It Is Time to Move Beyond the Linear No-Threshold Theory for Low-Dose Radiation Protection

A Revised System of Radiological Protection Is Needed

ABSTRACT

The system of radiological protection has been based on linear no-threshold theory and related dose-response models for health detriment (in part related to cancer induction) by ionizing radiation exposure for almost 70 y. The indicated system unintentionally promotes radiation phobia, which has harmed many in relationship to the Fukushima nuclear accident evacuations and led to some abortions following the Chernobyl nuclear accident. Linear no-threshold model users (mainly epidemiologists) imply that they can reliably assess the cancer excess relative risk (likely none) associated with tens or hundreds of nanogray (nGy) radiation doses to an organ (e.g., bone marrow); for 1,000 nGy, the excess relative risk is 1,000 times larger than that for 1 nGy. They are currently permitted this unscientific view (ignoring evolution-related natural defenses) because of the misinforming procedures used in data analyses of which many radiation experts are not aware. One such procedure is the intentional and unscientific vanishing of the excess relative risk uncertainty as radiation dose decreases toward assigned dose zero (for natural background radiation exposure). The main focus of this forum article is on correcting the serious error of discarding risk uncertainty and the impact of the correction. The result is that the last defense of the current system of radiological protection relying on linear no-threshold theory (i.e., epidemiologic studies implied findings of harm from very low doses) goes away. A revised system is therefore needed.

Interplay of immune modulation, adaptive response and hormesis: Suggestive of threshold for clinical manifestation of effects of ionizing radiation at low doses?

The health impacts of low-dose ionizing radiation exposures have been a subject of debate over the last three to four decades. While there has been enough evidence of "no adverse observable" health effects at low doses and low dose rates, the hypothesis of "Linear No Threshold" continues to rule and govern the principles of radiation protection and the formulation of regulations and public policies. In adopting this conservative approach, the role of the biological processes underway in the human body is kept at abeyance. This review consolidates the available studies that discuss all related biological pathways and repair mechanisms that inhibit the progression of deleterious effects at low doses and low dose rates of ionizing radiation. It is pertinent that, taking cognizance of these processes, there is a need to have a relook at policies of radiation protection, which as of now are too stringent, leading to undue economic losses and negative public perception about radiation.

Persons chronically exposed to low doses of ionizing radiation: A cytogenetic dosimetry study

The dosimetry and control of exposure for individuals chronically exposed to ionizing radiation are important and complex issues. Assessment may be optimized by evaluating individual adaptation and radiosensitivity, but it is not possible for a single model to account for all relevant parameters. Our goal was to develop approaches for the calculation of doses for persons chronically exposed to ionizing radiation, taking their radiosensitivities into consideration. On the basis of ex vivo radiation of blood samples, dose-effect models were constructed for dose ranges 0.01-2.0 and 0.01-0.4 Gy, using different cytogenetic criteria. The frequencies of "dicentric chromosomes and rings" at low doses are too low to have predictive value. The different responses of subjects to radiation made it possible to categorize them according to their radiosensitivities and to generate separate dose-effect curves for radiosensitive, average, and radioresistant individuals, reducing the amount of error in retrospective dosimetry.

Comet assay and hormesis

The paper provides the first assessment of the occurrence of hormetic dose responses using the Comet assay, a genotoxic assay. Using a priori evaluative criteria based on the Hormetic Database on peer-reviewed comet assay experimental findings, numerous examples of hormetic dose responses were obtained. These responses occurred in a large and diverse range of cell types and for agents from a broad range of chemical classes. Limited attempts were made to estimate the frequency of hormesis within comet assay experimental studies using a priori entry and evaluative criteria, with results suggesting a frequency in the 40% range. These findings are important as they show that a wide range of genotoxic chemicals display evidence that is strongly suggestive of hormetic dose responses. These findings have significant implications for study design issues, including the number of doses selected, dose range and spacing. Likewise, the widespread occurrence of hormetic dose responses in this genotoxic assay has important risk assessment implications.

The challenges of defining hormesis in epidemiological studies: The case of radiation hormesis

In the current radiation protection system, preventive measures and occupational exposure limits for controlling occupational exposure to ionizing radiation are based on the linear no-threshold extrapolation model. However, currently an increasing body of evidence indicates that this paradigm predicts very poorly biological responses in the low-dose exposure region. In addition, several in vitro and in vivo studies demonstrated the presence of hormetic dose response curves correlated to ionizing radiation low exposure. In this regard, it is noteworthy that also the findings of different epidemiological studies, conducted in different categories of occupationally exposed workers (e.g., healthcare, nuclear industrial and aircrew workers), observed lower rates of mortality and/or morbidity from cancer and/or other diseases in exposed workers than in unexposed ones or in the general population, then suggesting the possible occurrence of hormesis. Nevertheless, these results should be considered with caution since the identification of hormetic response in epidemiological studies is rather challenging because of a number of major limitations. In this regard, some of the most remarkable shortcomings found in epidemiological studies performed in workers exposed to ionizing radiation are represented by lack or inadequate definition of exposure doses, use of surrogates of exposure, narrow dose ranges, lack of proper control groups and poor evaluation of confounding factors. Therefore, considering the valuable role and contribution that epidemiological studies might provide to the complex risk assessment and management process, there is a clear and urgent need to overcome the aforementioned limits in order to achieve an adequate, useful and more real-life risk assessment that should also include the key concept of hormesis. Thus, in the present conceptual article we also discuss and provide possible approaches to improve the capacity of epidemiological studies to identify/define the hormetic response and consequently improve the complex process of risk assessment of ionizing radiation at low exposure doses.

The Future of Radioactive Medicine

The discovery of X rays in the late 19th century heralded the beginning of a new age in medicine, and the advent of channeling the power of radiation to diagnose and treat human disease. Radiation has been leveraged in medicine in a multitude of ways and is a critical element of cancer care including screening, diagnosis, surveillance, and interventional treatments. Modern radiotherapy techniques include a multitude of methodologies utilizing both externally and internally delivered radiation from a variety of approaches. This review provides a comprehensive overview of contemporary radiotherapy methodologies, the field of radiopharmaceuticals and theranostics, effects of low dose radiation and highlights the phenomena of fear of exposure to radiation and its impact in modern medicine.

Establishing a genomic radiation-age association for space exploration supplements lung disease differentiation

Purpose

One possible way to quantify each individual's response or damage from ionizing radiation is to estimate their accelerated biological age following exposure. Since there is currently no definitive way to know if biological age estimations are accurate, we aim to establish a rad-age association using genomics as its foundation.

Methods

Two datasets were combined and used to empirically find the age cutoff between young and old patients. With age as both a categorical and continuous variable, two other datasets that included radiation exposure are used to test the interaction between radiation and age. The gene lists are oriented in preranked lists for both pathway and diseases analysis. Finally, these genes are used to evaluate another dataset on the clinical relevance in differentiating lung disease given ethnicity and sex using both pairwise t-tests and linear models.

Results

Using 12 well-known genes associated with aging, a threshold of 29-years-old was found to be the difference between young and old patients. The two interaction tests yielded 234 unique genes such that pathway analysis flagged IL-1 signaling and PRPP biosynthesis as significant with high cell proliferation diseases and carcinomas being a common trend. LAPTM4B was the only gene with significant interaction among lung disease, ethnicity, and sex, with fold change greater than two.

Conclusion

The results corroborate an initial association between radiation and age, given inflammation and metabolic pathways and multiple genes emphasizing mitochondrial function, oxidation, and histone modification. Being able to tie rad-age genes to lung disease supplements future work for risk assessment following radiation exposure.

Intraoperative Fluoroscopy Radiation Using OEC 9900 Elite C-arm: Risk and Method for Decreasing Exposure

ABSTRACT

The use of intraoperative fluoroscopy in surgery produces scattered radiation that can expose all operating room personnel to measurable and, in some cases, substantial radiation doses. The goal of this work is to assess and document potential radiation doses to various staff positions in a simulated standard operating room environment. Adult-sized mannequins wearing standard lead protective aprons were placed at seven positions around large and small BMI cadavers. Doses were recorded in real time at thyroid level with Bluetooth-enabled dosimeters for a variety of fluoroscope settings and imaging views. A total of 320 images were acquired, resulting in 2,240 dosimeter readings from the seven mannequins. Doses were compared to cumulative air kerma (CAK) calculations provided by the fluoroscope. There was a strong correlation between the CAK and the recorded scattered radiation doses ( P < 0.001). Radiation doses could be reduced by manipulating C-arm manual technique settings [e.g., turning off the automatic exposure control (AEC) and using pulse (PULSE) or low dose (LD) settings]. Staff position and patient size also affected the recorded doses. The highest radiation doses were recorded across all settings for the mannequin positioned immediately adjacent to the C-arm x-ray tube. The larger BMI cadaver generated greater scattered radiation than the smaller BMI cadaver for all views and settings. This work provides suggestions for reducing exposure to operating room personnel beyond standard techniques of reducing beam-on time, increasing the distance from the radiation source, and use of shielding. Simple changes in C-arm settings (turning AEC off, avoiding DS setting, use of PULSE or LD settings) can markedly reduce dose to staff.

Performance Evaluation of Radiation-Shielding Materials and Process Technology for Manufacturing Skin Protection Cream

Personnel using X-ray devices, the main source of radiation in medical institutions, are primarily affected by scattered rays. When interventionists use radiation for examinations/treatments, their hands may enter the radiation-generating area. The shielding gloves used for protection against these rays restrict movement and cause discomfort. Here, a shielding cream that directly adheres to the skin was developed and examined as a personal protective device; further, its shielding performance was verified. Bismuth oxide and barium sulfate were selected as shielding materials and comparatively evaluated in terms of thickness, concentration, and energy. With increasing wt% of the shielding material, the protective cream became thicker, resulting in improved protection. Furthermore, the shielding performance improved with increasing mixing temperature. Because the shielding cream is applied to the skin and has a protective effect, it must be stable on the skin and easy to remove. During manufacturing, the bubbles were removed, and the dispersion improved by 5% with increasing stirring speed. During mixing, the temperature increased as the shielding performance increased by 5% in the low-energy region. In terms of the shielding performance, bismuth oxide was superior to barium sulfate by approximately 10%. This study is expected to facilitate the mass production of cream in the future.

Examining Clinical Opinion and Experience Regarding Utilization of Plain Radiography of the Spine: Evidence from Surveying the Chiropractic Profession

Plain Radiography of the spine (PROTS) is utilized in many forms of healthcare including the chiropractic profession; however, the literature reflects conflicting opinions regarding utilization and value. Despite being an essential part of Evidence-Based Practice (EBP), few studies assess Doctors of Chiropractic (DCs) clinical opinions and experience regarding the utilization of (PROTS) in practice. In this study, DCs were surveyed regarding utilization of PROTS in practice. The survey was administered to an estimated 50,000 licensed DCs by email. A total of 4301 surveys were completed, of which 3641 were United States (US) DCs. The Clinician Opinion and Experience on Chiropractic Radiography (COECR) scale was designed to analyze survey responses. This valid and reliable scale demonstrated good internal consistency using confirmatory factor analysis and the Rasch model. Survey responses show that 73.3% of respondents utilize PROTS in practice and 26.7% refer patients out for PROTS. Survey responses show that, among US DCs, 91.9% indicate PROTS has value beyond identification of pathology, 86.7% indicate that PROTS is important regarding biomechanical analysis of the spine, 82.9% indicate that PROTS is vital to practice, 67.4% indicate that PROTS aids in measuring outcomes, 98.6% indicate the opinion that PROTS presents very low to no risk to patients, and 93.0% indicate that sharing clinical findings from PROTS studies with patients is beneficial to clinical outcomes. The results of the study indicated that based on clinical experience, the majority of DCs find PROTS to be vital to practice and valuable beyond the identification of red flags.

Can Low-Level Ionizing Radiation Do Us Any Harm?

The current system of radiological protection relies on the linear no-threshold (LNT) hypothesis of cancer risk due to humans being exposed to ionizing radiation (IR). Under this tenet, effects of low doses (i.e. of those not exceeding 100 mGy or 0.1 mGy/min. of X- or γ-rays for acute and chronic exposures, respectively) are evaluated by downward linear extrapolation from regions of higher doses and dose rates where harmful effects are actually observed. However, evidence accumulated over many years clearly indicates that exposure of humans to low doses of radiation does not cause any harm and often promotes health. In this review, we discuss results of some epidemiological analyses, clinical trials and controlled experimental animal studies. Epidemiological data indicate the presence of a threshold and departure from linearity at the lowest dose ranges. Experimental studies clearly demonstrate the qualitative difference between biological mechanisms and effects at low and at higher doses of IR. We also discuss the genesis and the likely reasons for the persistence of the LNT tenet, despite its scientific implausibility and deleterious social consequences. It is high time to replace the LNT paradigm by a scientifically based dose-effect relationship where realistic quantitative hormetic or threshold models are exploited.

Applications of a patient-specific whole-body CT-mesh hybrid computational phantom in second cancer risk prediction

Objective. CT-mesh hybrid phantoms (or ‘hybrid(s)’) made from integrated patient CT data and mesh-type reference computational phantoms (MRCPs) can be beneficial for patient-specific whole-body dose evaluation, but this benefit has yet to be evaluated for second cancer risk prediction. The purpose of this study is to compare the hybrid’s ability to predict risk throughout the body with a patient-scaled MRCP against ground truth whole-body CTs (WBCTs). Approach. Head and neck active scanning proton treatment plans were created for and simulated on seven hybrids and the corresponding scaled MRCPs and WBCTs. Equivalent dose throughout the body was calculated and input into five second cancer risk models for both excess absolute and excess relative risk (EAR and ERR). The hybrid phantom was evaluated by comparing equivalent dose and risk predictions against the WBCT. Main results. The hybrid most frequently provides whole-body second cancer risk predictions which are closer to the ground truth when compared to a scaled MRCP alone. The performance of the hybrid relative to the scaled MRCP was consistent across ERR, EAR, and all risk models. For all in-field organs, where the hybrid shares the WBCT anatomy, the hybrid was better than or equal to the scaled MRCP for both equivalent dose and risk prediction. For out-of-field organs across all patients, the hybrid’s equivalent dose prediction was superior than the scaled MRCP in 48% of all comparisons, equivalent for 34%, and inferior for 18%. For risk assessment in the same organs, the hybrid’s prediction was superior than the scaled MRCP in 51.8% of all comparisons, equivalent in 28.6%, and inferior in 19.6%. Significance. Whole-body risk predictions from the CT-mesh hybrid have shown to be more accurate than those from a reference phantom alone. These hybrids could aid in risk-optimized treatment planning and individual risk assessment to minimize second cancer incidence.

Radiation-response in primary fibroblasts of long-term survivors of childhood cancer with and without second primary neoplasms: the KiKme study

Background

The etiology and most risk factors for a sporadic first primary neoplasm in childhood or subsequent second primary neoplasms are still unknown. One established causal factor for therapy-associated second primary neoplasms is the exposure to ionizing radiation during radiation therapy as a mainstay of cancer treatment. Second primary neoplasms occur in 8% of all cancer survivors within 30 years after the first diagnosis in Germany, but the underlying factors for intrinsic susceptibilities have not yet been clarified. Thus, the purpose of this nested case–control study was the investigation and comparison of gene expression and affected pathways in primary fibroblasts of childhood cancer survivors with a first primary neoplasm only or with at least one subsequent second primary neoplasm, and controls without neoplasms after exposure to a low and a high dose of ionizing radiation.

Methods

Primary fibroblasts were obtained from skin biopsies from 52 adult donors with a first primary neoplasm in childhood (N1), 52 with at least one additional primary neoplasm (N2+), as well as 52 without cancer (N0) from the KiKme study. Cultured fibroblasts were exposed to a high [2 Gray (Gy)] and a low dose (0.05 Gy) of X-rays. Messenger ribonucleic acid was extracted 4 h after exposure and Illumina-sequenced. Differentially expressed genes (DEGs) were computed using limma for R, selected at a false discovery rate level of 0.05, and further analyzed for pathway enrichment (right-tailed Fisher’s Exact Test) and (in-) activation (z ≥|2|) using Ingenuity Pathway Analysis.

Results

After 0.05 Gy, least DEGs were found in N0 (n = 236), compared to N1 (n = 653) and N2+ (n = 694). The top DEGs with regard to the adjusted p-value were upregulated in fibroblasts across all donor groups (SESN1, MDM2, CDKN1A, TIGAR, BTG2, BLOC1S2, PPM1D, PHLDB3, FBXO22, AEN, TRIAP1, and POLH). Here, we observed activation of p53 Signaling in N0 and to a lesser extent in N1, but not in N2+. Only in N0, DNA (excision-) repair (involved genes: CDKN1A, PPM1D, and DDB2) was predicted to be a downstream function, while molecular networks in N2+ were associated with cancer, as well as injury and abnormalities (among others, downregulation of MSH6, CCNE2, and CHUK). After 2 Gy, the number of DEGs was similar in fibroblasts of all donor groups and genes with the highest absolute log₂ fold-change were upregulated throughout (CDKN1A, TIGAR, HSPA4L, MDM2, BLOC1SD2, PPM1D, SESN1, BTG2, FBXO22, PCNA, and TRIAP1). Here, the p53 Signaling-Pathway was activated in fibroblasts of all donor groups. The Mitotic Roles of Polo Like Kinase-Pathway was inactivated in N1 and N2+. Molecular Mechanisms of Cancer were affected in fibroblasts of all donor groups. P53 was predicted to be an upstream regulator in fibroblasts of all donor groups and E2F1 in N1 and N2+. Results of the downstream analysis were senescence in N0 and N2+, transformation of cells in N0, and no significant effects in N1. Seven genes were differentially expressed in reaction to 2 Gy dependent on the donor group (LINC00601, COBLL1, SESN2, BIN3, TNFRSF10A, EEF1AKNMT, and BTG2).

Conclusion

Our results show dose-dependent differences in the radiation response between N1/N2+ and N0. While mechanisms against genotoxic stress were activated to the same extent after a high dose in all groups, the radiation response was impaired after a low dose in N1/N2+, suggesting an increased risk for adverse effects including carcinogenesis, particularly in N2+.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00520-6.

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.

Physicochemical characterization of monazite sand and its associated bacterial species from the beaches of southeastern Brazil

Beaches with monazitic sands show high natural radiation, and the knowledge of this radiation is fundamental to simulate the effects of natural terrestrial radiation on biological systems. Monazite-rich sand from a beach in the southeastern Brazil were collected and analyzed by X-ray fluorescence, X-ray diffraction, and magnetic susceptibility. The natural terrestrial radiation of the beach sand showed a positive correlation with the Th and Y elements, which are closely associated with Ce, Nd, Ca, and P, suggesting that this grouping is mainly associated with local natural radiation. Based on the sand characterization, a physical simulator of natural gamma radiation was built with parameters similar to those of the monazite beach sand, considering areas with high natural radiation levels. The simulation revealed that the natural radiation of the monazite sands has a significant effect on reducing the growth of the bacteria strains of E. coli and S. aureus present in the beach sand, with a reduction of 23.8% and 18.4%, respectively.

Effect of Low-Dose Ionizing Radiation on the Expression of Mitochondria-Related Genes in Human Mesenchymal Stem Cells

The concept of hormesis describes a phenomenon of adaptive response to low-dose ionizing radiation (LDIR). Similarly, the concept of mitohormesis states that the adaptive program in mitochondria is activated in response to minor stress effects. The mechanisms of hormesis effects are not clear, but it is assumed that they can be mediated by reactive oxygen species. Here, we studied effects of LDIR on mitochondria in mesenchymal stem cells. We have found that X-ray radiation at a dose of 10 cGy as well as oxidized fragments of cell-free DNA (cfDNA) at a concentration of 50 ng/mL resulted in an increased expression of a large number of genes regulating the function of the mitochondrial respiratory chain complexes in human mesenchymal stem cells (MSC). Several genes remained upregulated within hours after the exposure. Both X-ray radiation and oxidized cfDNA resulted in upregulation of FIS1 and MFN1 genes, which regulated fusion and fission of mitochondria, within 3-24 h after the exposure. Three hours after the exposure, the number of copies of mitochondrial DNA in cells had increased. These findings support the hypothesis that assumes oxidized cell-free DNA as a mediator of MSC response to low doses of radiation.

Reconceptualization of Hormetic Responses in the Frame of Redox Toxicology

Cellular adaptive mechanisms emerging after exposure to low levels of toxic agents or stressful stimuli comprise an important biological feature that has gained considerable scientific interest. Investigations of low-dose exposures to diverse chemical compounds signify the non-linear mode of action in the exposed cell or organism at such dose levels in contrast to the classic detrimental effects induced at higher ones, a phenomenon usually referred to as hormesis. The resulting phenotype is a beneficial effect that tests our physiology within the limits of our homeostatic adaptations. Therefore, doses below the region of adverse responses are of particular interest and are specified as the hormetic gain zone. The manifestation of redox adaptations aiming to prevent from disturbances of redox homeostasis represent an area of particular interest in hormetic responses, observed after exposure not only to stressors but also to compounds of natural origin, such as phytochemicals. Findings from previous studies on several agents demonstrate the heterogeneity of the specific zone in terms of the molecular events occurring. Major factors deeply involved in these biphasic phenomena are the bioactive compound per se, the dose level, the duration of exposure, the cell, tissue or even organ exposed to and, of course, the biomarker examined. In the end, the molecular fate is a complex toxicological event, based on beneficial and detrimental effects, which, however, are poorly understood to date.

Low Dose-Rate Irradiation of Gamma-Rays-Induced Cytotoxic and Genotoxic Alterations in Peripheral Erythrocytes of p53-Deficient Medaka (Oryzias latipes)

Morphological alterations and nuclear abnormalities in fish erythrocytes have been used in many studies as bioindicators of environmental mutagens including ionizing radiation. In this study, adult Japanese medaka (Oryzias latipes) were irradiated with gamma rays at a low dose rate (9.92 μGy/min) for 7 days, giving a total dose of 100 mGy; and morphological alterations, nuclear abnormalities, and apoptotic cell death induced in peripheral erythrocytes were investigated 8 h and 7 days after the end of the irradiation. A variety of abnormalities, such as tear-drop cell, crenated cell, acanthocyte, sickled cell, micronucleated cell, eccentric nucleus, notched nucleus, and schistocyte, were induced in the peripheral erythrocytes of the wild-type fish, and a less number of abnormalities and apoptotic cell death were induced in the p53-deficient fish. These results indicate that low dose-rate chronic irradiation of gamma rays can induce cytotoxic and genotoxic effects in the peripheral erythrocytes of medaka, and p53-deficient medaka are tolerant to the gamma-ray irradiation than the wild type on the surface.

US EPA's TSCA risk assessment approach: a case study of asbestos in automotive brakes

The United States Environmental Protection Agency (US EPA) is currently refining its approach for risk assessments conducted under the amended Toxic Substances Control Act (TSCA), largely based on recommendations from the National Academies of Sciences, Engineering, and Medicine (NASEM). We identified several issues with the current TSCA risk assessment approach that were not addressed by NASEM in its recommendations. Here, we demonstrate these issues with a case study of the 'Risk Evaluation for Asbestos, Part 1: Chrysotile Asbestos,' which US EPA released in December 2020. In this evaluation, US EPA found that occupational and some consumer uses of automotive brakes and clutches that contain asbestos result in unreasonable risks. These risks were calculated from estimated exposures during brake work and an inhalation unit risk (IUR) developed for chrysotile asbestos. We found that US EPA overestimated risk as a result of unrealistic inputs to both the exposure and toxicity components of the risk equation, and because the Agency did not fully consider relevant epidemiology and toxicity evidence in its systematic review. Our evaluation demonstrates areas in which the TSCA risk assessment approach could be improved to result in risk evaluations that are supported by the available scientific evidence.

Radiography and Clinical Decision-Making in Chiropractic

The concern over x-ray exposure risks can overshadow the potential benefit of radiography, especially in cases where manual therapy is employed. Spinal malalignment cannot be accurately visualized without imaging. Manual therapy and the load tolerances of injured spinal tissues raise different criteria for the use of x-rays for spinal disorders than in medical practice. Current regulatory bodies rely on radiography risk assessments based on Linear-No-Threshold (LNT) risk models. There is a need to consider radiography guidelines for chiropractic which are different from those for medical practice. Radiography practice guidelines are summaries dominated by frequentist interpretations in the analysis of data from studies. In contrast, clinicians often employ a pseudo-Bayesian form of reasoning during the clinical decision-making process. The overrepresentation of frequentist perspectives in evidence-based practice guidelines alter decision-making away from practical assessment of a patient's needs, toward an overly cautious standard applied to patients without regard to their risk/benefit likelihoods relating to radiography. Guidelines for radiography in chiropractic to fully assess the condition of the spine and spinal alignment prior to manual therapy, especially with high velocity, low amplitude spinal manipulation (HVLA-SM), should necessarily differ from those used in medical practice.

Effect of microplastics on aquatic biota: A hormetic perspective

As emerging pollutants, microplastics (MPs) have been found globally in various freshwater and marine matrices. This study recompiled 270 endpoints of 3765 individuals from 43 publications, reporting the onset of enhanced biological performance and reduced oxidative stress biomarkers induced by MPs in aquatic organisms at environmentally relevant concentrations (≤1 mg/L, median = 0.1 mg/L). The stimulatory responses of consumption, growth, reproduction and survival ranged from 131% to 144% of the control, with a combined response of 136%. The overall inhibitory response of 9 oxidative stress biomarkers was 71% of the control, and commonly below 75%. The random-effects meta-regression indicated that the extents of MPs-induced responses were independent of habitat, MP composition, morphology, particle size and exposure duration. The results implied that the exposure to MPs at low and high concentrations might induce opposite/non-monotonic responses in aquatic biota. Correspondingly, the hormetic dose response relationships were found at various endpoints, such as reproduction, genotoxicity, immunotoxicity, neurotoxicity and behavioral alteration. Hormesis offers a novel perspective for understanding the dose response mode of aquatic organisms exposed to low and high concentrations of MPs, highlighting the necessity to incorporate the hormetic dose response model into the ecological/environmental risk assessment of MPs.

The Threshold Effects of Low-Dose-Rate Radiation on miRNA-Mediated Neurodevelopment of Zebrafish

The biological effects and regulatory mechanisms of low-dose and low-dose-rate radiation are still rather controversial. Therefore, in this study we investigated the effects of low-dose-rate radiation on zebrafish neurodevelopment and the role of miRNAs in radiation-induced neurodevelopment. Zebrafish embryos received prolonged gamma-ray irradiation (0 mGy/h, 0.1 mGy/h, 0.2 mGy/h, 0.4 mGy/h) during development. Neurodevelopmental indicators included mortality, malformation rate, swimming speed, as well as the morphology changes of the lateral line system and brain tissue. Additionally, spatiotemporal expression of development-related miRNAs (dre-miR-196a-5p, dre-miR-210-3p, dre-miR-338) and miRNA processing enzymes genes (Dicer and Drosha) were assessed by qRT-PCR and whole mount in situ hybridization (WISH). The results revealed a decline in mortality, malformation and swimming speed, with normal histological and morphological appearance, in zebrafish that received 0.1 mGy/h; however, increased mortality, malformation and swimming speed were observed, with pathological changes, in zebrafish that received 0.2 mGy/h and 0.4 mGy/h. The expression of miRNA processing enzyme genes was altered after irradiation, and miRNAs expression was downregulated in the 0.1 mGy/h group, and upregulated in the 0.2 mGy/h and 0.4 mGy/h groups. Furthermore, ectopic expression of dre-miR-210-3p, Dicer and Drosha was also observed in the 0.4 mGy/h group. In conclusion, the effect of low-dose and low-dose-rate radiation on neurodevelopment follows the threshold model, under the regulation of miRNAs, excitatory effects occurred at a dose rate of 0.1 mGy/h and toxic effects occurred at a dose rate of 0.2 mGy/h and 0.4 mGy/h.

Radiation concerns in frequent flyer patients: Should imaging history influence decisions about recurrent imaging?

Radiation risks from diagnostic imaging have captured the attention of patients and medical practitioners alike, yet it remains unclear how these considerations can best be incorporated into clinical decision making. This manuscript presents a framework to consider these issues in a potentially at-risk population, the so called "frequent flyer" patients undergoing a large amount of recurrent imaging over time. Radiation risks from the low-dose exposures of diagnostic imaging are briefly reviewed, as applied to recurrent exposures. Some scenarios are then explored in which it may be helpful to incorporate knowledge of a patient's imaging history. There is no simple or uniformly applicable approach to these challenging and often nuanced clinical decisions. The complexity and variability of the underlying disease states and trajectories argues against alerting mechanisms based on a simple cumulative dose threshold. Awareness of imaging history may instead be beneficial in encouraging physicians and patients to take the long view, and to identify those populations of frequent flyers that might benefit from alternative imaging strategies.

Radiophobia Overreaction: College of Chiropractors of British Columbia Revoke Full X-Ray Rights Based on Flawed Study and Radiation Fear-Mongering

Fears over radiation have created irrational pressures to dissuade radiography use within chiropractic. Recently, the regulatory body for chiropractors practicing in British Columbia, Canada, the College of Chiropractors of British Columbia (CCBC), contracted Pierre Côté to review the clinical use of X-rays within the chiropractic profession. A "rapid review" was performed and published quickly and included only 9 papers, the most recent dating from 2005; they concluded, "Given the inherent risks of radiation, we recommend that chiropractors do not use radiographs for the routine and repeat evaluation of the structure and function of the spine." The CCBC then launched an immediate review of the use of X-rays by chiropractors in their jurisdiction. Member and public opinion were gathered but not presented to their members. On February 4, 2021, the College announced amendments to their Professional Conduct Handbook that revoked X-ray rights for routine/repeat assessment and management of patients with spine disorders. Here, we highlight current and historical evidence that substantiates that X-rays are not a public health threat. We also point out critical and insurmountable flaws in the single paper used to support irrational and unscientific policy that discriminates against chiropractors who practice certain forms of evidence-based X-ray-guided methods.

Radiation Reduction Strategies in Pediatric Orthopaedics

INTRODUCTION

Pediatric orthopaedic patients have the potential for significant radiation exposure from the use of imaging studies, such as computed tomography and bone scintigraphy. With the potential for long-term treatment, such as is required for scoliosis or osteogenesis imperfecta, patients are at even greater risk of radiation-induced carcinogenesis.

DISCUSSION

Although an association between radiation and cancer risk is evident, causation is difficult to prove because comorbidities or genetic predispositions may play a role in the higher baseline rates of malignancy later in life. Efforts have been made over the years to reduce exposure using more modern imaging techniques and simple radiation reduction strategies. Educational efforts and clinical practice guidelines are decreasing the rate of computed tomography scan use in pediatrics. Although considerable work is being done on the development of radiation-free imaging modalities, imaging that uses ionizing radiation will, in the near term, be necessary in specific circumstances to provide optimal care to pediatric orthopaedic patients.

CONCLUSION

Knowledge of the ionizing radiation exposure associated with commonly used tests as well as radiation-reduction strategies is essential for the optimal and safe care of pediatric orthopaedic patients.

Breast Cancer Screening Recommendations Inclusive of All Women at Average Risk: Update from the ACR and Society of Breast Imaging

Breast cancer remains the most common nonskin cancer, the second leading cause of cancer deaths, and the leading cause of premature death in US women. Mammography screening has been proven effective in reducing breast cancer deaths in women age 40 years and older. A mortality reduction of 40% is possible with regular screening. Treatment advances cannot overcome the disadvantage of being diagnosed with an advanced-stage tumor. The ACR and Society of Breast Imaging recommend annual mammography screening beginning at age 40, which provides the greatest mortality reduction, diagnosis at earlier stage, better surgical options, and more effective chemotherapy. Annual screening results in more screening-detected tumors, tumors of smaller sizes, and fewer interval cancers than longer screening intervals. Screened women in their 40s are more likely to have early-stage disease, negative lymph nodes, and smaller tumors than unscreened women. Delaying screening until age 45 or 50 will result in an unnecessary loss of life to breast cancer and adversely affects minority women in particular. Screening should continue past age 74 years, without an upper age limit unless severe comorbidities limit life expectancy. Benefits of screening should be considered along with the possibilities of recall for additional imaging and benign biopsy and the less tangible risks of anxiety and overdiagnosis. Although recall and biopsy recommendations are higher with more frequent screening, so are life-years gained and breast cancer deaths averted. Women who wish to maximize benefit will choose annual screening starting at age 40 years and will not stop screening prematurely.

Radiation Safety Concerns Related to PET/Computed Tomography Imaging for Assessing Pediatric Diseases and Disorders

The Image Gently Nuclear Medicine Working Group published a 10-year update in 2019. One of the future goals of this working group is to continue the efforts started in 2014 to harmonize the North American guidelines with the European Association of Nuclear Medicine pediatric dosing guidelines, continuing to publicize the use of the North American guidelines. The update also acknowledged the need for standardization of CT parameters in hybrid imaging and also will seek to tackle this issue as one of its future goals.

Relationship Between Terrestrial Background and Remedial Criteria for Naturally Occurring Radioactive Material in the United States

ABSTRACT

In the United States (US), Federal and State agencies have established radiological public exposure limits and remedial action ("clean up") criteria for naturally occurring radionuclides (NORM-primarily for uranium and thorium series radionuclides). Often, these criteria are intended to control human exposure to what is referred to in the US as technologically enhanced naturally occurring radioactive material (TENORM). This can be any naturally occurring radioactive material for which the potential for human exposure has been enhanced due to anthropogenic (human activities), e.g., removal from its "place in nature," and/or processed in some way resulting in concentration. In some cases, the values of these regulatory criteria can be similar to or even less than those levels of exposure and those concentrations of NORM that exists in nature independent of any previous human activity. The potential variability of NORM radionuclides in the soil and rocks can be significant, even over relatively short distances or depths due to factors such as geology, hydrology, and geochemistry. Given this, it is important to recognize that defining "the radiation background" for purposes of establishing and/or comparing remedial action criteria and/or exposure limits requires recognition of the specificity at the location(s) of interest, not in other geological and/or mineralogical regimes several miles away. The purpose of this paper is to demonstrate this variability for comparison to exposure levels and concentrations being defined in the US as levels above which require regulatory control and / or above which are being defined as an "unacceptable risk." The primary background exposure component of specific interest here is the annual dose contribution from terrestrial radiation exposure, i.e., from uranium and thorium series radionuclides in the ground, excluding radon inhalation. The exposure sources being controlled by some US regulatory limits are primarily associated with the primordial radionuclides in soil. The average annual terrestrial component of background can vary by upwards of a few tenths of a mSv across the US that can be several times higher than the applicable exposure limits. This can result in "unacceptable risk" or "remedial action" concentration criteria statistically equivalent to or less than the background concentrations of these same primordial nuclides. The statistical and analytical uncertainties of distinguishing naturally occurring radionuclides (i.e., NORM) from those resulting from anthropogenic (human caused) activities (i.e., TENORM) can be quite challenging and in some cases may be technically impossible. Consideration must be given to the relationship of the amount of actual total risk avoidance achieved if any, relative to the traditional health and safety risks of construction and associated construction and waste management costs for remedial activities, so that a practical and scientifically based approach for development of these criteria can be achieved.

Radiophobic Fear-Mongering, Misappropriation of Medical References and Dismissing Relevant Data Forms the False Stance for Advocating Against the Use of Routine and Repeat Radiography in Chiropractic and Manual Therapy

There is a faction within the chiropractic profession passionately advocating against the routine use of X-rays in the diagnosis, treatment and management of patients with spinal disorders (aka subluxation). These activists reiterate common false statements such as "there is no evidence" for biomechanical spine assessment by X-ray, "there are no guidelines" supporting routine imaging, and also promulgate the reiterating narrative that "X-rays are dangerous." These arguments come in the form of recycled allopathic "red flag only" medical guidelines for spine care, opinion pieces and consensus statements. Herein, we review these common arguments and present compelling data refuting such claims. It quickly becomes evident that these statements are false. They are based on cherry-picked medical references and, most importantly, expansive evidence against this narrative continues to be ignored. Factually, there is considerable evidential support for routine use of radiological imaging in chiropractic and manual therapies for 3 main purposes: 1. To assess spinopelvic biomechanical parameters; 2. To screen for relative and absolute contraindications; 3. To reassess a patient's progress from some forms of spine altering treatments. Finally, and most importantly, we summarize why the long-held notion of carcinogenicity from X-rays is not a valid argument.

Adverse outcome pathways, key events, and radiation risk assessment

The overall aim of this contribution to the 'Second Bill Morgan Memorial Special Issue' is to provide a high-level review of a recent report developed by a Committee for the National Council on Radiation Protection and Measurements (NCRP) titled 'Approaches for Integrating Information from Radiation Biology and Epidemiology to Enhance Low-Dose Health Risk Assessment'. It derives from previous NCRP Reports and Commentaries that provide the case for integrating data from radiation biology studies (available and proposed) with epidemiological studies (also available and proposed) to develop Biologically-Based Dose-Response (BBDR) models. In this review, it is proposed for such models to leverage the adverse outcome pathways (AOP) and key events (KE) approach for better characterizing radiation-induced cancers and circulatory disease (as the example for a noncancer outcome). The review discusses the current state of knowledge of mechanisms of carcinogenesis, with an emphasis on radiation-induced cancers, and a similar discussion for circulatory disease. The types of the various informative BBDR models are presented along with a proposed generalized BBDR model for cancer and a more speculative one for circulatory disease. The way forward is presented in a comprehensive discussion of the research needs to address the goal of enhancing health risk assessment of exposures to low doses of radiation. The use of an AOP/KE approach for developing a mechanistic framework for BBDR models of radiation-induced cancer and circulatory disease is considered to be a viable one based upon current knowledge of the mechanisms of formation of these adverse health outcomes and the available technical capabilities and computational advances. The way forward for enhancing low-dose radiation risk estimates will require there to be a tight integration of epidemiology data and radiation biology information to meet the goals of relevance and sensitivity of the adverse health outcomes required for overall health risk assessment at low doses and dose rates.

Knowledge of radiation protection among radiology professionals and students: A medical college-based study

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The overall knowledge of radiation protection among radiology professional and students was adequate.

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The knowledge of radiation protection among diploma graduate was inadequate.

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Radiation protection law should be promulgated as soon as possible in Nepal.

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This is the first study to perform principal component analysis in the research study of its kind.

BACKGROUND

Radiation protection is the core of radiography for safe radiation-based imaging practice. This study aims to determine the knowledge of radiation protection among radiology professionals and students in a medical college of Nepal.

MATERIAL AND METHODS

A questionnaire survey was carried out among 35 radiology staff and students at Universal College of Medical Sciences (UCMS), Bhairahawa, Nepal. The questionnaire survey consisted of socio-demographic variables and 17 questions, 3 questions were related to general information regarding training, knowledge, and experience and the remaining 14 multiple choice questions (MCQ) were related to radiation protection. Data were analyzed in SPSS Statistics software, version 27. The p-value was set at 5% level of significance. Nonparametric tests were applied since the data did not follow normal distribution. The knowledge score were categorized into lesser than 60 % inadequate, 60–80 % adequate and greater than or equal to 80 % excellent.

RESULTS

Out of total 35 participants, 28 were male and 7 were female with mean age 26.09 ± 7.18 years, range 18–54. The average radiation level of awareness was 9.6 (68.57 %), which was adequate, maximum 13 and minimum 4. There was not statistical significance of knowledge score by gender, age groups, work experience and studentship. Taking academic qualification, the level of knowledge of diploma graduates was inadequate 7.76 (55.42 %), and lower than other higher academic qualifications.

CONCLUSIONS

Adequate radiation protection course materials and training should be introduced for diploma graduates. Continuing professional education (CME) should be organized regularly. Moreover, radiation protection law is a must in Nepal now.

Chernobyl-level radiation exposure damages bumblebee reproduction: a laboratory experiment

The consequences for wildlife of living in radiologically contaminated environments are uncertain. Previous laboratory studies suggest insects are relatively radiation-resistant; however, some field studies from the Chernobyl Exclusion Zone report severe adverse effects at substantially lower radiation dose rates than expected. Here, we present the first laboratory investigation to study how environmentally relevant radiation exposure affects bumblebee life history, assessing the shape of the relationship between radiation exposure and fitness loss. Dose rates comparable to the Chernobyl Exclusion Zone (50-400 µGy h-1) impaired bumblebee reproduction and delayed colony growth but did not affect colony weight or longevity. Our best-fitting model for the effect of radiation dose rate on colony queen production had a strongly nonlinear concave relationship: exposure to only 100 µGy h-1 impaired reproduction by 30-45%, while further dose rate increases caused more modest additional reproductive impairment. Our data indicate that the practice of estimating effects of environmentally relevant low-dose rate exposure by extrapolating from high-dose rates may have considerably underestimated the effects of radiation. If our data can be generalized, they suggest insects suffer significant negative consequences at dose rates previously thought safe; we therefore advocate relevant revisions to the international framework for radiological protection of the environment.

Radiation Doses and Risks in Breast Screening

This article describes radiation doses and cancer risks of digital breast imaging technologies used for breast cancer detection. These include digital mammography (DM), digital breast tomosynthesis (DBT), and newer technologies such as contrast-enhanced digital or spectral mammography (CEM), whole-breast computed tomography, breast-specific gamma imaging (BSGI), molecular breast imaging (MBI), and positron emission mammography (PEM). This article describes the basis for radiation risk estimates, compares radiation doses and risks, and provides benefit-to-radiation-risk ratios for different breast imaging modalities that use ionizing radiation. Current x-ray-based screening modalities such as DM and DBT have small to negligible risks of causing radiation-induced cancers in women of normal screening age. Possible new screening modalities such as CEM have similar small cancer risks. Potential screening modalities that involve radionuclide injection such as BSGI, MBI, and PEM have significantly higher cancer risks unless efficient detection systems and reduced administered doses are used. Benefit-to-radiation-risk estimates are highly favorable for screening with DM and other modalities having comparable (or higher) cancer detection rates and comparably low radiation doses.

Replacing LNT: The Integrated LNT-Hormesis Model

Many scientists and regulators utilize the linear no-threshold (LNT) relationship to estimate the likelihood of carcinogenesis. The LNT model is incorrect and was adopted based upon false pretenses. The use of the model has been corrupted by many to claim that even the smallest ionizing radiation dose may initiate carcinogenesis. This claim has resulted in societal harm.

Nonlinear dose-time-response functions and health-protective exposure limits for inflammation-mediated diseases

Why have occupational safety regulations in the United States not been more successful in protecting worker health from mesothelioma risks, while apparently succeeding relatively well in reducing silicosis risks? This paper briefly discusses biological bases for thresholds and nonlinearities in exposure-response functions for respirable crystalline silica (RCS) and asbestos, based on modeling a chronic inflammation mode of action (mediated by activation of the NLRP3 inflammasome, for both RCS and asbestos). It applies previously published physiologically based pharmacokinetic (PBPK) models to perform computational experiments illuminating how different time courses of exposure with the same time-weighted average (TWA) concentration affect internal doses in target tissues (lung for RCS and mesothelium for asbestos). Key conclusions are that (i) For RCS, but not asbestos, limiting average (TWA) exposure concentrations also tightly constrains internal doses and ability to trigger chronic inflammation and resulting increases in disease risks (ii) For asbestos, excursions (i.e., spikes in concentrations); and especially the times between them are crucial drivers of internal doses and time until chronic inflammation; and hence (iii) These dynamic aspects of exposure, which are not addressed by current occupational safety regulations, should be constrained to better protect worker health. Adjusting permissible average exposure concentration limits (PELs) and daily excursion limits (ELs) is predicted to have little impact on reducing mesothelioma risks, but increasing the number of days between successive excursions is predicted to be relatively effective in reducing worker risks, even if it has little or no impact on TWA average concentrations.

Reasons for Undergoing CT During Childhood: Can CT-Exposed and CT-Naive Populations Be Compared?

Several epidemiological studies suggested an increased risk of cancer and other tumors in individuals undergoing computed tomography (CT) examination during childhood; however, it was questioned whether the group undergoing CT was comparable to that not undergoing CT. To address this issue, we investigated the reasons for undergoing CT in 763 children aged 0 to 19 years in 2013. Their medical records were fully evaluated and symptoms, underlying conditions, reasons for CT, and clinical courses after CT were investigated. Among the 763 children, 66.1% underwent repeat CT after the first examination, and 19.3% underwent CT 8 times or more. Among all the examined children, 8.8% had cancer and 4.7% had cancer-prone conditions such as Down syndrome, tuberous sclerosis, and cirrhosis. Only 11.4% of the 763 children underwent CT because of trauma, and 32.2% of the children had some types of congenital anomaly. The rate of trauma decreased with an increase in the frequency of CT examinations. Since the incidence of congenital anomalies is below 2.5% in the general population, it was concluded that the population of children undergoing CT is completely different from that not undergoing CT. The 2 groups should not be compared.

The Impact of Dose Rate on DNA Double-Strand Break Formation and Repair in Human Lymphocytes Exposed to Fast Neutron Irradiation

The lack of information on how biological systems respond to low-dose and low dose-rate exposures makes it difficult to accurately assess the carcinogenic risks. This is of critical importance to space radiation, which remains a serious concern for long-term manned space exploration. In this study, the γ-H2AX foci assay was used to follow DNA double-strand break (DSB) induction and repair following exposure to neutron irradiation, which is produced as secondary radiation in the space environment. Human lymphocytes were exposed to high dose-rate (HDR: 0.400 Gy/min) and low dose-rate (LDR: 0.015 Gy/min) p(66)/Be(40) neutrons. DNA DSB induction was investigated 30 min post exposure to neutron doses ranging from 0.125 to 2 Gy. Repair kinetics was studied at different time points after a 1 Gy neutron dose. Our results indicated that γ-H2AX foci formation was 40% higher at HDR exposure compared to LDR exposure. The maximum γ-H2AX foci levels decreased gradually to 1.65 ± 0.64 foci/cell (LDR) and 1.29 ± 0.45 (HDR) at 24 h postirradiation, remaining significantly higher than background levels. This illustrates a significant effect of dose rate on neutron-induced DNA damage. While no significant difference was observed in residual DNA damage after 24 h, the DSB repair half-life of LDR exposure was slower than that of HDR exposure. The results give a first indication that the dose rate should be taken into account for cancer risk estimations related to neutrons.

What Can Chemical Carcinogenesis Shed Light on the LNT Hypothesis in Radiation Carcinogenesis?

To protect the public’s health from exposure to physical, chemical, and microbiological agents, it is important that any policy be based on rigorous scientifically based research. The concept of “linear no-threshold” (LNT) has been implemented to provide guideline exposures to these agents. The practical limitation to testing this hypothesis is to provide sufficient samples for experimental or epidemiological studies. While there is no universally accepted understanding of most human diseases, there seems to be better understanding of cancer that might help resolve the “LNT” model. The public’s concern, after being exposed to radiation, is the potential of producing cancer. The most rigorous hypothesis of human carcinogenesis is the “multistage, multimechanism” chemical carcinogenesis model. The radiation carcinogenesis LNT model, rarely, if ever, built it into their support. It will be argued that this multistage, multimechanism model of carcinogenesis, involving the “initiation” of a single cell by a mutagen event, followed by chronic exposure to threshold levels of epigenetic agents or conditions that stimulate the clonal expansion of the “initiated” cell, can convert these benign cells to become invasive and metastatic. This “promotion” process can be interrupted, thereby preventing these initiated cells from transitioning to the “progression” process of invasion and metastasis.

Gamma Radiation-Induced Disruption of Cellular Junctions in HUVECs Is Mediated through Affecting MAPK/NF-κB Inflammatory Pathways

Ionizing radiation-induced cardiovascular diseases (CVDs) have been well documented. However, the mechanisms of CVD genesis are still not fully understood. In this study, human umbilical vein endothelial cells (HUVECs) were exposed to gamma irradiation at different doses ranging from 0.2 Gy to 5 Gy. Cell viability, migration ability, permeability, oxidative and nitrosative stresses, inflammation, and nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) pathway activation were evaluated postirradiation. It was found that gamma irradiation at doses ranging from 0.5 Gy to 5 Gy inhibited the migration ability of HUVECs without any significant effects on cell viability at 6 h and 24 h postirradiation. The decreased transendothelial electrical resistance (TEER), increased permeability, and disruption of cellular junctions were observed in HUVECs after gamma irradiation accompanied by the lower levels of junction-related proteins such as ZO-1, occludin, vascular endothelial- (VE-) cadherin, and connexin 40. The enhanced oxidative and nitrosative stresses, e.g., ROS and NO₂ ^- levels and inflammatory cytokines IL-6 and TNF-α were demonstrated in HUVECs after gamma irradiation. Western blot results showed that protein levels of mitogen-activated protein kinase (MAPK) pathway molecules p38, p53, p21, and p27 increased after gamma irradiation, which further induced the activation of the NF-κB pathway. BAY 11-7085, an inhibitor of NF-κB activation, was demonstrated to partially block the effects of gamma radiation in HUVECs examined by TEER and FITC-dextran permeability assay. We therefore concluded that the gamma irradiation-induced disruption of cellular junctions in HUVECs was through the inflammatory MAPK/NF-κB signaling pathway.

Reforming the debate around radiation risk

The back-and-forth debate on radiation risk, in the recent years, has unscientifically drifted away from proportionality and become increasingly antagonistic. A handful of authors have used exaggerated claims which are corroborated by their own previous work and presented using heated and superlative language. With unwarranted certainty, many have also referenced studies which report inconclusive findings and given undue weight to the results of laboratory animal and cellular studies, regardless of their exact positions on radiation risk. The passion and subjective interpretation with which the debate is now presented detracts from rational, scientific evaluation. A reform of the debate is needed to reach grounded consensus in the community and, if appropriate, begin the process of amending the legislation to reflect it. In this article we have analysed key research on the topic and discussed the fundamental limitations of science in providing satisfactory answers to our questions.