Biological Effects Of Radiation Research Articles

Ionizing Radiation, Higher Plants, and Radioprotection: From Acute High Doses to Chronic Low Doses.

Understanding the effects of ionizing radiation (IR) on plants is important for environmental protection, for agriculture and horticulture, and for space science but plants have significant biological differences to the animals from which much relevant knowledge is derived. The effects of IR on plants are understood best at acute high doses because there have been; (a) controlled experiments in the field using point sources, (b) field studies in the immediate aftermath of nuclear accidents, and (c) controlled laboratory experiments. A compilation of studies of the effects of IR on plants reveals that although there are numerous field studies of the effects of chronic low doses on plants, there are few controlled experiments that used chronic low doses. Using the Bradford-Hill criteria widely used in epidemiological studies we suggest that a new phase of chronic low-level radiation research on plants is desirable if its effects are to be properly elucidated. We emphasize the plant biological contexts that should direct such research. We review previously reported effects from the molecular to community level and, using a plant stress biology context, discuss a variety of acute high- and chronic low-dose data against Derived Consideration Reference Levels (DCRLs) used for environmental protection. We suggest that chronic low-level IR can sometimes have effects at the molecular and cytogenetic level at DCRL dose rates (and perhaps below) but that there are unlikely to be environmentally significant effects at higher levels of biological organization. We conclude that, although current data meets only some of the Bradford-Hill criteria, current DCRLs for plants are very likely to be appropriate at biological scales relevant to environmental protection (and for which they were intended) but that research designed with an appropriate biological context and with more of the Bradford-Hill criteria in mind would strengthen this assertion. We note that the effects of IR have been investigated on only a small proportion of plant species and that research with a wider range of species might improve not only the understanding of the biological effects of radiation but also that of the response of plants to environmental stress.

Role of High-Linear Energy Transfer Radiobiology in Space Radiation Exposure Risks.

Many manned missions to the Moon and Mars are scheduled in the near future. However, space radiation presents a major hazard to humans, and astronauts are constantly exposed to radiation, including high linear energy transfer (LET) radiation, which differs from radiation on Earth. Thus, there is thus an urgent need to clarify the biological effects of space radiation and reduce the associated risks. In this review, we consider the role of high-LET radiobiology in relation to space-radiation exposure.

Microdosimetry and nanodosimetry for internal emitters

In this review, the multiscale approach in radiation dosimetry in relation to biological effects is first briefly introduced. The need of dosimetry in microscopic regions, for example in cells, is then addressed, followed by a review of the basic microdosimetric quantities of internal emitters. The requirement of understanding the molecular biological effects of radiation leads to the dosimetric concept in the nanometer ranges, where the initial events produced at the molecular level cause the subsequent cellular and tissue effects that may lead to cancer. Track structure theory is particularly introduced in nanodosimetry for internal emitters. The relationship between the quantities in macroscopic dosimetry, e.g. absorbed dose, the microdosimetric quantities, e.g. specific energy and lineal energy, and the nanodosimetric characteristics, the track structures is inherently established in a derivational way. The significance of microdosimetric and nanodosimetric quantities in understanding and interpreting the mechanisms of radiobiological effects is addressed. Several applications of microdosimetry and nanodosimetry for internal emitters in radon and thoron progeny dosimetry and risk analysis, in targeted radionuclide therapy, in modelling of DNA damages and as a tool in the potential interpretation of dose-response relationship at low doses and dose rates are given. Finally, the potential future development of internal microdosimetry and nanodosimetry is outlined.

Radiación ionizante: revisión de tema y recomendaciones para la práctica

Radiation safety is a current topic. The harmful effects of this diagnostic and therapeutic tool are observed daily. The majority of associated secondary to radiation exposure could be prevented with suitable safety and protective measures. A review article is presented with the aim of explaining the most relevant aspects of radiation in detail, including the formation of x-rays, their dosimetry definition and classification, the biological effects of radiation, the recommended limits, as well as the protection measures for the exposure to radiation.

Оценка неопределенности ОБЭ рентгеновского излучения, связанной с определением поглощенной дозы в радиобиологических экспериментах

Purpose: Determining the absorbed dose produced by photons, it is often assumed that it is equal to the radiation kerma. This assumption is valid only in the presence of an electronic equilibrium, which in turn is never ensured in practice. It leads to some uncertainty in determining the absorbed dose in the irradiated sample during radiobiological experiments. Therefore, it is necessary to estimate the uncertainty in determining the relative biological effectiveness of X-rays associated with uncertainty in the determination of the absorbed dose. Material and methods: The monochromatic X-ray photon emission is simulated through a standard 25 cm2 plastic flask containing 5 ml of the model culture medium (biological tissue with elemental composition C5H40O18N). The calculation of the absorbed dose in a culture medium is carried out in two ways: 1) the standard method, according to which the ratio of the absorbed dose in the medium and the ionization chamber is equal to the ratio of kerma in the medium and air; 2) determination of the absorbed dose in the medium and in the sensitive volume of the ionization chamber by computer simulation and calculating the ratio of these doses. For each primary photon energies, 108 histories are modeled, which makes it possible to achieve a statistical uncertainty not worse than 0.1 %. The energy step was 1 keV. The spectral distribution of X-ray energy is modeled separately for each set of anode materials, thickness and materials of the primary and secondary filters. The specification of the X-ray beams modeled in this work corresponds to the standards ISO 4037 and IEC 61267. Within the linear-quadratic model, the uncertainty of determining the RBEmax values is directly proportional to the uncertainty in the determination of the dose absorbed by the sample under study. Results: At energy of more than 60 keV, the ratios for water and biological tissue practically do not differ. At lower energies, up to about 20 keV, the ratio of the coefficients of air and water is slightly less than that of air and biological tissue. The maximum difference is ~ 1 % than usual and the equality of absorbed doses in the ionization chamber and sample is justified. At photon energy of 60 keV for the geometry in question, the uncertainty in determining the dose is about 50 %. For non-monochromatic radiation, the magnitude of the uncertainty is determined by the spectral composition of the radiation, since the curves vary greatly in the energy range 10–100 keV. It is shown that, depending on the spectral composition of X-ray radiation, uncertainty in the determination of the absorbed dose can reach 40–60 %. Such large uncertainty is due to the lack of electronic equilibrium in the radiation geometry used in practice. The spread of RBE values determined from the data of radiobiological experiments carried out by different authors can be determined both by differences in the experimental conditions and by uncertainty in the determination of the absorbed dose. Using Fricke dosimeters instead of ionization chambers in the same geometry allows you to reduce the uncertainty approximately 2 times, up to 10–30 %. Conclusion: The computer simulation of radiobiological experiments to determine the relative biological effectiveness of X-ray radiation is performed. The geometry of the experiments corresponds to the conditions for the use of standard bottles placed in the side holders. It is shown that the ratio of absorbed doses and kerma in the layers of biological tissue and air differ among themselves with an uncertainty up to 60 %. Depending on the quality of the beam, the true absorbed dose may differ from the one calculated on the assumption of kerma and dose equivalence by 50 %. Uncertainty in determining the RBE in these experiments is of the same order. The results are presented for X-ray beams with negligible fraction of photons with energies less than 10 keV. For beams of a different quality, the uncertainty in determination can significantly increase. For the correct evaluation of RBE, it is necessary to develop a uniform standard for carrying out radiobiological experiments. This standard should regulate both the geometry of the experiments and the conduct of dosimetric measurements.

Responses of entomopathogenic fungi to the mutagen 4-nitroquinoline 1-oxide

Survival of entomopathogenic fungi under solar ultraviolet (UV) radiation is paramount to the success of biological control of insect pests and disease vectors. The mutagenic compound 4-nitroquinoline 1-oxide (4-NQO) is often used to mimic the biological effects of UV radiation on organisms. Therefore, we asked whether tolerance to 4-NQO could predict tolerance to UV radiation in thirty isolates of entomopathogenic fungi and one isolate of a xerophilic fungus. A dendrogram obtained from cluster analyses based on the 50 and 90 % inhibitory concentrations (IC50 and IC90, respectively) divided the fungal isolates into six clusters numbered consecutively based on their tolerance to 4-NQO. Cluster 6 contained species with highest tolerance to 4-NQO (IC50 > 4.7 μM), including Mariannaea pruinosa, Lecanicillium aphanocladii, and Torrubiella homopterorum. Cluster 1 contained species least tolerant to 4-NQO (IC50 < 0.2 μM), such as Metarhizium acridum (ARSEF 324), Tolypocladium geodes, and Metarhizium brunneum (ARSEF 7711). With few exceptions, the majority of Metarhizium species showed moderate to low tolerances (IC50 between 0.4 and 0.9 μM) and were placed in cluster 2. Cluster 3 included species with moderate tolerance (IC50 between 1.0 and 1.2 μM). In cluster 4 were species with moderate to high tolerance (IC50 between 1.3 and 1.6 μM). Cluster 5 contained the species with high tolerance (IC50 between 1.9 and 4.0 μM). The most UV tolerant isolate of M. acridum, ARSEF 324, was the least tolerant to 4-NQO. Also, L. aphanocladii, which is very susceptible to UV radiation, showed high tolerance to 4-NQO. Our results indicate that tolerance to 4-NQO does not correlate with tolerance to UV radiation. Therefore this chemical compound is not a predictor of UV tolerance in entomopathogenic fungi.

Microwave Signal at the U.S. Embassy in Moscow [Health Matters

Lately, there has been a great deal of scientific, public, and media attention about the health and safety effects of prolonged human exposure to RF radiation, especially with regard to cancer. The situation has been acerbated, in part, by dissemination of a report from a U.S. government sponsored experimental study. Indeed, the release of the laboratory rat cancer result was deemed as something of a public health obligation by the reporting government entity-the National Institute of Environmental Health Sciences/National Toxicology Program.The recent interest in this topic prompted me to recall an event that occurred in the mid1970s, when the biological and health effects of RF and microwave radiation were brought to the fore by the revelation in 1976 that two U.S. ambassadors to Moscow had died of cancer;the ambassador at that time, Walter Stoessel, threatened to resign because of widespread staff concerns regarding the potential health implications of an unusual microwave signal the Soviets were di recting at the U.S. embassy in Moscow.

Gamma irradiation during gametogenesis in young adult zebrafish causes persistent genotoxicity and adverse reproductive effects

The biological effects of gamma radiation may exert damage beyond that of the individual through its deleterious effects on reproductive function. Impaired reproductive performance can result in reduced population size over consecutive generations. In a continued effort to investigate reproductive and heritable effects of ionizing radiation, we recently demonstrated adverse effects and genomic instability in progeny of parents exposed to gamma radiation. In the present study, genotoxicity and effects on the reproduction following subchronic exposure during a gametogenesis cycle to 60Co gamma radiation (27 days, 8.7 and 53 mGy/h, total doses 5.2 and 31 Gy) were investigated in the adult wild-type zebrafish (Danio rerio). A significant reduction in embryo production was observed one month after exposure in the 53 mGy/h exposure group compared to control and 8.7 mGy/h. One year later, embryo production was significantly lower in the 53 mGy/h group compared only to control, with observed sterility, accompanied by a regression of reproductive organs in 100% of the fish 1.5 years after exposure. Histopathological examinations revealed no significant changes in the testis in the 8.7 mGy/h group, while in 62.5% of females exposed to this dose rate the oogenesis was found to be only at the early previtellogenic stage. The DNA damage determined in whole blood, 1.5 years after irradiation, using a high throughput Comet assay, was significantly higher in the exposed groups (1.2 and 3-fold increase in 8.7 and 53 mGy/h females respectively; 3-fold and 2-fold increase in 8.7 and 53 mGy/h males respectively) compared to controls. A significantly higher number of micronuclei (4–5%) was found in erythrocytes of both the 8.7 and 53 mGy/h fish compared to controls. This study shows that gamma radiation at a dose rate of ≥ 8.7 mGy/h during gametogenesis causes adverse reproductive effects and persistent genotoxicity (DNA damage and increased micronuclei) in adult zebrafish.

Radiation Measured for Chinese Satellite SJ‐10 Space Mission

AbstractsSpace biological effects are mainly a result of space radiation particles with high linear energy transfer (LET); therefore, accurate measurement of high LET space radiation is vital. The radiation in low Earth orbits is composed mainly of high‐energy galactic cosmic rays (GCRs), solar energetic particles, particles of radiation belts, the South Atlantic Anomaly, and the albedo neutrons and protons scattered from the Earth's atmosphere. CR‐39 plastic nuclear track detectors sensitive to high LET are the best passive detectors to measure space radiation. The LET method that employs CR‐39 can measure all the radiation LET spectra and quantities. CR‐39 detectors can also record the incident directions and coordinates of GCR heavy ions that pass through both CR‐39 and biosamples, and the impact parameter, the distance between the particle's incident point and the seed's spore, can then be determined. The radiation characteristics and impact parameter of GCR heavy ions are especially beneficial for in‐depth research regarding space radiation biological effects. The payload returnable satellite SJ‐10 provided an excellent opportunity to investigate space radiation biological effects with CR‐39 detectors. The space bio‐effects experiment was successfully conducted on board the SJ‐10 satellite. This paper introduces space radiation in low Earth orbits and the LET method in radiation‐related research and presents the results of nuclear tracks and biosamples hitting distributions of GCR heavy ions, the radiation LET spectra, and the quantities measured for the SJ‐10 space mission. The SJ‐10 bio‐experiment indicated that radiation may produce significant bio‐effects.

Tritium biology in Japan: A search for a new approach

The health effects of tritium are a major public concern in Japan due to the presence of tritium (HTO) contaminated water at the Fukushima Dai-ichi Nuclear Power Plant (Fukushima NPP). From a scientific view, the biological effects of the contaminant HTO at the Fukushima NPP could conceivably be quite small, but the possibility of stochastic effects from tritium radiation cannot be neglected. This reasoning is based on the linear no-threshold (LNT) model, which is cited in ICRP recommendations and suggests an elevation in the frequency of the stochastic effects of radiation, even when the doses are less than 100 mGy. However, at the present, only a small amount of experimental data is available describing the biological effects of low doses radiation, and there are no established experimental systems that can clearly show whether or not the LNT model is appropriate. This is due to a wide scatter in data for the incidence of stochastic effects, which makes it difficult to distinguish radiation-induced events from spontaneous events. We propose overcoming this difficulty for radiobiology experiments using low doses or low dose rate radiation by establishing hypersensitive assay systems, and report on the current status of work investigating tritium radiobiology in Japan.

Investigation on the correlation between energy deposition and clustered DNA damage induced by low-energy electrons.

This study presents the correlation between energy deposition and clustered DNA damage, based on a Monte Carlo simulation of the spectrum of direct DNA damage induced by low-energy electrons including the dissociative electron attachment. Clustered DNA damage is classified as simple and complex in terms of the combination of single-strand breaks (SSBs) or double-strand breaks (DSBs) and adjacent base damage (BD). The results show that the energy depositions associated with about 90% of total clustered DNA damage are below 150eV. The simple clustered DNA damage, which is constituted of the combination of SSBs and adjacent BD, is dominant, accounting for 90% of all clustered DNA damage, and the spectra of the energy depositions correlating with them are similar for different primary energies. One type of simple clustered DNA damage is the combination of a SSB and 1-5 BD, which is denoted as SSB + BD. The average contribution of SSB + BD to total simple clustered DNA damage reaches up to about 84% for the considered primary energies. In all forms of SSB + BD, the SSB + BD including only one base damage is dominant (above 80%). In addition, for the considered primary energies, there is no obvious difference between the average energy depositions for a fixed complexity of SSB + BD determined by the number of base damage, but average energy depositions increase with the complexity of SSB + BD. In the complex clustered DNA damage constituted by the combination of DSBs and BD around them, a relatively simple type is a DSB combining adjacent BD, marked as DSB + BD, and it is of substantial contribution (on average up to about 82%). The spectrum of DSB + BD is given mainly by the DSB in combination with different numbers of base damage, from 1 to 5. For the considered primary energies, the DSB combined with only one base damage contributes about 83% of total DSB + BD, and the average energy deposition is about 106eV. However, the energy deposition increases with the complexity of clustered DNA damage, and therefore, the clustered DNA damage with high complexity still needs to be considered in the study of radiation biological effects, in spite of their small contributions to all clustered DNA damage.

High LET radiation shows no major cellular and functional effects on primary cardiomyocytes in vitro

It is well known that ionizing radiation causes adverse effects on various mammalian tissues. However, there is little information on the biological effects of heavy ion radiation on the heart. In order to fill this gap, we systematically examined DNA-damage induction and repair, as well as proliferation and apoptosis in avian cardiomyocyte cultures irradiated with heavy ions such as titanium and iron, relevant for manned space-flight, and carbon ions, as used for radiotherapy. Further, and to our knowledge for the first time, we analyzed the effect of heavy ion radiation on the electrophysiology of primary cardiomyocytes derived from chicken embryos using the non-invasive microelectrode array (MEA) technology. As electrophysiological endpoints beat rate and field action potential duration were analyzed.The cultures clearly exhibited the capacity to repair induced DNA damage almost completely within 24 h, even at doses of 7 Gy, and almost completely recovered from radiation-induced changes in proliferative behavior. Interestingly, no significant effects on apoptosis could be detected. Especially the functionality of primary cardiac cells exhibited a surprisingly high robustness against heavy ion radiation, even at doses of up to 7 Gy. In contrast to our previous study with X-rays the beat rate remained more or less unaffected after heavy ion radiation, independently of beam quality. The only change we could observe was an increase of the field action potential duration of up to 30% after titanium irradiation, diminishing within the following three days. This potentially pathological observation may be an indication that heavy ion irradiation at high doses could bear a long-term risk for cardiovascular disease induction.

Analytical dose modeling for preclinical proton irradiation of millimetric targets.

Due to the considerable development of proton radiotherapy, several proton platforms have emerged to irradiate small animals in order to study the biological effectiveness of proton radiation. A dedicated analytical treatment planning tool was developed in this study to accurately calculate the delivered dose given the specific constraints imposed by the small dimensions of the irradiated areas. The treatment planning system (TPS) developed in this study is based on an analytical formulation of the Bragg peak and uses experimental range values of protons. The method was validated after comparison with experimental data from the literature and then compared to Monte Carlo simulations conducted using Geant4. Three examples of treatment planning, performed with phantoms made of water targets and bone-slab insert, were generated with the analytical formulation and Geant4. Each treatment planning was evaluated using dose-volume histograms and gamma index maps. We demonstrate the value of the analytical function for mouse irradiation, which requires a targeting accuracy of 0.1mm. Using the appropriate database, the analytical modeling limits the errors caused by misestimating the stopping power. For example, 99% of a 1-mm tumor irradiated with a 24-MeV beam receives the prescribed dose. The analytical dose deviations from the prescribed dose remain within the dose tolerances stated by report 62 of the International Commission on Radiation Units and Measurements for all tested configurations. In addition, the gamma index maps show that the highly constrained targeting accuracy of 0.1mm for mouse irradiation leads to a significant disagreement between Geant4 and the reference. This simulated treatment planning is nevertheless compatible with a targeting accuracy exceeding 0.2mm, corresponding to rat and rabbit irradiations. Good dose accuracy for millimetric tumors is achieved with the analytical calculation used in this work. These volume sizes are typical in mouse models for radiation studies. Our results demonstrate that the choice of analytical rather than simulated treatment planning depends on the animal model under consideration.

The Statistical Models Project (SMp) for Evaluations of Biological Radiation Effects

This document provides probabilistic-mechanistic models for describing the cell kill (K) and cell sub-lethal damage (SL) for one fraction with a dose of radiation that is absorbed by a living tissue; also this provides the K and SL formalisms for fractioned irradiation regimens. These models and formalisms are based on real mean behavior of cell survival (S) - a complement of K- and strong probabilistic-radiobiological foundations. The K and SL formalisms include all possible factors affecting the biological radiation effects: dose (d), fractionations (n), SL, and the temporal factors: cell repair and cell repopulation. It is discussed some aspects about the widely used linear-quadratic (LQ) S(d) model and LQ S(n,d) formalism, and one of its derivations, the BED (biologically effective dose). The SMp K(d) parameters can be obtained from S data, or using graphical/analytical tools developed by this study. These new formalisms will be useful for simulations of treatments, and together regional damage distribution for optimizations of the treatment planning.

75 - LET dependent hydroxyl radical generation in water by heavy-ion beam irradiation

Nano-geometry of hydroxyl radical (•OH) generation in water caused by heavy-ion beam irradiation was evaluated using a fluorescent probe, disodium terephthalate (TPA-Na). Since •OH is recognized as a primary product in biological effects of radiation, elimination of •OH may be important to regulate the side effect of radiation therapy. Recently, using the electron paramagnetic resonance (EPR) spin-trapping technique, we reported that the two different types of •OH generations by ionizing radiation. In this study, linear energy transfer (LET) dependence on the density of localized •OH generation was evaluated using TPA-Na. The irradiation of heavy-ion beams was performed at the Heavy-Ion Medical Accelerator in Chiba (HIMAC, National Institute of Radiological Sciences, Japan). Several concentrations (0.5-208 mM) of TPA-Na in aqueous solutions were irradiated with 32 Gy of a heavy-ion beam (C400, Si490 or Fe500) at several different LET. The amount of •OH adduct of TPA-Na (hTPA) thus generated was measured by fluorophotometer (Ex. 310 nm/Em. 425 nm). The relationship between molecular density of TPA-Na and hTPA generated was analyzed. The amount of hTPA generated by low-LET heavy-ion beam was increased in proportion to the molecular density of TPA-Na and reached a plateau through an unclear inflexion point. In the case of high-LET heavy-ion beam, however, another linear trend that passed through the origin was again observed when TPA-Na density was extremely high (TPA-Na conc.: 156-208 mM). The linear increasing trend observed at high TPA-Na density suggested an extremely dense •OH generation.

Effects of ultraviolet radiation on photosynthetic performance and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; fixation in &amp;lt;i&amp;gt;Trichodesmium erythraeum&amp;lt;/i&amp;gt; IMS 101

Abstract. Biological effects of ultraviolet radiation (UVR; 280–400 nm) on marine primary producers are of general concern, as oceanic carbon fixers that contribute to the marine biological CO2 pump are being exposed to increasing UV irradiance due to global change and ozone depletion. We investigated the effects of UV-B (280–320 nm) and UV-A (320–400 nm) on the biogeochemically critical filamentous marine N2-fixing cyanobacterium Trichodesmium (strain IMS101) using a solar simulator as well as under natural solar radiation. Short exposure to UV-B, UV-A, or integrated total UVR significantly reduced the effective quantum yield of photosystem II (PSII) and photosynthetic carbon and N2 fixation rates. Cells acclimated to low light were more sensitive to UV exposure compared to high-light-grown ones, which had more UV-absorbing compounds, most likely mycosporine-like amino acids (MAAs). After acclimation under natural sunlight, the specific growth rate was lower (by up to 44 %), MAA content was higher, and average trichome length was shorter (by up to 22 %) in the full spectrum of solar radiation with UVR, than under a photosynthetically active radiation (PAR) alone treatment (400–700 nm). These results suggest that prior shipboard experiments in UV-opaque containers may have substantially overestimated in situ nitrogen fixation rates by Trichodesmium, and that natural and anthropogenic elevation of UV radiation intensity could significantly inhibit this vital source of new nitrogen to the current and future oligotrophic oceans.

A History of the International Commission on Non-Ionizing Radiation Protection

Concern about health risks from exposure to non-ionizing radiation (NIR) commenced in the 1950s after tracking radars were first introduced during the Second World War. Soon after, research on possible biological effects of microwave radiation in the former Soviet Union and the U.S. led to public and worker exposure limits being much lower in Eastern European than in Western countries, mainly because of different protection philosophies. As public concern increased, national authorities began introducing legislation to limit NIR exposures from domestic microwave ovens and workplace devices such as visual display units. The International Radiation Protection Association (IRPA) was formed in 1966 to represent national radiation protection societies. To address NIR protection issues, IRPA established a Working Group in 1974, then a Study Group in 1975, and finally the International NIR Committee (INIRC) in 1977. INIRC's publications quickly became accepted worldwide, and it was logical that it should become an independent commission. IRPA finally established the International Commission on Non-Ionizing Radiation Protection (ICNIRP), chartering its remit in 1992, and defining NIR as electromagnetic radiation (ultraviolet, visible, infrared), electromagnetic waves and fields, and infra- and ultrasound. ICNIRP's guidelines have been incorporated into legislation or adopted as standards in many countries. While ICNIRP has been subjected to criticism and close scrutiny by the public, media, and activists, it has continued to issue well-received, independent, science-based protection advice. This paper summarizes events leading to the formation of ICNIRP, its key activities up to 2017, ICNIRP's 25th anniversary year, and its future challenges.

The Mistaken Birth and Adoption of LNT: An Abridged Version.

The historical foundations of cancer risk assessment were based on the discovery of X-ray-induced gene mutations by Hermann J. Muller, its transformation into the linear nonthreshold (LNT) single-hit theory, the recommendation of the model by the US National Academy of Sciences, Biological Effects of Atomic Radiation I, Genetics Panel in 1956, and subsequent widespread adoption by regulatory agencies worldwide. This article summarizes substantial recent historical revelations of this history, which profoundly challenge the standard and widely acceptable history of cancer risk assessment, showing multiple significant scientific errors and incorrect interpretations, mixed with deliberate misrepresentation of the scientific record by leading ideologically motivated radiation geneticists. These novel historical findings demonstrate that the scientific foundations of the LNT single-hit model were seriously flawed and should not have been adopted for cancer risk assessment.

Nuclear science and society: social inclusion through scientific education

This article presents a web-based educational project focused on the potential value of Information and Communication Technology to enhance communication and education on nuclear science throughout Brazil. The project is designed to provide trustworthy information about the beneficial uses of nuclear technology, educating children and teenagers, as well as their parents and teachers, demystifying paradigms and combating misinformation. Making use of a range of interactive activities, the website presents short courses and curiosities, with different themes that comprise the several aspects of the beneficial applications of nuclear science. The intention of the many interactive activities is to encourage research and to enhance learning opportunities through a self-learning universe where the target public is introduced to the basic concepts of nuclear physics, such as nuclides and isotopes, atomic interactions, radioactive decay, biological effects of radiation, nuclear fusion, nuclear fission, nuclear reactors, nuclear medicine, radioactive dating methods and natural occurring radiation, among other ideas and concepts in nuclear physics. Democratization of scientific education can inspire new thoughts, stimulate development and encourage scientific and technological researches.

Relative biological effectiveness (RBE) and distal edge effects of proton radiation on early damage in vivo

Introduction: The aim of the present study was to examine the RBE for early damage in an in vivo mouse model, and the effect of the increased linear energy transfer (LET) towards the distal edge of the spread-out Bragg peak (SOBP).Method: The lower part of the right hind limb of CDF1 mice was irradiated with single fractions of either 6 MV photons, 240 kV photons or scanning beam protons and graded doses were applied. For the proton irradiation, the leg was either placed in the middle of a 30-mm SOBP, or to assess the effect in different positions, irradiated in 4 mm intervals from the middle of the SOBP to behind the distal dose fall-off. Irradiations were performed with the same dose plan at all positions, corresponding to a dose of 31.25 Gy in the middle of the SOBP. Endpoint of the study was early skin damage of the foot, assessed by a mouse foot skin scoring system.Results: The MDD50 values with 95% confidence intervals were 36.1 (34.2–38.1) Gy for protons in the middle of the SOBP for score 3.5. For 6 MV photons, it was 35.9 (34.5–37.5) Gy and 32.6 (30.7–34.7) Gy for 240 kV photons for score 3.5. The corresponding RBE was 1.00 (0.94–1.05), relative to 6 MV photons and 0.9 (0.85–0.97) relative to 240 kV photons. In the mice group positioned at the SOBP distal dose fall-off, 25% of the mice developed early skin damage compared with 0–8% in other groups. LETd,z = 1 was 8.4 keV/μm at the distal dose fall-off and the physical dose delivered was 7% lower than in the central SOBP position, where LETd,z =1 was 3.3 keV/μm.Conclusions: Although there is a need to expand the current study to be able to calculate an exact enhancement ratio, an enhanced biological effect in vivo for early skin damage in the distal edge was demonstrated.