Residential radon appears to prevent lung cancer

Radiophobia Harm, Its Main Cause, and a Proposed Solution

Background: We are exposed to natural ionizing radiation and other genomic stressors throughout life and radiophobia has caused much harm to society. The main basis for radiophobia is the invalid linear no-threshold (LNT) hypothesis for cancer induction, which the System of Radiological Protection (SRP) is linked to. Largely unknown to the public, evolution-associated genomic stress adaptation (gensadaptation) over many previous generations now provides protection to all lifeforms from low radiation doses. Objective: To help bring about an improved SRP not linked to the invalid LNT hypothesis for radiation-caused health detriment and to promote low-dose radiation therapy for different diseases. Methods: All-solid-cancer mortality risk dose-response relationships for A-bomb survivors were generated based on published LNT-modeling-related results. Dose-response relationships for lung cancer prevention by low-dose radiation were generated by linear interpolation based on published data from a study using > 15,000 mice. Uncertainty characterization was based on Monte Carlo calculations for binomial and Poisson distributions. New dose characterization tools were used for threshold dose-response relationships for radiation-caused cancer mortality. Results: The all-solid-cancer mortality risk for A-bomb survivors transitioned from LNT to threshold-linear when adjusted for key missing uncertainty at low doses. The prevention of lung cancer in mice by low radiation doses depends on the radiation absorbed dose and type. Conclusions: The SRP should be linked to population dose thresholds rather than the invalid LNT hypothesis and small likely harmless radiation doses could possibly be used in treating different diseases.

Radon level in groundwater in Kwara State, Nigeria, and the potential radiation dose due to intake

Radon in groundwater for domestic purposes contributes to indoor radon and at high concentration levels could be hazardous to inhabitants. Rn-222 concentrations in 101 groundwater samples from some Local Government Areas (LGAs) of Kwara State, Nigeria, were determined by AlphaGUARD portable radon monitor. The mean activity concentrations for the LGAs varied from 4.28 ± 2.29 to 14.59 ± 8.92 Bq.l-1. Radon concentrations were <100 Bq.l-1 guidance level recommended by CEC and WHO. Eighteen percent exceeded the recommended 11.1 Bq.l-1 by the United States Environmental Protection Agency. All the samples exceeded the 0.1 Bq.l-1 Maximum Permitted Level of the Standard Organization of Nigeria for radionuclide contaminant. Mean effective dose from ingestion was estimated for adults, children and infants. Inhalation dose was also estimated. The mean annual effective doses in five LGAs were higher than the 0.1 mSv reference dose level of committed effective dose from the intake of drinking water for 1 y as recommended by the ICRP.

HIGHLIGHTS

The Hormesis Concept: Strengths and Shortcomings

Hormesis implies that the effects of various materials or conditions that organisms are exposed to, may not have linear dose-response characteristics but rather, can be biphasic. Thus the response to a low dose of a stressor may be the opposite to that occurring at higher doses. Such a dual response is postulated for many toxicants and physical conditions and may involve a beneficial adaptive response. Such a non-linear effect is undoubtedly present in many useful pharmacological and nutraceutical agents with can be toxic at high concentrations. This somewhat divisive topic is an area of study that should be objectively studied and not clouded by political and policy considerations. The objective of this review is to examine claims concerning those exposures where hormesis seems to exist and also those where there is no good supporting evidence. The breadth of this phenomenon and potential mechanisms underlying hormetic events are discussed together with their limitations.

The Radiation-Specific Components Generated in the Second Step of Sequential Reactions Have a Mountain-Shaped Function

A mathematical model for radiation hormesis below 100 mSv has previously been reported, but the origins of the formula used in the previous report were not provided. In the present paper, we first considered a sequential reaction model with identical rate constants. We showed that the function of components produced in the second step of this model agreed well with the previously reported function. Furthermore, in a general sequential reaction model with different rate constants, it was mathematically proved that the function representing the component produced in the second step is always mountain-shaped: the graph has a peak with one inflection point on either side, and such a component may induce radiation hormesis.

Correlative links between natural radiation and life expectancy in the US population

The linear no-threshold (LNT) hypothesis is still the ruling concept which dictates the radiation protection health policy and regulations. However, more and more studies show that not only that low dose radiation pose no danger to our health, but also exhibits clear beneficial health effects. Here, we evaluated the correlative links of the natural sources of radiation-terrestrial radiation (TR), cosmic radiation (CR), and Radon-222, with life expectancy, the most integrative index of population health. The results of this study show that the different sources of natural radiation display positive correlative links to life expectancy, which is in line with the hypothesis of radiation hormesis.

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.

Inhalations with thermal waters in respiratory diseases

ETHNOPHARMACOLOGICAL RELEVANCE

Inhalations with thermal waters are an old therapeutic method used in the therapy of respiratory diseases as a treatment of choice showing a long-lasting outcome with no side effects. Paradoxically, there is little well-established research on their mechanisms of action.

AIM OF THE STUDY

The aim of this paper is therefore to summarize the influence of inhalatory treatment with thermal waters on the main symptoms and features of respiratory disorders including allergy-like symptoms, inflammation, oxidant-anti-oxidant balance, cellular influx, disturbed mucus secretions, recurrent infections, pulmonary and nasal function and quality of life. A short history of inhalations is also presented.

MATERIALS AND METHODS

The present paper is a sum-up of research articles on the use of inhalations with thermal waters in respiratory disorders.

RESULTS

According to the herein presented literature, the use of thermal water inhalations is beneficial for almost all manifestations of respiratory diseases. The mode of their action remains still unclear; however, it seems that the most important one relies on the restoration of proper defense mechanisms of the organism.

CONCLUSIONS

Inhalations with thermal waters alleviate symptoms of respiratory diseases. They also improve the quality of life of the patients and seem to be a good add-on therapy in the treatment of disorders of the respiratory system.

Effects of Chronic Low-Dose Internal Radiation on Immune-Stimulatory Responses in Mice

The Linear-No-Threshold (LNT) model predicts a dose-dependent linear increase in cancer risk. This has been supported by biological and epidemiological studies at high-dose exposures. However, at low-doses (LDR ≤ 0.1 Gy), the effects are more elusive and demonstrate a deviation from linearity. In this study, the effects of LDR on the development and progression of mammary cancer in FVB/N-Tg(MMTVneu)202Mul/J mice were investigated. Animals were chronically exposed to total doses of 10, 100, and 2000 mGy via tritiated drinking water, and were assessed at 3.5, 6, and 8 months of age. Results indicated an increased proportion of NK cells in various organs of LDR exposed mice. LDR significantly influenced NK and T cell function and activation, despite diminishing cell proliferation. Notably, the expression of NKG2D receptor on NK cells was dramatically reduced at 3.5 months but was upregulated at later time-points, while the expression of NKG2D ligand followed the opposite trend, with an increase at 3.5 months and a decrease thereafter. No noticeable impact was observed on mammary cancer development, as measured by tumor load. Our results demonstrated that LDR significantly influenced the proportion, proliferation, activation, and function of immune cells. Importantly, to the best of our knowledge, this is the first report demonstrating that LDR modulates the cross-talk between the NKG2D receptor and its ligands.

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.

Indoor Radon Concentration and Risk Assessment in 27 Districts of a Public Healthcare Company in Naples, South Italy

Radon is a major source of ionizing radiation exposure for the general population. It is known that exposure to radon is a risk factor for the onset of lung cancer. In this study, the results of a radon survey conducted in all districts of a Public Healthcare in Italy, are reported. Measurements of indoor radon were performed using nuclear track detectors, CR-39. The entire survey was conducted according to a well-established quality assurance program. The annual effective dose and excess lifetime cancer risk were also calculated. Results show that the radon concentrations varied from 7 ± 1 Bq/m3 and 5148 ± 772 Bq/m3, with a geometric mean of 67 Bq/m3 and geometric standard deviation of 2.5. The annual effective dose to workers was found to be 1.6 mSv/y and comparable with the worldwide average. In Italy, following the transposition of the European Directive 59/2013, great attention was paid to the radon risk in workplaces. The interest of the workers of the monitored sites was very high and this, certainly contributed to the high return rate of the detectors after exposure and therefore, to the presence of few missing data. Although it was not possible to study the factors affecting radon concentrations, certainly the main advantage of this study is that it was the first in which an entire public health company was monitored in regards to all the premises on the underground and ground floor.

Residential Radon in Manizales, Colombia: Results of a Pilot Study

Radon is a colorless, odorless, and tasteless noble gas, causally related with the onset of lung cancer. We aimed to describe the distribution of radon exposure in the municipality of Manizales, Colombia, in order to estimate the population's exposure and establish the percentage of dwellings that surpass reference levels. A cross-sectional study representing all geographical areas was carried out by measuring indoor radon concentrations. Participants answered a short questionnaire. Alpha-track type radon detectors were installed in all residences for six months. The detectors were subsequently processed at the Galician Radon Laboratory, an accredited laboratory at the University of Santiago de Compostela. A total of 202 homes were measured. Seventy-seven percent of the sampled houses were three stories high, their median age was 30 years, and half were inhabited by three people or fewer. For most dwellings, the building materials of walls and flooring were brick and covered cement, respectively. Results showed a geometric mean of radon concentration of 8.5 Bq/m³ and a maximum value of 50 Bq/m³. No statistically significant differences were found either between the geometric mean of the dwelling's site, the height at which detectors were placed inside the home, or the wall and flooring materials, or between mean ²²²Rn concentrations in rural and urban areas. No dwelling surpassed the ²²²Rn reference level established by the WHO. This study shows that residential radon levels in Manizales, Colombia, seem to be low, though a more in-depth approach should be carried out. Despite these results, it is essential to create a national radon program and establish a radon concentration reference level for Colombia in line with international recommendations.

The downfall of the linear non-threshold model

The linear non-threshold model (LNTM) is a theoretical dose-response function as a result of extrapolating the late effects of high-dose exposure to ionizing radiation to the low-dose range, but there is great uncertainty about its validity. The acceptance of LNTM as the dominant probabilistic model have survived to the present day and it is actually the cornerstone of current radiation protection policies. In the last decades, advances in molecular and evolutive biology, cancer immunology, and many epidemiological and animal studies have cast serious doubts about the reliability of the NLTM, as well as suggesting alternative models, like the hormetic theory. Considering the given evidences, a discussion between the involved scientific societies and the regulatory commissions is promtly required in order to to reach a redefiniton of theradiation protection basis, as it would be specially crucial in the medical field.

An Investigation into Indoor Radon Concentrations in Certified Passive House Homes

The Energy Performance of Buildings Directive (EPBD) has introduced the concept of Nearly Zero Energy Buildings (NZEB) specifying that by 31 December 2020 all new buildings must meet the nearly zero- energy standard, the Passive House standard has emerged as a key enabler for the Nearly Zero Energy Building standard. The combination of Passive House with renewables represents a suitable solution to move to low/zero carbon. The hypothesis in this study is that a certified passive house building with high levels of airtightness with a balanced mechanical ventilation with heat recovery (MVHR) should yield lower indoor radon concentrations. This article presents results and analysis of measured radon levels in a total of 97 certified passive house dwellings using CR-39³ alpha track diffusion radon gas detectors. The results support the hypothesis that certified passive house buildings present lower radon levels. A striking observation to emerge from the data shows a difference in radon distribution between upstairs and downstairs when compared against regular housing. The study is a first for Ireland and the United Kingdom and it has relevance to a much wider context with the significant growth of the passive house standard globally.

Genomic Instability and Carcinogenesis of Heavy Charged Particles Radiation: Clinical and Environmental Implications

One of the uses of ionizing radiation is in cancer treatment. The use of heavy charged particles for treatment has been introduced in recent decades because of their priority for deposition of radiation energy in the tumor, via the Bragg peak phenomenon. In addition to medical implications, exposure to heavy charged particles is a crucial issue for environmental and space radiobiology. Ionizing radiation is one of the most powerful clastogenic and carcinogenic agents. Studies have shown that although both low and high linear energy transfer (LET) radiations are carcinogenic, their risks are different. Molecular studies have also shown that although heavy charged particles mainly induce DNA damage directly, they may be more potent inducer of endogenous generation of free radicals compared to the low LET gamma or X-rays. It seems that the severity of genotoxicity for non-irradiated bystander cells is potentiated as the quality of radiation increases. However, this is not true in all situations. Evidence suggests the involvement of some mechanisms such as upregulation of pro-oxidant enzymes and change in the methylation of DNA in the development of genomic instability and carcinogenesis. This review aimed to report important issues for genotoxicity of carcinogenic effects of heavy charged particles. Furthermore, we tried to explain some mechanisms that may be involved in cancer development following exposure to heavy charged particles.

Hormesis and immunity: A review

The hormesis concept demonstrates that in contrast to the toxic effect of high doses of materials, irradiation, etc., low doses of them are beneficial and, in addition, help to eliminate (prevent) the deleterious effect of high doses given after it. By this effect, it is an important factor of (human) evolution protecting man from harmful impacts, similarly to the role of immunity. However, immunity is also continuously influenced by hormetic effects of environmental [chemical (pollutions), physical (background irradiations and heat), etc.] and medical (drugs and therapeutic irradiations) and food interactions. In contrast to earlier beliefs, the no-threshold irradiation dogma is not valid in low-dose domains and here the hormesis concept is valid. Low-dose therapeutic irradiation, as well as background irradiations (by radon spas or moderately far from the epicenter of atomic bomb or nuclear facilities), is rather beneficial than destructive and the fear from them seems to be unreasonable from immunological point of view. Practically, all immune parameters are beneficially influenced by all forms of low-dose radiations.

The LNT model for cancer induction is not supported by radiobiological data

The hallmarks of cancer have been the focus of much research and have influenced the development of risk models for radiation-induced cancer. However, natural defenses against cancer, which constitute the hallmarks of cancer prevention, have largely been neglected in developing cancer risk models. These natural defenses are enhanced by low doses and dose rates of ionizing radiation, which has aided in the continuation of human life over many generations. Our natural defenses operate at the molecular, cellular, tissue, and whole-body levels and include epigenetically regulated (epiregulated) DNA damage repair and antioxidant production, selective p53-independent apoptosis of aberrant cells (e.g. neoplastically transformed and tumor cells), suppression of cancer-promoting inflammation, and anticancer immunity (both innate and adaptive components). This publication reviews the scientific bases for the indicated cancer-preventing natural defenses and evaluates their implication for assessing cancer risk after exposure to low radiation doses and dose rates. Based on the extensive radiobiological evidence reviewed, it is concluded that the linear-no-threshold (LNT) model (which ignores natural defenses against cancer), as it relates to cancer risk from ionizing radiation, is highly implausible. Plausible models include dose-threshold and hormetic models. More research is needed to establish when a given model (threshold, hormetic, or other) applies to a given low-dose-radiation exposure scenario.

Epidemiologic Studies Cannot Reveal the True Shape of the Dose-Response Relationship for Radon-Induced Lung Cancer

A long-standing controversy is the correct shape of the dose-response relationship for lung cancer induction by inhaled radon (eg, residential radon) at low levels. A probabilistic approach is used in this commentary to show that cohort and case-control epidemiologic studies cannot reveal the true shape of the dose-response relationship for radon-induced lung cancer. Using the indicated approach, it is found that while the dose response for radon-induced lung cancer is expected to be threshold-increasing, the dose-response curve for the cancer incidence when cancers caused by smoking and other carcinogens are included is expected to be threshold-decreasing (ie, threshold-hormetic), as low-level radon can protect from cancer induction by other carcinogens via stimulating the body's natural defenses against cancer. These defenses include DNA damage repair, removal of aberrant cells via apoptosis, suppression of cancer promoting inflammation, and anticancer immunity.

Health Impacts of Low-Dose Ionizing Radiation: Current Scientific Debates and Regulatory Issues

Health impacts of low-dose ionizing radiation are significant in important fields such as X-ray imaging, radiation therapy, nuclear power, and others. However, all existing and potential applications are currently challenged by public concerns and regulatory restrictions. We aimed to assess the validity of the linear no-threshold (LNT) model of radiation damage, which is the basis of current regulation, and to assess the justification for this regulation. We have conducted an extensive search in PubMed. Special attention has been given to papers cited in comprehensive reviews of the United States (2006) and French (2005) Academies of Sciences and in the United Nations Scientific Committee on Atomic Radiation 2016 report. Epidemiological data provide essentially no evidence for detrimental health effects below 100 mSv, and several studies suggest beneficial (hormetic) effects. Equally significant, many studies with in vitro and in animal models demonstrate that several mechanisms initiated by low-dose radiation have beneficial effects. Overall, although probably not yet proven to be untrue, LNT has certainly not been proven to be true. At this point, taking into account the high price tag (in both economic and human terms) borne by the LNT-inspired regulation, there is little doubt that the present regulatory burden should be reduced.

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.

Treatment of Cancer and Inflammation With Low-Dose Ionizing Radiation: Three Case Reports

There is considerable evidence from experimental studies in animals, as well as from clinical reports, that low-dose radiation hormesis is effective for the treatment of cancer and ulcerative colitis. In this study, we present 3 case reports that support the clinical efficacy of low-dose radiation hormesis in patients with these diseases. First, a patient with prostate cancer who had undergone surgical resection showed a subsequent increase in prostate-specific antigen (PSA). His PSA value started decreasing immediately after the start of repeated low-dose X-ray irradiation treatment and remained low thereafter. Second, a patient with prostate cancer with bone metastasis was treated with repeated low-dose X-ray irradiation. His PSA level decreased to nearly normal within 3 months after starting the treatment and remained at the low level after the end of hormesis treatment. His bone metastasis almost completely disappeared. Third, a patient with ulcerative colitis showed a slow initial response to repeated low-dose irradiation treatment using various modalities, including drinking radon-containing water, but within 8 months, his swelling and bleeding had completely disappeared. After 1 year, the number of bowel movements had become normal. Interest in the use of radiation hormesis in clinical practice is increasing, and we hope that these case reports will encourage further clinical investigations.

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.

100 kBq m-3 Radon Activity Concentration in the Atmosphere of a Bathroom Supplied with Groundwater From A Gneissic Rock Area with Consanguineous Intrusions

Inhalation of escaping radon from groundwater comprises the largest part of radiological hazard from groundwater radionuclides in the uranium and thorium series. Groundwater containing 1.5 mg dm uranium and 3 kBq dm radon activity concentration supplied an ordinary bathroom of 15 m in a home. Using the showerhead, atmospheric levels of radon activity in the bathroom exceeded 100 kBq m within a period of about 1 h.

Lung Cancer Risk from Radon in Marcellus Shale Gas in Northeast U.S. Homes

The amount of radon in natural gas varies with its source. Little has been published about the radon from shale gas to date, making estimates of its impact on radon-induced lung cancer speculative. We measured radon in natural gas pipelines carrying gas from the Marcellus Shale in Pennsylvania and West Virginia. Radon concentrations ranged from 1,520 to 2,750 Bq/m³ (41-74 pCi/L), and the throughput-weighted average was 1,983 Bq/m³ (54 pCi/L). Potential radon exposure due to the use of Marcellus Shale gas for cooking and space heating using vent-free heaters or gas ranges in northeastern U.S. homes and apartments was assessed. Though the measured radon concentrations are higher than what has been previously reported, it is unlikely that exposure from natural gas cooking would exceed 1.2 Bq/m³ (<1% of the U.S. Environmental Protection Agency's action level). Using worst-case assumptions, we estimate the excess lifetime (70 years) lung cancer risk associated with cooking to be 1.8×10^-4 (interval spanning 95% of simulation results: 8.5×10^-5 , 3.4×10^-4 ). The risk profile for supplemental heating with unvented gas appliances is similar. Individuals using unvented gas appliances to provide primary heating may face lifetime risks as high as 3.9×10^-3 . Under current housing stock and gas consumption assumptions, expected levels of residential radon exposure due to unvented combustion of Marcellus Shale natural gas in the Northeast United States do not result in a detectable change in the lung cancer death rates.

Time to Reject the Linear-No Threshold Hypothesis and Accept Thresholds and Hormesis: A Petition to the U.S. Nuclear Regulatory Commission

On February 9, 2015, I submitted a petition to the U.S. Nuclear Regulatory Commission (NRC) to reject the linear-no threshold (LNT) hypothesis and ALARA as the bases for radiation safety regulation in the United States, using instead threshold and hormesis evidence. In this article, I will briefly review the history of LNT and its use by regulators, the lack of evidence supporting LNT, and the large body of evidence supporting thresholds and hormesis. Physician acceptance of cancer risk from low dose radiation based upon federal regulatory claims is unfortunate and needs to be reevaluated. This is dangerous to patients and impedes good medical care. A link to my petition is available: http://radiationeffects.org/wp-content/uploads/2015/03/Hormesis-Petition-to-NRC-02-09-15.pdf, and support by individual physicians once the public comment period begins would be extremely important.

Threshold for Radon-Induced Lung Cancer From Inhaled Plutonium Data

Cohen's lung cancer mortality data, from his test of the LNT theory, do not extend to the no observed adverse effects level (NOAEL) above which inhaled radon decay products begin to induce excess lung cancer mortality. Since there is concern about the level of radon in homes, it is important to set the radon limit near the NOAEL to avoid the risk of losing a health benefit. Assuming that dogs model humans, data from a study on inhaled plutonium dioxide particulates in dogs were assessed, and the NOAEL for radon-induced lung tumors was estimated to be about 2100 Bq/m(3). The US Environmental Protection Agency should consider raising its radon action level from 150 to at least 1000 Bq/m(3).

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.

Radiation-hormesis phenotypes, the related mechanisms and implications for disease prevention and therapy

Humans are continuously exposed to ionizing radiation throughout life from natural sources that include cosmic, solar, and terrestrial. Much harsher natural radiation and chemical environments existed during our planet's early years. Mammals survived the harsher environments via evolutionarily-conserved gifts ̶ a continuously evolving system of stress-induced natural protective measures (i.e., activated natural protection [ANP]). The current protective system is differentially activated by stochastic (i.e., variable) low-radiation-dose thresholds and when optimally activated in mammals includes antioxidants, DNA damage repair, p53-related apoptosis of severely-damaged cells, reactive-oxygen-species (ROS)/reactive-nitrogen-species (RNS)- and cytokine-regulated auxiliary apoptosis that selectively removes aberrant cells (e.g., precancerous cells), suppression of disease promoting inflammation, and immunity against cancer cells. The intercellular-signaling-based protective system is regulated at least in part via epigenetic reprogramming of adaptive-response genes. When the system is optimally activated, it protects against cancer and some other diseases, thereby leading to hormetic phenotypes (e.g., reduced disease incidence to below the baseline level; reduced pain from inflammation-related problems). Here, some expressed radiation hormesis phenotypes and related mechanisms are discussed along with their implications for disease prevention and therapy.

Commentary: ethical issues of current health-protection policies on low-dose ionizing radiation

The linear no-threshold (LNT) model of ionizing-radiation-induced cancer is based on the assumption that every radiation dose increment constitutes increased cancer risk for humans. The risk is hypothesized to increase linearly as the total dose increases. While this model is the basis for radiation safety regulations, its scientific validity has been questioned and debated for many decades. The recent memorandum of the International Commission on Radiological Protection admits that the LNT-model predictions at low doses are "speculative, unproven, undetectable and 'phantom'." Moreover, numerous experimental, ecological, and epidemiological studies show that low doses of sparsely-ionizing or sparsely-ionizing plus highly-ionizing radiation may be beneficial to human health (hormesis/adaptive response). The present LNT-model-based regulations impose excessive costs on the society. For example, the median-cost medical program is 5000 times more cost-efficient in saving lives than controlling radiation emissions. There are also lives lost: e.g., following Fukushima accident, more than 1000 disaster-related yet non-radiogenic premature deaths were officially registered among the population evacuated due to radiation concerns. Additional negative impacts of LNT-model-inspired radiophobia include: refusal of some patients to undergo potentially life-saving medical imaging; discouragement of the study of low-dose radiation therapies; motivation for radiological terrorism and promotion of nuclear proliferation.

Low-dose gamma-radiation inhibits benzo[a]pyrene-induced lung adenoma development in a/j mice

Low-dose ionizing radiation (LDR) may lead to suppression of smoking-related lung cancer. We examined the effects of a known cigarette smoke carcinogen Benzo[a]pyrene (B[a]P) alone or in combination with fractionated low-dose gamma radiation (60 - 600 mGy total dose) on the induction of lung neoplasms in the A/J mouse. Our results show that 600 mGy of gamma radiation delivered in six biweekly fractions of 100 mGy starting 1 month after B[a]P injection significantly inhibits the development of lung adenomas per animal induced by B[a]P. Our data also indicated that the six biweekly doses suppressed the occurrence of spontaneous hyperplastic foci in the lung, although this suppression failed to reach statistical significance when analyzed as average foci per lung possibly related to the small sample sizes used for the control and test groups.

Small γ-Ray Doses Prevent Rather than Increase Lung Tumors in Mice

We show evidence for low doses of γ rays preventing spontaneous hyperplastic foci and adenomas in the lungs of mice, presumably via activating natural anticancer defenses. The evidence partly relates to a new study we conducted whereby a small number of female A/J mice received 6 biweekly dose fractions (100 mGy per fraction) of γ rays to the total body which prevented the occurrence of spontaneous hyperplastic foci in the lung. We also analyzed data from a much earlier Oak Ridge National Laboratory study involving more than 10,000 female RFMf/Un mice whereby single γ-ray doses from 100 to 1,000 mGy prevented spontaneous lung adenomas. We point out the possibility that the decrease in lung cancer mortality observed in The National Lung Screening Trial Research Team study involving lung tumor screening using low-dose computed tomography (CT) may relate at least in part to low-dose X-rays activating the body's natural anticancer defenses (i.e., radiation hormesis). This possibility was apparently not recognized by the indicated research team.

The new radiobiology: returning to our roots

In 2005, two expert advisory bodies examined the evidence on the effects of low doses of ionizing radiation. The U.S. National Research Council concluded that current scientific evidence is consistent with the linear no-threshold dose-response relationship (NRCNA 2005) while the French National Academies of Science and Medicine concluded the opposite (Aurengo et al. 2005). These contradictory conclusions may stem in part from an emphasis on epidemiological data (a "top down" approach) versus an emphasis on biological mechanisms (a "bottom up" approach). In this paper, the strengths and limitations of the top down and bottom up approaches are discussed, and proposals for strengthening and reconciling them are suggested. The past seven years since these two reports were published have yielded increasing evidence of nonlinear responses of biological systems to low radiation doses delivered at low dose-rates. This growing body of evidence is casting ever more doubt on the extrapolation of risks observed at high doses and dose-rates to estimate risks associated with typical environmental and occupational exposures. This paper compares current evidence on low dose, low dose-rate effects against objective criteria of causation. Finally, some questions for a post-LNT world are posed.

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.

Shifting the paradigm in radiation safety

The current radiation safety paradigm using the linear no-threshold (LNT) model is based on the premise that even the smallest amount of radiation may cause mutations increasing the risk of cancer. Autopsy studies have shown that the presence of cancer cells is not a decisive factor in the occurrence of clinical cancer. On the other hand, suppression of immune system more than doubles the cancer risk in organ transplant patients, indicating its key role in keeping occult cancers in check. Low dose radiation (LDR) elevates immune response, and so it may reduce rather than increase the risk of cancer. LNT model pays exclusive attention to DNA damage, which is not a decisive factor, and completely ignores immune system response, which is an important factor, and so is not scientifically justifiable. By not recognizing the importance of the immune system in cancer, and not exploring exercise intervention, the current paradigm may have missed an opportunity to reduce cancer deaths among atomic bomb survivors. Increased antioxidants from LDR may reduce aging-related non-cancer diseases since oxidative damage is implicated in these. A paradigm shift is warranted to reduce further casualties, reduce fear of LDR, and enable investigation of potential beneficial applications of LDR.

First generation stochastic gene episilencing (step1) model and applications to in vitro carcinogen exposure

A novel first-generation stochastic gene episilencing (STEP1) model is introduced for quantitatively characterizing the probability of in vitro epigenetically silencing (episilencing) specific tumor-suppressor-microRNA (miRNA) genes by carcinogen exposure. Although the focus is mainly on in-vitro exposure of human cells to ionizing radiation, the mathematical formulations presented are general and can be applied to other carcinogens. With the STEP1 model, a fraction fj of the surviving target cells can have their tumor-suppressor-miRNA gene of type j silenced while the remaining fraction, 1 - fj , of the surviving cells do not undergo gene episilencing. Suppressor gene episilencing is assumed to arise as a Poisson process characterized with and exponential distribution of episilencing doses with mean dj . In addition to providing mathematical functions for evaluating the single-target-gene episilencing probability, functions are also provided for the multi-target-gene episilencing probability for simultaneously silencing of multiple tumor-suppressor-miRNA genes. Functional relationships are first developed for moderate doses where adaptive responses are unlikely and are then modified for low doses where adaptation can occur. Results apply to a specific follow-up time t after carcinogen exposure that exceeds the maximum time for the occurrence of an induced episilencing event.