The retrieved scientific literature shows that while numerous publications explore and advocate for radiation hormesis, there are also substantial peer-reviewed studies, critical reviews, and reports—such as BEIR VII—that contradict or question the validity, mechanistic basis, and generalizability of the hormesis hypothesis.
The paper provides an account of how the hormetic dose response has emerged in recent years as a serious dose-response model in toxicology and risk assessment after decades of extreme marginalization. In addition to providing the toxicological basis of this dose-response revival, the paper reexamines the concept of a default dose model in toxicology and risk assessment and makes the argument that the hormetic model satisfies criteria (e.g., generalizability, frequency, application to risk assessment endpoints, false positive/negative potential, requirements for hazard assessment, reliability of estimating risks, capacity for validation of risk estimates, public health implications of risk estimates) for such a default model better than its chief competitors, the threshold and linear at low dose models. The selection of the hormetic model as the default model in risk assessment for noncarcinogens and specifically for carcinogens would have a profound impact on the practice of risk assessment and its societal implications.
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.
Welsh’s point was that there is every reason to consider evolutionary biological —cellular and immunological—processes to explain well-known laboratory-proven defenses and protections against low-dose radiation. He offered this not as an explanation of nondetectability of effect, but rather as a much-neglected description of scientific reality. It was Hall and Brenner who missed Welsh’s point. In fact, they explicitly argue against appeals to biology in favor of considerations of poor signal-to-noise ratios (a statistical issue) as the explanation for the nondetectability of harm.
The BEIR VII report in Appendix D: Hormesis notes on page 332 that the evidence for a repair mechanism that acts to reduce both spontaneous and radiation-induced damage to below spontaneous levels, thus causing a hormetic effect, is weak and indirect and is contradicted by direct measures of DSB (double-strand breaks) repair foci at low doses. For this conclusion they cite a study by Rothkamm and Löbrich ( 2003 ). However, the BEIR VII report misrepresents the cited reference, as this study actually comes to the opposite conclusion when not cherry picked. The report (BEIR VII 2006 , p.
NCI cites these papers as support for their advice to the NRC that they reject the three petitions calling for an end to the use of LNT (Berrington de González et al. 2015 ). In addition to their uncritical reliance on such flawed studies, the NCI authors commit the error of invoking, in typical fashion, the lack of statistical power as their explanation for the non-detectability of the presumed carcinogenic effects of low-dose radiation in many other studies. Again, typically, they never question whether such detrimental effects actually obtain.
ended their response with, It seems to us that the “Scientists for Accurate Radiation Information” a priori exclude the possibility that low-dose radiation could increase the risk of cancer. They will therefore not accept studies that challenge their foregone conclusion. (Spycher et al. 2015b ) Thus they ignored the fact that the existence of a threshold and the reality of hormesis rest on solid evidence while LNT rests precariously on a sandpile of assumption, instead charging that it was our response rather than their study that reflected a priori bias.
The authors conclude that the LNT model is incorrect and that it should be replaced with a threshold model; they espouse the concept of hormesis whereby a small dose of ionizing radiation up-regulates cellular defenses and DNA repair efficiencies which effectively protect against genetic lesions that lead to cancer and other health effects in those exposed or presumably, through the same mechanisms, their progeny. In their worldview, small doses of radiation are “good for you.” The concept of hormesis is based upon a failure of scientific philosophy.
They fail to understand that the concept of dose itself is not valid for internal exposures, which convey the predominant risks from radiation. This error is also present in all the nuclear worker studies that reference their results to the low-dose group rather than to a proper control group or the national database. The latest example of this questionable epidemiology is the INWORKS nuclear workers studies (Richardson et al. 2015 ).
This epidemiological failure problem began with the Japanese LSS studies where, following the finding that there were low levels of cancer in the control group, the Not-in-City (NIC) group (the externally unexposed controls) were abandoned in favor of
But then, contradicting his agreement with us that “It would seem reasonable that evolution would have provided a mechanism for protecting against radiation,” Busby charges us with proposing “a truly dangerous thesis because adopting the measures that [our article] suggests will result in a serious increase in illness and genetic damage in members of the public and workers who are currently protected under a regime which itself fails to take into account evidence (including that presented by the advocates of hormesis).” As we point out in our article, the dangers, and indeed deaths, that are a direct result of policies and fears based on the LNT hypothesis, and that are not due to low - dose radiation exposure , number in the hundreds to thousands.
Current guidelines for limiting exposure of humans to ionizing radiation are based on the linear-no-threshold (LNT) hypothesis for radiation carcinogenesis under which cancer risk increases linearly as the radiation dose increases. With the LNT model even a very small dose could cause cancer and the model is used in establishing guidelines for limiting radiation exposure of humans. A slope change at low doses and dose rates is implemented using an empirical dose and dose rate effectiveness factor (DDREF). This imposes usually unacknowledged nonlinearity but not a threshold in the dose-response curve for cancer induction. In contrast, with the hormetic model, low doses of radiation reduce the cancer incidence while it is elevated after high doses. Based on a review of epidemiological and other data for exposure to low radiation doses and dose rates, it was found that the LNT model fails badly. Cancer risk after ordinarily encountered radiation exposure (medical X-rays, natural background radiation, etc.) is much lower than projections based on the LNT model and is often less than the risk for spontaneous cancer (a hormetic response). Understanding the mechanistic basis for hormetic responses will provide new insights about both risks and benefits from low-dose radiation exposure.
The current system of radiation protection for humans is based on the linear-no-threshold (LNT) risk-assessment paradigm. Perceived harm to irradiated nuclear workers and the public is mainly reflected through calculated hypothetical increased cancers. The LNT-based system of protection employs easy-to-implement measures of radiation exposure. Such measures include the equivalent dose (a biological-damage-potential-weighted measure) and the effective dose (equivalent dose multiplied by a tissue-specific relative sensitivity factor for stochastic effects). These weighted doses have special units such as the sievert (Sv) and millisievert (mSv, one thousandth of a sievert). Radiation-induced harm is controlled via enforcing exposure limits expressed as effective dose. Expected cancer cases can be easily computed based on the summed effective dose (person-sievert) for an irradiated group or population. Yet the current system of radiation protection needs revision because radiation-induced natural protection (hormesis) has been neglected. A novel, nonlinear, hormetic relative risk model for radiation-induced cancers is discussed in the context of establishing new radiation exposure limits for nuclear workers and the public.
Energy needs worldwide are expected to increase for the foreseeable future, but fuel supplies are limited. Nuclear reactors could supply much of the energy demand in a safe, sustainable manner were it not for fear of potential releases of radioactivity. Such releases would likely deliver a low dose or dose rate of radiation, within the range of naturally occurring radiation, to which life is already accustomed. The key areas of concern are discussed. Studies of actual health effects, especially thyroid cancers, following exposures are assessed. Radiation hormesis is explained, pointing out that beneficial effects are expected following a low dose or dose rate because protective responses against stresses are stimulated. The notions that no amount of radiation is small enough to be harmless and that a nuclear accident could kill hundreds of thousands are challenged in light of experience: more than a century with radiation and six decades with reactors. If nuclear energy is to play a significant role in meeting future needs, regulatory authorities must examine the scientific evidence and communicate the real health effects of nuclear radiation. Negative images and implications of health risks derived by unscientific extrapolations of harmful effects of high doses must be dispelled.
Ionizing radiation induces reactive oxygen species (ROS) and inflammatory signaling that contribute to both therapeutic efficacy and normal tissue toxicity. While the effects of high-dose radiation are well characterized, responses to low-dose-rate radiation (LDRR) remain inconsistent and are not adequately explained by conventional linear dose-response models. To address this gap, we conducted a narrative review of recent experimental studies across multiple biological systems, including body fluids, joint microenvironments, and reproductive tissues, focusing on redox and immune-related responses under LDRR conditions (dose rates: 0.39-3.49 mGy/h). Literature was identified through PubMed/MEDLINE, Web of Science, and Google Scholar, with emphasis on studies published between 2015 and 2026. These studies demonstrate that LDRR elicits nonlinear, dose-dependent effects that vary across biological compartments and involve coordinated changes in oxidative stress, immune signaling, and metabolic regulation. Based on this synthesis, we propose a unifying framework of nonlinear redox-immune coupling, in which oxidative stress functions as a threshold-dependent regulator and immune responses follow a biphasic trajectory characterized by activation at lower dose rates and attenuation or adaptation at higher levels. These responses are strongly influenced by the local microenvironment, resulting in compartment-specific variability. This integrated perspective supports a shift from dose-centric to systems-level interpretations of radiation biology and provides a basis for improving biomarker development, risk assessment, and therapeutic strategies in chronic low-dose radiation exposure settings. Future research priorities include time-resolved mechanistic studies to define compartment-specific redox thresholds, validation of candidate biomarkers under identical multi-compartment experimental conditions (e.g., GSH/GSSG ratio, 8-OHdG, circulating cytokine panels including IL-10/TNF-α ratio), and integration of subject-specific biological variables (e.g., age, sex, and baseline redox capacity) into predictive models of LDRR response.
Radiation hormesis is the hypothesis that low doses of ionizing radiation (within the region of and just above natural background levels) are beneficial
Radiation hormesis is the hypothesis that low doses of ionizing radiation (within the region of and just above natural background levels) are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation. The reserve repair mechanisms are hypothesized to be sufficiently effective when stimulated as to not only canc
Radiation hormesis proposes that radiation exposure comparable to and just above the natural background level of radiation is not harmful but beneficial, while accepting that much higher levels of radiation are hazardous. Proponents of radiation hormesis typically claim that radio-protective responses in cells and the immune system not only counter the harmful effects of radiation but additionally act to inhibit spontaneous cancer not related to radiation exposure. Radiation hormesis stands in stark contrast to the more generally accepted linear no-threshold model (LNT), which states that the radiation dose-risk relationship is linear across all doses, so that small doses are still damaging, albeit less so than higher ones. Opinion pieces on chemical and radiobiological hormesis appeared in the journals Nature and Science in 2003.
Assessing the risk of radiation at low doses…
Until the [...] uncertainties on low-dose response are resolved, the Committee believes that an increase in the risk of tumour induction proportionate to the radiation dose is consistent with developing knowledge and that it remains, accordingly, the most scientifically defensible approximation of low-dose response. However, a strictly linear dose response should not be expected in all circumstances.
This is a reference to the fact that very low doses of radiation have only marginal impacts on individual health outcomes. It is therefore difficult to detect the 'signal' of decreased or increased morbidity and mortality due to low-level radiation exposure in the 'noise' of other effects. The notion of radiation hormesis has been rejected by the National Research Council's (part of the National Academy of Sciences) 16-year-long study on the Biological Effects of Ionizing Radiation. "The scientific research base shows that there is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless or beneficial. The health risks – particularly the development of solid cancers in organs – rise proportionally with exposure" says Richard R. Monson, associate dean for professional education and professor of epidemiology, Harvard School of Public Health, Boston.
Radiation is a known carcinogen because of the world-wide health scare that was created in 1960. However, there is no evidence that radiation is a carcinogen below some threshold. Prof. Edward Calabrese pursued the emergence of the linear no-threshold theory (LNT) and questioned whether it ever had a scientific basis. After the Chernobyl accident many publications appeared with LNT-based prognostications, for example, of millions of victims from nuclear accidents, reviewed previously. Apparently, certain writers’ exaggeration of medical and ecological consequences of the moderate anthropogenic increase in the background radiation contributed to a strangulation of the atomic energy, which was in the interests of fossil fuel producers. Some dose-effect correlations may be attributed to a dosedependent selection, self-selection and recall bias noticed in exposed cohorts. It can be reasonably assumed that individuals, knowing that they had higher doses would be more motivated to undergo medical examinations being at the same time given more attention. Therefore, diagnosis of diseases would be on the average more likely in people with higher doses. For example, the dose-dependent increase in incidence of cardioand cerebrovascular diseases among Mayak Production Association (MPA) workers was not accompanied by a corresponding elevation of mortality, which can be attributed to a more frequent recording of mild cases in people with higher doses. The excess relative risk per unit dose for leukemia amongMPAworkers, using incidence data, has been considerably higher than that using mortality data. A more efficient detection of latent leukemia with occasional registration of unverified cases is a probable explanation. Elevated risks of non-malignant diseases have been found in Chernobyl, MPA, and Techa River populations. For example, the excess relative risk of cerebrovascular diseases, per unit dose, among MPAworkers was reportedly higher than in the atomic bomb survivors, where the exposure was acute and thus would be expectedly higher. Remarkably, the dosedependent incidence increase in cerebrovascular and ischemic heart disease among MPA workers was not accompanied by any increase in mortality, which can be explained by a dosedependent diagnostic efficiency with recording of mild and borderline cases in people with higher dose estimates. According to the same researchers, the incidence of cerebrovascular diseases was significantly increased among MPA workers with cumulative external doses ≥ 0.1 Gy. For comparison, UNSCEAR could not make any conclusions about immediate causal relationships between doses ≤ 1–2 Gy and excess incidence of cardiovascular or generally of non-malignant diseases. The value 1–2 Gy may be an undervaluation due to bias in epidemiological studies. Doubtful correlations between low-dose exposures and nonmalignant conditions call into question the cause–effect character of such correlations for malignancies reported by the same researchers. A promising approach for research of dose-response relationships is lifelong animal experiments. Life span duration is known to be a sensitive endpoint, attributable to radiation exposures, which can reflect the net harm or potential benefit within a certain range, according to the concept of hormesis. The experimental evidence in favor of radiation hormesis is considerable. Admittedly, not all experiments supported hormesis, for example, showing no life lengthening of exposed mice; other studies did report life lengthening of rodents and other species; details and references are in reviews.
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<h4>Objective</h4>This analysis is a critical assessment of current hormesis literature. I discuss definitions, characterization, generalizability, mechanisms, absence of empirical data specific for hormesis hypothesis testing, and arguments that hormesis be the "default assumption" in risk assessment.<h4>Data sources</h4>Hormesis, a biological phenomenon typically described as low-dose stimulation from substances producing higher-dose inhibition, has recently garnered interest in several quarters. The principal sources of published materials for this analysis are the writings of certain proponents of hormesis. Surprisingly few systematic critiques of current hormesis literature exist. Limits to the phenomenon's appropriate role in risk assessment and health policy have been published.<h4>Data synthesis</h4>Serious gaps in scientific understanding remain: a stable definition; generalizability, especially for humans; a clear mechanistic basis; limitations in the presence of multiple toxic end points, target organs, and mechanisms. Absence of both arms-length, consensus-driven, scientific evaluations and empirical data from studies specifically designed for hormesis testing have limited its acceptance.<h4>Conclusions</h4>Definition, characterization, occurrence, and mechanistic rationale for hormesis will remain speculative, absent rigorous studies done specifically for hormesis testing. Any role for hormesis in current risk assessment and regulatory policies for toxics remains to be determined.
<h4>Background</h4>Hormesis is a binary response phenomenon with low-dose stimulation (or inhibition) of effects by substances producing opposite high-dose responses. Hormesis, after decades of obscurity, has undergone a renaissance in recent years, with rapid growth benefiting greatly from the systematized efforts of such proponents as the hormesis group at the University of Massachusetts-Amherst led by Edward J. Calabrese.<h4>Objective</h4>In this commentary I analyze chemical hormesis methodology with reference to ad hoc scientific approaches for defining and characterizing hormesis.<h4>Discussions</h4>Proponents of hormesis have attempted a scientific characterization of hormesis through a battery of ad hoc methodologies using unvalidated criteria and other mechanisms for persistent database searches rather than through de novo hypothesis testing specific for hormesis. Here I discuss various scientific problems with this search-over-experiment approach, as well as other aspects of attempts at defining and characterizing the field.<h4>Conclusions</h4>Wide acceptance of hormesis by the broad scientific community and adoption of hormesis by public agencies for inclusion in health and regulatory policies have not occurred. Reasons may include the singular nature of hormesis research and directions followed in hormesis methodologies.
Low-dose radiation exposure to Canadians is exponentially increasing due to the influx of diagnostic imaging and medical procedures that utilize radiation. Despite the use of medical radiation since 1896, the standardized acceptable dose for the Canadian public is still debated. The current annual dose limit for the public is set at 1 millisievert (mSv). This set dose limit intrinsically restricts the use of medical radiation for diagnosis due to concerns of public health. This systematic review is in the form of a retrospective meta-analysis of previous experimental studies and observational reviews of low-dose radiation health effects. A database search using PubMed and Medscape identified 1,296 articles using the terms "low-dose radiation", "radiation hormesis", "radiation safety", "dose exposure", and "medical radiation". Full text articles were excluded for the following reasons: radiation dose level not <100mSv, results of radiation effects not included, or no inclusion of biologic effects on living tissue. After screening, 15 studies were selected for inclusion. The concerns of radiation exposure are based on epidemiological and experimental studies that have indicated that high-dose ionizing radiation has toxic effects and increases cancer risk. In contrast, low-dose radiation has experimentally demonstrated various beneficial effects through a combination of molecular and cohort studies, randomized control trials, and observational analysis. The limitation of radiation in medical imaging is founded on the assumption that low-dose radiation health risks are a linear extrapolation of high-dose radiation. Through a systematic review of research, it is proposed that the current dose-response extrapolation for radiation-related health risks cannot be linearly based on the effects at high doses. By altering this knowledge, we could effectively improve patient diagnosis and public health by redefining the restrictions of current radiation limits within diagnostic imaging.
Background/Objectives: Low-dose ionizing radiation (LDIR) is commonly used in medical diagnoses and certain professions, but its long-term effects on noncancer diseases, particularly cardiovascular disease (CVD), remain uncertain. While LDIR has recognized diagnostic benefits, its influence on CVD mortality and disease progression is still debated, with some suggesting that low doses may even have beneficial effects, as per the hormesis theory. Methods: This meta-analysis aimed to evaluate the impact of LDIR on cardiovascular health outcomes. The study followed a systematic approach, using the PRISMA guidelines to select and analyze relevant studies from databases such as PubMed, Scopus, Web of Science, and Embase. Out of 167 identified studies, 8 were chosen for analysis, including 6 cohort studies and 2 experimental studies. Results: The findings indicated a significant link between LDIR exposure and increased CVD mortality and progression, though some studies also noted potential benefits of LDIR in certain conditions, aligning with the hormesis theory. Conclusions: These mixed results raise questions about the specific conditions under which LDIR might be beneficial or harmful. Overall, the study emphasizes the need for strict radiation control measures and health monitoring for individuals regularly exposed to LDIR, both in clinical and occupational settings.
pmc J Clin Med J Clin Med 2745 jclinmed jcm Journal of Clinical Medicine 2077-0383 Multidisciplinary Digital Publishing Institute (MDPI) PMC11594962 PMC11594962.1 11594962 11594962 39598053 10.3390/jcm13226909 jcm-13-06909 1 Systematic Review Meta-Analysis of the Impact of Low-Dose Ionizing Radiation on Mortality and Progression of Heart Disease in the General Patient Population: Insights from Hormesis Theory in Cardiology Pocięgiel Mateusz 1 * Opyd Piotr 1 Zawodny Tomasz 1 Lis Michał 1 2 https://orcid.org/0000-0002-6563-0877 Filipiak Krzysztof J.
Results: The findings indicated a significant link between LDIR exposure and increased CVD mortality and progression, though some studies also noted potential benefits of LDIR in certain conditions, aligning with the hormesis theory. Conclusions: These mixed results raise questions about the specific conditions under which LDIR might be beneficial or harmful. Overall, the study emphasizes the need for strict radiation control measures and health monitoring for individuals regularly exposed to LDIR, both in clinical and occupational settings. low-dose ionizing radiation cardiovascular disease mortality disease progression hormesis meta-analysis This research received no external funding.
This systematic review and meta-analysis will therefore sum up the existing data on the adverse effects and possible cardioprotective benefits of LDIR. In this way, we try to offer a more conclusive view that would be useful for clinical practice, occupational health strategies, and further studies. Research Questions What is the impact of LDIR on CVD mortality in the general population? How does LDIR influence the progression of heart disease in patients exposed to low doses of ionizing radiation? What insights can be drawn from hormesis theory regarding the potential beneficial or harmful effects of LDIR on cardiovascular health? 2. Methodology 2.1.
Search Strategy The results of this systematic review and meta-analysis were prepared following the guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The databases used in the literature search were PubMed, Scopus, Web of Science, and Embase. To find the studies, the following keywords and MeSH terms were used in the search strategy: low-dose ionizing radiation, cardiovascular disease, mortality, heart disease progression, radiation exposure, and hormesis. Boolean connectors AND and OR were used to link the keywords and filter the results. 2.2.
Inclusion Criteria Studies were included based on the following criteria: (i) exposure to low-dose ionizing radiation (0.1–0.2 Gy per fraction and cumulative totals ranging from 1 to 4 Gy), (ii) cardiovascular disease mortality or progression, (iii) cohort studies, case–control studies, or experimental studies, (iv) publication in peer-reviewed journals, and (v) sufficient data for extraction and analysis. 2.3.
In summary, the meta-analysis confirms the increased mortality and further progression of cardiac diseases in patients exposed to LDIR. The studies suggesting a positive impact of low-dose ionizing radiation (LDIR) on reducing mortality and slowing disease progression represent observational trends only and lack statistical significance. These observed effects may be attributable to various uncontrolled risk factors to which the study population may have been exposed and which were not accounted for in the published analyses.
The results of increased mortality and progression of heart disease among the population exposed to LDIR suggest the possibility of more rigorous monitoring of radiation doses and provide a starting point for future periodic follow-up studies among affected individuals to better understand the molecular mechanisms in the future. Moreover, the evidence of hormesis obtained in some investigations implies that low levels of radiation can be helpful and further research regarding this phenomenon is needed.
Individual dosimetry Significant positive dose–response relationship; higher risk than other occupational cohorts and atomic bomb survivors Significant positive dose–response relationship observed for both men and women with
Long-term low-dose ionizing radiation exposure was found to stimulate neutrophils and inhibit their production of NETs, resulting in the inhibition of atherosclerosis. In the high-fat diet group, the effect was particularly evident. ERR—excess relative risks; CI—confidence interval; WLM—working level months; MCP-1—mean chemo-attractant; AMI—acute myocardial ischemia; NETs—neuroendocrine tumors; IR—ionizing radiation.
Everything we examined (13)
This check searched the claim as stated. It did not run a separate search for evidence against it.