Pooled Bayesian analysis of twenty-eight studies on radon induced lung cancers

Radon hazard vs. radon risk - On the effectiveness of radon priority areas

The detrimental health effects of radon have been acknowledged by national and international legislation such as the European Union Basic Safety Standards (EURATOM-BSS Article 103/3) which requires member states to delineate radon priority areas. These radon priority areas are conventionally based on the concept of hazard by using indoor radon concentration or geogenic radon potential for its delineation. While this approach is efficient for finding many affected buildings with limited resources and, hence, reducing the individual risk, it is probably inefficient for reducing the collective risk if hazard and risk areas differ. In this study we map collective radon risk for Germany by linking information of geogenic radon hazard with exposure (residential building stock). The resulting map of affected residential buildings reveals distinct spatial contrasts compared to the hazard-based map. Further, an analysis based on hypothetical hazard zones elucidates that in Germany the vast majority of affected buildings (i.e., above threshold concentration) are located outside of areas of high and very high hazard. Consequently, in Germany, a radon policy focusing on areas of very high hazard only and within these areas on high concentration buildings only would presumably have no significant effect on the reduction of the total number of radon attributable lung cancer fatalities, i.e. less than 1% of annual radon attributable lung cancer fatalities. We conclude that for reducing the collective risk significantly, also complementary measures are of particular relevance.

Analysis of Indoor Radon Data Using Bayesian, Random Binning, and Maximum Entropy Methods

Three statistical methods: Bayesian, randomized data binning and Maximum Entropy Method (MEM) are described and applied in the analysis of US radon data taken from the US registry. Two confounding factors-elevation of inhabited dwellings, and UVB (ultra-violet B) radiation exposure-were considered to be most correlated with the frequency of lung cancer occurrence. MEM was found to be particularly useful in extracting meaningful results from epidemiology data containing such confounding factors. In model testing, MEM proved to be more effective than the least-squares method (even via Bayesian analysis) or multi-parameter analysis, routinely applied in epidemiology. Our analysis of the available residential radon epidemiology data consistently demonstrates that the relative number of lung cancers decreases with increasing radon concentrations up to about 200 Bq/m³, also decreasing with increasing altitude at which inhabitants live. Correlation between UVB intensity and lung cancer has also been demonstrated.

A radon chamber specifically designed for environmentally relevant exposures of small animals

In order to facilitate direct testing of the biological effects of radon, we designed and constructed a 3.1 m³ radon chamber specifically for radon exposures to small animals. The chamber is designed to operate as a sealed enclosure with a controlled atmosphere containing a known concentration of radon and its radioactive decay products. Sensors for air flow rate, temperature, humidity, HEPA filter and differential pressure ensure an optimal environment for exposure subjects. The radon gas is supplied to the chamber from a generator containing Radium-226 in a dilute acid solution. Air containing radon can be pumped continuously using a constant flow rate to maintain a steady state supply. The source flow rate was partitioned to achieve a chamber concentration at 200 Bq/m³ (R² = 0.9341) or 1000 Bq/m³ (R² = 0.9715). Small particles are injected into the re-circulating air stream via a particle generator to provide condensation nuclei for attachment of radon decay products as they form in the chamber atmosphere. Particles measured at 0.3 μm, 0.5 μm and 5.0 μm averaged concentrations 5.7 ± 0.6 × 10⁷/m³, 2.5 ± 0.7 × 10⁷/m³ and 2.3 ± 2.4 × 10³/m³, respectively. A desired Equilibrium Factor can easily be achieved by varying the air circulation rate through the chamber. The Equilibrium Factor ranged from 0.4 to 0.8 at 200 Bq/m³ and 0.5 to0.6 at 1000 Bq/m³. The chamber was designed to conduct short term exposures to assess the acute cellular changes induced by radon exposure. To our knowledge, this is currently the only radon chamber designed specifically to investigate environmentally relevant exposure time and doses of radon gas and decay products in small animal models.

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.

Low-dose ionizing radiation increases the mortality risk of solid cancers in nuclear industry workers: A meta-analysis

Low-dose ionizing radiation (LDIR) may increase the mortality of solid cancers in nuclear industry workers, but only few individual cohort studies exist, and the available reports have low statistical power. The aim of the present study was to focus on solid cancer mortality risk from LDIR in the nuclear industry using standard mortality ratios (SMRs) and 95% confidence intervals. A systematic literature search through the PubMed and Embase databases identified 27 studies relevant to this meta-analysis. There was statistical significance for total, solid and lung cancers, with meta-SMR values of 0.88, 0.80, and 0.89, respectively. There was evidence of stochastic effects by IR, but more definitive conclusions require additional analyses using standardized protocols to determine whether LDIR increases the risk of solid cancer-related mortality.

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.

Radon, smoking and HPV as lung cancer risk factors in ecological studies

OBJECTIVES

Cohen's ecological analyses revealed negative correlation between the lung cancer mortality and average indoor radon concentration in the US counties, that contradicts to linear non-threshold (LNT) model and is inconsistent with results of case-control studies. The aim of this study was to analyze dependence between radon exposure and lung cancer mortality rate taking into account more complete data on smoking and new findings on association of the lung cancer with human papillomavirus (HPV) infection.

MATERIALS AND METHODS

Information on the cancer rates in the US counties and Russian oblasts, smoking prevalence and indoor radon concentration was found in literature. The cervix cancer incidence rate was used as surrogate of the HPV infection prevalence. The analysis included calculation of the coefficients of linear dependence between radon exposure and lung cancer mortality rate with adjustment to smoking and HPV infection prevalence.

RESULTS

After adjustment for the most relevant data on smoking and HPV infection, correlation between the lung cancer mortality and indoor radon was found to be consistent with results of the case control studies.

CONCLUSIONS

Analysis of geographically aggregated data on the lung cancer mortality and radon concentration in dwellings with adjustment to the significant risk factors confirms both the linear non-threshold dependency and results obtained in studies with individual accounting for the smoking and radon.

Radon: a radioactive therapeutic element

This paper presents selected issues related to the use of 222Rn in therapeutic treatments. Radon is a radioactive element whose usage in medicine for more than 100 years is based on the radiation hormesis theory. However, owing to the radioactive character of this element and the fact that its alpha-radioactive decay is the source of other radionuclides, its therapeutic application has been raising serious doubts. The author points to potential sources and carriers of radon in the environment that could supply radon for use in a variety of therapies. Except for centuries-long tradition of using radon groundwaters, and later also the air in caves and underground workings, the author would also like to focus on soil air, which is still underestimated as a source of radon. The text presents different methods of obtaining this radioactive gas from groundwaters, the air in caves, mining galleries and soil air, and it presents new possibilities in this field. The author also discusses problems related to the transportation and storage of radon obtained from the environment.

Within radon-prone areas, it is often necessary to de-radon groundwaters that are intended for human consumption and household usage. Also, dry radon wells are used to prevent radon migration from the ground into residential buildings. The author proposes using radon released from radon groundwaters and amassed in dry radon wells for radonotherapy treatments. Thanks to this, it is possible to reduce the cost of radiological protection of people within radon-prone areas while still exploiting the 222Rn obtained for a variety of therapies.

With regard to the ongoing and still unsettled dispute concerning the beneficial or detrimental impact of radon on the human organism, the author puts special emphasis on the necessity of strictly monitoring both the activity concentration of 222Rn in media used for therapeutic treatments and of its radioactive decay products. Monitoring should be also extended to the environments in which such treatments are delivered (inhalatoriums, baths, saunas, showers, pools and other facilities), as well as to the patients – during and after the radonotherapy treatments. It is also essential to monitor the dose of radon and its daughters that is received by persons undergoing radon therapy. This should facilitate the assessment of the effectiveness of these treatments, which may contribute to a fuller understanding of the mechanisms of radon impact, and ionizing radiation in general, on the human organism. This will make it easier to ultimately confirm or reject the radiation hormesis theory. It is also essential to monitor the effective dose that is received by medical and technical staff employed to deliver the radonotherapy treatments.

Epidemiology Without Biology: False Paradigms, Unfounded Assumptions, and Specious Statistics in Radiation Science (with Commentaries by Inge Schmitz-Feuerhake and Christopher Busby and a Reply by the Authors)

Radiation science is dominated by a paradigm based on an assumption without empirical foundation. Known as the linear no-threshold (LNT) hypothesis, it holds that all ionizing radiation is harmful no matter how low the dose or dose rate. Epidemiological studies that claim to confirm LNT either neglect experimental and/or observational discoveries at the cellular, tissue, and organismal levels, or mention them only to distort or dismiss them. The appearance of validity in these studies rests on circular reasoning, cherry picking, faulty experimental design, and/or misleading inferences from weak statistical evidence. In contrast, studies based on biological discoveries demonstrate the reality of hormesis: the stimulation of biological responses that defend the organism against damage from environmental agents. Normal metabolic processes are far more damaging than all but the most extreme exposures to radiation. However, evolution has provided all extant plants and animals with defenses that repair such damage or remove the damaged cells, conferring on the organism even greater ability to defend against subsequent damage. Editors of medical journals now admit that perhaps half of the scientific literature may be untrue. Radiation science falls into that category. Belief in LNT informs the practice of radiology, radiation regulatory policies, and popular culture through the media. The result is mass radiophobia and harmful outcomes, including forced relocations of populations near nuclear power plant accidents, reluctance to avail oneself of needed medical imaging studies, and aversion to nuclear energy-all unwarranted and all harmful to millions of people.

Pooled Bayesian meta-analysis of two Polish studies on radiation-induced cancers

The robust Bayesian regression method was applied to perform meta-analysis of two independent studies on influence of low ionising radiation doses on the occurrence of fatal cancers. The re-analysed data come from occupational exposure analysis of nuclear workers in Świerk (Poland) and from ecological study of cancer risk from natural background radiation in Poland. Such two different types of data were analysed, and three popular models were tested: constant, linear and quadratic dose-response dependencies. The Bayesian model selection algorithm was used for all models. The Bayesian statistics clearly indicates that the popular linear no-threshold (LNT) assumption is not valid for presented cancer risks in the range of low doses of ionising radiation. The subject of LNT hypothesis use in radiation risk prediction and assessment is also discussed.

Cancer Mortality Among People Living in Areas With Various Levels of Natural Background Radiation

There are many places on the earth, where natural background radiation exposures are elevated significantly above about 2.5 mSv/year. The studies of health effects on populations living in such places are crucially important for understanding the impact of low doses of ionizing radiation. This article critically reviews some recent representative literature that addresses the likelihood of radiation-induced cancer and early childhood death in regions with high natural background radiation. The comparative and Bayesian analysis of the published data shows that the linear no-threshold hypothesis does not likely explain the results of these recent studies, whereas they favor the model of threshold or hormesis. Neither cancers nor early childhood deaths positively correlate with dose rates in regions with elevated natural background 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.

Potential treatment of inflammatory and proliferative diseases by ultra-low doses of ionizing radiations

Ultra-low doses and dose- rates of ionizing radiation are effective in preventing disease which suggests that they also may be effective in treating disease. Limited experimental and anecdotal evidence indicates that low radiation doses from radon in mines and spas, thorium-bearing monazite sands and enhanced radioactive uranium ore obtained from a natural geological reactor may be useful in treating many inflammatory conditions and proliferative disorders, including cancer. Optimal therapeutic applications were identified via a literature survey as dose-rates ranging from 7 to 11μGy/hr or 28 to 44 times world average background rates. Rocks from an abandoned uranium mine in Utah were considered for therapeutic application and were examined by γ-ray and laser-induced breakdown fluorescence spectroscopy. The rocks showed the presence of transuranics and fission products with a γ-ray energy profile similar to aged spent uranium nuclear fuel (93% dose due to β particles and 7% due to γ rays). Mud packs of pulverized uranium ore rock dust in sealed plastic bags delivering bag surface β,γ dose-rates of 10-450 μGy/h were used with apparent success to treat several inflammatory and proliferative conditions in humans.

The cancer mortality in high natural radiation areas in poland

The cancer mortality ratios (CMRs) in Poland in high and low level radiation areas were analyzed based on information from national cancer registry. Presented ecological study concerned six regions, extending from the largest administration areas (a group of voivodeships), to the smallest regions (single counties). The data show that the relative risk of cancer deaths is lower in the higher radiation level areas. The decrease by 1.17%/mSv/year (p = 0.02) of all cancer deaths and by 0.82%/mSv/year (p = 0.2) of lung cancers only are observed.Tribute to Prof. Zbigniew Jaworowski (1927-2011).