Minimum reporting standards about dosimetry of radiation sources used in radiation research studies.

The necessity of precise dosimetry and its documentation in research is less obvious than in medicine and in radiological protection. However, in radiation research, results can only be validated if experiments were carried out with sufficient precision and described with sufficient details, especially information regarding dosimetry. In order to ensure this, an initiative was launched to establish reproducible dosimetry reporting parameters in published studies. Minimum standards for reporting radiation dosimetry information were developed and published in parallel in the International Journal of Radiation Biology and Radiation Research. As editors of Radiation and Environmental Biophysics, we support this initiative and reproduce the agreed minimum irradiation parameters that should be reported in publications on radiation biology submitted to our journal.

ICRP workshop on the review and revision of the system of radiological protection: a focus on research priorities-feedback from the international community.

In September 2022, the International Commission on Radiological Protection (ICRP) organised a workshop in Estoril, Portugal, on the 'Review and Revision of the System of Radiological Protection: A Focus on Research Priorities'. The workshop, which was a side event of the European Radiation Protection Week, offered an opportunity to comment on a recent paper published by ICRP on areas of research to support the System of Radiological Protection. Altogether, about 150 individuals participated in the workshop. After the workshop, 16 of the 30 organisations in formal relations with ICRP provided written feedback. All participants and organisations followed ICRP's view that further research in various areas will offer additional support in improving the System in the short, medium, and long term. In general, it was emphasised that any research should be outcome-focused in that it should improve protection of people or the environment. Many research topics mentioned by the participants were in line with those already identified by ICRP in the paper noted above. In addition, further ideas were expressed such as, for example, that lessons learned during the COVID-19 pandemic with regards to the non-radiological social, economic and environment impacts, should be analysed for their usefulness to enhance radiological protection, and that current protection strategies and application of current radiological protection principles may need to be adapted to military scenarios like those observed recently during the military conflict in the Ukraine or the detonation of a nuclear weapon. On a broader perspective, it was discussed how radiation research and radiological protection can contribute towards the Sustainable Development Goals announced by the United Nations in 2015. This paper summarises the views expressed during the workshop and the major take home messages identified by ICRP.

Radiation dose rate effects: what is new and what is needed?

Despite decades of research to understand the biological effects of ionising radiation, there is still much uncertainty over the role of dose rate. Motivated by a virtual workshop on the "Effects of spatial and temporal variation in dose delivery" organised in November 2020 by the Multidisciplinary Low Dose Initiative (MELODI), here, we review studies to date exploring dose rate effects, highlighting significant findings, recent advances and to provide perspective and recommendations for requirements and direction of future work. A comprehensive range of studies is considered, including molecular, cellular, animal, and human studies, with a focus on low linear-energy-transfer radiation exposure. Limits and advantages of each type of study are discussed, and a focus is made on future research needs.

On the choice of methodology for evaluating dose-rate effects on radiation-related cancer risks.

Recently, several compilations of individual radiation epidemiology study results have aimed to obtain direct evidence on the magnitudes of dose-rate effects on radiation-related cancer risks. These compilations have relied on meta-analyses of ratios of risks from low dose-rate studies and matched risks from the solid cancer Excess Relative Risk models fitted to the acutely exposed Japanese A-bomb cohort. The purpose here is to demonstrate how choices of methodology for evaluating dose-rate effects on radiation-related cancer risks may influence the results reported for dose-rate effects. The current analysis is intended to address methodological issues and does not imply that the authors recommend a particular value for the dose and dose-rate effectiveness factor. A set of 22 results from one recent published study has been adopted here as a test set of data for applying the many different methods described here, that nearly all produced highly consistent results. Some recently voiced concerns, involving the recalling of the well-known theoretical point-the ratio of two normal random variables has a theoretically unbounded variance-that could potentially cause issues, are shown to be unfounded when aimed at the published work cited and examined in detail here. In the calculation of dose-rate effects for radiation protection purposes, it is recommended that meta-estimators should retain the full epidemiological and dosimetric matching information between the risks from the individual low dose-rate studies and the acutely exposed A-bomb cohort and that a regression approach can be considered as a useful alternative to current approaches.

Dose limits for occupational exposure to ionising radiation and genotoxic carcinogens: a German perspective.

This paper summarises the view of the German Commission on Radiological Protection ("Strahlenschutzkommission", SSK) on the rationale behind the currently valid dose limits and dose constraints for workers recommended by the International Commission on Radiological Protection (ICRP). The paper includes a discussion of the reasoning behind current dose limits followed by a discussion of the detriment used by ICRP as a measure for stochastic health effects. Studies on radiation-induced cancer are reviewed because this endpoint represents the most important contribution to detriment. Recent findings on radiation-induced circulatory disease that are currently not included in detriment calculation are also reviewed. It appeared that for detriment calculations the contribution of circulatory diseases plays only a secondary role, although the uncertainties involved in their risk estimates are considerable. These discussions are complemented by a review of the procedures currently in use in Germany, or in discussion elsewhere, to define limits for genotoxic carcinogens. To put these concepts in perspective, actual occupational radiation exposures are exemplified with data from Germany, for the year 2012, and regulations in Germany are compared to the recommendations issued by ICRP. Conclusions include, among others, considerations on radiation protection concepts currently in use and recommendations of the SSK on the limitation of annual effective dose and effective dose cumulated over a whole working life.

Current knowledge on radon risk: implications for practical radiation protection? radon workshop, 1/2 December 2015, Bonn, BMUB (Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit; Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety).

ICRP suggested a strategy based on the distinction between a protection approach for dwellings and one for workplaces in the previous recommendations on radon. Now, the Commission recommends an integrated approach for the protection against radon exposure in all buildings irrespective of their purpose and the status of their occupants. The strategy of protection in buildings, implemented through a national action plan, is based on the application of the optimisation principle below a derived reference level in concentration (maximum 300 Bq m(-3)). A problem, however, arises that due to new epidemiological findings and application of dosimetric models, ICRP 115 (Ann ICRP 40, 2010) presents nominal probability coefficients for radon exposure that are approximately by a factor of 2 larger than in the former recommendations of ICRP 65 (Ann ICRP 23, 1993). On the basis of the so-called epidemiological approach and the dosimetric approach, the doubling of risk per unit exposure is represented by a doubling of the dose coefficients, while the risk coefficient of ICRP 103 (2007) remains unchanged. Thus, an identical given radon exposure situation with the new dose coefficients would result in a doubling of dose compared with the former values. This is of serious conceptual implications. A possible solution of this problem was presented during the workshop.

A puzzling case of contamination with 241Am.

Two people were exposed to and contaminated with 241Am. In vivo determinations of the incorporated 241Am were performed using a whole-body counter and two partial-body counters for the skull and lung, respectively. Additionally, urine samples were analysed to estimate the systemic activity removed from the body. To improve the geometry of the skull measurements, an optimised detector configuration was used, a calibration with three physical phantoms of the human head was conducted, and the morphological variability between the individuals was also considered. The results of the measurements indicate that activity is not deposited in the deep tissues, rather in the skin tissues close to the body surface. Unfortunately, the many open questions relating to the actual circumstances during and after the incident make the interpretation of this case difficult if at all possible.

Dose and dose-rate effects of ionizing radiation: a discussion in the light of radiological protection.

The biological effects on humans of low-dose and low-dose-rate exposures to ionizing radiation have always been of major interest. The most recent concept as suggested by the International Commission on Radiological Protection (ICRP) is to extrapolate existing epidemiological data at high doses and dose rates down to low doses and low dose rates relevant to radiological protection, using the so-called dose and dose-rate effectiveness factor (DDREF). The present paper summarizes what was presented and discussed by experts from ICRP and Japan at a dedicated workshop on this topic held in May 2015 in Kyoto, Japan. This paper describes the historical development of the DDREF concept in light of emerging scientific evidence on dose and dose-rate effects, summarizes the conclusions recently drawn by a number of international organizations (e.g., BEIR VII, ICRP, SSK, UNSCEAR, and WHO), mentions current scientific efforts to obtain more data on low-dose and low-dose-rate effects at molecular, cellular, animal and human levels, and discusses future options that could be useful to improve and optimize the DDREF concept for the purpose of radiological protection.

Estimating the absorption of soil-derived uranium in humans.

The aim of the present study was to improve the estimation of soil-derived uranium absorption in humans. For this purpose, an in vitro solubility assay was combined with a human study by using a specific edible soil low in uranium. The mean bioaccessibility of the soil-derived uranium, determined by the solubility assay in artificial gastrointestinal fluid, was found to be 7.7% with a standard deviation of 0.2%. The corresponding bioavailability of the soil-derived uranium in humans was assumed to be log-normal distributed with a geometric mean of 0.04% and a 95% confidence interval ranging from 0.0049% to 0.34%. Both results were used to calculate a factor, denoted as fA(sol), which describes the relation between the bioaccessibility and the bioavailability of soil-derived uranium. The geometric mean of fA(sol) was determined to be 0.53% with a 95% confidence interval ranging from 0.06% to 4.43%. Based on fA(sol), it is possible to estimate more realistic values on the bioavailability of uranium for highly uranium-contaminated soils in humans by just performing the applied solubility assay. The results of this study can be further used to obtain more reliable results on the internal dose assessment of ingested highly uranium-contaminated soils.

Assessing the impact of neutron relative biological effectiveness on all solid cancer mortality risks in the Japanese atomic bomb survivors.

PURPOSE: Risk analyses, based on relative biological effectiveness (RBE) estimates for neutrons relative to gammas, were performed; and the change in the curvature of the risk to dose response with increasing neutron RBE was analyzed using all solid cancer mortality data from the Radiation Effect Research Foundation (RERF). Results were compared to those based on incidence data. MATERIALS AND METHODS: This analysis is based on RERF mortality data with separate neutron and gamma doses for colon doses, from which organ averaged doses could be calculated. A model for risk ratio variation with RBE was developed. RESULTS: The best estimate of the neutron RBE considering mortality data was 200 (95% confidence interval (CI): 50-1010) for colon dose using the weighted-dose approach and for organ averaged dose 110 (95% CI: 30-350). The ERR risk ratios for all solid cancers combined, for the best fitting neutron RBE estimate and the neutron RBE of 10 result in a ratio of 0.54 (95% CI: 0.17-0.85) for colon dose and 0.55 (95% CI: 0.18-0.87) for organ averaged dose. The risk to dose response curvature became significantly negative (concave down) with increasing RBE, at a neutron RBE of 170 using colon dose and at an RBE of 90 using organ averaged dose for males when fitting a linear-quadratic dose response. For females, the curvature decreased toward linearity with increasing neutron RBE and remained significantly positive until RBE of 80 and 40 using colon and organ averaged dose, respectively. For higher neutron RBEs, no significant conclusion could be drawn about the shape of the dose-response curve. CONCLUSIONS: Application of neutron RBE values higher than 10 results in substantially reduced cancer mortality risk estimates and a significant reduction in curvature of the risk to dose responses for males. Using mortality data, the best fitting neutron RBE is much higher than when incidence data is used. The neutron RBE ranges covered by the overlap in the CIs from both the mortality and incidence analyses are 50-190 using colon dose and in all cases, the best fitting neutron RBE and lower 95% CI are higher than the value of 10 traditionally applied by the RERF. Therefore, it is recommended to consider uncertainties in neutron RBE values when calculating radiation risks and discussing the shape of dose responses using Japanese A-bomb survivors data.

Time-integrated radiation risk metrics and interpopulation variability of survival.

Task Group 115 of the International Commission on Radiological Protection is focusing on mission-related exposures to space radiation and concomitant health risks for space crew members including, among others, risk of cancer development. Uncertainties in cumulative radiation risk estimates come from the stochastic nature of the considered health outcome (i.e., cancer), uncertainties of statistical inference and model parameters, unknown secular trends used for projections of population statistics and unknown variability of survival properties between individuals or population groups. The variability of survival is usually ignored when dealing with large groups, which can be assumed well represented by the statistical data for the contemporary general population, either in a specific country or world averaged. Space crew members differ in many aspects from individuals represented by the general population, including, for example, their lifestyle and health status, nutrition, medical care, training and education. The individuality of response to radiation and lifespan is explored in this modelling study. Task Group 115 is currently evaluating applicability and robustness of various risk metrics for quantification of radiation-attributed risks of cancer for space crew members. This paper demonstrates the impact of interpopulation variability of survival curves on values and uncertainty of the estimates of the time-integrated radiation risk of cancer.

Space agency-specific standards for crew dose and risk assessment of ionising radiation exposures for the International Space Station.

The Partner Agencies of the International Space Station (ISS) maintain separate career exposure limits and shared Flight Rules that control the ionising radiation exposures that crewmembers can experience due to ambient environments throughout their space missions. In low Earth orbit as well as further out in space, energetic ions referred to as galactic cosmic radiation (GCR) easily penetrate spacecraft and spacecraft contents and consequently are always present at low dose rates. Protons and electrons that are trapped in the Earth's geomagnetic field are encountered intermittently, and a rare energetic solar particle event (SPE) may expose crew to (mostly) energetic protons. Space radiation protection goals are to optimize radiation exposures to maintain deleterious late effects at known and acceptable levels and to prevent any early effects that might compromise crew health and mission success. The conventional radiation protection metric effective dose provides a basic framework for limiting exposures associated with human spaceflight and can be communicated to all stakeholders. Additional metrics and uncertainty analyses are required to understand more completely and to convey nuanced information about potential impacts to an individual astronaut or to a space mission. Missions to remote destinations well beyond low Earth orbit (BLEO) are upcoming and bestow additional challenges that shape design and radiation protection needs. NASA has recently adopted a more permissive career exposure limit based upon effective dose and new restrictions on mission exposures imposed by nuclear technologies. This manuscript reviews the exposure limits that apply to the ISS crewmembers. This work was performed in collaboration with the advisory and guidance efforts of International Commission on Radiological Protection (ICRP) Task Group 115 and will be summarized in an upcoming ICRP Report.

Comparison of dose and risk estimates between ISS Partner Agencies for a 30-day lunar mission.

The International Partner Agencies of the International Space Station (ISS) present a comparison of the ionizing radiation absorbed dose and risk quantities used to characterize example missions in lunar space. This effort builds on previous collaborative work that characterizes radiation environments in space to support radiation protection for human spaceflight on ISS in low-Earth orbit (LEO) and exploration missions beyond (BLEO). A "shielded" ubiquitous galactic cosmic radiation (GCR) environment combined with--and separate from--the transient challenge of a solar particle event (SPE) was modelled for a simulated 30-day mission period. Simple geometries of relatively thin and uniform shields were chosen to represent the space vehicle and other available shielding, and male or female phantoms were used to represent the body's self-shielding. Absorbed dose in organs and tissues and the effective dose were calculated for males and females. Risk parameters for cancer and other outcomes are presented for selected organs. The results of this intracomparison between ISS Partner Agencies itself provide insights to the level of agreement with which space agencies can perform organ dosimetry and calculate effective dose. This work was performed in collaboration with the advisory and guidance efforts of the International Commission on Radiological Protection (ICRP) Task Group 115 and will be presented in an ICRP Report.

Assessing the impact of different neutron RBEs on the all solid cancer radiation risks obtained from the Japanese A-bomb survivors data.

PURPOSE: Development of a model characterizing risk variation with RBE to investigate how the incidence risk for all solid cancers combined varies with higher neutron RBEs and different organ dose types. MATERIAL AND METHODS: The model is based on RERF data with separate neutron and gamma dose information. RESULTS: For both additive and multiplicative linear excess risks per unit organ averaged dose, a reduction of 50% in the risk coefficient per weighted dose arises when a neutron RBE of 110 is used instead of 10. Considering risk per unit liver dose, this reduction occurs for an RBE of 130 and for risks per unit colon dose for an RBE of 190. The change in the shape of the dose response curve when using higher neutron RBEs is evaluated. The curvature changed and became significantly negative for males at an RBE of 140 for colon dose, 100 for liver dose and 80 for organ averaged dose. For females this is the case at an RBE of 110, 80 and 60, respectively. CONCLUSIONS: Uncertainties in neutron RBE values should be considered when radiation risks and the shape of dose responses are deduced from cancer risk data from the atomic bomb survivors.

The European Radiation Dosimetry Group-a 40 year success story.

The European Radiation Dosimetry Group (EURADOS) was founded in 1982. Since then, the group has continuously developed and is currently a network of 80 institutions and more than 600 individual scientists across Europe, including exchange with the scientific community outside of Europe. EURADOS supports research and development of dosimetry and harmonising dosimetric practices. This paper describes the major milestones in the history of the organization. It starts from the very beginning when the idea was born and describes periods during which the role and strategy of the network had to be defined, elaborated and refined. Finally, it ends to date where EURADOS appears as an independent self-sustainable association, which is a reliable partner for various international organisations in radiation research and radiation protection. Major activities of EURADOS are highlighted such as (1) establishment and coordination of Working Groups, (2) regular organization of dosimetric intercomparisons for quality assurance of dosimetry procedures, (3) development and organization of education and training events, and (4) contributions towards the development of strategic and integrated radiation research in Europe.