Studies of the mortality of atomic bomb survivors, Report 14, 1950-2003: an overview of cancer and noncancer diseases

Comparison of All Solid Cancer Mortality and Incidence Dose-Response in the Life Span Study of Atomic Bomb Survivors, 1958-2009

Recent analysis of all solid cancer incidence (1958-2009) in the Life Span Study (LSS) revealed evidence of upward curvature in the radiation dose response among males but not females. Upward curvature in sex-averaged excess relative risk (ERR) for all solid cancer mortality (1950-2003) was also observed in the 0-2 Gy dose range. As reasons for non-linearity in the LSS are not completely understood, we conducted dose-response analyses for all solid cancer mortality and incidence applying similar methods [1958-2009 follow-up, DS02R1 doses, including subjects not-in-city (NIC) at the time of the bombing] and statistical models. Incident cancers were ascertained from Hiroshima and Nagasaki cancer registries, while cause of death was ascertained from death certificates throughout Japan. The study included 105,444 LSS subjects who were alive and not known to have cancer before January 1, 1958 (80,205 with dose estimates and 25,239 NIC subjects). Between 1958 and 2009, there were 3.1 million person-years (PY) and 22,538 solid cancers for incidence analysis and 3.8 million PY and 15,419 solid cancer deaths for mortality analysis. We fitted sex-specific ERR models adjusted for smoking to both types of data. Over the entire range of doses, solid cancer mortality dose-response exhibited a borderline significant upward curvature among males (P = 0.062) and significant upward curvature among females (P = 0.010); for solid cancer incidence, as before, we found a significant upward curvature among males (P = 0.001) but not among females (P = 0.624). The sex difference in magnitude of dose-response curvature was statistically significant for cancer incidence (P = 0.017) but not for cancer mortality (P = 0.781). The results of analyses in the 0-2 Gy range and restricted lower dose ranges generally supported inferences made about the sex-specific dose-response shape over the entire range of doses for each outcome. Patterns of sex-specific curvature by calendar period (1958-1987 vs. 1988-2009) and age at exposure (0-19 vs. 20-83) varied between mortality and incidence data, particularly among females, although for each outcome there was an indication of curvature among 0-19-year-old male survivors in both calendar periods and among 0-19-year-old female survivors in the recent period. Collectively, our findings indicate that the upward curvature in all solid cancer dose response in the LSS is neither specific to males nor to incidence data; its evidence appears to depend on the composition of sites comprising all solid cancer group and age at exposure or time. Further follow up and site-specific analyses of cancer mortality and incidence will be important to confirm the emerging trend in dose-response curvature among young survivors and unveil the contributing factors and sites.

Modulation of Secondary Cancer Risks from Radiation Exposure by Sex, Age and Gonadal Hormone Status: Progress, Opportunities and Challenges

Available data on cancer secondary to ionizing radiation consistently show an excess (2-fold amount) of radiation-attributable solid tumors in women relative to men. This excess risk varies by organ and age, with the largest sex differences (6- to more than 10-fold) found in female thyroid and breasts exposed between birth until menopause (~50 years old) relative to age-matched males. Studies in humans and animals also show large changes in cell proliferation rates, radiotracer accumulation and target density in female reproductive organs, breast, thyroid and brain in conjunction with physiological changes in gonadal hormones during the menstrual cycle, puberty, lactation and menopause. These sex differences and hormonal effects present challenges as well as opportunities to personalize radiation-based treatment and diagnostic paradigms so as to optimize the risk/benefit ratios in radiation-based cancer therapy and diagnosis. Specifically, Targeted Radionuclide Therapy (TRT) is a fast-expanding cancer treatment modality utilizing radiopharmaceuticals with high avidity to specific molecular tumor markers, many of which are influenced by sex and gonadal hormone status. However, past and present dosimetry studies of TRT agents do not stratify results by sex and hormonal environment. We conclude that cancer management using ionizing radiation should be personalized and informed by the patient sex, age and hormonal status.

Incidence of Diabetes in the Atomic Bomb Survivors: 1969-2015

CONTEXT

Recent epidemiological studies have shown increased risk of diabetes among childhood cancer survivors who received high therapeutic doses of radiation, particularly to the total body or to the abdomen. However, the effect of low-to-moderate dose radiation (<4 Gy) on the risk of diabetes is still unknown.

OBJECTIVES

To investigate the radiation effect on diabetes incidence among atomic bomb (A-bomb) survivors, and whether the dose response is modified by other factors including city, sex, and age at time of bombing (ATB).

METHODS

9131 participants without diabetes at baseline were observed through biennial clinical exams from 1969 to 2015. A Cox proportional hazards model was used to estimate hazard ratios (HR) to evaluate the dose response for diabetes incidence.

RESULTS

During the study period, 1417 incident diabetes cases were identified. The overall crude incidence rate was 7.01/103 person-years. Radiation dose was significantly associated with diabetes incidence, with effect modification by city and age ATB. In Hiroshima, at ages 10 and 30 ATB, the HRs at 1 Gy of pancreatic radiation dose were 1.47 (95% CI, 1.31-1.66) and 1.13 (95% CI, 0.97-1.31), respectively. However, no significant radiation dose response was observed at these ages in Nagasaki. The HR for radiation dose was higher among those who were younger ATB and decreased 1% for each additional year of age.

CONCLUSIONS

Among A-bomb survivors, a radiation association was suggested for incidence of diabetes. Results were inconsistent by city and age ATB, which could indicate potential confounding of the radiation association with diabetes.

A Risk Comparison between Lifestyle, Socioeconomic Status, and Radiation: A Cohort Study of Cancer Mortality among Japanese Nuclear Workers (J-EPISODE)

ABSTRACT

The health effects of low-dose radiation exposure have been a source of controversy. One possible reason is that epidemiological studies that compare radiation risk with other factors, such as lifestyle or socioeconomic status, have been limited. The aim of this study is to conduct a comparison of the cancer risk of mortality between radiation, lifestyle habits (such as smoking), and socioeconomic status (such as years of education) among Japanese nuclear workers. We assembled a cohort of 41,742 male nuclear workers in Japan who answered a lifestyle questionnaire survey conducted during 2003-2004. To exclude systematic errors caused by missing values, we used multiple imputation and Poisson regression to estimate relative risks and confidence intervals for lifestyle habits, socioeconomic status, and radiation. The total person-y from 2005 to 2010 were 215,000. The mean age and cumulative dose were 54.9 y and 24.8 mSv (10-y lagged dose), respectively. Significantly high relative risks were determined for smoking, alcohol consumption, frequency of medical examination, breakfast intake, sleep, and body mass index. Further, significantly high relative risks of radiation were shown for lung cancer and smoking-related cancers. Since the simultaneous inclusion of radiation and non-radiation variables in the model for relative risk (RR) calculation means that the calculated radiation RR is the result of adjustment by other variables, the risk of cancer from low-dose radiation, if any, is less than smoking and probably less than other lifestyle factors.

Association between body mass index and oesophageal cancer mortality: a pooled analysis of prospective cohort studies with >800 000 individuals in the Asia Cohort Consortium

BACKGROUND

The association between body mass index (BMI) and oesophageal cancer (OC) has been consistently negative among Asians, whereas different associations based on histological OC subtypes have been observed in Europeans and North Americans. We examined the association between BMI and OC mortality in the Asia Cohort Consortium.

METHODS

We performed a pooled analysis to evaluate the association between BMI and OC mortality among 842 630 Asians from 18 cohort studies. Cox regression models were used to estimate hazard ratios (HRs) and 95% CIs.

RESULTS

A wide J-shaped association between BMI and overall OC mortality was observed. The OC mortality risk was increased for underweight (BMI <18.5 kg/m2: HR = 2.20, 95% CI 1.80-2.70) and extreme obesity (BMI ≥35 kg/m2: HR = 4.38, 95% CI 2.25-8.52) relative to the reference BMI (23-25 kg/m2). This association pattern was confirmed by several alternative analyses based on OC incidence and meta-analysis. A similar wide J-shaped association was observed in oesophageal squamous cell carcinoma (OSCC). Smoking and alcohol synergistically increased the OC mortality risk in underweight participants (HR = 6.96, 95% CI 4.54-10.67) relative to that in reference BMI participants not exposed to smoking and alcohol.

CONCLUSION

Extreme obesity and being underweight were associated with an OC mortality risk among Asians. OC mortality and BMI formed a wide J-shaped association mirrored by OSCC mortality. Although the effect of BMI on OSCC and oesophageal adenocarcinoma mortality can be different in Asians, further research based on a large case-control study is recommended.

Dose Limits and Countermeasures for Mitigating Radiation Risk in Moon and Mars Exploration

After decades of research on low-Earth orbit, national space agencies and private entrepreneurs are investing in exploration of the Solar system. The main health risk for human space exploration is late toxicity caused by exposure to cosmic rays. On Earth, the exposure of radiation workers is regulated by dose limits and mitigated by shielding and reducing exposure times. For space travel, different international space agencies adopt different limits, recently modified as reviewed in this paper. Shielding and reduced transit time are currently the only practical solutions to maintain acceptable risks in deep space missions.

Lung Cancer Screening with Low-Dose CT: Radiation Risk and Benefit-Risk Assessment for Different Screening Scenarios

Lung cancer is a severe disease that affects predominantly smokers and represents a leading cause of cancer death in Europe. Recent meta-analyses of randomized controlled trials (RCTs) have yielded that low-dose computed tomography (LDCT) screening can significantly reduce lung cancer mortality in heavy smokers or ex-smokers by about 20% compared to a control group of persons who did not receive LDCT. This benefit must be weighed against adverse health effects associated with LDCT lung screening, in particular radiation risks. For this purpose, representative organ doses were determined for a volume CT dose index of 1 mGy that can be achieved on modern devices. Using these values, radiation risks were estimated for different screening scenarios by means of sex-, organ-, and age-dependent radio-epidemiologic models. In particular, the approach was adjusted to a Western European population. For an annual LDCT screening of (ex-)smokers aged between 50 and 75 years, the estimated radiation-related lifetime attributable risk to develop cancer is below 0.25% for women and about 0.1% for men. Assuming a mortality reduction of about 20% and taking only radiation risks into account, this screening scenario results in a benefit–risk ratio of about 10 for women and about 25 for men. These benefit–risk ratio estimates are based on the results of RCTs of the highest evidence level. To ensure that the benefit outweighs the radiation risk even in standard healthcare, strict conditions and requirements must be established for the entire screening process to achieve a quality level at least as high as that of the considered RCTs.

Reanalysis of cancer mortality using reconstructed organ-absorbed dose: J-EPISODE 1991‒2010

The Japanese Epidemiological Study on Low-Dose Radiation Effects (J-EPISODE) has been conducted since 1990 by the Radiation Effects Association to analyse health effects for nuclear workers. It uses the recorded doses, i.e. dosimeter readings, evaluated inH_p(10) for estimation of radiation risk; however, the International Commission on Radiological Protection does not recommend the use of effective doses for epidemiological evaluation and instead recommends the use of organ-absorbed doses for assessing cancer risk. Recently, the J-EPISODE has developed a conversion factor that can convert dosimeter readings to organ-absorbed doses following, in principle, the approach adopted by the International Agency for Research on Cancer 15-Country Collaborative Study. The approach was modified based on recent dosimeter usage practices and the Japanese physique. The aim of this study was to reanalyse the excess relative risk (ERR) of cancer mortality for the J-EPISODE using the previous analysis method but substituting the organ-absorbed dose for the recorded dose to confirm the adaptability and relevance of organ-absorbed doses for the J-EPISODE. The organ-absorbed doses from 1957 to 2010 were reconstructed for the whole cohort. The cancer mortality risk was reanalysed with Poisson regression methods, first by comparing the ERR/Gy for all cancers excluding leukaemia with the risk after excluding lung cancer for the whole cohort of 204 103 participants. In the whole cohort, all cancers excluding leukaemia, lung cancer and non-Hodgkin's lymphoma had statistically significant positive ERR/Gy estimates; leukaemia excluding chronic lymphocytic leukaemia had negative but not statistically significant estimates. Gallbladder cancer and pancreatic cancer showed statistically significant negative. Then, a subcohort of 71 733 respondents was selected based on lifestyle surveys with data on qualitative smoking status as well as quantitative smoking information on pack-years. Pack-years for current smokers and former smokers and years since the cessation of smoking for former smokers were used for the smoking-adjusted model. The most important feature of the J-EPISODE revealed to date was a decreasing tendency of the ERR/Sv by the smoking adjustment. For almost all causes of death such as lung cancer and stomach cancer, the estimated ERR/Gy decreased by the smoking adjustment, although those for the colon, prostate and kidney and other urinary organs were almost the same after the adjustment. This tendency remained unchanged even when using the organ-absorbed dose, indicating the appropriateness of using organ-absorbed doses for further risk analysis. At the same time, it indicated that confounding by smoking seriously biased the radiation risk estimates in the J-EPISODE and thus should be accounted even if organ dose is used.

Radiation risks of lymphoma and multiple myeloma incidence in the updated NRRW-3 cohort in the UK: 1955-2011

The effect of external radiation on lymphoma, including non-Hodgkin lymphoma (NHL), Hodgkin lymphoma (HL) and multiple myeloma (MM) incidence was evaluated in the National Registry for Radiation Workers based upon the third analysis cohort but with an additional 10 years of follow-up. The study includes 172 452 workers, of whom (90%) were men with 5.25 million person-years of follow-up from 1955 through to the end of 2011. A total of 711 cases of NHL, 113 cases of HL and 279 cases of MM were registered. Poisson regression was used to estimate the excess relative risk per unit of cumulative exposure to ionising radiation. A statistically significant association was found between radiation dose and the incidence of NHL and MM. There was no evidence of radiation associated excess risk for HL. The reported associations are based on a very small proportion of exposed workers, in particular among workers with cumulative doses above 0.5 Sv so should be treated with caution, further investigations are necessary to confirm our results.

Environmental Risk Factors for Childhood Acute Lymphoblastic Leukemia: An Umbrella Review

Leukemia is the most common type of cancer among children and adolescents worldwide. The aim of this umbrella review was (1) to provide a synthesis of the environmental risk factors for the onset of childhood acute lymphoblastic leukemia (ALL) by exposure window, (2) evaluate their strength of evidence and magnitude of risk, and as an example (3) estimate the prevalence in the German population, which determines the relevance at the population level. Relevant systematic reviews and pooled analyses were identified and retrieved through PubMed, Web of Science databases and lists of references. Only two risk factors (low doses of ionizing radiation in early childhood and general pesticide exposure during maternal preconception/pregnancy) were convincingly associated with childhood ALL. Other risk factors including extremely low frequency electromagnetic field (ELF-MF), living in proximity to nuclear facilities, petroleum, benzene, solvent, and domestic paint exposure during early childhood, all showed some level of evidence of association. Maternal consumption of coffee (high consumption/>2 cups/day) and cola (high consumption) during pregnancy, paternal smoking during the pregnancy of the index child, maternal intake of fertility treatment, high birth weight (≥4000 g) and caesarean delivery were also found to have some level of evidence of association. Maternal folic acid and vitamins intake, breastfeeding (≥6 months) and day-care attendance, were inversely associated with childhood ALL with some evidence. The results of this umbrella review should be interpreted with caution; as the evidence stems almost exclusively from case-control studies, where selection and recall bias are potential concerns, and whether the empirically observed association reflect causal relationships remains an open question. Hence, improved exposure assessment methods including accurate and reliable measurement, probing questions and better interview techniques are required to establish causative risk factors of childhood leukemia, which is needed for the ultimate goal of primary prevention.

Incidence of lymphoid neoplasms among atomic bomb survivors by histological subtype, 1950 to 1994

Epidemiological data have provided limited and inconsistent evidence on the relationship between radiation exposure and lymphoid neoplasms. We classified 553 lymphoid neoplasm cases diagnosed between 1950 and 1994 in the Life Span Study cohort of atomic bomb survivors into World Health Organization subtypes. Mature B-cell neoplasms represented 58%, mature T-cell and natural killer (NK)-cell neoplasms 20%, precursor cell neoplasms 5%, and Hodgkin lymphoma (HL) 3%, with the remaining 15% classified as non-Hodgkin lymphoid (NHL) neoplasms or lymphoid neoplasms not otherwise specified. We used Poisson regression methods to assess the relationship between radiation exposure and the more common subtypes. As in earlier reports, a significant dose response for NHL neoplasms as a group was seen for males but not females. However, subtype analyses showed that radiation dose was strongly associated with increased precursor cell neoplasms rates, with an estimated excess relative risk per Gy of 16 (95% Confidence interval: 7.0, >533) at age 50. The current data based primarily of tissue-based diagnoses suggest that the association between radiation dose and lymphoid neoplasms as a group is largely driven by the radiation effect on precursor cell neoplasms while presenting no evidence of a radiation dose response for major categories of mature cell neoplasms, either B- or T-/NK-cell, or more specific disease entities (diffuse large B-cell lymphoma, plasma cell myeloma, adult T-cell leukemia/lymphoma) or HL.

Lead-rubber shielding effect on radiation dose to the gonads from a bilateral hand X-ray examination

INTRODUCTION

Recent guidance from the British Institute of Radiology (BIR) and the American Association of Physicists in Medicine (AAPM) focuses on cessation of patient Lead-rubber (Pb) shielding placed within the Field of View (FOV) that may influence image exposure or quality. Furthermore, the BIR assert shielding organs greater than 5 cm from the primary X-ray beam will have a negligible effect to the received radiation dose. Bilateral hand X-rays are frequently and repeatedly requested for the diagnosis and ongoing management of arthritic conditions. There is a lack of literature regarding the effect of Pb shielding during bilateral hand X-ray examinations. This research aimed to investigate the scattered secondary radiation dose to the gonads during a bilateral hand X-ray, with and without the use of Pb shielding outside the FOV at a greater distance than 5 cm from the primary beam.

METHODS

Using an anthropomorphic phantom and constructed upper limbs, radiation was recorded to the male and female gonads. Thermoluminescent dosimeters (TLD's) (⅛" x ⅛" x 0.15″ TLD-100H) were placed in groups of three upon the testes and within the left and right ovary to record the ionising radiation dose. Three collimated exposures were completed using a standard clinical practice hand X-ray protocol of 60 kVp and 2.5 mAs with a source to image distance (SID) of 100 cm. The mean and standard deviation of the radiation dose was calculated for both with and without Pb shielding. A paired two-sample t-test was conducted to determine statistical significance (p ≤ 0.05).

RESULTS

Data analysis demonstrated dose measured to the testes of 5.3 μGy (SD 0.8) without Pb shielding and 2.3 μGy (SD 0.2) with Pb (reduction of 3 μGy; 56.6%). Left ovary doses measured 40.6 μGy (SD 1.2) without Pb shielding and 28.8 μGy (SD 1.7) with Pb (reduction of 11.9 μGy; 29.2%) and right ovary doses measured 39.5 μGy (SD 1.9) without Pb shielding and 26.6 μGy (SD 1.0) with Pb (reduction of 12.8 μGy; 32.4%). The paired two-sample t-test presented a statistically significant dose reduction (p = 0.0039).

CONCLUSION

The study demonstrated dose limitation from scattered secondary radiation to the gonads when Pb shielding was used during a bilateral hand X-ray at distances greater than 5 cm from the primary X-ray beam on anatomy outside the FOV.

IMPLICATIONS FOR PRACTICE

The use of Pb shielding over the gonad area during a bilateral hand X-ray examination aligns to ALARP best practice and provides prospects for patient (male and female) dose reduction.

Should I irradiate with computed tomography or sedate for magnetic resonance imaging?

In the context of pediatric cross-sectional imaging, the risk of ionizing radiation for CT and the potential adverse effects associated with sedation/anesthesia for MRI continue to provoke lively discussions in the pediatric literature and lay press. This is particularly true for issues relating to the risks of ionizing radiation for CT, which has been a topic of discussion for nearly two decades. In addition to understanding these potential risks and the importance of minimizing individual pediatric patient exposure to ionizing radiation, it is equally important for radiologists to be able to frame these risks with respect to the potential for adverse outcomes associated with the use of anesthesia for cross-sectional imaging in the pediatric population. Notably, before such risks can be estimated and compared, one should always consider the potential utility of each imaging modality for a given diagnosis. If one cross-sectional imaging modality is likely to be far superior to the other for a specific clinical question, every effort must be made to safely image the child, even if sedation/anesthesia is required.

Cancer risk following low doses of ionising radiation - Current epidemiological evidence and implications for radiological protection

Recent studies suggest that every year worldwide about a million patients might be exposed to doses of the order of 100 mGy of low-LET radiation, due to recurrent application of radioimaging procedures. This paper presents a synthesis of recent epidemiological evidence on radiation-related cancer risks from low-LET radiation doses of this magnitude. Evidence from pooled analyses and meta-analyses also involving epidemiological studies that, individually, do not find statistically significant radiation-related cancer risks is reviewed, and evidence from additional and more recent epidemiological studies of radiation exposures indicating excess cancer risks is also summarized. Cohorts discussed in the present paper include Japanese atomic bomb survivors, nuclear workers, patients exposed for medical purposes, and populations exposed environmentally to natural background radiation or radioactive contamination. Taken together, the overall evidence summarized here is based on studies including several million individuals, many of them followed-up for more than half a century. In summary, substantial evidence was found from epidemiological studies of exposed groups of humans that ionizing radiation causes cancer at acute and protracted doses above 100 mGy, and growing evidence for doses below 100 mGy. The significant radiation-related solid cancer risks observed at doses of several 100 mGy of protracted exposures (observed, for example, among nuclear workers) demonstrate that doses accumulated over many years at low dose rates do cause stochastic health effects. On this basis, it can be concluded that doses of the order of 100 mGy from recurrent application of medical imaging procedures involving ionizing radiation are of concern, from the viewpoint of radiological protection.

Association between occupational testicular radiation exposure and lower male sex ratio of offspring among orthopedic surgeons

Background

Exposure to occupational radiation can lower the male sex ratio. However, specific radiation exposure to the testes has not been evaluated.

Objective

This study aimed to examine the association between testicular radiation exposure and lower male sex ratio in children.

Methods

A comprehensive questionnaire survey was administered to 62 full-time male doctors with children aged < 10 years at 5 hospitals. Based on the possibility of testicular radiation exposure 1 year before the child’s birth, participants were assigned to 3 groups as follows: RT (orthopedic surgery), RNT (cardiology/neurosurgery), and N (others). Intergroup differences in the proportion of female children were ascertained, and the female sex ratio (number of female/total number) of each group was compared against the standard value of 0.486. Multivariate logistic regression analysis with a generalized estimating equation was used to model the effects on the probability of female birth while controlling for the correlation among the same fathers.

Results

The study population included 62 fathers and 109 children, 49 were female: 19/27, 11/30, and 19/52 in the RT, RNT, and N group, respectively; the RT group had the highest proportion of females (p = 0.009). The p values for comparisons with the standard sex ratio (0.486) were 0.02, 0.19, and 0.08 for the RT, RNT, and N groups, respectively. Based on the N group, the adjusted odds ratios for the child to be female were 4.40 (95% confidence interval 1.60–2.48) and 1.03 (0.40–2.61) for the RT and RNT groups, respectively.

Conclusions

Our results imply an association between testicular radiation exposure and low male sex ratio of offspring. Confirmatory evidence is needed from larger studies which measure the pre-conceptional doses accumulated in various temporal periods, separating out spermatogonial and spermatid effects.

First Steps towards a National Approach for Radon Survey in Romanian Schools

Schools are a category of public buildings with a high radon exposure risk, due to their high occupancy factor. In Romania, the elaboration of a methodology for radon measurements in schools is a necessity imposed both by the European legislation and by the relatively high percentage (about 10%) of the mapped territory with a potential increased risk of exposure to the action of ionizing radiation emitted by radon. In order to optimize the design of a national survey aimed to evaluate radon exposure of children in Romanian schools, we conducted a pilot study in two schools in Cluj-Napoca, following the screening measurements carried out in 109 schools and kindergartens from five counties. The specific steps that must be followed were described, taking into account the international protocols and particularities of Romanian territory. The proposed approach could act as a guide for other large buildings and is implicit for the implementation of National Radon Action Plan, approved by HG no. 526/12 July 2018 in accordance with Council Directive 2013/59/EURATOM. The obtained results indicate that a high probability of annual radon concentration above the national reference level is to be expected in schools.

Estimation of radiation-induced health hazards from a "dirty bomb" attack with radiocesium under different assault and rescue conditions

In the case of a terrorist attack by a "dirty bomb", blast injuries, external irradiation and the incorporation of radioactivity are to be expected. Departing from information about the radiological attack scenario with cesium-137 in the U.S. National Scenario Planning Guide, we estimated the radiological doses absorbed. Similar calculations were performed for a smaller plume size and a detonation in a subway. For conditions as described in the U.S. scenario, the committed effective dose amounted to a maximum of 848 mSv, even for very unfavorable conditions. Red bone marrow equivalent doses are insufficient to induce acute radiation sickness (ARS). In the case of a smaller plume size, the ARS threshold may be exceeded in some cases. In a subway bombing, doses are much higher and the occurrence of ARS should be expected. The health hazards from a dirty bomb attack will depend on the location and the explosive device. The derived Haddon matrix indicates that preparing for such an event includes education of all the medical staff about radiation effects, the time lines of radiation damages and the treatment priorities. Further determinants of the outcome include rapid evacuation even from difficult locations, the availability of a specific triage tool to rapidly identify victims at risk for ARS, the availability of an antidote stockpile and dedicated hospital beds to treat seriously irradiated victims.

Zero-fluoroscopy ablation for cardiac arrhythmias: A single-center experience in Japan

BACKGROUND

Exposure to radiation during catheter ablation procedures poses a risk to the heath of both the patient and electrophysiology laboratory staff. Recently, the feasibility and effectiveness of zero-fluoroscopy ablation have been reported. However, studies on the outcomes of zero-fluoroscopy ablation in Japan remain limited. This study investigated the outcomes of zero-fluoroscopy ablation for cardiac arrhythmias at a Japanese institute.

METHODS AND RESULTS

We present a retrospective analysis of the safety, efficacy, and feasibility data from 221 consecutive patients who underwent zero-fluoroscopy ablation. Of these patients, 181 had atrial fibrillation, 17 had paroxysmal supraventricular tachycardia, 13 had atrial tachycardia, 6 had ventricular tachycardia, and 4 had ventricular premature contractions. We performed zero-fluoroscopy ablation using three-dimensional electro-anatomical mapping systems and intracardiac echocardiography imaging. Ultrasound-guided sheath insertion was performed on all cases. Our experience includes exclusively endocardial cardiac ablations. The mean follow-up was 24 months. The recurrence rates were 25.4% for atrial fibrillation, 5.9% for paroxysmal supraventricular tachycardia, 15.4% for atrial tachycardia, 33.3% for ventricular tachycardia, and 25% for ventricular premature contraction. Complications occurred in two patients (0.9%), and there was no occurrence of death. A fluoroscopic guide was used in three cases for the confirmation of vascular access (one case) and for complications (two cases).

CONCLUSIONS

Zero-fluoroscopy ablation was routinely performed without compromising on safety and efficacy. This approach may eliminate the exposure to radiation for all individuals involved in this procedure.

Quantitative evaluation of conservatism in the concept of committed dose from internal exposure for radiation workers

For compliance with dose limits, the International Commission on Radiological Protection (ICRP) recommends that the committed dose be assigned to the year in which radionuclide intake occurred in the case of internal exposure. For radiation workers, the committed dose is evaluated over the 50 year period following the intake, which is a rounded value for the working-life expectancy of a young person entering the workforce. In this study, we develop an approach to the quantitative evaluation of the conservatism in the concept of the committed dose from internal exposure for radiation workers from the viewpoint of radiological risk. Actual annual doses due to an intake of radionuclides for strontium-90 (⁹⁰Sr), caesium-137 (¹³⁷Cs), and plutonium-239 (²³⁹Pu) were simulated. Risks of fatal cancer, i.e. unconditional death probability rates, were calculated in accordance with the risk estimation method in ICRP Publication 60. It was found that the conservatism ranged from 1.1 to 1.6 for⁹⁰Sr, 1.0 to 1.6 for¹³⁷Cs, and 1.6 to 2.2 for²³⁹Pu. The importance of understanding the extent of this conservatism and the uncertainty for practical radiological protection are also discussed.

Non-cancer disease prevalence and association with occupational radiation exposure among Korean radiation workers

Radiation-induced cancer risks have known stochastic effects; however, regarding non-cancer diseases, evidence of risk at low radiation doses remains unclear. We aimed to identify underlying characteristics concerning non-cancer disease prevalence and determine associations with radiation dose among Korean radiation workers. Using a nationwide baseline survey, 20,608 workers were enrolled. Data concerning participant demographics, occupational characteristics, lifestyle, and lifetime prevalence of non-cancer diseases were linked to a national dose registry. We compared non-cancer disease prevalences in the Korean general population with those in this cohort and undertook a dose-response analysis concerning the cumulative dose. Hyperlipidemia (10.6%), circulatory (9.6%), and respiratory (4.1%) system diseases, followed by thyroid diseases (3.5%), had the highest prevalences, with hyperlipidemia, thyroid diseases, and hepatitis prevalence being higher in the cohort than in the general population. Radiation doses were associated with elevated prevalences of most diseases; however, associations were attenuated and not significant after adjusting for confounders, except for musculoskeletal system diseases (prevalence odds ratio [POR]/10 mSv, 1.03; 95% confidence interval [CI] 1.00-1.07) and cataracts (POR/10 mSv, 1.04; 95% CI 1.00-1.07). Further studies are warranted to investigate the causality of those non-cancer diseases involving more varied confounders such as physical and psychosocial stresses and ultraviolet light.

A million persons, a million dreams: a vision for a national center of radiation epidemiology and biology

BACKGROUND

Epidemiologic studies of radiation-exposed populations form the basis for human safety standards. They also help shape public health policy and evidence-based health practices by identifying and quantifying health risks of exposure in defined populations. For more than a century, epidemiologists have studied the consequences of radiation exposures, yet the health effects of low levels delivered at a low-dose rate remain equivocal.

MATERIALS AND METHODS

The Million Person Study (MPS) of U.S. Radiation Workers and Veterans was designed to examine health effects following chronic exposures in contrast with brief exposures as experienced by the Japanese atomic bomb survivors. Radiation associations for rare cancers, intakes of radionuclides, and differences between men and women are being evaluated, as well as noncancers such as cardiovascular disease and conditions such as dementia and cognitive function. The first international symposium, held November 6, 2020, provided a broad overview of the MPS. Representatives from four U.S. government agencies addressed the importance of this research for their respective missions: U.S. Department of Energy (DOE), the Centers for Disease Control and Prevention (CDC), the U.S. Department of Defense (DOD), and the National Aeronautics and Space Administration (NASA). The major components of the MPS were discussed and recent findings summarized. The importance of radiation dosimetry, an essential feature of each MPS investigation, was emphasized.

RESULTS

The seven components of the MPS are DOE workers, nuclear weapons test participants, nuclear power plant workers, industrial radiographers, medical radiation workers, nuclear submariners, other U.S. Navy personnel, and radium dial painters. The MPS cohorts include tens of thousands of workers with elevated intakes of alpha particle emitters for which organ-specific doses are determined. Findings to date for chronic radiation exposure suggest that leukemia risk is lower than after acute exposure; lung cancer risk is much lower and there is little difference in risks between men and women; an increase in ischemic heart disease is yet to be seen; esophageal cancer is frequently elevated but not myelodysplastic syndrome; and Parkinson's disease may be associated with radiation exposure.

CONCLUSIONS

The MPS has provided provocative insights into the possible range of health effects following low-level chronic radiation exposure. When the 34 MPS cohorts are completed and combined, a powerful evaluation of radiation-effects will be possible. This final article in the MPS special issue summarizes the findings to date and the possibilities for the future. A National Center for Radiation Epidemiology and Biology is envisioned.

Organ Dose Reconstruction Applicable for a Japanese Nuclear Worker Cohort: J-EPISODE

ABSTRACT

An evaluation of cancer risk based on organ-absorbed dose is underway for the Japanese Epidemiological Study on Low-Dose Radiation Effects (J-EPISODE), which has analyzed health effects in association with radiation exposure evaluated with the personal dose equivalent Hp(10). Although the concept of effective dose and its operational definition of Hp(10) are widely used for radiological protection purposes, effective dose is not recommended for epidemiological evaluation. Organ-absorbed dose was instead adopted for the IARC 15-Country Collaborative study (15-Country study), the International Nuclear Workers Study (INWORKS), the Mayak worker study, and the Life Span Study (LSS) of atomic bomb survivors. The reconstruction method in J-EPISODE followed in principle the approach adopted in the 15-Country Study. As part of the approach of J-EPISODE, a conversion factor from photon dosimeter reading to air kerma was developed using dosimeter response data, which were measured by the experiment using an anthropomorphic phantom, and it was confirmed that the 15-Country study's assumption of photon energy and geometry distribution in a work environment applied to Japanese nuclear workers. This article focuses on a method for reconstructing the conversion factor from photon dosimeter reading to organ-absorbed photon dose for a Japanese nuclear worker cohort. The model for estimating the conversion factor was defined under the assumption of a lognormal distribution from three concerned bias factors: (1) a dosimeter reading per air kerma, i.e., dosimeter response; (2) an organ-absorbed dose per air kerma; and (3) a factor relating to the differences in dose concepts and calibration practices between the roentgen dosimeter era and the present. Dosimeter response data were cited from the companion paper. Data on organ-absorbed photon dose per air kerma were estimated using a voxel phantom with the average Japanese adult male height and weight. The bias factor for the recorded dose in the roentgen era was defined, considering the backscatter radiation from the human body. The estimated values of organ-absorbed photon dose per air kerma were almost the same as those in ICRP Publication 116, revealing that the effect of differences in body size was almost negligible. The conversion factors from dosimeter reading to organ-absorbed dose were estimated by period (the roentgen era or from then), nuclear facility type (nuclear power plant or other), dosimeter type, and tissue or organ. The estimated conversion factors ranged from 0.7 to 0.9 (Gy Sv-1). The estimated cumulative organ-absorbed photon dose for the participants of J-EPISODE demonstrated that organ-absorbed dose values were approximately 0.8 times the recorded doses if neglecting dose-unit differences. J-EPISODE reconstructed an organ-absorbed dose conversion factor and will evaluate the risk of cancer mortality and morbidity using the organ-absorbed dose in the future.

Mortality from Leukemia, Cancer and Heart Disease among U.S. Nuclear Power Plant Workers, 1957-2011

BACKGROUND

The aim of the Million Person Study (MPS) of Low Dose Health Effects is to examine the level of radiation risk for chronic exposures received gradually over time and not acutely as was the case for the Japanese atomic bomb survivors. Nuclear power plant (NPP) workers comprise nearly 15 percent of the MPS. Leukemia, selected cancers, Parkinson's disease, ischemic heart disease (IHD) and other causes of death are evaluated.

METHODS AND MATERIAL

The U.S. Nuclear Regulatory Commission's Radiation Exposure Information and Reporting System (REIRS) and the Landauer, Inc. dosimetry databases identified 135,193 NPP workers first monitored 1957-1984. Annual personal dose equivalents [Hp(10)] were available for each worker. Radiation records from all places of employment were sought. Vital status was determined through 2011. Mean absorbed doses to red bone marrow (RBM), esophagus, lung, colon, brain and heart were estimated by adjusting the recorded Hp(10) for each worker by scaling factors, accounting for exposure geometry and energy of the incident gamma radiation. Standardized mortality ratios (SMR) were calculated. Radiation risks were estimated using Cox proportional hazards models.

RESULTS

Nearly 50% of workers were employed for more than 20 years. The mean duration of follow-up was 30.2 y. Overall, 29,076 total deaths occurred, 296 from leukemia other than chronic lymphocytic leukemia (CLL), 3,382 from lung cancer, 140 from Parkinson's disease and 5,410 from IHD. The mean dose to RBM was 37.9 mGy (maximum 1.0 Gy; percent >100 mGy was 9.2%), 43.2 mGy to lung, 43.7 mGy to colon, 33.2 mGy to brain, and 43.9 mGy to heart. The SMRs (95% CI) were 1.06 (0.94;1.19) for leukemia other than CLL, 1.10 (1.07;1.14) for lung cancer, 0.90 (0.76;1.06) for Parkinson's disease, and 0.80 (0.78; 0.82) for IHD. The excess relative risk (ERR) per 100 mGy for leukemia other than CLL was 0.15 (90% CI 0.001; 0.31). For all solid cancers the ERR per 100 mGy (95% CI) was 0.01 (-0.03; 0.05), for lung cancer -0.04 (-0.11; 0.02), for Parkinson's disease 0.24 (-0.02; 0.50), and for IHD -0.01 (-0.06; 0.04).

CONCLUSION

Prolonged exposure to radiation increased the risk of leukemia other than CLL among NPP workers. There was little evidence for a radiation-association for all solid cancers, lung cancer or ischemic heart disease. Increased precision will be forthcoming as the different cohorts within the MPS are combined, such as industrial radiographers and medical radiation workers who were assembled and evaluated in like manner.

Technical Note: validation of a material assignment method for a retrospective study of carbon-ion radiotherapy using Monte Carlo simulation

We propose a two-step method to converse human tissue materials from patient computed tomography (CT) images, which is required in dose reconstructions for a retrospective study of carbon-ion radiotherapy (CIRT) using Monte Carlo (MC) simulation. The first step was to assign the standard tissues of the International Commission on Radiological Protection reference phantoms according to the CT-number. The second step was to determine the mass density of each material based on the relationship between CT-number and stopping power ratio (Hounsfield unit [HU]-SPR) registered in treatment planning system (TPS). Direct implementation of the well-calibrated HU-SPR curve allows the reproduction of previous clinical treatments recorded in TPS without uncertainty due to a mismatch of the CT scanner or scanning conditions, whereas MC simulation with realistic human tissue materials can fulfill the out-of-field dose, which was missing in the record. To validate our proposed method, depth-dose distributions in the homogenous and heterogeneous phantoms irradiated by a 400 MeV/u carbon beam with an 8 cm spread-out Bragg peak (SOBP) were computed by the MC simulation in combination with the proposed methods and compared with those of TPS. Good agreement of the depth-dose distributions between the TPS and MC simulation (within a 1% discrepancy in range) was obtained for different materials. In contrast, fluence distributions of secondary particles revealed the necessity of MC simulation using realistic human tissue. The proposed material assignment method will be used for a retrospective study using previous clinical data of CIRT at the National Institute of Radiological Sciences (NIRS).

Association of occupational direct radiation exposure to the hands with longitudinal melanonychia and hand eczema in spine surgeons: a survey by the society for minimally invasive spinal treatment (MIST)

PURPOSE

To investigate the association between occupational direct radiation exposure to the hands and longitudinal melanonychia (LM) and hand eczema in spine surgeons.

METHODS

A web-based questionnaire survey of the Society for Minimally Invasive Spinal Treatment (MIST) in Japan was conducted. The proportion of LM and hand eczema in hands with high and low-radiation exposure was compared using Fisher's exact test. The odds ratios (ORs) and their 95% confidence intervals (CIs) for the prevalence of LM and hand eczema in the high-radiation exposure hands were calculated using generalized estimating equations for logistic regression as control for the correlation of observations among the same individuals and possible confounders.

RESULTS

Among 324 members of the society, responses were received from 229 members (70.7%). A total of 454 hands from 227 participants were analysed. The prevalence of LM and hand eczema was 43% and 29%, respectively. In a hand-by-hand comparison, more hands had LM in the high-radiation exposure group than the low-radiation exposure group (90 [40%] vs. 39 [17%], respectively, p < 0.001). A similar trend was observed for hand eczema (63 [28%] vs. 33 [15%], respectively, p = 0.001). The adjusted OR for high-radiation exposure hands was 3.18 (95% CI: 2.24-4.52). Consistent results were obtained for hand eczema, with an adjusted OR of 2.26 (95% CI: 1.67-3.06).

CONCLUSION

The present study suggests that direct radiation exposure to physician's hands is associated with LM and hand eczema. Those with LM and radially biased hand eczema may have had high direct radiation exposure.

Perturbed transcriptional profiles after chronic low dose rate radiation in mice

Adverse health outcomes of ionizing radiation given chronically at low dose rates are highly debated, a controversy also relevant for other stressors. Increased knowledge is needed for a more comprehensive understanding of the damaging potential of ionizing radiation from all dose rates and doses. There is a lack of relevant low dose rate data that is partly ascribed to the rarity of exposure facilities allowing chronic low dose rate exposures. Using the FIGARO facility, we assessed early (one day post-radiation) and late (recovery time of 100-200 days) hepatic genome-wide transcriptional profiles in male mice of two strains (CBA/CaOlaHsd and C57BL/6NHsd) exposed chronically to a low dose rate (2.5 mGy/h; 1200h, LDR), a mid-dose rate (10 mGy/h; 300h, MDR) and acutely to a high dose rate (100 mGy/h; 30h, HDR) of gamma irradiation, given to an equivalent total dose of 3 Gy. Dose-rate and strain-specific transcriptional responses were identified. Differently modulated transcriptional responses across all dose rate exposure groups were evident by the representation of functional biological pathways. Evidence of changed epigenetic regulation (global DNA methylation) was not detected. A period of recovery markedly reduced the number of differentially expressed genes. Using enrichment analysis to identify the functional significance of the modulated genes, perturbed signaling pathways associated with both cancer and non-cancer effects were observed, such as lipid metabolism and inflammation. These pathways were seen after chronic low dose rate and were not restricted to the acute high dose rate exposure. The transcriptional response induced by chronic low dose rate ionizing radiation suggests contribution to conditions such as cardiovascular diseases. We contribute with novel genome wide transcriptional data highlighting dose-rate-specific radiation responses and emphasize the importance of considering both dose rate, duration of exposure, and variability in susceptibility when assessing risks from ionizing radiation.

Space Radiation Protection Countermeasures in Microgravity and Planetary Exploration

BACKGROUND

Space radiation is one of the principal environmental factors limiting the human tolerance for space travel, and therefore a primary risk in need of mitigation strategies to enable crewed exploration of the solar system.

METHODS

We summarize the current state of knowledge regarding potential means to reduce the biological effects of space radiation. New countermeasure strategies for exploration-class missions are proposed, based on recent advances in nutrition, pharmacologic, and immune science.

RESULTS

Radiation protection can be categorized into (1) exposure-limiting: shielding and mission duration; (2) countermeasures: radioprotectors, radiomodulators, radiomitigators, and immune-modulation, and; (3) treatment and supportive care for the effects of radiation. Vehicle and mission design can augment the overall exposure. Testing in terrestrial laboratories and earth-based exposure facilities, as well as on the International Space Station (ISS), has demonstrated that dietary and pharmacologic countermeasures can be safe and effective. Immune system modulators are less robustly tested but show promise. Therapies for radiation prodromal syndrome may include pharmacologic agents; and autologous marrow for acute radiation syndrome (ARS).

CONCLUSIONS

Current radiation protection technology is not yet optimized, but nevertheless offers substantial protection to crews based on Lunar or Mars design reference missions. With additional research and human testing, the space radiation risk can be further mitigated to allow for long-duration exploration of the solar system.

Intracellular reactive oxygen species level in blood cells of atomic bomb survivors is increased due to aging and radiation exposure

Although reactive oxygen species (ROS) play important roles in immune responses, excessive ROS production and accumulation might enhance the risk of inflammation-related diseases. Moreover, impaired immune function and the acceleration of pre-clinically persistent inflammation due to aging and radiation exposure have been observed in atomic bomb (A-bomb) survivors more than 60 years post-exposure. Meanwhile, the effects of aging and radiation exposure on ROS production in immune cells have not been characterized. This study investigated the relationship between intracellular ROS (H₂O₂ and O₂^•-) levels in blood cells or T cell subsets and serum iron, ferritin, and C-reactive protein (CRP) levels, as well as how these variables are affected by age and radiation exposure in A-bomb survivors. We examined 2495 Hiroshima A-bomb survivors. Multiple linear regression models adjusted for confounding factors indicated that intracellular O₂^•- levels in monocytes, granulocytes, and lymphocytes, and particularly in memory CD8⁺ T cells, including effector memory and terminally differentiated effector memory CD8⁺ T cells, increased with radiation dose. Additionally, serum iron, ferritin, and CRP levels affected intracellular ROS levels in specific blood cell types and T cell subsets. Serum CRP levels increased significantly with increasing age and radiation dose. Finally, when divided into three groups according to serum CRP levels, dose-dependent increases in the intracellular O₂^•- levels in blood cells and central memory and effector memory CD8⁺ T cells were most prominently observed in the high-CRP group. These results suggest that an increase in the levels of certain intracellular ROS, particularly after radiation exposure, might be linked to enhanced inflammatory status, including elevated serum CRP levels and reduced serum iron levels. This study reveals that aging and radiation exposure increase oxidative stress in blood cells, which is involved in impaired immune function and accelerated pre-clinically persistent inflammation in radiation-exposed individuals.

Reexamining the role of tissue inflammation in radiation carcinogenesis: a hypothesis to explain an earlier onset of cancer

PURPOSE

Ionizing radiation is a well-known carcinogen, and epidemiologic efforts have been made to evaluate cancer risks following a radiation exposure. The basic approach has been to estimate increased levels of cancer mortality resulting from exposures to radiation, which is consistent with the somatic mutation theory of cancer. However, the possibility that an irradiation might cause an earlier onset of cancer has also been raised since the earliest days of animal studies. Recently, the mutation induction model has been challenged because it is unable to explain the observed dose-related parallel shift of entire mouse survival curves toward younger ages following an irradiation. This is because if it is assumed that only a fraction of the irradiated individuals are affected, the irradiated population would consist of two subpopulations with different mean lifespans, which makes the overall distribution of individual lifespans broader, and hence the slope of the survival curves shallower. To explain this parallel shift, it is necessary to assume that all individuals of a population are affected. As a result of these observations, possible mechanisms which could account for the parallel shift of mouse survival curves were sought by examining the radiation induction of various types of tissue damage which could facilitate an earlier onset of spontaneously arising cancers.

CONCLUSION

A proposed mechanism postulates that a radiation exposure leads to tissue inflammation which subsequently stimulates spontaneously arising cancers and allows them to appear earlier than usual. This notion is not unprecedented, and because the background incidence of cancer increases exponentially with an increase in age, a slight shift of the onset age toward younger ages may make it appear as if the risk is increased. In this scenario, a radiation exposure induces DNA damage, cell death, chromosome aberrations etc., which leads to the multi-pathway responses including activation of stromal fibroblasts, macrophages and various inflammatory factors. Such an inflamed microenvironment favors the growth of spontaneously arising tumor cells although currently, the sequential order or relative importance of the individual factors remains to be known.

A dedicated paediatric [18F]FDG PET/CT dosage regimen

BACKGROUND

The role of 2-[¹⁸F]fluoro-2-deoxy-D-glucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) in children is still expanding. Dedicated paediatric dosage regimens are needed to keep the radiation dose as low as reasonably achievable and reduce the risk of radiation-induced carcinogenesis. The aim of this study is to investigate the relation between patient-dependent parameters and [¹⁸F]FDG PET image quality in order to propose a dedicated paediatric dose regimen.

METHODS

In this retrospective analysis, 102 children and 85 adults were included that underwent a diagnostic [¹⁸F]FDG PET/CT scan. The image quality of the PET scans was measured by the signal-to-noise ratio (SNR) in the liver. The SNR liver was normalized (SNRnorm) for administered activity and acquisition time to apply curve fitting with body weight, body length, body mass index, body weight/body length and body surface area. Curve fitting was performed with two power fits, a nonlinear two-parameter model α p^-d and a linear single-parameter model α p^-0.5. The fit parameters of the preferred model were combined with a user preferred SNR to obtain at least moderate or good image quality for the dosage regimen proposal.

RESULTS

Body weight demonstrated the highest coefficient of determination for the nonlinear (R² = 0.81) and linear (R² = 0.80) models. The nonlinear model was preferred by the Akaike's corrected information criterion. We decided to use a SNR of 6.5, based on the expert opinion of three nuclear medicine physicians. Comparison with the quadratic adult protocol confirmed the need for different dosage regimens for both patient groups. In this study, the amount of administered activity can be considerably reduced in comparison with the current paediatric guidelines.

CONCLUSION

Body weight has the strongest relation with [¹⁸F]FDG PET image quality in children. The proposed nonlinear dosage regimen based on body mass will provide a constant and clinical sufficient image quality with a significant reduction of the effective dose compared to the current guidelines. A dedicated paediatric dosage regimen is necessary, as a universal dosing regimen for paediatric and adult is not feasible.

Transcriptomic analysis links hepatocellular carcinoma (HCC) in HZE ion irradiated mice to a human HCC subtype with favorable outcomes

High-charge, high-energy ion particle (HZE) radiations are extraterrestrial in origin and characterized by high linear energy transfer (high-LET), which causes more severe cell damage than low-LET radiations like γ-rays or photons. High-LET radiation poses potential cancer risks for astronauts on deep space missions, but the studies of its carcinogenic effects have relied heavily on animal models. It remains uncertain whether such data are applicable to human disease. Here, we used genomics approaches to directly compare high-LET radiation-induced, low-LET radiation-induced and spontaneous hepatocellular carcinoma (HCC) in mice with a human HCC cohort from The Cancer Genome Atlas (TCGA). We identified common molecular pathways between mouse and human HCC and discovered a subset of orthologous genes (mR-HCC) that associated high-LET radiation-induced mouse HCC with a subgroup (mrHCC2) of the TCGA cohort. The mrHCC2 TCGA cohort was more enriched with tumor-suppressing immune cells and showed a better prognostic outcome than other patient subgroups.

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

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

Mortality among workers at the Los Alamos National Laboratory, 1943-2017

BACKGROUND

During World War II (WWII), the Manhattan Engineering District established a secret laboratory in the mountains of northern New Mexico. The mission was to design, construct and test the first atomic weapon, nicknamed 'The Gadget' that was detonated at the TRINITY site in Alamogordo, NM. After WWII, nuclear weapons research continued, and the laboratory became the Los Alamos National Laboratory (LANL).

MATERIALS AND METHODS

The mortality experience of 26,328 workers first employed between 1943 and 1980 at LANL was determined through 2017. Included were 6157 contract workers employed by the ZIA Company. Organ dose estimates for each worker considered all sources of exposure, notably photons, neutrons, tritium, ²³⁸Pu and ²³⁹Pu. Vital status determination included searches within the National Death Index, Social Security Administration and New Mexico State Mortality Files. Standardized Mortality Ratios (SMR) and Cox regression models were used in the analyses.

RESULTS

Most workers (55%) were hired before 1960, 38% had a college degree, 25% were female, 81% white, 13% Hispanic and 60% had died. Vital status was complete, with only 0.1% lost to follow-up. The mean dose to the lung for the 17,053 workers monitored for radiation was 28.6 weighted-mGy (maximum 16.8 weighted-Gy) assuming a Dose Weighting Factor of 20 for alpha particle dose to lung. The Excess Relative Risk (ERR) at 100 weighted-mGy was 0.01 (95%CI -0.02, 0.03; n = 839) for lung cancer. The ERR at 100 mGy was -0.43 (95%CI -1.11, 0.24; n = 160) for leukemia other than chronic lymphocytic leukemia (CLL), -0.06 (95%CI -0.16, 0.04; n = 3043) for ischemic heart disease (IHD), and 0.29 (95%CI 0.02, 0.55; n = 106) for esophageal cancer. Among the 6499 workers with measurable intakes of plutonium, an increase in bone cancer (SMR 2.44; 95%CI 0.98, 5.03; n = 7) was related to dose. The SMR for berylliosis was significantly high, based on 4 deaths. SMRs for Hispanic workers were significantly high for cancers of the stomach and liver, cirrhosis of the liver, nonmalignant kidney disease and diabetes, but the excesses were not related to radiation dose.

CONCLUSIONS

There was little evidence that radiation increased the risk of lung cancer or leukemia. Esophageal cancer was associated with radiation, and plutonium intakes were linked to an increase of bone cancer. IHD was not associated with radiation dose. More precise evaluations will await the pooled analysis of workers with similar exposures such as at Rocky Flats, Savannah River and Hanford.

Lifetime risk of suicide among survivors of the atomic bombings of Japan

AIMS

The long-term physical health effects of the atomic bombings of Hiroshima and Nagasaki are well characterised, but the psychological effects remain unclear. Therefore, we sought to determine whether measures of exposure severity, as indirect measures of psychological trauma arising from exposure to the atomic bombings, are associated with suicide mortality among atomic bomb survivors.

METHODS

The Life Span Study is a prospective cohort study of 93 741 Japanese atomic bomb survivors who were located within 10 km of the hypocentre in Hiroshima or Nagasaki at the time of the bombings in 1945, and 26 579 residents of Hiroshima and Nagasaki who were not in either city at the time of the bombings, matched to survivors on city, sex and age. Measures of exposure severity included: proximity to the hypocentre, type of shielding between the survivor and the blast and self-reported occurrence of acute radiation and thermal injuries. Date of death was obtained from the Japanese National Family Registry system. Cause of death was obtained from death certificates. Adjusted hazard ratios (HRs) were estimated from Cox regression models overall and stratified by sex and age.

RESULTS

During the 60-year follow-up period (1950-2009), 1150 suicide deaths were recorded among 120 231 participants (23.6 per 100 000 person-years): 510 among 70 092 women (17.2 per 100 000 person-years) and 640 among 50 139 men (33.6 per 100 000 person-years). Overall, there was no association of proximity, type of shielding or the occurrence of acute injuries with suicide mortality. Among those <25 years of age at the time of the bombings, increased suicide risk was observed for survivors outside v. shielded inside any structure (HR: 1.24; 95% confidence interval (CI): 1.03, 1.48; interaction p = 0.054) and for those who reported flash burns (HR: 1.32; 95% CI: 1.00, 1.73; interaction p = 0.025). Sex-stratified analyses indicated that these associations were limited to men. Among women, closer proximity to the hypocentre was associated with a non-significant increase in suicide risk, with a positive association between proximity and suicide risk observed among women <15 years of age (HR: 1.09 per km; 95% CI: 1.00, 1.18; interaction p = 0.067).

CONCLUSIONS

Proximity to the hypocentre, shielding and acute injury presence do not generally appear to influence suicide mortality among atomic bomb survivors. However, heterogeneity may exist by age and sex, with younger survivors potentially more sensitive to psychological trauma. Coupled with other studies, our results suggest the importance of long-term monitoring of mental health among young populations exposed to catastrophic events or mass trauma.

Whole-Exome Sequencing of Radiation-Induced Thymic Lymphoma in Mouse Models Identifies Notch1 Activation as a Driver of p53 Wild-Type Lymphoma

Mouse models of radiation-induced thymic lymphoma are widely used to study the development of radiation-induced blood cancers and to gain insights into the biology of human T-cell lymphoblastic leukemia/lymphoma. Here we aimed to identify key oncogenic drivers for the development of radiation-induced thymic lymphoma by performing whole-exome sequencing using tumors and paired normal tissues from mice with and without irradiation. Thymic lymphomas from irradiated wild-type (WT), p53^+/-, and Kras^LA1 mice were not observed to harbor significantly higher numbers of nonsynonymous somatic mutations compared with thymic lymphomas from unirradiated p53^-/- mice. However, distinct patterns of recurrent mutations arose in genes that control the Notch1 signaling pathway based on the mutational status of p53. Preferential activation of Notch1 signaling in p53 WT lymphomas was also observed at the RNA and protein level. Reporter mice for activation of Notch1 signaling revealed that total-body irradiation (TBI) enriched Notch1^hi CD44⁺ thymocytes that could propagate in vivo after thymocyte transplantation. Mechanistically, genetic inhibition of Notch1 signaling in immature thymocytes prevented formation of radiation-induced thymic lymphoma in p53 WT mice. Taken together, these results demonstrate a critical role of activated Notch1 signaling in driving multistep carcinogenesis of thymic lymphoma following TBI in p53 WT mice. SIGNIFICANCE: These findings reveal the mutational landscape and key drivers in murine radiation-induced thymic lymphoma, a classic animal model that has been used to study radiation carcinogenesis for over 70 years.

Moving Forward in the Next Decade: Radiation Oncology Sciences for Patient-Centered Cancer Care

In a time of rapid advances in science and technology, the opportunities for radiation oncology are undergoing transformational change. The linkage between and understanding of the physical dose and induced biological perturbations are opening entirely new areas of application. The ability to define anatomic extent of disease and the elucidation of the biology of metastases has brought a key role for radiation oncology for treating metastatic disease. That radiation can stimulate and suppress subpopulations of the immune response makes radiation a key participant in cancer immunotherapy. Targeted radiopharmaceutical therapy delivers radiation systemically with radionuclides and carrier molecules selected for their physical, chemical, and biochemical properties. Radiation oncology usage of “big data” and machine learning and artificial intelligence adds the opportunity to markedly change the workflow for clinical practice while physically targeting and adapting radiation fields in real time. Future precision targeting requires multidimensional understanding of the imaging, underlying biology, and anatomical relationship among tissues for radiation as spatial and temporal “focused biology.” Other means of energy delivery are available as are agents that can be activated by radiation with increasing ability to target treatments. With broad applicability of radiation in cancer treatment, radiation therapy is a necessity for effective cancer care, opening a career path for global health serving the medically underserved in geographically isolated populations as a substantial societal contribution addressing health disparities. Understanding risk and mitigation of radiation injury make it an important discipline for and beyond cancer care including energy policy, space exploration, national security, and global partnerships.

Risk trade-off analysis of returning home and radiation exposure after a nuclear disaster using a happy life expectancy indicator

It is crucial to evaluate ethical issues regarding evacuation orders, especially after a nuclear disaster. After the Fukushima accident in 2011, the Japanese government ordered the affected people to evacuate. The evacuation orders have now been lifted in many areas. A risk trade-off analysis between benefits and risk associated with returning home would help in evaluating the justification for the lifting of the evacuation order in the aftermath of a nuclear disaster. Here, we performed a risk trade-off analysis among people returning home after the lifting of an evacuation order between an increase in emotional happiness (positive effect) and loss of life expectancy due to additional radiation exposure (negative effect), using a happy life expectancy (HpLE) indicator. Emotional happiness was estimated using questionnaires distributed among the affected people who lived in municipalities where evacuation orders were lifted. Loss of life expectancy was estimated under a scenario that returnees received 20 mSv in the year of return and subsequent radiation exposure. Increase in emotional happiness due to returning home was ~1-2 orders of magnitude higher among women aged 20, 40 and 65 years than the loss of life expectancy due to additional radiation exposure. This finding has implications for the justification for the lifting of evacuation orders.

Transplantation of Unirradiated Bone Marrow Cells after Total-Body Irradiation Prevents the Development of Thymic Lymphoma in Mice through Niche Competition

Mouse models of radiation-induced thymic lymphoma are commonly used to study the biological effects of total-body irradiation (TBI) on the formation of hematologic malignancies. It is well documented that radiation-induced thymic lymphoma can be inhibited by protecting the bone marrow (BM) from irradiation; however, the mechanisms underlying this phenomenon are poorly understood. Here, we aimed to address this question by performing transplantation of BM cells from genetically engineered mice that have defects in tumor immunosurveillance or occupying different thymic niches. We found that BM cells from mice that have impaired tumor immunosurveillance, by deleting tumor necrosis factor alpha (TNFα), interferon gamma (IFNγ) or perforin-1 (PRF1), remained sufficient to suppress the formation of radiation-induced thymic lymphoma. On the other hand, BM cells from Rag2-/-; γc-/- mice and Rag2-/- mice, which have defects in occupying thymic niches beyond double negative (DN2) and DN3, respectively, failed to inhibit radiation-induced lymphomagenesis in the thymus. Taken together, based on our findings, we propose a model where unirradiated BM cells suppress radiation-induced lymphomagenesis in the thymus by competing with tumor-initiating cells for thymic niches beyond the DN3 stage.

Establishing Pediatric Mouse Models of the Hematopoietic Acute Radiation Syndrome and the Delayed Effects of Acute Radiation Exposure

Medical countermeasures (MCMs) for hematopoietic acute radiation syndrome (H-ARS) should be evaluated in well-characterized animal models, with consideration of at-risk populations such as pediatrics. We have developed pediatric mouse models of H-ARS and delayed effects of acute radiation exposure (DEARE) for efficacy testing of MCMs against radiation. Male and female C57BL/6J mice aged 3, 4, 5, 6, 7 and 8 weeks old (±1 day) were characterized for baseline hematopoietic and gastrointestinal parameters, radiation response, efficacy of a known MCM, and DEARE at six and 12 months after total-body irradiation (TBI). Weanlings (age 3 weeks) were the most radiosensitive age group with an estimated LD50/30 of 712 cGy, while mice aged 4 to 8 weeks were more radioresistant with an estimated LD50/30 of 767-787 cGy. Female weanlings were more radiosensitive than males at 3 and 4 weeks old but became significantly more radioresistant after the pubertal age of 5 weeks. The most dramatic increase in body weight, RBC counts and intestinal circumference length occurred from 3 to 5 weeks of age. The established radiomitigator Neulasta® (pegfilgrastim) significantly increased 30-day survival in all age groups, validating these models for MCM efficacy testing. Analyses of DEARE among pediatric survivors revealed depressed weight gain in males six months post-TBI, and increased blood urea nitrogen at 12 months post-TBI which was more severe in females. Hematopoietic DEARE at six months post-TBI appeared to be less severe in survivors from the 3- and 4-week-old groups but was equally severe in all age groups by 12 months of age. Similar to our other acute radiation mouse models, there was no appreciable effect of Neulasta used as an H-ARS MCM on the severity of DEARE. In summary, these data characterize a pediatric mouse model useful for assessing the efficacy of MCMs against ARS and DEARE in children.

Radiation Risks for the Incidence of Kidney, Bladder and Other Urinary Tract Cancers: 1958-2009

As part of the recent series of articles to create a comprehensive description of the radiation risks of solid cancer incidence after ionizing radiation exposure, based on the atomic bomb survivors' Life Span Study (LSS), this work focuses on the risks of urinary tract cancer (UTC) and kidney cancer. Analyses covered a 52-year period of follow-up, through 2009, among 105,444 eligible survivors who were alive and cancer free in 1958. This represents an additional 11 years of follow-up since the last comprehensive report, with a total of 3,079,502 person-years. We observed 790 UTC and 218 kidney cancer cases. Adjusted for smoking, there was a strong linear radiation dose response for UTC. The sex-averaged excess relative risk per 1 Gy (ERR/Gy) was 1.4 (95% confidence interval, CI: 0.82 to 2.1). Both males and females showed significantly increased ERRs/Gy with female point estimates at a factor of 3.4 (95% CI: 1.4 to 8.6) greater than male estimates. UTC radiation risks were largely unmodified by age at exposure or attained age. The attributable fraction of UTC to radiation exposure was approximately 18% while that attributed to smoking was 48%. Kidney cancer showed an increased ERR due to smoking (0.56 per 50 pack-years; 95% CI -0.007 to 1.6; P = 0.054), but we did not observe any strong associations of kidney cancer with radiation exposure, although sex-specific dose responses were found to be statistically different.

Comparing second cancer risk for multiple radiotherapy modalities in survivors of hodgkin lymphoma

OBJECTIVES

To assess if excess absolute risk (EAR) of radiation-induced solid cancer can be used to rank radiotherapy plans for treatment of Hodgkin lymphoma (HL) in a statistically significant way.

METHODS

EAR models, calibrated with data from the Life Span Study and HL survivors, have been incorporated into a voxelised risk-calculation software, which is used to compare four treatment modalities planned for five virtual HL patients. Organ-specific parameters are generated repeatedly in a Monte Carlo fashion to model their uncertainties. This in turn enables a quantitative estimation of the EAR uncertainties.

RESULTS

Parameter-driven uncertainties on total EAR are around 13%, decreasing to around 2-5% for relative EAR comparisons. Total EAR estimations indicate that intensity modulated proton therapy decreases the average risk by 40% compared to the intensity modulated radiation therapy plan, 28% compared to the volumetric modulated arc therapy plan whereas the three-dimensional conformal radiation therapy plan is equivalent within the uncertainty.

CONCLUSION

Relative EAR is a useful metric for distinguishing between radiotherapy plans in terms of second cancer risk.

ADVANCES IN KNOWLEDGE

Relative EAR is not dominated by model or parameter uncertainties and can be used to guide the choice of radiotherapy for HL patients.

The use of ionising radiation in orthopaedic surgery: principles, regulations and managing risk to surgeons and patients

The use of ionising radiation for plain film radiography and computerised tomography is fundamental in both diagnostics and treatment for orthopaedics. However, radiation is not without risk as high exposure can increase the risk of cancer. Little time is spent educating doctors about the relative risks of radiation, both to patients and themselves. In addition, there are common misunderstandings about the best ways to mitigate such risk. We aim to provide an overview of the fundamental principles of the use of ionising radiation and its risks within the context of orthopaedic surgery. While providing a narrative review of the current literature, we discuss the basic physics, standards of good practice and relevant UK and European regulations. We discuss the risks to patients and surgeons and suggest ways that these can be mitigated in the operating theatre. A thorough understanding of the risks, and appropriate procedural rules, with respect to the use of ionising radiation is essential for those in orthopaedic practice.

Female breast cancer risk in Bryansk Oblast, Russia, following prolonged low dose rate exposure to radiation from the Chernobyl power station accident

BACKGROUND

Ionizing radiation is a known cause of female breast cancer, but there have been few studies of the risk after prolonged radiation exposure at low dose rates.

METHODS

This population-based case-control study estimated breast cancer risk after ∼25 years' exposure to radiation from the Chernobyl accident. Cases (n = 468) were women ≤55 years old when first diagnosed with invasive breast cancer during October 2008 through  February 2013, who lived in Bryansk Oblast, Russia at the time of the accident and their diagnoses. Controls, individually matched to cases on birth year, administrative district of residence and urban vs non-urban settlement during the accident, were women without breast cancer who lived in Bryansk Oblast at the time of the accident and on their cases' diagnosis dates (n = 468). Subjects were interviewed regarding residence, dietary and food source histories to support individualized estimation of their radiation doses to the breast, which ranged from 0.04 - 41 centigray (cGy) (mean 1.3 cGy).

RESULTS

In multivariable analyses, the odds ratio for breast cancer risk was 3.0 [95% confidence interval (CI): 1.3, 7.0] and 2.7 (95% CI: 1.0, 7.3) in the seventh and eighth dose octiles, respectively, relative to the lowest octile. Analyses of dose effect modification suggested that radiation-related risk may have been higher in women who were younger at the time of the accident and/or at the time of diagnosis.

CONCLUSIONS

This study suggests that prolonged exposure to ionizing radiation at low dose rates can increase risk of breast cancer.

The diagnostic performance of chest computed tomography in the detection of rib fractures in children investigated for suspected physical abuse: a systematic review and meta-analysis

Objectives

To assess the diagnostic performance of chest CT in the detection of rib fractures in children investigated for suspected physical abuse (SPA).

Methods

Medline, Web of Science and Cochrane databases were searched from January 1980 to April 2020. The QUADAS-2 tool was used to assess the quality of the eligible English-only studies following which a formal narrative synthesis was constructed. Studies reporting true-positive, false-positive, true-negative, and false-negative results were included in the meta-analysis. Overall sensitivity and specificity of chest CT for rib fracture detection were calculated, irrespective of fracture location, and were pooled using a univariate random-effects meta-analysis. The diagnostic accuracy of specific locations along the rib arc (anterior, lateral or posterior) was assessed separately.

Results

Of 242 identified studies, 4 met the inclusion criteria. Of these, 2 were included in the meta-analysis. Chest CT identified 142 rib fractures compared to 79 detected by initial skeletal survey chest radiographs in live children with SPA. Post-mortem CT (PMCT) has low sensitivity (34%) but high specificity (99%) in the detection of rib fractures when compared to the autopsy reference standard. PMCT has low sensitivity (45%, 21% and 42%) but high specificity (99%, 97% and 99%) at anterior, lateral and posterior rib locations, respectively.

Conclusions

Chest CT detects more rib fractures than initial skeletal survey chest radiographs in live children with SPA. PMCT has low sensitivity but high specificity for detecting rib fractures in children investigated for SPA.

Key Points

• PMCT has low sensitivity (34%) but high specificity (99%) in the detection of rib fractures; extrapolation to CT in live children is difficult.

• No studies have compared chest CT with the current accepted practice of initial and follow-up skeletal survey chest radiographs in the detection of rib fractures in live children investigated for SPA.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-021-07775-3.

Observed-to-expected incidence ratios of second malignant neoplasms after radiation therapy for medulloblastoma: A Surveillance, Epidemiology, and End Results analysis

BACKGROUND

The authors analyzed the incidence and types of second malignant neoplasms (SMNs) in patients treated for medulloblastoma.

METHODS

The authors compared the incidence of SMNs after radiotherapy (RT) for medulloblastoma in patients treated in 1973-2014 with the incidence in the general population with the multiple primary-standardized incidence ratio function of Surveillance, Epidemiology, and End Results 9. Observed-to-expected incidence (O/E) ratios and 95% confidence intervals (CIs) were reported for the entire cohort and by disease site according to age at diagnosis, treatment era, and receipt of chemotherapy. P values < .05 were considered statistically significant.

RESULTS

Of the 1294 patients with medulloblastoma who received RT, 68 developed 75 SMNs. The O/E ratio for SMNs among all patients was 4.49 (95% CI, 3.53-5.62; P < .05). The site at highest risk was the central nervous system (CNS; O/E, 40.62; 95% CI, 25.46-61.51), which was followed by the endocrine system (O/E, 15.95; 95% CI, 9.12-25.91), bone (O/E, 14.45; 95% CI, 1.75-52.21), soft tissues (O/E, 9.01; 95% CI, 1.09-32.56), the digestive system (O/E, 5.03; 95% CI, 2.51-9.00), and the lymphatic/hematopoietic system (O/E, 3.37; 95% CI, 1.35-6.94). The O/E ratio was higher for patients given chemotherapy and RT (O/E, 5.52; 95% CI, 3.75-7.83) than for those given RT only (O/E, 3.96; 95% CI, 2.88-5.32).

CONCLUSIONS

Patients with medulloblastoma are at elevated risk for SMNs in comparison with the general population. Variations in O/E for SMNs by organ systems were found for treatment modality, age at diagnosis, and time of diagnosis. The most common site, the CNS, was involved more often in younger patients and those given chemotherapy with RT.

Risk of cancer associated with low-dose radiation exposure: comparison of results between the INWORKS nuclear workers study and the A-bomb survivors study

The Life Span Study (LSS) of Japanese atomic bomb survivors has served as the primary basis for estimates of radiation-related disease risks that inform radiation protection standards. The long-term follow-up of radiation-monitored nuclear workers provides estimates of radiation-cancer associations that complement findings from the LSS. Here, a comparison of radiation-cancer mortality risk estimates derived from the LSS and INWORKS, a large international nuclear worker study, is presented. Restrictions were made, so that the two study populations were similar with respect to ages and periods of exposure, leading to selection of 45,625 A-bomb survivors and 259,350 nuclear workers. For solid cancer, excess relative rates (ERR) per gray (Gy) were 0.28 (90% CI 0.18; 0.38) in the LSS, and 0.29 (90% CI 0.07; 0.53) in INWORKS. A joint analysis of the data allowed for a formal assessment of heterogeneity of the ERR per Gy across the two studies (P = 0.909), with minimal evidence of curvature or of a modifying effect of attained age, age at exposure, or sex in either study. There was evidence in both cohorts of modification of the excess absolute risk (EAR) of solid cancer by attained age, with a trend of increasing EAR per Gy with attained age. For leukemia, under a simple linear model, the ERR per Gy was 2.75 (90% CI 1.73; 4.21) in the LSS and 3.15 (90% CI 1.12; 5.72) in INWORKS, with evidence of curvature in the association across the range of dose observed in the LSS but not in INWORKS; the EAR per Gy was 3.54 (90% CI 2.30; 5.05) in the LSS and 2.03 (90% CI 0.36; 4.07) in INWORKS. These findings from different study populations may help understanding of radiation risks, with INWORKS contributing information derived from cohorts of workers with protracted low dose-rate exposures.

Low- and moderate-dose non-cancer effects of ionizing radiation in directly exposed individuals, especially circulatory and ocular diseases: a review of the epidemiology

PURPOSE

There are well-known correlations between high and moderate doses (>0.5 Gy) of ionizing radiation exposure and circulatory system damage, also between radiation and posterior subcapsular cataract. At lower dose correlations with circulatory disease are emerging in the Japanese atomic bomb survivors and in some occupationally exposed groups, and are still to some extent controversial. Heterogeneity in excess relative risks per unit dose in epidemiological studies at low (<0.1 Gy) and at low-moderate (>0.1 Gy, <0.5 Gy) doses may result from confounding and other types of bias, and effect modification by established risk factors. There is also accumulating evidence of excess cataract risks at lower dose and low dose rate in various cohorts. Other ocular endpoints, specifically glaucoma and macular degeneration have been little studied. In this paper, we review recent epidemiological findings, and also discuss some of the underlying radiobiology of these conditions. We briefly review some other types of mainly neurological nonmalignant disease in relation to radiation exposure.

CONCLUSIONS

We document statistically significant excess risk of the major types of circulatory disease, specifically ischemic heart disease and stroke, in moderate- or low-dose exposed groups, with some not altogether consistent evidence suggesting dose-response non-linearity, particularly for stroke. However, the patterns of risk reported are not straightforward. We also document evidence of excess risks at lower doses/dose-rates of posterior subcapsular and cortical cataract in the Chernobyl liquidators, US Radiologic Technologists and Russian Mayak nuclear workers, with fundamentally linear dose-response. Nuclear cataracts are less radiogenic. For other ocular endpoints, specifically glaucoma and macular degeneration there is very little evidence of effects at low doses; radiation-associated glaucoma has been documented only for doses >5 Gy, and so has the characteristics of a tissue reaction. There is some evidence of neurological detriment following low-moderate dose (∼0.1-0.2 Gy) radiation exposure in utero or in early childhood.