Practical guidance on the assessment of radiation risks for diagnostic radiological examinations.

Patient doses cannot be limited; instead, radiological examinations should be justified and optimised to ensure the necessary diagnostic or therapeutic effect with the lowest patient dose achievable. Assessment of the radiation risks from patient exposure is important part of the justification process. Hence, medical staff within the framework of their professional activities should possess necessary information on the data on radiation risk from different types of radiological procedures. An approach has been developed that allows considering age and gender dependences of the risk coefficients of radiogenic cancer and the age and gender distribution of patients for various radiological examinations to assess the individual radiation risk for patient and collective risk for population from medical exposure. The approach is based on a new expanded use of the effective dose concept proposed in ICRP Publication 147 and demonstrated using the medical exposure in the Russian Federation as the example. For 30 radiological examinations that compose about 80% of the collective dose from medical exposure of the public in the Russian Federation radiation risk was assessed based on calculated age and gender specific risk coefficients per unit effective dose. For the rest of the examinations a simplified approach was used to assess the risk, which was based on using an age and gender specific risk coefficient determined for one of 4 anatomical regions (head, neck, chest and abdomen) or for uniform irradiation of the whole body. The proposed approach allows significantly improving the assessment of the radiation risk while continuing to use the effective dose as a dosimetric quantity within the framework of the state program in the Russian Federation. As a result the collective risk from medical examinations in the Russian Federation in 2022 was lower by the factor of 3 compared to the previous assessment based on the effective dose with the nominal risk coefficient.

NCRP commentary no. 33-recommendations for stratification of equipment use and radiation safety training for fluoroscopy.

National Council on Radiation Protection and Measurements Commentary No. 33 'Recommendations for Stratification of Equipment Use and Radiation Safety Training for Fluoroscopy' defines an evidence-based, radiation risk classification for fluoroscopically guided procedures (FGPs), provides radiation-related recommendations for the types of fluoroscopes suitable for each class of procedure, and indicates the extent and content of training that ought to be provided to different categories of facility staff who might enter a room where fluoroscopy is or may be performed. For FGP, radiation risk is defined by the type and likelihood of radiation hazards that could be incurred by a patient undergoing a FGP. The Commentary also defines six training groups of facility staff based on their role in the fluoroscopy room. The training groups are based on a combination of job descriptions and the procedures in which these individuals might be involved. The Commentary recommends the extent and content of training that should be provided to each of these training groups. It also provides recommendations on training formats, training frequency, and methods for demonstrating that the learner has acquired the necessary knowledge.

Biodistribution of naturally occurring radionuclides and radiocesium in wild European perch (Perca fluviatilis).

Wild European perch (Perca fluviatilis) is one of the most important freshwater fish species, in Sweden, due to its widespread and his value for recreational fishing. Little it is known regarding the biodistribution of naturally occurring radionuclides such as 238U, 234U, 226Ra, 210Po in perch. Therefore, in this study, perches from five lakes located in different counties in Sweden were collected to investigate the biodistribution of 238U, 234U, 226Ra, 210Po and 137Cs in organs and tissues of perch as well as their radiological impact. The results showed that uranium radionuclides ranged between 0.1 and 6 Bq/kg with an average value of 1.1 ± 1.5 Bq/kg. 226Ra varied from 0.4 to 8 Bq/kg with a mean concentration of 1.7 ± 1.9 Bq/kg. The ranged of 210Po was 0.5 - 250 Bq/kg, with an average value of 24 ± 52 Bq/kg. On the other hand, the highest activity concentration of 137Cs, 151 ± 1 Bq/kg, was detected in muscle samples of perch from Redsjösjön lake. For uranium radionuclides and 226Ra uptake from water is the main source whereas for 210Po and 137Cs the uptake is controlled by the perch diet. Regarding naturally occurring radionuclides, the perch tended to accumulated uranium radionuclides in fins, gills, and skin; 226Ra in bones, fins and skin and 210Po in the organs linked to digestive system. Finally, in case of consumption, it is advised the consumption of skinned fillets of perch due to the higher bioaccumulation of the radionuclides investigated in the skin and scales.

The quality of beef in the conditions of the former Semipalatinsk Test Site.

The territory of the Semipalatinsk Nuclear Test Site represents vast areas of grassy steppes, their use as pastures seems promising. The purpose of work was to compare beef samples obtained from settlements belonging to different categories of radiation risk: Kokpekty village, Chagan urban-type settlement, Krivinka village, Sarzhal village, three samples were examined from each settlement. Organoleptic analysis, radiometric determination of 137 Cs, was used as criteria. Also, an analysis of the amino acid composition by the high-performance liquid chromatograph method was carried out and a calculation of protein indicators was made: meat tenderness, amino acid usefulness, nutrition value. The organoleptic examination showed the compliance of all samples with the standards, with the exception of one sample from the Sarzhal village. The study of the specific activity of 137 Cs showed a direct correlation between the category of radiation risk and the content of this radioisotope in meat from different zones. The availability of some deviations in the samples indicators obtained from the Sarzhal village indicates the need to approach the products control from this zone more carefully, and radioisotope analysis should become a decisive criterion in determining the safety profile of the product.

In-vivo dose determination in a human after radon exposure: proof of principle.

Radon-222 is pervasive in our environment and the second leading cause of lung cancer induction after smoking while it is simultaneously used to mediate anti-inflammatory effects. During exposure, radon gas distributes inhomogeneously in the body, making a spatially resolved dose quantification necessary to link physical exposure conditions with accompanying risks and beneficial effects. Current dose predictions rely on biokinetic models based on scarce input data from animal experiments and indirect exhalation measurements of a limited number of humans, which shows the need for further experimental verification. We present direct measurements of radon decay in the abdomen and thorax after inhalation as proof of principle in one patient. At both sites, most of the incorporated radon is removed within ~ 3 h, whereas a smaller fraction is retained longer and accounts for most of the deposited energy. The obtained absorbed dose values were [Formula: see text] µGy (abdomen, radon gas) and [Formula: see text] µGy (thorax, radon and progeny) for a one-hour reference exposure at a radon activity concentration of 55 kBq m-3. The accumulation of long-retained radon in the abdomen leads to higher dose values at that site than in the thorax. Contrasting prior work, our measurements are performed directly at specific body sites, i.e. thorax and abdomen, which allows for direct spatial distinction of radon kinetics in the body. They show more incorporated and retained radon than current approaches predict, suggesting higher doses. Although obtained only from one person, our data may thus represent a challenge for the barely experimentally benchmarked biokinetic dose assessment model.

Interpreting Quality Improvement When Introducing New Technology: A Collaborative Experience in ASD Device Closures.

The objective of this study was to evaluate the impact of the regular introduction of new technologies into interventional cardiac catheterization procedures, in this case new atrial septal defect (ASD) closure devices, while conducting a multi-center collaborative initiative to reduce radiation usage during all procedures. Data were collected prospectively by 8 C3PO institutions between January 1, 2014 and December 31, 2017 for ASD device closure procedures in the cardiac catheterization lab during a quality improvement (QI) initiative aimed at reducing patient radiation exposure. Radiation exposure was measured in dose area product per body weight (µGy*m2/kg). Use of proposed practice change strategies at the beginning and end of the QI intervention period was assessed. Radiation exposure was summarized by institution and by initial type of device used for closure. This study included 602 ASD device closures. Without changes in patient characteristics, total fluoroscopy duration, or number of digital acquisitions, median radiation exposure decreased from 37 DAP/kg to 14 DAP/kg from 2014 to 2017. While all individual centers decreased overall median DAP/kg, the use of novel devices for ASD closure correlated with a temporary period of worsening institutional radiation exposure and increased fluoroscopy time. The introduction of new ASD closure devices resulted in increased radiation exposure during a QI project designed to reduce radiation exposure. Therefore, outcome assessment must be contextualized in QI projects, hospital evaluation, and public reporting, to acknowledge the expected variation during innovation and introduction of novel therapies.

Communication of radiation risk from imaging studies: an IAEA-coordinated international survey.

The purpose of this IAEA-coordinated international study was to understand aspects related to the communication of radiation risk from imaging studies, such as how often imaging department personnel and referring physicians are asked about radiation risks in diagnostic imaging, who asks about these risks, how often professionals are able to provide satisfactory answers using qualitative metrics and how often quantitative risk estimates are needed. A web-based questionnaire with ten questions was completed by 386 healthcare professionals from 63 countries from all four continents, including clinicians/referring physicians (42.5%), radiologists or nuclear medicine physicians (26.7%), medical physicists (23.1%), radiographers/radiological technologists (6.2%) and others (1.6%). The results indicate that radiation risk-related questions are largely asked by patients (73.1%) and parents of child patients (38.6%), and 78% of the professionals believe they are able to answer those questions using qualitative metrics such as very small/minimal, small, medium rather than number of cancers likely occurring. The vast majority, with over three times higher frequency, indicated the purpose of knowing previous radiological exams as 'both clinical information and radiation exposure history' rather than 'only clinical information'. Nearly two-thirds of the clinicians/referring physicians indicated that knowing the radiation exposure history of the patient will affect their decision-making for the next exam, as against only about one-fifth who said 'no, it will not affect their decision-making'. The same question, when addressed to radiologists, resulted in a slightly larger fraction of about three-quarters who said 'yes', as opposed to a smaller fraction of about 12% who said 'no, it will not affect their decision-making'. Mapping the present situation of communication of benefits and risks for patients is important and may be the basis of further analysis, regular monitoring and possibly a target for clinical audits. Further studies focused on specific professional groups might help in obtaining á deeper understanding of the need for practical communication tools.

Assessment of extremity exposure to technologists working manually with99mTc-labelled radiopharmaceuticals and with an automatic injection system for18F-FDG.

The hands of nuclear medicine (NM) personnel involved in radiopharmaceutical preparation and administration can receive significant radiation doses. The dose distribution across the hand is nonuniform and the Hp(0.07) doses obtained by an individual passive ring dosimeter do not always present a real situation. The aim of this study was to assess the extremity exposure of NM workers working with99mTc-labelled radiopharmaceuticals and with an automatic IRIDE (COMECER, Italy)18F-FDG injection system. Hp(0.07) doses were measured using calibrated thermoluminescent dosimeters-100 (TLD-100) and were read by a RIALTO TLD (NE Technology) reader. It was found that the most exposed parts of the hand during work with18F and99mTc radionuclides are the fingertips of the thumb, index finger and middle finger. The maximum fingertip doses were 1.3-2.4 times higher compared with the doses from the typical monitoring position (base of the middle finger of the dominant hand). When working with99mTc, the average hand doses were relatively high, i.e. 0.17 ± 0.04 and 0.37 ± 0.13 mSv Gbq-1for the left and the right hand, respectively, during preparation, and 58 ± 20 and 53 ± 13µSv GBq-1for the left and the right hand, respectively, during administration of99mTc labelled radiopharmaceuticals. Meanwhile, the lowest doses were found for hands during administration of18F-FDG (average hand dose 28 ± 13µSv GBq-1for the left hand and 28 ± 7µSv GBq-1for the right hand), which shows the advantages of automated injection/infusion systems, thus implementation of automatic infusion/injection in hospitals could be an expedient way to optimize Hp(0.07) doses to NM workers.

What's better for our health? Conducting protective actions during a nuclear emergency or accepting a certain radiation dose?

The threat caused by ionising radiation has resulted in the establishment of strict radiation protection guidelines. This is especially true for severe nuclear power plant (NPP) accident scenarios, which may involve the release of significant amounts of ionising radiation. However, we believe that the fine balance between the benefit of a certain protective action (e.g. evacuation) and its risks is not always accounted for properly. Deaths and mental health problems have been associated with protective actions (e.g. evacuation) implemented in the response to the Fukushima Daiichi (NPP) accident in 2011. The protective actions were implemented consistent with international recommendations, to reduce radiation-induced health effects, even though the off-site effective doses were too low to indicate that there would be any discernible radiation-induced health effects. In this paper, we will provide a first step for the development of tools to evaluate the risk of protective actions versus the radiation-induced health risk. Over 50 papers were selected as useful from more than 600 reviewed papers to characterise the health impact of protective actions taken during different emergencies (including, technical and natural emergencies). An analysis was performed comparing the radiation-induced health effects averted by protective actions with the health effects associated with the protective actions. We concentrated our analysis on deaths and mental health problems associated with protective actions compared with the inferred radiation-induced deaths averted by the protective actions. Our analysis is stated in terms of absolute risk (cases per 1000) of health effects to allow for a direct comparison. It indicates that taking protective actions consistent with dose criteria typically used in many countries could result in more excess deaths than the inferred radiation-induced deaths prevented, as well as resulting in mental health problems. We identified that residents of facilities for long stays and the elderly are particularly vulnerable and a significant number of the deaths among the general public are associated with a lack of emergency preparedness provisions.

Radiation exposure and risk assessment to earthworms in areas contaminated with naturally occurring radionuclides.

The assessment of radiation exposure on biota is one of the main parts of environment protection system. Earthworms have been recognized as an important organism group in the terrestrial ecosystems. According to many researchers the potential risks of naturally occurring radionuclides for soil invertebrates were not significant because the exposure doses to the invertebrate populations were low. Our study aimed to assess the radiation exposure and the radiological risks from naturally occurring radionuclides for earthworm populations at four sites. This research was based on three dosimetric approaches simultaneously: ERICA and RESRAD-BIOTA-the commonly used ones, and also on the original method proposed by Thomas and Liber (Environment International, 27, 341-353, 2001) for aquatic organisms. To calculate radiation dose rates to soil invertebrates inhabiting background and contaminated areas, the specific activities of radionuclides in soil, and, depending on the model, the default, or determined in this study, input mass-geometric parameters had been applied. The weighted absorbed dose rates calculated by different models and site-specific data were 0.3-1.4 µGy/h for the background and from 3.4 to 170 µGy/h for the contaminated sites. Analysis of radiation risks for earthworms indicated that 226Ra was the key contributor to the external dose rate; 226Ra and 210Po played a dominant role in formation of internal dose rate for radioecological situations in our study. More conservative radiation risk assessments were derived from RESRAD-BIOTA tool. Dose assessments obtained using various models had shown that there are real environmental situations in which the radiological risks to reference organisms are significantly higher than the lowest benchmark protection level proposed for ecosystems.

A software tool for organ-specific second cancer risk assessment from exposure to therapeutic doses.

The aim of this study was the development of a software tool (SCRcalc) for the automatic estimation of the patient- and organ-specific cancer risk due to radiotherapy. SCRcalc was developed using the Python 3.8.7 programming language. It incorporates equations and parameters of mechanistic models for the calculation of the organ equivalent dose (OED), the excess absolute risk (EA R) and the lifetime attributable risk (LA R) of carcinogenesis for various organs due to radiotherapy. Data from differential dose-volume histograms, as defined by a treatment planning system, could be automatically inserted into the program. Eighteen different cancer risk estimates for various organs were performed of patients subjected to radiation therapy with conventional and modulated techniques. These software estimates were compared with manual calculations. SCRcalc was developed as a standalone executable program without any dependencies. It enables direct estimations of the OED and LAR for various organs at risk. An important aspect of the software is that it does not require pre-processing of the DVH data. No differences were found between the SCRcalc results and those derived from manual calculations. The newly developed software offers the possibility to medical physicists and radiation oncologists to directly estimate the probability of radiotherapy-induced secondary malignancies for various organs at risk.

Mortality among individuals exposed to atomic bomb radiation in utero: 1950-2012.

We examined the mortality risks among 2463 individuals who were exposed in utero to atomic bomb radiation in Hiroshima or Nagasaki in August 1945 and were followed from October 1950 through 2012. Individual estimates of mother's weighted absorbed uterine dose (DS02R1) were used. Poisson regression method was used to estimate the radiation-associated excess relative risk per Gy (ERR/Gy) and 95% confidence intervals (CI) for cause-specific mortality. Head size, birth weight, and parents' survival status were evaluated as potential mediators of radiation effect. There were 339 deaths (216 males and 123 females) including deaths from solid cancer (n = 137), lymphohematopoietic cancer (n = 8), noncancer disease (n = 134), external cause (n = 56), and unknown cause (n = 4). Among males, the unadjusted ERR/Gy (95% CI) was increased for noncancer disease mortality (1.22, 0.10-3.14), but not for solid cancer mortality (- 0.18, < - 0.77-0.95); the unadjusted ERR/Gy for external cause mortality was not statistically significant (0.28, < - 0.60-2.36). Among females, the unadjusted ERRs/Gy were increased for solid cancer (2.24, 0.44-5.58), noncancer (2.86, 0.56-7.64), and external cause mortality (2.57, 0.20-9.19). The ERRs/Gy adjusted for potential mediators did not change appreciably for solid cancer mortality, but decreased notably for noncancer mortality (0.39, < - 0.43-1.91 for males; 1.48, - 0.046-4.55 for females) and external cause mortality (0.10, < - 0.57-1.96 for males; 1.38, < - 0.46-5.95 for females). In conclusion, antenatal radiation exposure is a consistent risk factor for increased solid cancer mortality among females, but not among males. The effect of exposure to atomic bomb radiation on noncancer disease and external cause mortality among individuals exposed in utero was mediated through small head size, low birth weight, and parental loss.

Reduction of radiations exposure in endodontics: comparative analysis of direct (GX S-700, Gendex) and semidirect (VistaScan Mini View, Dürr) digital systems.

The importance of intraoral periapical radiography is crucial as it represents a fundamental mean of evaluation and diagnosis for supporting bone and teeth hard tissues diseases and pathologies. Even though conventional film technology is still widespread, presently there are many digital radiography alternatives. Direct digital systems are devices with an intraoral sensor wired or paired wireless with a computer. These devices do generate an image immediately during exposure and acquisition. The semi direct digital systems instead are based on phosphor image plates. Digital radiography offers many chances to improve our patient's healthcare standards reducing exposition to X-rays and the related stochastic radiation risk. Aim of this study is to compare the quality of images for endodontic purposes comparing three systems: conventional films, direct digital radiography and semidirect digital radiography.

Estimating long-term health risks after breast cancer radiotherapy: merging evidence from low and high doses.

In breast cancer radiotherapy, substantial radiation exposure of organs other than the treated breast cannot be avoided, potentially inducing second primary cancer or heart disease. While distant organs and large parts of nearby ones receive doses in the mGy-Gy range, small parts of the heart, lung and bone marrow often receive doses as high as 50 Gy. Contemporary treatment planning allows for considerable flexibility in the distribution of this exposure. To optimise treatment with regards to long-term health risks, evidence-based risk estimates are required for the entire broad range of exposures. Here, we thus propose an approach that combines data from medical and epidemiological studies with different exposure conditions. Approximating cancer induction as a local process, we estimate organ cancer risks by integrating organ-specific dose-response relationships over the organ dose distributions. For highly exposed organ parts, specific high-dose risk models based on studies with medical exposure are applied. For organs or their parts receiving relatively low doses, established dose-response models based on radiation-epidemiological data are used. Joining the models in the intermediate dose range leads to a combined, in general non-linear, dose response supported by data over the whole relevant dose range. For heart diseases, a linear model consistent with high- and low-dose studies is presented. The resulting estimates of long-term health risks are largely compatible with rate ratios observed in randomised breast cancer radiotherapy trials. The risk models have been implemented in a software tool PASSOS that estimates long-term risks for individual breast cancer patients.

A bespoke health risk assessment methodology for the radiation protection of astronauts.

An alternative approach that is particularly suitable for the radiation health risk assessment (HRA) of astronauts is presented. The quantity, Radiation Attributed Decrease of Survival (RADS), representing the cumulative decrease in the unknown survival curve at a certain attained age, due to the radiation exposure at an earlier age, forms the basis for this alternative approach. Results are provided for all solid cancer plus leukemia incidence RADS from estimated doses from theoretical radiation exposures accumulated during long-term missions to the Moon or Mars. For example, it is shown that a 1000-day Mars exploration mission with a hypothetical mission effective dose of 1.07 Sv at typical astronaut ages around 40 years old, will result in the probability of surviving free of all types of solid cancer and leukemia until retirement age (65 years) being reduced by 4.2% (95% CI 3.2; 5.3) for males and 5.8% (95% CI 4.8; 7.0) for females. RADS dose-responses are given, for the outcomes for incidence of all solid cancer, leukemia, lung and female breast cancer. Results showing how RADS varies with age at exposure, attained age and other factors are also presented. The advantages of this alternative approach, over currently applied methodologies for the long-term radiation protection of astronauts after mission exposures, are presented with example calculations applicable to European astronaut occupational HRA. Some tentative suggestions for new types of occupational risk limits for space missions are given while acknowledging that the setting of astronaut radiation-related risk limits will ultimately be decided by the Space Agencies. Suggestions are provided for further work which builds on and extends this new HRA approach, e.g., by eventually including non-cancer effects and detailed space dosimetry.

Communicating radiation risk: the role of public engagement in reaching ALARA.

The ALARA (an acronym for 'as low as reasonably achievable') principle, keeping the likelihood of incurring exposure, the number of people exposed and the magnitude of their individual doses 'as low as reasonably achievable, taking into account economic and societal factors', is at the core of radiation protection. For many decades the principle has been an area of continuous development, with recent work highlighting the importance of engaging not only with the decision-makers in the ALARA process but all stakeholders who may incur an exposure. This paper considers a particular case study in which the dredging of non-hazardous sediment in the United Kingdom near a now decommissioned nuclear power station raised substantial public concern about radiological exposure. This turned what was a straightforward construction activity into a complex public engagement and reassurance task, at a significant cost disproportionate to the level of radiological risk. This paper highlights the key lessons learnt from the case study, including not only the importance of engaging the public as part of the ALARA process but also of considering the societal impact arising from stress and concerns if misinformation is allowed to promulgate. A discussion is included on the need to underpin any engagement with a clear plan, including pre-engagement, implementation and reinforcement of messages. In addition, the role of the radiation protection professional is considered in ensuring that all stakeholders are informed, so that ultimately they can come to their own decision on what is safe.

IRPA practical guidance for engagement with the public on radiation and risk.

The International Radiation Protection Association, IRPA, promotes the worldwide enhancement of professional competence, radiation protection (RP) culture and practice by providing benchmarks of good practice, as well as encouraging the application of the highest standards of professional conduct, skills and knowledge for the benefit of individuals and society. Enhancing public understanding of radiation and risk is highlighted by experiences from past emergencies, including the accident at Tokyo Electric Power Company's (TEPCO) Fukushima Daiichi Nuclear Power Plant in 2011 and the following post-disaster recovery, as one of the most important challenges, and this challenge is common across almost all public interfaces regarding radiation and risk. To this end IRPA has been continuing a Task Group activity for Public Understanding since 2013. After a series of workshops in various regions of the world, the IRPA draft guidance was developed and issued for consultation of the Associate Societies in 2019. Through these processes, IRPA received a lot of helpful comments and suggestions. IRPA finally published 'Practical Guidance for Engagement with the Public on Radiation and Risk' on the IRPA website in October 2020. The objective of the guidance is two-fold. Firstly, it is to enthuse all of us in our profession to become more active public advocates for RP. Secondly, it is to provide information, experiences and techniques to help us to become more effective and comfortable in this challenging task. This paper provides a key summary of the published IRPA guidance.

Referring physician perspective on how to handle frequent use of CT imaging.

The increasing use of computed tomography (CT) and other relatively high radiation dose exams in a recurrent manner result in radiation risks to individual patients. Recent studies have provided alarming information not only to the radiological community but also to referring physicians. We, as referring physicians, are often implicated in the overuse of imaging. However, a recent paper rightfully summarized the situation that despite the best use of available clinical decision support system for prescribing an imaging exam at a major hospital in the USA, many patients were found to have high cumulative doses. Motivated by the cue provided by the paper in this very journal, we decided to come forward with a possible solution taking the example of the drug prescription system that we routinely use. We provide a template to translate prescription drug monitoring program to ionising radiation imaging. We suggest that all body CT exams should be monitored at an individual, prescriber, and institution level for frequency of use. Furthermore, there should be radiation risk stratification of an individual patient based on the cumulative radiation burden in recent years. Further, an individual's radiation risk-stratified in different risk levels should be available for use by the referring/ordering clinicians at the point of care. Finally, we feel distanced by the use of multiple scary radiation dose quantities in different imaging modalities and would prefer as simple a metric as 'milligram.'

Review of engagement activities to promote awareness of radiation and its associated risk amongst the Japanese public before and after the Fukushima Daiichi Nuclear Power Plant accident.

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, many radiation experts directly experienced a vast gap between ideal and real public understanding (PU) of radiation in risk communication. Therefore, this study collated and reviewed information about PU activities for radiation and its risk that six Japanese academic societies-which seem to be socially neutral expert communities-related to radiation and radiation risk conducted before and after the accident. Activities these radiation-related societies provided to the general public were discussed from the following perspectives: (a) difficulties in two-way communication due to resources, motivation and public interest and concerns; (b) balance between academic research and PU activities; (c) academic societies' building trust with the public while ensuring member experts' neutrality and independence; and (d) discussions among academic societies to prepare for public engagement. We hope that this paper encourages experts and academic societies in radiation protection to hold more national and international discussions about their roles in public communication and outreach.

Let Chromosomes Speak: The Cytogenetics Project at the Atomic Bomb Casualty Commission (ABCC).

Hibakusha (atomic bomb survivors) are "witnesses" of the atomic bombings, not just in a standard sense but also in the instrumental sense. For medical and scientific experts, hibakusha are biological resources of unparalleled scientific value. Over the past seventy years, the hibakusha bodies have narrated what it means to be exposed to radiation. In this paper, I explore studies at the Atomic Bomb Casualty Commission (ABCC) that examined hibakusha bodies as sites where risk could be read. I focus on a period from the mid-1950s to 1975, during which new methods, practices, and technologies allowed ABCC scientists to investigate chromosomes as a way to study radiation exposure and human risk. By focusing on chromosomal aberrations, ABCC scientists connected their work directly to the emerging infrastructure for radiobiology at the time. ABCC administrators actively sought out such prestige, especially given their relationship with the Atomic Energy Commission (AEC). The shift in approach would also alleviate some public relations problems with which the institution was struggling. Launching a cytogenetics program required some older practices that had assumed American privilege and dominance to be abandoned. Eventually, the decision to let chromosomes speak of radiation exposure brought about fundamental changes in ABCC, which came to symbolize the model for future studies at the organization, especially as ABCC was transitioning to a US-Japan binational organization. More broadly, this case highlights the intricate scientific negotiation of radiation risk where uncertainties necessarily prevail.