensity and lung cancer risk. Long-term DME exposure was associated with an increased risk of lung cancer, particularly to squamous cell carcinoma and the group of undifferentiated, large cell, anaplastic or mixed carcinomas.

Seasonal variability of equilibrium factor and unattached fractions of radon and thoron in different regions of Punjab, India

A survey was conducted to estimate equilibrium factor and unattached fractions of radon and thoron in different regions of Punjab state, India. Pin hole based twin cup dosimeters and direct progeny sensor techniques have been utilized for estimation of concentration level of radon, thoron and their progenies. Equilibrium factor calculated from radon, thoron and their progenies concentration has been found to vary from 0.15 to 0.80 and 0.008 to 0.101 with an average value of 0.44 and 0.036 for radon and thoron respectively. Equilibrium factor for radon has found to be highest in winter season and lowest in summer season whereas for thoron highest value is observed in winter and rainy season and lowest in summer. Unattached fractions of radon and thoron have been found to vary from 0.022 to 0.205 and 0.013 to 0.212 with an average value of 0.099 and 0.071 respectively. Unattached fractions have found to be highest in winter season and lowest in rainy and summer season.

Advances in spatial epidemiology and geographic information systems

The field of spatial epidemiology has evolved rapidly in the past 2 decades. This study serves as a brief introduction to spatial epidemiology and the use of geographic information systems in applied research in epidemiology. We highlight technical developments and highlight opportunities to apply spatial analytic methods in epidemiologic research, focusing on methodologies involving geocoding, distance estimation, residential mobility, record linkage and data integration, spatial and spatio-temporal clustering, small area estimation, and Bayesian applications to disease mapping. The articles included in this issue incorporate many of these methods into their study designs and analytical frameworks. It is our hope that these studies will spur further development and utilization of spatial analysis and geographic information systems in epidemiologic research.

An updated review of case-control studies of lung cancer and indoor radon-Is indoor radon the risk factor for lung cancer?

Lung cancer is a leading cause of cancer-related death in the world. Smoking is definitely the most important risk factor for lung cancer. Radon (²²²Rn) is a natural gas produced from radium (²²⁶Ra) in the decay series of uranium (²³⁸U). Radon exposure is the second most common cause of lung cancer and the first risk factor for lung cancer in never-smokers.

Case–control studies have provided epidemiological evidence of the causative relationship between indoor radon exposure and lung cancer. Twenty-four case–control study papers were found by our search strategy from the PubMed database. Among them, seven studies showed that indoor radon has a statistically significant association with lung cancer. The studies performed in radon-prone areas showed a more positive association between radon and lung cancer. Reviewed papers had inconsistent results on the dose–response relationship between indoor radon and lung cancer risk.

Further refined case–control studies will be required to evaluate the relationship between radon and lung cancer. Sufficient study sample size, proper interview methods, valid and precise indoor radon measurement, wide range of indoor radon, and appropriate control of confounders such as smoking status should be considered in further case–control studies.

Lymphocytes with multiple chromosomal damages in a large cohort of West Siberia residents: Results of long-term monitoring

Cells with specific multiple chromosome aberrations, defined as rogue cells (RC) have been described in different populations, predominantly those exposed to radiation. The frequency, etiology and related health risks have still not been elucidated due to their low frequency of occurrences and rarely performed studies. This study reports RC frequency using chromosome aberration (CA) assay in peripheral lymphocytes in the group of 3242 subjects, during a 30-year long follow-up study in a general rural and urban population, children environmentally exposed to radon, occupationally exposed population and lung cancer patients from the Kemerovo region (Siberia, Russian Federation). Results show that the highest RC frequency was present in children environmentally exposed to radon and the lowest in the general urban population. Total frequency of CA did not correlate with frequency of RC. Genotoxic analysis of air and water samples excluded anthropogenic pollution as a possible cause of genome damage and RC frequency. In 85% of RCs, double minutes, observed in a large number of human tumors, were present. Results of CA analysis suggested that radon and its decay products (alpha-emitters) were the leading factors causing RC in subjects exposed to high LET radiation. Thus, RC may be a candidate biomarker for exposure to this type of radiation.

Lung cancer risk from radon exposure in dwellings in Sweden: how many cases can be prevented if radon levels are lowered?

Purpose

Residential exposure to radon is considered to be the second cause of lung cancer after smoking. The purpose of this study was to estimate the number of lung cancer cases prevented from reducing radon exposure in Swedish dwellings.

Methods

Measurements of indoor radon are available from national studies in 1990 and 2008 with 8992 and 1819 dwellings, considered representative of all Swedish dwellings. These data were used to estimate the distribution of radon in Swedish dwellings. Lung cancer risk was assumed to increase by 16 % per 100 becquerels per cubic meter (Bq/m³) indoor air radon. Estimates of future and saved cases of lung cancer were performed at both constant and changed lung cancer incidence rates over time.

Results

The arithmetic mean concentration of radon was 113 Bq/m³ in 1990 and 90 Bq/m³ in 2008. Approximately 8 % of the population lived in houses with >200 Bq/m³. The estimated current number of lung cancer cases attributable to previous indoor radon exposure was 591 per year, and the number of future cases attributable to current exposure was 473. If radon levels above 100 Bq/m³ are lowered to 100 Bq/m³, 183 cases will be prevented. If levels >200 Bq/m³ are lowered to 140 Bq/m³ (mean in the present stratum 100–200 Bq/m³), 131 cases per year will be prevented.

Conclusions

Although estimates are somewhat uncertain, 35–40 % of the radon attributed lung cancer cases can be prevented if radon levels >100 Bq/m³ are lowered to 100 Bq/m³.

Lung cancer hormesis in high impact states where nuclear testing occurred

BACKGROUND

Hormesis is a favorable biological response to low toxin exposure. In the case of radiation, large doses are carcinogenic, but low doses might be protective. In the current study, we analyzed lung cancer incidence in high-impact radiation states where nuclear testing occurred and compared it with lung cancer incidence in the remaining normal-impact radiation states and the District of Columbia.

MATERIALS AND METHODS

Lung cancer incidence data were from the American Cancer Society. Tobacco use 2012 data were from the Centers for Disease Control and Prevention. The distribution of states grouped according to lung cancer incidence interval was from the Centers for Disease Control and Prevention. Total background radiation measurements (terrestrial + cosmic + radon) were from Assessment of Variations in Radiation Exposure in the United States (2005). Data on high- and normal-impact states were from the National Radiation Exposure Screening & Education Program (RESEP). Congress passed the Radiation Exposure Compensation Act Amendments of 2000, creating RESEP, to help thousands of people diagnosed with cancer and other diseases caused by exposure to nuclear fallout or radioactive materials such as uranium. These people live in 12 high-impact states where nuclear testing had occurred. High-impact states were not designated according to measurements of background radiation.

RESULTS

Lung cancer incidence is significantly lower in high-impact states in men (t = 5.4 for unequal variance; P < .001) and women (t = 3.0; P < .001). The clustering of the 12 high-impact states in the 2 lowest lung cancer incidence intervals (26.8-56.9 and 57.0-63.2) is statistically significant (P < .001, Fisher exact test, 2-tailed). Because cigarette smoking is ordinarily the most powerful risk factor for lung cancer, multivariate linear regression analysis of the effect of U.S. state group (normal-impact, high-impact, or extra high-impact for Nevada, Utah, and Arizona) on lung cancer incidence in men and women was performed. (In Nevada, Utah, and Arizona, men and women would have been downwind.) The U.S. state group impact was significant (P < .001 for men; P = .015 for women). The effect of percentage of smokers in the population was significant (P < .001 for men; P < .001 for women). The effect of total background radiation was significant (P = .029 for men; P < .029 for women); like the state group impact, more background radiation exposure was associated with less lung cancer.

CONCLUSION

Hormesis is still mired in controversy. Yet, it is of vital medical importance because of the continuing debate over whether the low-level radiation doses from diagnostic x-ray procedures, such as computed tomography scans, are harmful. Our analysis adds to the body of evidence suggesting that the linear no threshold model of radiation carcinogenicity in lung cancer might not be correct. Low-level radiation exposure might protect against lung cancer rather than cause it.

Lung cancer in never-smokers: a case-control study in a radon-prone area (Galicia, Spain)

The aim of the study was to assess the effect of residential radon exposure on the risk of lung cancer in never-smokers and to ascertain if environmental tobacco smoke modifies the effect of residential radon. We designed a multicentre hospital-based case-control study in a radon-prone area (Galicia, Spain). All participants were never-smokers. Cases had an anatomopathologically confirmed primary lung cancer and controls were recruited from individuals undergoing minor, non-oncological surgery. Residential radon was measured using alpha track detectors. We included 521 individuals, 192 cases and 329 controls, 21% were males. We observed an odds ratio of 2.42 (95% CI 1.45-4.06) for individuals exposed to ≥200 Bq·m(-3) compared with those exposed to <100 Bq·m(-3). Environmental tobacco smoke exposure at home increased lung cancer risk in individuals with radon exposure>200 Bq·m(-3). Individuals exposed to environmental tobacco smoke and to radon concentrations>200 Bq·m(-3) had higher lung cancer risk than those exposed to lower radon concentrations and exposed to environmental tobacco smoke. Residential radon increases lung cancer risk in never-smokers. An association between residential radon exposure and environmental tobacco smoke on the risk of lung cancer might exist.

Radon survey and soil gamma doses in primary schools of Batman, Turkey

A survey was conducted to evaluate levels of indoor radon and gamma doses in 42 primary schools located in Batman, southeastern Anatolia, Turkey. Indoor radon measurements were carried out using CR-39 solid-state nuclear track detector-based radon dosimeters. The overall mean annual (222)Rn activity in the surveyed area was found to be 49 Bq m(-3) (equivalent to an annual effective dose of 0.25 mSv). However, in one of the districts (Besiri) the maximum radon value turned out to be 307 Bq m(-3). The estimated annual effective doses are less than the recommended action level (3-10 mSv). It is found that the radon concentration decreases with increasing floor number. The concentrations of natural and artificial radioisotopes were determined using gamma-ray spectroscopy for soil samples collected in close vicinity of the studied schools. The mean gamma activity concentrations in the soil samples were 31, 25, 329 and 12 Bq kg(-1) for (226)Ra, (232)Th, (40)K and (137)Cs, respectively. The radiological parameters such as the absorbed dose rate in air and the annual effective dose equivalent were calculated. These radiological parameters were evaluated and compared with the internationally recommended values.

Differences in lung cancer mortality trends from 1986-2012 by radon risk areas in British Columbia, Canada

Residential exposure to radon gas is associated with increased risk of lung cancer, especially in smokers. Most evidence about the health effects of radon has been derived from meta-analyses on global epidemiologic studies, but administrative data can help public health authorities to explore the local impacts. Eighty health units in British Columbia (BC), Canada, were classified as having low, moderate, or high radon risk using more than 3,800 residential measurements. Vital statistics records were used to identify deaths due to lung cancer and to all natural causes. The annual ratio of lung cancer mortality to all natural mortality was plotted for the 1986-2012 study period for each radon classification. Visualizations were stratified by gender and by smoking prevalence. The overall ratio increased throughout the study period in high radon areas and remained stable in low and moderate radon areas. The increase was most pronounced for females, especially when plots were stratified by smoking prevalence. These limited but interesting findings confirm that radon is one risk factor for lung cancer mortality in BC and that its effects differ across gender and smoking strata. The results would be strengthened by replication, and more rigorous methods are required to assess other contributing factors.

Using risk model judgements to better understand perceptions of synergistic risks

Numerous scientific studies show that risk factors can interact to synergistically increase the likelihood of certain adverse and life-threatening outcomes. Yet, the extent to which individuals know that specific risk factor combinations present 'synergistic risks' is unclear and little is known about the determinants of such knowledge. This is largely because epistemological progress concerning this topic has been frustrated by a reliance on metrics that have latterly been judged to be of questionable validity. To address this issue, this paper presents two studies that assess an alternative approach (i.e., risk model judgements) which requires respondents to judge the risk for a factor combination relative to, rather than in isolation from, the risk attributable to each constituent factor. Results from both studies indicate that risk model judgements overcome the drawbacks of traditional metrics. More importantly, the results provide epistemological insights into what can determine whether an individual understands that a factor combination presents a synergistic risk; these determinants include experiential and intuitive insights into the effects of combining specific risk factors, domain-specific judgemental experience and exposure to effective learning opportunities. These findings can be utilized in interventions aimed at helping individuals to make better decisions concerning multiple risk factors.

Residential radon and lung cancer in never smokers. A systematic review

Radon exposure is considered the second cause of lung cancer and the first in never smokers. We aim to assess the effect of residential radon exposure on the risk of lung cancer in never smokers through a systematic review applying predefined inclusion and exclusion criteria. 14 Studies were included. Some of them point to a relationship between residential radon and lung cancer while others show no association. Further studies are necessary to test this association and to assess if other risk factors such as environmental tobacco smoke could modify the effect of residential radon exposure on lung cancer.

Prediction of residential radon exposure of the whole Swiss population: comparison of model-based predictions with measurement-based predictions

Radon plays an important role for human exposure to natural sources of ionizing radiation. The aim of this article is to compare two approaches to estimate mean radon exposure in the Swiss population: model-based predictions at individual level and measurement-based predictions based on measurements aggregated at municipality level. A nationwide model was used to predict radon levels in each household and for each individual based on the corresponding tectonic unit, building age, building type, soil texture, degree of urbanization, and floor. Measurement-based predictions were carried out within a health impact assessment on residential radon and lung cancer. Mean measured radon levels were corrected for the average floor distribution and weighted with population size of each municipality. Model-based predictions yielded a mean radon exposure of the Swiss population of 84.1 Bq/m(3) . Measurement-based predictions yielded an average exposure of 78 Bq/m(3) . This study demonstrates that the model- and the measurement-based predictions provided similar results. The advantage of the measurement-based approach is its simplicity, which is sufficient for assessing exposure distribution in a population. The model-based approach allows predicting radon levels at specific sites, which is needed in an epidemiological study, and the results do not depend on how the measurement sites have been selected.

Dose-response relationship of lung cancer to amount smoked, duration and age starting

AIM: To quantify smoking/lung cancer relationships accurately using parametric modelling.

METHODS: Using the International Epidemiological Studies on Smoking and Lung Cancer database of all epidemiological studies of 100+ lung cancer cases published before 2000, we analyzed 97 blocks of data for amount smoked, 35 for duration of smoking, and 27 for age started. Pseudo-numbers of cases and controls (or at risk) estimated from RRs by dose level formed the data modelled. We fitted various models relating log_e RR to dose (d), including βd, βd^Y and βlog_e (1 + Wd), and investigated goodness-of-fit and heterogeneity between studies.

RESULTS: The best-fitting models for log_e RR were 0.833 log_e [1 + (8.1c/10)] for cigarettes/d (c), 0.792 (y/10)^0.74 for years smoked (y) and 0.176 [(70 - a)/10]^1.44 for age of start (a). Each model fitted well overall, though some blocks misfitted. RRs rose from 3.86 to 22.31 between c = 10 and 50, from 2.21 to 13.54 between y = 10 and 50, and from 3.66 to 8.94 between a = 30 and 12.5. Heterogeneity (P < 0.001) existed by continent for amount, RRs for 50 cigarettes/d being 7.23 (Asia), 26.36 (North America) and 22.16 (Europe). Little heterogeneity was seen for duration of smoking or age started.

CONCLUSION: The models describe the dose-relationships well, though may be biased by factors including misclassification of smoking status and dose.

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.

Residential radon and lung cancer risk: an updated meta- analysis of case-control studies

BACKGROUND

Numbers of epidemiological studies assessing residential radon exposure and risk of lung cancer have yielded inconsistent results.

METHODS

We therefore performed a meta-analysis of relevant published case- control studies searched in the PubMed database through July 2011 to examine the association. The combined odds ratio (OR) were calculated using fixed- or random-effects models. Subgroup and dose-response analyses were also performed.

RESULTS

We identified 22 case-control studies of residential radon and lung cancer risk involving 13,380 cases and 21,102 controls. The combined OR of lung cancer for the highest with the lowest exposure was 1.29 (95% CI 1.10-1.51). Dose-response analysis showed that every 100 Bq/m3 increment in residential radon exposure was associated with a significant 7% increase in lung cancer risk. Subgroup analysis displayed a more pronounced association in the studies conducted in Europe. Studies restricted to female or non-smokers demonstrated weakened associations between exposure and lung cancer.

CONCLUSIONS

This meta- analysis provides new evidence supporting the conclusion that residential exposure to radon can significantly increase the risk of lung cancer in a dose-response manner.

Residential radon and lung cancer incidence in a Danish cohort

High-level occupational radon exposure is an established risk factor for lung cancer. We assessed the long-term association between residential radon and lung cancer risk using a prospective Danish cohort using 57,053 persons recruited during 1993-1997. We followed each cohort member for cancer occurrence until 27 June 2006, identifying 589 lung cancer cases. We traced residential addresses from 1 January 1971 until 27 June 2006 and calculated radon at each of these addresses using information from central databases regarding geology and house construction. Cox proportional hazards models were used to estimate incidence rate ratios (IRR) and 95% confidence intervals (CI) for lung cancer risk associated with residential radon exposure with and without adjustment for sex, smoking variables, education, socio-economic status, occupation, body mass index, air pollution and consumption of fruit and alcohol. Potential effect modification by sex, traffic-related air pollution and environmental tobacco smoke was assessed. Median estimated radon was 35.8 Bq/m(3). The adjusted IRR for lung cancer was 1.04 (95% CI: 0.69-1.56) in association with a 100 Bq/m(3) higher radon concentration and 1.67 (95% CI: 0.69-4.04) among non-smokers. We found no evidence of effect modification. We find a positive association between radon and lung cancer risk consistent with previous studies but the role of chance cannot be excluded as these associations were not statistically significant. Our results provide valuable information at the low-level radon dose range.

Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BACKGROUND

Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. We summarize evidence for various indices.

METHODS

Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Data were extracted on design, exposures, histological types and confounder adjustment. RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose-response. Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma ("squamous") and adenocarcinoma ("adeno").

RESULTS

287 studies (20 subsidiary) were identified. Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Relationships were somewhat stronger in later starting and larger studies. RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. Covariate-adjustment little affected RR estimates.

CONCLUSIONS

The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. This emphasises the causal nature of the relationship. Our results quantify the relationships more precisely than previously.

Cigarette smoke and adverse health effects: An overview of research trends and future needs

A large volume of data has accumulated on the issues of tobacco and health worldwide. The relationship between tobacco use and health stems initially from clinical observations about lung cancer, the first disease definitively linked to tobacco use. Almost 35 years ago, the Office of the Surgeon General of the United States Health Service reviewed over 7000 research papers on the topic of smoking and health, and publicly recognized the role of smoking in various diseases, including lung cancer. Since then, numerous studies have been published that substantiate the strong association of tobacco use with a variety of adverse human health effects, most prominently with cancer and cardiovascular diseases. Cigarette smoking is regarded as a major risk factor in the development of lung cancer, which is the main cause of cancer deaths in men and women in the United States and the world. Major advances have been made by applying modern genetic technologies to examine the relationship between exposure to tobacco smoke and the development of diseases in human populations. The present review summarizes the major research areas of the past decade, important advances, future research needs and federal funding trends.

Radiation and smoking effects on lung cancer incidence by histological types among atomic bomb survivors

While the risk of lung cancer associated separately with smoking and radiation exposure has been widely reported, it is not clear how smoking and radiation together contribute to the risk of specific lung cancer histological types. With individual smoking histories and radiation dose estimates, we characterized the joint effects of radiation and smoking on type-specific lung cancer rates among the Life Span Study cohort of Japanese atomic bomb survivors. Among 105,404 cohort subjects followed between 1958 and 1999, 1,803 first primary lung cancer incident cases were diagnosed and classified by histological type. Poisson regression methods were used to estimate excess relative risks under several interaction models. Adenocarcinoma (636 cases), squamous-cell carcinoma (330) and small-cell carcinoma (194) made up 90% of the cases with known histology. Both smoking and radiation exposure significantly increased the risk of each major lung cancer histological type. Smoking-associated excess relative risks were significantly larger for small-cell and squamous-cell carcinomas than for adenocarcinoma. The gender-averaged excess relative risks per 1 Gy of radiation (for never-smokers at age 70 after radiation exposure at age 30) were estimated as 1.49 (95% confidence interval 0.1-4.6) for small-cell carcinoma, 0.75 (0.3-1.3) for adenocarcinoma, and 0.27 (0-1.5) for squamous-cell carcinoma. Under a model allowing radiation effects to vary with levels of smoking, the nature of the joint effect of smoking and radiation showed a similar pattern for different histological types in which the radiation-associated excess relative risk tended to be larger for moderate smokers than for heavy smokers. However, in contrast to analyses of all lung cancers as a group, such complicated interactions did not describe the data significantly better than either simple additive or multiplicative interaction models for any of the type-specific analyses.

Radon measurement in schools located in three priority investigation areas in the province of Quebec, Canada

The purpose of this study was to measure radon concentration in public primary schools located in priority investigation areas, with the aim of decreasing occupants' exposure to radon in public buildings where concentrations exceed the Canadian Federal guidelines (i.e. 200 Bq m(-3)). In addition, the association between radon levels, substratum geological characteristics and schools' structural characteristics were investigated. The results showed that radon concentrations measured in the 65 investigated schools are generally below the Federal guideline levels. Eleven schools (17 %) had at least one measurement above the Federal guideline, while one had a level above 600 Bq m(-3). On average, targeted schools' occupants are exposed to radon concentrations of 56 Bq m(-3). Although statistical analysis, which was limited by the sample size, did not show any link between aggregated radon measurements and geochemical or radiological signatures of investigated sites, the geological evidence that led to the choice of the studied regions remains relevant.

We're only in it for the knowledge? A problem solving turn in environment and health expert elicitation

BACKGROUND

The FP6 EU HENVINET project aimed at synthesizing the scientific information available on a number of topics of high relevance to policy makers in environment and health. The goal of the current paper is to reflect on the methodology that was used in the project, in view of exploring the usefulness of this and similar methodologies to the policy process. The topics investigated included health impacts of the brominated flame retardants decabrominated diphenylether (decaBDE) and hexabromocyclododecane (HBCD), phthalates highlighting di(2-ethylhexyl)phthalate (DEHP), the pesticide chlorpyrifos (CPF), nanoparticles, the impacts of climate change on asthma and other respiratory disorders, and the influence of environment health stressors on cancer induction.

METHODS

Initially the focus was on identifying knowledge gaps in the state of the art in scientific knowledge. Literature reviews covered all elements that compose the causal chain of the different environmental health issues from emissions to exposures, to effects and to health impacts. Through expert elicitation, knowledge gaps were highlighted by assessing expert confidence using calibrated confidence scales. During this work a complementary focus to that on knowledge gaps was developed through interdisciplinary reflections. By extending the scope of the endeavour from only a scientific perspective, to also include the more problem solving oriented policy perspective, the question of which kind of policy action experts consider justifiable was addressed. This was addressed by means of a questionnaire. In an expert workshop the results of both questionnaires were discussed as a basis for policy briefs.

RESULTS

The expert elicitation, the application of the calibrated confidence levels and the problem solving approach were all experienced as being quite challenging for the experts involved, as these approaches did not easily relate to mainstream environment and health scientific practices. Even so, most experts were quite positive about it. In particular, the opportunity to widen one's own horizon and to interactively exchange knowledge and debate with a diversity of experts seemed to be well appreciated in this approach. Different parts of the approach also helped in focussing on specific relevant aspects of scientific knowledge, and as such can be considered of reflective value.

CONCLUSIONS

The approach developed by HENVINET was part of a practice of learning by doing and of interdisciplinary cooperation and negotiation. Ambitions were challenged by unforeseen complexities and difference of opinion and as no Holy Grail approach was at hand to copy or follow, it was quite an interesting but also complicated endeavour. Perfection, if this could be defined, seemed out of reach all the time. Nevertheless, many involved were quite positive about it. It seems that many felt that it fitted some important needs in current science when addressing the needs of policy making on such important issues, without anyone really having a clue on how to actually do this. Challenging questions remain on the quality of such approach and its product. Practice tells us that there probably is no best method and that the best we can do is dependent on contextual negotiation and learning from experiences that we think are relevant.

Residential radon exposure, histologic types, and lung cancer risk. A case-control study in Galicia, Spain

BACKGROUND

Lung cancer is an important public health problem, and tobacco is the main risk factor followed by residential radon exposure. Recommended exposure levels have been progressively lowered. Galicia, the study area, has high residential radon concentrations. We aim (i) to assess the risk of lung cancer linked to airborne residential radon exposure, (ii) to ascertain whether tobacco modifies radon risk, and (iii) to know whether there is a lung cancer histologic type more susceptible to radon.

METHODS

A hospital-based case-control design was conducted in two Spanish hospitals. Consecutive cases with histologic diagnosis of lung cancer and controls undergoing trivial surgery not tobacco-related were included. Residential radon was measured using standard procedures. Results were obtained using logistic regression.

RESULTS

Three hundred and forty-nine cases and 513 controls were included. Radon exposure posed a risk even with a low exposure, with those exposed to 50 to 100 Bq/m(3) having an OR of 1.87 [95% confidence interval (CI), 1.21-2.88] and of 2.21 (95% CI, 1.33-3.69) for those exposed to 148 Bq/m(3) or more. Tobacco increased appreciably the risk posed by radon, with an OR of 73 (95% CI, 19.88-268.14) for heavy smokers exposed to more than 147 Bq/m(3). Less frequent histologic types (including large cell carcinomas), followed by small cell lung cancer, had the highest risk associated with radon exposure.

CONCLUSIONS

The presence of airborne radon even at low concentrations poses a risk of developing lung cancer, with tobacco habit increasing considerably this risk.

IMPACT

Public health initiatives should address the higher risk of lung cancer for smokers exposed to radon.

ICRP Publication 115. Lung cancer risk from radon and progeny and statement on radon

Recent epidemiological studies of the association between lung cancer and exposure to radon and its decay products are reviewed. Particular emphasis is given to pooled case-control studies of residential exposures, and to cohorts of underground miners exposed to relatively low levels of radon. The residential and miner epidemiological studies provide consistent estimates of the risk of lung cancer, with significant associations observed at average annual concentrations of approximately 200 Bq/m³ and cumulative occupational levels of approximately 50 working level months (WLM), respectively. Based on recent results from combined analyses of epidemiological studies of miners, a lifetime excess absolute risk of 5 × 10⁻⁴ per WLM [14 × 10⁻⁵ per (mJh/m³)] should now be used as the nominal probability coefficient for radon- and radon-progeny-induced lung cancer, replacing the previous Publication 65 (ICRP, 1993) value of 2.8 × 10⁻⁴ per WLM [8 × 10⁻⁵ per (mJh/m³)]. Current knowledge of radon-associated risks for organs other than the lungs does not justify the selection of a detriment coefficient different from the fatality coefficient for radon-induced lung cancer. Publication 65 (ICRP, 2003) recommended that doses from radon and its progeny should be calculated using a dose conversion convention based on epidemiological data. It is now concluded that radon and its progeny should be treated in the same way as other radionuclides within the ICRP system of protection; that is, doses from radon and its progeny should be calculated using ICRP biokinetic and dosimetric models. ICRP will provide dose coefficients per unit exposure to radon and its progeny for different reference conditions of domestic and occupational exposure, with specified equilibrium factors and aerosol characteristics.