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In this article we review the history of key epidemiological studies of populations exposed to ionizing radiation. We highlight historical and recent findings regarding radiation-associated risks for incidence and mortality of cancer and non-cancer outcomes with emphasis on study design and methods of exposure assessment and dose estimation along with brief consideration of sources of bias for a few of the more important studies. We examine the findings from the epidemiological studies of the Japanese atomic bomb survivors, persons exposed to radiation for diagnostic or therapeutic purposes, those exposed to environmental sources including Chornobyl and other reactor accidents, and occupationally exposed cohorts. We also summarize results of pooled studies. These summaries are necessarily brief, but we provide references to more detailed information. We discuss possible future directions of study, to include assessment of susceptible populations, and possible new populations, data sources, study designs and methods of analysis., (© 2024 by Radiation Research Society. All rights of reproduction in any form reserved.)

Ionizing radiation is one of the known risk factors for cataract development, however, there is still debate regarding the level of risk after low dose exposures. One of the largest sources of radiation exposure to the lens of the eye is diagnostic CT scans. The aim of this study was to examine whether ionizing radiation associated with head CT scans increases cataract risk in residents of Ontario, Canada. Data were collected from January 1, 1994 to December 31, 2015 (22 years) from anonymized Ontario Health Insurance Plan (OHIP) medical records for over 16 million subjects. A lens dose was estimated for each CT scan using the National Cancer Institute dosimetry system for CT (NCICT) program combined with Canada-specific CTDIvol data. Multivariate Cox proportional hazards analysis was performed with cataract extraction surgery as the primary outcome and lens dose as the main variable of interest, with inclusion of various medical and demographic covariates. Lag periods of 3, 5 and 7 years were incorporated. When lens dose was treated as a continuous variable, hazard ratios (per 100 mGy) ranged from 0.82 (0.80-0.84) to 1.10 (1.09-1.11) depending on the lag period. As a secondary analysis, when individuals were binned based on their total cumulative dose, no significant dose response pattern was observed in the low dose region. Overall, within the bounds of this study, the data do not support an increased risk of vision impairing cataracts after diagnostic head CT scan radiation exposure., (© 2024 by Radiation Research Society.)

Background: Many high-dose groups demonstrate increased leukaemia risks, with risk greatest following childhood exposure; risks at low/moderate doses are less clear., Methods: We conducted a pooled analysis of the major radiation-associated leukaemias (acute myeloid leukaemia (AML) with/without the inclusion of myelodysplastic syndrome (MDS), chronic myeloid leukaemia (CML), acute lymphoblastic leukaemia (ALL)) in ten childhood-exposed groups, including Japanese atomic bomb survivors, four therapeutically irradiated and five diagnostically exposed cohorts, a mixture of incidence and mortality data. Relative/absolute risk Poisson regression models were fitted., Results: Of 365 cases/deaths of leukaemias excluding chronic lymphocytic leukaemia, there were 272 AML/CML/ALL among 310,905 persons (7,641,362 person-years), with mean active bone marrow (ABM) dose of 0.11 Gy (range 0-5.95). We estimated significant (P < 0.005) linear excess relative risks/Gy (ERR/Gy) for: AML (n = 140) = 1.48 (95% CI 0.59-2.85), CML (n = 61) = 1.77 (95% CI 0.38-4.50), and ALL (n = 71) = 6.65 (95% CI 2.79-14.83). There is upward curvature in the dose response for ALL and AML over the full dose range, although at lower doses (<0.5 Gy) curvature for ALL is downwards., Discussion: We found increased ERR/Gy for all major types of radiation-associated leukaemia after childhood exposure to ABM doses that were predominantly (for 99%) <1 Gy, and consistent with our prior analysis focusing on <100 mGy., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Background: There is accumulating evidence of excess risk of cancer in various populations exposed at acute doses below several tens of mSv or doses received over a protracted period. There is also evidence that relative risks are generally higher after radiation exposures in utero or in childhood., Methods and Findings: We reviewed and summarised evidence from 89 studies of cancer following medical diagnostic exposure in utero or in childhood, in which no direct estimates of radiation dose are available. In all of the populations studied exposure was to sparsely ionizing radiation (X-rays). Several of the early studies of in utero exposure exhibit modest but statistically significant excess risks of several types of childhood cancer. There is a highly significant (p < 0.0005) negative trend of odds ratio with calendar period of study, so that more recent studies tend to exhibit reduced excess risk. There is no significant inter-study heterogeneity (p > 0.3). In relation to postnatal exposure there are significant excess risks of leukaemia, brain and solid cancers, with indications of variations in risk by cancer type (p = 0.07) and type of exposure (p = 0.02), with fluoroscopy and computed tomography scans associated with the highest excess risk. However, there is highly significant inter-study heterogeneity (p < 0.01) for all cancer endpoints and all but one type of exposure, although no significant risk trend with calendar period of study., Conclusions: Overall, this large body of data relating to medical diagnostic radiation exposure in utero provides support for an associated excess risk of childhood cancer. However, the pronounced heterogeneity in studies of postnatal diagnostic exposure, the implied uncertainty as to the meaning of summary measures, and the distinct possibilities of bias, substantially reduce the strength of the evidence from the associations we observe between radiation imaging in childhood and the subsequent risk of cancer being causally related to radiation exposure., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Richard Wakeford receives a consultancy fee as a member of the Technical Working Party of the Compensation Scheme for Radiation-linked Diseases (http://www.csrld.org.uk). No other authors report conflicts of interest., (Crown Copyright © 2022. Published by Elsevier B.V. All rights reserved.)

Recently, it has been proposed that the doses received from 133Xe released during the accident in 1979 at the Three Mile Island (TMI) plant in Pennsylvania were much higher than has been conventionally assessed, due to a gross underestimation of the relative biological effectiveness of electrons from beta-particle-emitting radionuclides within the body. The central evidence cited in support of this proposal was the doses derived from cytogenetic analyses of blood sampled in the mid-1990s from people living near TMI at the time of the accident. However, the chromosome aberration data show a marked discrepancy in biodosimetric estimates evaluated from the frequencies of stable translocations and unstable dicentrics (corrected for temporal attenuation), strongly suggesting that exposures to clastogenic agents occurred long after the TMI accident. Few details have been reported on the people providing the blood samples and how they were selected for study. Crucially, this lack of information includes the distributions in the exposed and control groups of age at sampling, which is a critical factor in interpreting translocation data. Contrary to the recent claim, these cytogenetic data offer no support to the suggestion of a serious underestimation of internal doses from beta particles or from 133Xe discharged during the TMI accident., (©2021 by Radiation Research Society. All rights of reproduction in any form reserved.)

Objectives: To evaluate cumulative occupational radiation dose response and haematopoietic malignancy mortality risks in the US radiologic technologist cohort., Methods: Among 110 297 radiologic technologists (83 655 women, 26 642 men) who completed a baseline questionnaire sometime during 1983-1998, a retrospective cohort study was undertaken to assess cumulative, low-to-moderate occupational radiation dose and haematopoietic malignancy mortality risks during 1983-2012. Cumulative bone marrow dose (mean 8.5 mGy, range 0-430 mGy) was estimated based on 921 134 badge monitoring measurements during 1960-1997, work histories and historical data; 35.4% of estimated doses were based on badge measurements. Poisson regression was used to estimate excess relative risk of haematopoietic cancers per 100 milligray (ERR/100 mGy) bone-marrow absorbed dose, adjusting for attained age, sex and birth year., Results: Deaths from baseline questionnaire completion through 2012 included 133 myeloid neoplasms, 381 lymphoid neoplasms and 155 leukaemias excluding chronic lymphocytic leukaemia (CLL). Based on a linear dose-response, no significant ERR/100 mGy occurred for acute myeloid leukaemia (ERR=0.0002, 95% CI <-0.02 to 0.24, p-trend>0.5, 85 cases) or leukaemia excluding CLL (ERR=0.05, 95% CI <-0.09 to 0.24, p-trend=0.21, 155 cases). No significant dose-response trends were observed overall for CLL (ERR<-0.023, 95% CI <-0.025 to 0.18, p-trend=0.45, 32 cases), non-Hodgkin lymphoma (ERR=0.03, 95% CI <-0.2 to 0.18, p-trend=0.4, 201 cases) or multiple myeloma (ERR=0.003, 95% CI -0.02 to 0.16, p-trend>0.5, 112 cases). Findings did not differ significantly by demographic factors, smoking or specific radiological procedures performed., Conclusion: After follow-up averaging 22 years, there was little evidence of a relationship between occupational radiation exposure and myeloid or lymphoid haematopoietic neoplasms., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: Previous analyses of cataract in radiation-exposed populations have assessed relative risk; radiogenic excess additive risk (EAR), arguably of more public health importance, has not been estimated. Previous analysis of a large prospective cohort of US radiologic technologists (USRT) quantified excess relative risk of cataract in relation to occupational radiation dose. We aim to assess EARs of cataract., Methods: We estimated EARs of cataract/cataract surgery in the USRT cohort using generalised additive models in relation to occupational radiation exposure, and assessed risk modification by a priori-selected cataract risk factors (diabetes, body mass index, smoking, race, sex, birth-year, ultraviolet B (UVB) radiation exposure)., Results: There were 11 345 cataract diagnoses and 5440 of cataract surgery during 832 462 and 888 402 person-years of follow-up, respectively. Cumulative occupational radiation exposure was associated with self-reported cataract, but not with cataract surgery, with EAR/10 4 person-year Gy=94 (95% CI: 47 to 143, p<0.001) and EAR/10 4 person-year Gy=13 (95% CI: <0 to 57, p=0.551), respectively. There was marked (p<0.001) variation of EAR by age and by diabetes status, with risk higher among persons ≥75 years and diabetics. There were indications of elevated risk among those with higher UVB radiation (p=0.045), whites (p=0.056) and among those with higher levels of cigarette smoking (p=0.062). Elevated additive risk was observed for estimated occupational radiation eye-lens doses <100 mGy (p=0.004) with no dose-response curvature (p=0.903)., Conclusions: The elevated additive risks associated with low-dose radiation, if confirmed elsewhere, have important public health and clinical implications for radiation workers as well as regulatory measures., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Chronic inflammation underlies many autoimmune diseases, including hypothyroidism, hyperthyroidism, and rheumatoid arthritis, also type-2 diabetes and osteoarthritis. Associations have been suggested of high-dose ionising radiation exposure with type-2 diabetes and elevated levels of C-reactive protein, a marker of chronic inflammation. In this analysis we used a proportional hazards model to assess effects of radiotherapy on risks of subsequent inflammatory disease morbidity in 110,368 US radiologic technologists followed from a baseline survey (1983-1989/1994-1998) through 2008. We used a linear model to assess log-transformed C-reactive protein concentration following radiotherapy in 1326 technologists. Relative risk of diabetes increased following radiotherapy (p < 0.001), and there was a borderline significant increasing trend per treatment (p = 0.092). For osteoarthritis there was increased relative risk associated with prior radiotherapy on all questionnaires (p = 0.005), and a significant increasing trend per previous treatment (p = 0.024). No consistent increases were observed for other types of inflammatory disease (hypothyroidism, hyperthyroidism, rheumatoid arthritis) associated with radiotherapy. There was a borderline significant (p = 0.059) increasing trend with dose for C-reactive protein with numbers of prior radiotherapy treatments. Our results suggest that radiotherapy is associated with subsequent increased risk of certain inflammatory conditions, which is reinforced by our finding of elevated levels of C-reactive protein.

Glaucoma is a group of optic neuropathies causing optic nerve damage and visual field defects, and is one of the leading causes of blindness. Nearly a century has passed since the first report of glaucoma manifested following ionizing radiation therapy of cancers. Nevertheless, associations between glaucoma and radiation exposures, a dose response relationship, and the mechanistic underpinnings remain incompletely understood. Here we review the current knowledge on manifestations and mechanisms of radiogenic glaucoma. There is some evidence that neovascular glaucoma is manifest relatively quickly, within a few years after high-dose and high dose-rate radiotherapeutic exposure, but little evidence of excess risks of glaucoma after exposure to much lower doses or dose rates. As such, glaucoma appears to have some of the characteristics of a tissue reaction effect, with a threshold of at least 5 Gy but possibly much higher., (Copyright © 2019 Elsevier B.V. All rights reserved.)

It has long been known that relatively high-dose ionising radiation exposure (> 1 Gy) can induce cataract, but there has been no evidence that this occurs at low doses (< 100 mGy). To assess low-dose risk, participants from the US Radiologic Technologists Study, a large, prospective cohort, were followed from date of mailed questionnaire survey completed during 1994-1998 to the earliest of self-reported diagnosis of cataract/cataract surgery, cancer other than non-melanoma skin, or date of last survey (up to end 2014). Cox proportional hazards models with age as timescale were used, adjusted for a priori selected cataract risk factors (diabetes, body mass index, smoking history, race, sex, birth year, cumulative UVB radiant exposure). 12,336 out of 67,246 eligible technologists reported a history of diagnosis of cataract during 832,479 person years of follow-up, and 5509 from 67,709 eligible technologists reported undergoing cataract surgery with 888,420 person years of follow-up. The mean cumulative estimated 5-year lagged eye-lens absorbed dose from occupational radiation exposures was 55.7 mGy (interquartile range 23.6-69.0 mGy). Five-year lagged occupational radiation exposure was strongly associated with self-reported cataract, with an excess hazard ratio/mGy of 0.69 × 10 -3 (95% CI 0.27 × 10 -3 to 1.16 × 10 -3 , p < 0.001). Cataract risk remained statistically significant (p = 0.030) when analysis was restricted to < 100 mGy cumulative occupational radiation exposure to the eye lens. A non-significantly increased excess hazard ratio/mGy of 0.34 × 10 -3 (95% CI - 0.19 × 10 -3 to 0.97 × 10 -3 , p = 0.221) was observed for cataract surgery. Our results suggest that there is excess risk for cataract associated with radiation exposure from low-dose and low dose-rate occupational exposures.

Although childhood exposure to ionizing radiation is a well-established risk factor for thyroid cancer, the risk associated with adulthood exposure remains unclear. We prospectively examined the association between cumulative, low-to-moderate dose occupational radiation exposure to the thyroid and thyroid cancer incidence in the U.S. Radiologic Technologists cohort. The study included 89,897 members who completed at least two of four mailed questionnaires and were cancer-free at the time of the first questionnaire. Cumulative occupational thyroid radiation dose (mean = 57 mGy, range = 0-1,600 mGy) was estimated based on self-reported work histories, historical data and, during the years 1960-1997, 783,000 individual film badge measurements. During follow-up, we identified 476 thyroid cancer cases. We used Poisson regression to estimate excess relative risk of thyroid cancer per 100 milliGray (ERR/100 mGy) absorbed dose to the thyroid gland. After adjusting for attained age, sex, birth year, body mass index and pack-years smoked, we found no association between thyroid dose and thyroid cancer risk (ERR/100 mGy = -0.05, 95% CI <-0.10, 0.34). In this large cohort study of radiologic technologists, protracted, low-to-moderate dose ionizing radiation exposure to the thyroid gland in adulthood was not associated with an increased risk of thyroid cancer., (© 2018 UICC.)

There are well-documented associations of glaucoma with high-dose radiation exposure, but only a single study suggesting risk of glaucoma, and less conclusively macular degeneration, associated with moderate-dose exposure. We assessed risk of glaucoma and macular degeneration associated with occupational eye-lens radiation dose, using participants from the US Radiologic Technologists Study, followed from the date of surveys in 1994-1998, 2003-2005 to the earliest of diagnosis of glaucoma or macular degeneration, cancer other than non-melanoma skin cancer, or date of last survey (2012-2014). We excluded those with baseline disease or previous radiotherapy history. Cox proportional hazards models with age as timescale were used. There were 1631 cases of newly self-reported doctor-diagnosed cases of glaucoma and 1331 of macular degeneration among 69,568 and 69,969 eligible subjects, respectively. Estimated mean cumulative eye-lens absorbed dose from occupational radiation exposures was 0.058 Gy. The excess relative risk/Gy for glaucoma was -0.57 (95% CI -1.46, 0.60, p = 0.304) and for macular degeneration was 0.32 (95% CI -0.32, 1.27, p = 0.381), suggesting that there is no appreciable risk for either endpoint associated with low-dose and low dose-rate radiation exposure. Since this is the first examination of glaucoma and macular degeneration associated with low-dose radiation exposure, this result needs to be replicated in other low-dose studies.

Understanding space radiation health effects is critical due to potential increased morbidity and mortality following spaceflight. We evaluated whether there is evidence for excess cardiovascular disease or cancer mortality in early NASA astronauts and if a correlation exists between space radiation exposure and mortality. Astronauts selected from 1959-1969 were included and followed until death or February 2017, with 39 of 73 individuals still alive at that time. Calculated standardized mortality rates for tested outcomes were significantly below U.S. white male population rates, including all-cardiovascular disease (n = 7, SMR = 33; 95% CI, 14-65) and all-cancer (n = 7, SMR = 43; 95% CI, 18-83), as anticipated in a healthy worker population. Space radiation doses for cohort members ranged from 0-78 mGy. No significant associations between space radiation dose and mortality were found using logistic regression with an internal reference group, adjusting for medical radiation. Statistical power of the logistic regression was <6%, remaining <12% even when expected risk level or observed deaths were assumed to be 10 times higher than currently reported. While no excess radiation-associated cardiovascular or cancer mortality risk was observed, findings must be tempered by the statistical limitations of this cohort; notwithstanding, this small unique cohort provides a foundation for assessment of astronaut health.

Objective: To assess whether personal medical diagnostic procedures over life, but particularly those associated with exposure in adulthood, were associated with increased thyroid cancer risk., Design: Participants from the US Radiologic Technologists Study, a large, prospective cohort, were followed from the date of first mailed questionnaire survey completed during 1983-1989 to the earliest date of self-reported diagnosis of thyroid cancer or of any other cancer than non-melanoma skin cancer (NMSC) in any of three subsequent questionnaires up to the last in 2012-2014., Setting: US nationwide, occupational cohort., Participants: US radiologic technologists with exclusion of: those who reported a previous cancer apart from NMSC on the first questionnaire; those who reported a cancer with an unknown date of diagnosis on any of the questionnaires; and those who did not respond to both the first questionnaire and at least one subsequent questionnaire., Primary Outcome Measure: We used Cox proportional hazards models with age as timescale to compute HRs and 95% CI for thyroid cancer in relation to cumulative 5-year lagged diagnostic thyroid dose., Results: There were 414 self-reported thyroid cancers (n=275 papillary) in a cohort of 76 415 persons. Cumulative thyroid dose was non-significantly positively associated with total (excess relative risk/Gy=2.29 (95% CI -0.91 to 7.01, p=0.19)) and papillary thyroid cancer (excess relative risk/Gy=4.15 (95% CI -0.39, 11.27, p=0.08)) risk. These associations were not modified by age at, or time since, exposure and were independent of occupational exposure., Conclusion: Our study provides weak evidence that thyroid dose from diagnostic radiation procedures over the whole of life, in particular associated with exposure in adulthood, influences adult thyroid cancer risk., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Background: Chronic lymphocytic leukemia (CLL) was the predominant leukemia in a recent study of Chornobyl cleanup workers from Ukraine exposed to radiation (UR-CLL). Radiation risks of CLL significantly increased with increasing bone marrow radiation doses. Current analysis aimed to clarify whether the increased risks were due to radiation or to genetic mutations in the Ukrainian population., Methods: A detailed characterization of the genomic landscape was performed in a unique sample of 16 UR-CLL patients and age- and sex-matched unexposed general population Ukrainian-CLL (UN-CLL) and Western-CLL (W-CLL) patients (n = 28 and 100, respectively)., Results: Mutations in telomere-maintenance pathway genes POT1 and ATM were more frequent in UR-CLL compared to UN-CLL and W-CLL (both p < 0.05). No significant enrichment in copy-number abnormalities at del13q14, del11q, del17p or trisomy12 was identified in UR-CLL compared to other groups. Type of work performed in the Chornobyl zone, age at exposure and at diagnosis, calendar time, and Rai stage were significant predictors of total genetic lesions (all p < 0.05). Tumor telomere length was significantly longer in UR-CLL than in UN-CLL (p = 0.009) and was associated with the POT1 mutation and survival., Conclusions: No significant enrichment in copy-number abnormalities at CLL-associated genes was identified in UR-CLL compared to other groups. The novel associations between radiation exposure, telomere maintenance and CLL prognosis identified in this unique case series provide suggestive, though limited data and merit further investigation.

Background: Serum thyroglobulin (Tg) is associated with the presence of thyroid disease and has been proposed as a biomarker of iodine status. Few studies have examined factors related to serum Tg in populations environmentally exposed to ionizing radiation and living in regions with endemic mild-to-moderate iodine deficiency., Methods: We screened 10,430 individuals who were living in Ukraine and under 18 years of age at the time of the 1986 Chernobyl Nuclear Power Plant accident for thyroid disease from 2001 to 2003. We estimated the percent change (PC) in serum Tg associated with demographic factors, iodine-131 thyroid dose, and indicators of thyroid structure and function using linear regression. We also examined these relationships for individuals with and without indications of thyroid abnormality., Results: Mean and median serum Tg levels were higher among participants with abnormal thyroid structure/function. Percent change in serum Tg increased among females, smokers and with older age (p-values<0.001), and Tg increased with increasing thyroid volume, and serum thyrotropin (p-values for trend<0.001). We found no evidence of significant associations between iodine-131 thyroid dose and Tg. Serum Tg levels were inversely associated with iodized salt intake (PC=-7.90, 95% confidence interval: -12.08, -3.52), and over the range of urinary iodine concentration, the odds of having elevated serum Tg showed a U-shaped curve with elevated Tg at low and high urinary iodine concentrations., Conclusion: Serum Tg may be a useful indicator of population iodine status and a non-specific biomarker of structural and functional thyroid abnormalities in epidemiological studies., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Objective: Childhood exposure to acute, high-dose radiation has consistently been associated with risk of benign and malignant intracranial tumors of the brain and CNS, but data on risks of adulthood exposure to protracted, low-to-moderate doses of radiation are limited. In a large cohort of radiologic technologists, we quantified the association between protracted, low-to-moderate doses of radiation and malignant intracranial tumor mortality., Materials and Methods: The study population included 83,655 female and 26,642 male U.S. radiologic technologists who were certified for at least 2 years as of 1982. The cohort was followed from the completion date of the first or second survey (1983-1989 or 1994-1998) to the date of death, loss to follow-up, or December 31, 2012, whichever was earliest. Occupational brain doses through 1997 were based on work history, historical data, and, for most years after the mid 1970s, individual film badge measurements. Radiation-related excess relative risks (ERRs) and 95% CIs were estimated from Poisson regression models adjusted for attained age and sex., Results: Cumulative mean absorbed brain dose was 12 mGy (range, 0-290 mGy). During follow-up (median, 26.7 years), 193 technologists died of a malignant intracranial neoplasm. Based on models incorporating a 5-year lagged cumulative brain dose, cumulative brain dose was not associated with malignant intracranial tumor mortality (overall ERR per 100 mGy, 0.1; 95% CI, < -0.3 to 1.5). No effect modification was observed by sex or birth cohort., Conclusion: In this nationwide cohort of radiologic technologists, cumulative occupational radiation exposure to the brain was not associated with malignant intracranial tumor mortality.

Previous analysis has shown that astronauts have a significantly lower standardized mortality ratio for circulatory disease mortality compared to the U.S. population, which is consistent with the rigorous selection process and healthy lifestyles of astronauts, and modest space radiation exposures from past space missions. However, a recent report by Delp et al. estimated the proportional mortality ratio for ages of 55-64 y of Apollo lunar mission astronauts to claim a high risk of cardiovascular disease due to space radiation compared to the U.S. population or to non-flight astronauts. In this Commentary we discuss important deficiencies in the methods and assumptions on radiation exposures used by Delp et al. that we judge cast serious doubt on their conclusions., (Copyright © 2016 The Committee on Space Research (COSPAR). All rights reserved.)

Objective: Although CT scans provide great medical benefits, concerns have been raised about the magnitude of possible associated cancer risk, particularly in children who are more sensitive to radiation than adults. Unnecessary high doses during CT examinations can also be delivered to children, if the scan parameters are not adjusted for patient age and size. We conducted the first survey to directly assess the trends in CT scan parameters and doses for paediatric CT scans performed in Great Britain between 1978 and 2008., Methods: We retrieved 1073 CT film sets from 36 hospitals. The patients were 0-19 years old, and CT scans were conducted between 1978 and 2008. We extracted scan parameters from each film including tube current-time product [milliampere seconds (mAs)], tube potential [peak kilovoltage (kVp)] and manufacturer and model of the CT scanner. We estimated the mean mAs for head and trunk (chest and abdomen/pelvis) scans, according to patient age (0-4, 5-9, 10-14 and 15-19 years) and scan year (<1990, 1990-1994, 1995-1999 and ≥2000), and then derived the volumetric CT dose index and estimated organ doses., Results: For head CT scans, mean mAs decreased by about 47% on average from before 1990 to after 2000, with the decrease starting around 1990. The mean mAs for head CTs did not vary with age before 1990, whereas slightly lower mAs values were used for younger patients after 1990. Similar declines in mAs were observed for trunk CTs: a 46% decline on an average from before 1990 to after 2000. Although mean mAs for trunk CTs did not vary with age before 1990, the value varied markedly by age, from 63 mAs for age 0-4 years compared with 315 mAs for those aged >15 years after 2000. No material changes in kVp were found. Estimated brain-absorbed dose from head CT scans decreased from 62 mGy before 1990 to approximately 30 mGy after 2000. For chest CT scans, the lung dose to children aged 0-4 years decreased from 28 mGy before 1990 to 4 mGy after 2000., Conclusion: We found that mAs for head and trunk CTs was approximately halved starting around 1990, and age-specific mAs was generally used for paediatric scans after this date. These changes will have substantially reduced the radiation exposure to children from CT scans in Great Britain., Advances in Knowledge: The study shows that mAs and major organ doses for paediatric CT scans in Great Britain began to decrease around 1990.

Objectives: Although fluoroscopically guided interventional procedures (FGIP) have provided major advances in the treatment of various common diseases, radiation exposures associated with these procedures may cause adverse health effects in workers. We assess risk of circulatory disease incidence and mortality in medical radiation workers performing FGIP., Methods: A US nationwide prospective cohort study of 90,957 radiologic technologists who completed a cohort survey during 1994-1998 was followed until completion of a subsequent survey during 2003-2005 for circulatory disease incidence, or until 31 December 2008 for mortality. Incidence analyses were restricted to the 63,482 technologists who completed both the second survey (1994-1998) and the third survey (2003-2005). Cox proportional hazards models were used to assess adjusted HR and 95% CIs for mortality from all causes, all circulatory diseases, all heart diseases, ischaemic heart disease, stroke, acute myocardial infarction and hypertension in participants who reported ever performing FGIP compared to technologists who never performed FGIP procedures. Adjusted HRs were calculated for self-reported hypertension, stroke and myocardial infarction., Results: We observed a 34% increase in stroke incidence (HR=1.34, 95% CI 1.10 to 1.64) in technologists who performed FGIP compared to those who never performed these procedures. Mortality from stroke was also modestly elevated, although not statistically significant (HR=1.22, 95% CI 0.85 to 1.73). We observed no statistically significant excess risks of incidence or mortality from any other outcome evaluated., Conclusions: Our finding of elevated risk of stroke in workers performing FGIP needs to be confirmed in studies with individual radiation dose data, but nonetheless underlines the need to keep radiation exposure as low as reasonably achievable without compromising key diagnostic information., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Background: There are limited data on the histopathology of papillary thyroid carcinomas (PTCs) diagnosed in irradiated populations. We evaluated the associations between iodine-131 dose and the histopathological characteristics of post-Chernobyl PTCs, the changes in these characteristics over time, and their associations with selected somatic mutations., Methods: This study included 115 PTCs diagnosed in a Ukrainian-American cohort (n=13,243) during prescreening and four successive thyroid screenings. Of these PTCs, 65 were subjected to somatic mutation profiling. All individuals were <18 years at the time of the Chernobyl accident and had direct thyroid radioactivity measurements. Statistical analyses included multivariate linear and logistic regression., Results: We identified a borderline significant linear-quadratic association (P=0.063) between iodine-131 dose and overall tumour invasiveness (presence of extrathyroidal extension, lymphatic/vascular invasion, and regional or distant metastases). Irrespective of dose, tumours with chromosomal rearrangements were more likely to have lymphatic/vascular invasion than tumours without chromosomal rearrangements (P=0.020) or tumours with BRAF or RAS point mutations (P=0.008). Controlling for age, there were significant time trends in decreasing tumour size (P<0.001), the extent of lymphatic/vascular invasion (P=0.005), and overall invasiveness (P=0.026)., Conclusions: We determined that the invasive properties of PTCs that develop in iodine-131-exposed children may be associated with radiation dose. In addition, based on a subset of cases, tumours with chromosomal rearrangements appear to have a more invasive phenotype. The increase in small, less invasive PTCs over time is a consequence of repeated screening examinations.

A meta-analytic summary effect estimate often is calculated as an inverse-variance-weighted average of study-specific estimates of association. The variances of published estimates of association often are derived from their associated confidence intervals under assumptions typical of Wald-type statistics, such as normality of the parameter. However, in some research areas, such as radiation epidemiology, epidemiological results typically are obtained by fitting linear relative risk models, and associated likelihood-based confidence intervals are often asymmetric; consequently, reasonable estimates of variances associated with study-specific estimates of association may be difficult to infer from the standard approach based on the assumption of a Wald-type interval. Here, a novel method is described for meta-analysis of published results from linear relative risk models that uses a parametric transformation of published results to improve on the normal approximation used to assess confidence intervals. Using simulations, it is illustrated that the meta-analytic summary obtained using the proposed approach yields less biased summary estimates, with better confidence interval coverage, than the summary obtained using the more classical approach to meta-analysis. The proposed approach is illustrated using a previously published example of meta-analysis of epidemiological findings regarding circulatory disease following exposure to low-level ionizing radiation.

Over the last two decades, there has been emerging evidence suggesting that ionizing radiation exposures could be associated with elevated risks of cardiovascular disease (CVD), particularly ischemic heart disease (IHD). Excess CVD risks have been observed in a number of exposed groups, with generally similar risk estimates both at low and high radiation doses and dose rates. In 2014, we reported for the first time significantly higher risks of IHD mortality when radiation doses were delivered over a protracted period of time (an inverse dose-fractionation effect) in the Canadian Fluoroscopy Cohort Study. Here we review the current evidence on the dose-fractionation effect of radiation exposure, discuss potential implication for radiation protection policies and suggest further directions for research in this area. [ABSTRACT FROM AUTHOR]

BackgroundSerum thyroglobulin (Tg) is associated with the presence of thyroid disease and has been proposed as a biomarker of iodine status. Few studies have examined factors related to serum Tg in populations environmentally exposed to ionizing radiation and living in regions with endemic mild-to-moderate iodine deficiency.MethodsWe screened 10,430 individuals who were living in Ukraine and under 18 years of age at the time of the 1986 Chernobyl Nuclear Power Plant accident for thyroid disease from 2001 to 2003. We estimated the percent change (PC) in serum Tg associated with demographic factors, iodine-131 thyroid dose, and indicators of thyroid structure and function using linear regression. We also examined these relationships for individuals with and without indications of thyroid abnormality.ResultsMean and median serum Tg levels were higher among participants with abnormal thyroid structure/function. Percent change in serum Tg increased among females, smokers and with older age (p-values

We derived the first comprehensive organ dose library for Canadian pediatric and adult patients who underwent computed tomography (CT) scans between 1992 and 2019 to support epidemiological analysis of radiation risk. We calculated organ absorbed doses for Canadian CT patients in two steps. First, we modeled Computed Tomography Dose Index (CTDI) values by patient age, scan body part, and scan year for the scan period between 1992 and 2019 using national survey data conducted in Canada and partially the United Kingdom survey data as surrogates. Second, we converted CTDI values to organ absorbed doses using a library of organ dose conversion coefficients built in an organ dose calculation program, the National Cancer Institute dosimetry system for CT. In result, we created a library of doses delivered to 33 organs and tissues by different patient ages and genders, scan body parts and scan years. In the scan period before 2000, the organs receiving the greatest dose in the head, chest and abdomen–pelvis scans were the active marrow (3.7–15.2 mGy), lungs (54.7–62.8 mGy) and colon (54.9–68.5 mGy), respectively. We observed organ doses reduced by 24% (pediatric head and torso scans, and adult head scans) and 55% (adult torso scans) after 2000. The organ dose library will be used to analyse the risk of radiation exposure from CT scans in the Canadian CT patient cohort. [ABSTRACT FROM AUTHOR]

Purpose: The projected existence and magnitude of carcinogenic effects of ionizing radiation at low doses and low-dose rates is perhaps the most important issue in radiation protection today. Studies of childhood cancer and natural background radiation have the potential to throw direct light on this question, into a dose range below a few tens of mSv. This paper describes the studies that have been undertaken and their context, discusses some problems that arise and summarizes the present position. Conclusions: Many such studies have been undertaken, but most were too small to have a realistic chance of detecting the small effects expected from such low doses, based on risk projections from higher exposures. Case--control or cohort studies are to be preferred methodologically to ecological studies but can be prone to problems of registration/participation bias. Interview-based studies of the requisite size would be prohibitively expensive and would undoubtedly also run into problems of participation bias. Register-based studies can be very large and are free of participation bias. However, they need to estimate the radiation exposure of study subjects using models rather than individual measurements in the homes of those concerned. At present, no firm conclusions can be drawn from the studies that have been published to date. Further data and perhaps pooled studies offer a way forward. [ABSTRACT FROM AUTHOR]

Purpose: Currently, there are about 15 ongoing clinical studies on low dose radiation therapy for Coronavirus Disease 2019 pneumonia. One of the underlying assumptions is that irradiation of 0.5 to 1.5 Gy is effective at ameliorating viral pneumonia. We aimed to reanalyze all available experimental radiobiologic data to assess evidence for such amelioration.Methods and Materials: With standard statistical survival models, and based on a systematic literature review, we reanalyzed 13 radiobiologic animal data sets published in 1937 to 1973 in which animals (guinea pigs/dogs/cats/rats/mice) received radiation before or after bacterial or viral inoculation, and assessing various health endpoints (mortality/pneumonia morbidity). In most data sets absorbed doses did not exceed 7 Gy.Results: For 6 studies evaluating postinoculation radiation exposure (more relevant to low dose radiation therapy for Coronavirus Disease 2019 pneumonia) the results are heterogeneous, with one study showing a significant increase (P < .001) and another showing a significant decrease (P < .001) in mortality associated with radiation exposure. Among the remaining 4 studies, mortality risk was nonsignificantly increased in 2 studies and nonsignificantly decreased in 2 others (P > .05). For preinoculation exposure the results are also heterogeneous, with 6 (of 8) data sets showing a significant increase (P < .01) in mortality risk associated with radiation exposure and the other 2 showing a significant decrease (P < .05) in mortality or pneumonitis morbidity risk.Conclusions: These data do not provide support for reductions in morbidity or mortality associated with postinfection radiation exposure. For preinfection radiation exposure the inconsistency of direction of effect is difficult to interpret. One must be cautious about adducing evidence from such published reports of old animal data sets. [ABSTRACT FROM AUTHOR]

The empirical estimation of cancer risks in children associated with low-dose ionising radiation (<100 mSv) remains a challenge. The main reason is that the required combination of large sample sizes with accurate and comprehensive exposure assessment is difficult to achieve. An international scientific workshop, 'Childhood cancer and background radiation', organised by the Institute of Social and Preventive Medicine of the University of Bern, brought together researchers in this field to evaluate how epidemiological studies of background radiation and childhood cancer can best improve our understanding of the effects of low-dose ionising radiation. This review summarises and evaluates the findings of these studies with regard to their methodological differences, identifies key limitations and challenges, and proposes ways to move forward. Large childhood cancer registries, such as those in Great Britain, France and Germany, now permit the conducting of studies that should have sufficient statistical power to detect the effects predicted by standard risk models. Nevertheless, larger studies or pooled studies will be needed to investigate disease subgroups. The main challenge is to accurately assess children's individual exposure to radiation from natural sources and from other sources, as well as potentially confounding non-radiation exposures, in such large study populations. For this, the study groups should learn from each other to improve exposure estimation and develop new ways to validate exposure models with personal dosimetry. [ABSTRACT FROM AUTHOR]

In April 1986, the Chernobyl nuclear accident resulted in wide-scale contamination of Belarus with significantly elevated levels of radioiodine isotopes, mainly iodine-131 (131I), and long-lived radiocaesium isotopes, mainly caesium-137 (137Cs). Various groups of the population were affected by exposure to ionising radiation, including pregnant women and their foetuses. This paper describes the methods and results related to the establishment of a cohort of 2965 Belarusian people exposed in utero due to Chernobyl fallout. The cohort consists of individuals whose mothers resided in the most radioactively contaminated areas in Belarus at the time of the accident. Prenatal and postnatal doses to the thyroid due to intake of 131I, external irradiation and ingestion of radiocaesium isotopes were estimated for all cohort members. Ongoing research on this unique cohort will provide important information on adverse health effects following prenatal and postnatal exposure to radioiodine and radiocaesium isotopes, for which available epidemiological data are scant. [ABSTRACT FROM AUTHOR]

Background: Basal cell carcinoma of the skin (BCC) is the most common cancer in populations of European ancestry. Although consistently linked with basal cell carcinoma of the skin in case-control studies, few prospective cohort studies have evaluated the shape of the exposure-response of basal cell carcinoma associated with cumulative radiant solar ultraviolet exposure (UVR).Methods: We followed 63,912 white cancer-free US radiologic technologists from entry (1983-1998) to exit (2003-2005) with known ultraviolet irradiance at up to 5 residential locations. Using generalized-additive and relative risk models we analyzed the exposure-response of basal cell carcinomas associated with ambient cumulative ultraviolet radiant exposure using ground-based National Solar Radiation database Average Daily Total Global data and satellite-based National Aeronautics and Space Administration Total Ozone Mapping Spectrometer data.Results: There were 2151 technologists with an incident primary basal cell carcinoma. Risk of basal cell carcinoma rose with increasing cumulative ultraviolet radiation exposure using both measures, such that 1 MJ cm- 2 increased basal cell carcinoma risk by 8.48 (95% CI 5.22, 11.09, p < 0.001) and by 10.15 (95% CI 6.67, 13.10, p < 0.001) per 10,000 persons per year using the Average Daily Total Global and Total Ozone Mapping Spectrometer ultraviolet data, respectively; relative risk was likewise elevated. There was some evidence of upward curvature in the cumulative ultraviolet exposure response using both exposure measures with a greater increase in risk of basal cell carcinoma at higher levels of ultraviolet radiation exposure, but less evidence for curvature in relative risk. There are indications of substantial variation of relative risk with time after exposure and age at exposure, so that risk is highest for the period 10-14 years after ultraviolet radiation exposure and for those exposed under the age of 25.Conclusions: We observed increases in risk of basal cell carcinoma and a similar exposure-response for ground-based and satellite ultraviolet radiation measures. Our observations suggest that interventions should concentrate on persons with higher levels of ultraviolet radiation exposure. [ABSTRACT FROM AUTHOR]

Radiotherapy with sparsely ionizing photons is a cornerstone of successful cancer treatment. Age at time of exposure to radiation is known to influence biological outcomes for many end points. The effect of dose and age at exposure upon the occurrence of radiogenic cardiovascular disease is poorly understood. The goal of this work was to determine the response of maleWAG/RijCmcr rats at 6 months of age to gamma rays, and at 6 months or 6 weeks of age to X rays, using clinically relevant biomarkers of cardiovascular disease and kidney injury. Overall, there were significant radiation-induced effects on the levels of bicarbonate (P=0.0016), creatinine (P=0.0002), calcium (P = 0.0009), triglycerides (P = 0.0269) and blood urea nitrogen, albumin, protein, AST, alkaline phosphatase, total cholesterol and HDL (all P < 0.0001). Of those variables with a significant radiation-dose effect, there were significant modifications by age at time of exposure for bicarbonate (P = 0.0033), creatinine (P = 0.0015), AST (P = 0.0040), total cholesterol (P = 0.0006) and blood urea nitrogen, calcium, albumin, protein, alkaline phosphatase and HDL (all P < 0.0001). Cardiac perivascular collagen content was significantly increased in rats that were 8.0 Gy X-ray irradiated at 6 weeks of age (P < 0.047) but not at 6 months of age. While systemic blood pressure was elevated in both cohorts after 8.0 Gy X-ray irradiation (compared to agematched sham-irradiated controls), the magnitude of the increase above baseline was greater in the younger rats (P < 0.05). These findings indicate that dose and age at time of irradiation determine the timeline and severity of cardiac and renal injury. [ABSTRACT FROM AUTHOR]

Solar ultraviolet radiation is the primary risk factor for skin cancers and sun‐related eye disorders. Estimates of individual ambient ultraviolet irradiance derived from ground‐based solar measurements and from satellite measurements have rarely been compared. Using self‐reported residential history from 67 189 persons in a nationwide occupational US radiologic technologists' cohort, we estimated ambient solar irradiance using data from ground‐based meters and noontime satellite measurements. The mean distance moved from city of longest residence in childhood increased from 137.6 km at ages 13–19 to 870.3 km at ages ≥65, with corresponding increases in absolute latitude difference moved. At ages 20/40/60/80, the Pearson/Spearman correlation coefficients of ground‐based and satellite‐derived potential solar ultraviolet exposure, using irradiance and cumulative radiant exposure metrics, were high (=0.87–0.92). There was also moderate correlation (Pearson/Spearman correlation coefficients = 0.51–0.60) between irradiance at birth and at last‐known address, for ground‐based and satellite data. Satellite‐based lifetime estimates of ultraviolet radiation were generally 14–15% lower than ground‐based estimates, albeit with substantial uncertainties, possibly because ground‐based estimates incorporate fluctuations in cloud and ozone, which are incompletely incorporated in the single noontime satellite‐overpass ultraviolet value. If confirmed elsewhere, the findings suggest that ground‐based estimates may improve exposure assessment accuracy and potentially provide new insights into ultraviolet radiation–disease relationships in epidemiologic studies. The results of this study showed that in this large (~70 000) US occupational cohort of medical radiation workers, measures of potential irradiance and potential cumulative radiant exposure associated with solar ultraviolet radiation derived from ground‐based measures are highly correlated with measures derived from NASA satellite data. Satellite‐based lifetime estimates of ultraviolet radiation were generally 14–15% lower than ground‐based estimates, albeit with substantial uncertainties. There is also moderate correlation with irradiance at last known address and at birth, a reflection of the modest distance moved from city of residence in childhood over the course of life for persons in this cohort. [ABSTRACT FROM AUTHOR]

Background: Exposure to ionizing radiation during childhood is a well-established risk factor for thyroid cancer. However, the genetic mechanisms of radiation-associated carcinogenesis remain not fully understood.Methods: In this study, we used targeted next-generation sequencing and RNA-Seq to study 65 papillary thyroid cancers (PTCs) from patients in the Ukrainian-American cohort with measurement-based iodine-131 (I-131) thyroid doses received as a result of the Chernobyl accident. We fitted linear regression models to evaluate differences in distribution of risk factors for PTC according to type of genetic alteration and logistic regression models to evaluate the I-131 dose response. All statistical tests were two-sided.Results: Driver mutations were identified in 96.9% of these thyroid cancers, including point mutations in 26.2% and gene fusions in 70.8% of cases. Novel driver fusions such as POR-BRAF, as well as STRN-ALK fusions that have not been implicated in radiation-associated cancer before, were found. The mean I-131 dose in cases with point mutations was 0.2 Gy (range = 0.013-1.05 Gy), statistically significantly lower than 1.4 Gy (range = 0.009-6.15 Gy) for cases with fusions (P < .001). No driver point mutations were found in tumors from individuals who received more than 1.1 Gy of radiation. Relative to tumors with point mutations, the proportion of tumors with gene fusions increased with radiation dose, reaching 87.8% among individuals exposed to 0.3 Gy or higher. With a limited study sample size, the estimated odds ratio at 1 Gy was 20.01 (95% confidence interval = 2.57 to 653.02, P < .001). In addition, after controlling for I-131 dose, we found higher odds ratios for gene fusion-positive PTCs associated with several specific demographic and geographic features.Conclusions: Our data provide support for a link between I-131 thyroid dose and generation of carcinogenic gene fusions, the predominant mechanism of thyroid cancer associated with radiation exposure from the Chernobyl accident. [ABSTRACT FROM AUTHOR]

BACKGROUND: There are well-known associations of ionizing radiation with female breast cancer, and emerging evidence also for male breast cancer. In the United Kingdom, female breast cancer following occupational radiation exposure is among that set of cancers eligible for state compensation and consideration is currently being given to an extension to include male breast cancer. OBJECTIVES: We compare radiation-associated excess relative and absolute risks of male and female breast cancers. METHODS: Breast cancer incidence and mortality data in the Japanese atomic-bomb survivors were analyzed using relative and absolute risk models via Poisson regression. RESULTS: We observed significant (p ≤ 0.01) dose-related excess risk for male breast cancer incidence and mortality. For incidence and mortality data, there are elevations by factors of approximately 15 and 5, respectively, of relative risk for male compared with female breast cancer incidence, the former borderline significant (p = 0.050). In contrast, for incidence and mortality data, there are elevations by factors of approximately 20 and 10, respectively, of female absolute risk compared with male, both statistically significant (p < 0.001). There are no indications of differences between the sexes in age/time-since-exposure/age-at-exposure modifications to the relative or absolute excess risk. The probability of causation of male breast cancer following radiation exposure exceeds by at least a factor of 5 that of many other malignancies. CONCLUSIONS: There is evidence of much higher radiation-associated relative risk for male than for female breast cancer, although absolute excess risks for males are much less than for females. However, the small number of male cases and deaths suggests a degree of caution in interpretation of this finding. CITATION: Little MP, McElvenny DM. 2017. Male breast cancer incidence and mortality risk in the Japanese atomic bomb survivors -- differences in excess relative and absolute risk from female breast cancer. Environ Health Perspect 125:223-229; http://dx.doi.org/10.1289/EHP151 [ABSTRACT FROM AUTHOR]

Exposure to therapeutic doses of ionizing radiation is associated with damage to the heart and coronary arteries. However, only recently have studies with high-quality individual dosimetry data allowed this risk to be quantified while also adjusting for concomitant chemotherapy, and medical and lifestyle risk factors. At lower levels of exposure the evidence is less clear. In this article I review radiation-associated risks of circulatory disease in groups treated with radiotherapy for malignant and non-malignant disease, and in occupationally- or environmentally-exposed groups receiving rather lower levels of radiation dose, also for medical diagnostic purposes. Results of a meta-analysis suggest that excess relative risks per unit dose for various types of heart disease do not exhibit statistically significant ( p > 0.2) heterogeneity between studies. Although there are no marked discrepancies between risks derived from the high-dose therapeutic and medical diagnostic studies and from the moderate/low dose occupational and environmental studies, at least for ischemic heart disease and stroke there are indications of larger risks per unit dose for lower dose rate and fractionated exposures. Risks for stroke and other types of circulatory disease are significantly more variable ( p < 0.0001), possibly resulting from confounding and effect-modification by well known (but unobserved) risk factors. Adjustment for any of mean dose, dose fractionation or age at exposure results in the residual heterogeneity for cerebrovascular disease becoming non-significant. The review provides strong evidence in support of a causal association between both low and high dose radiation exposure and most types of circulatory disease. [ABSTRACT FROM AUTHOR]

The 1986 accident at the Chernobyl nuclear power plant remains the most serious nuclear accident in history, and excess thyroid cancers, particularly among those exposed to releases of iodine-131 remain the best-documented sequelae. Failure to take dose-measurement error into account can lead to bias in assessments of dose-response slope. Although risks in the Ukrainian-US thyroid screening study have been previously evaluated, errors in dose assessments have not been addressed hitherto. Dose-response patterns were examined in a thyroid screening prevalence cohort of 13,127 persons aged <18 at the time of the accident who were resident in the most radioactively contaminated regions of Ukraine. We extended earlier analyses in this cohort by adjusting for dose error in the recently developed TD-10 dosimetry. Three methods of statistical correction, via two types of regression calibration, and Monte Carlo maximum-likelihood, were applied to the doses that can be derived from the ratio of thyroid activity to thyroid mass. The two components that make up this ratio have different types of error, Berkson error for thyroid mass and classical error for thyroid activity. The first regression-calibration method yielded estimates of excess odds ratio of 5.78 Gy−1 (95% CI 1.92, 27.04), about 7% higher than estimates unadjusted for dose error. The second regression-calibration method gave an excess odds ratio of 4.78 Gy−1 (95% CI 1.64, 19.69), about 11% lower than unadjusted analysis. The Monte Carlo maximum-likelihood method produced an excess odds ratio of 4.93 Gy−1 (95% CI 1.67, 19.90), about 8% lower than unadjusted analysis. There are borderline-significant (p = 0.101–0.112) indications of downward curvature in the dose response, allowing for which nearly doubled the low-dose linear coefficient. In conclusion, dose-error adjustment has comparatively modest effects on regression parameters, a consequence of the relatively small errors, of a mixture of Berkson and classical form, associated with thyroid dose assessment. [ABSTRACT FROM AUTHOR]

• There is mounting evidence of cancer risk from low dose radiation in childhood. • A systematic review was conducted of cancer after exposure in utero or childhood. • There were excess cancer risks associated with radiation exposure in childhood. • There were excess cancer risks associated with radiation exposure in utero. • Excess cancer risks were seen at levels approaching 0.02 Gy. The detrimental health effects associated with the receipt of moderate (0.1–1 Gy) and high (>1 Gy) acute doses of sparsely ionising radiation are well established from human epidemiological studies. There is accumulating direct evidence of excess risk of cancer in a number of populations exposed at lower acute doses or doses received over a protracted period. There is evidence that relative risks are generally higher after radiation exposures in utero or in childhood. We reviewed and summarised evidence from 60 studies of cancer or benign neoplasms following low- or moderate-level exposure in utero or in childhood from medical and environmental sources. In most of the populations studied the exposure was predominantly to sparsely ionising radiation, such as X-rays and gamma-rays. There were significant (p < 0.001) excess risks for all cancers, and particularly large excess relative risks were observed for brain/CNS tumours, thyroid cancer (including nodules) and leukaemia. Overall, the totality of this large body of data relating to in utero and childhood exposure provides support for the existence of excess cancer and benign neoplasm risk associated with radiation doses < 0.1 Gy, and for certain groups exposed to natural background radiation, to fallout and medical X-rays in utero , at about 0.02 Gy. [ABSTRACT FROM AUTHOR]

Atherosclerosis is the main cause of coronary heart disease and stroke, the two major causes of death in developed society. There is emerging evidence of excess risk of cardiovascular disease at low radiation doses in various occupationally exposed groups receiving small daily radiation doses. Assuming that they are causal, the mechanisms for effects of chronic fractionated radiation exposures on cardiovascular disease are unclear. We outline a spatial reaction-diffusion model for atherosclerosis and perform stability analysis, based wherever possible on human data. We show that a predicted consequence of multiple small radiation doses is to cause mean chemo-attractant (MCP-1) concentration to increase linearly with cumulative dose. The main driver for the increase in MCP-1 is monocyte death, and consequent reduction in MCP-1 degradation. The radiation-induced risks predicted by the model are quantitatively consistent with those observed in a number of occupationally-exposed groups. The changes in equilibrium MCP-1 concentrations with low density lipoprotein cholesterol concentration are also consistent with experimental and epidemiologic data. This proposed mechanism would be experimentally testable. If true, it also has substantive implications for radiological protection, which at present does not take cardiovascular disease into account. The Japanese A-bomb survivor data implies that cardiovascular disease and cancer mortality contribute similarly to radiogenic risk. The major uncertainty in assessing the low-dose risk of cardiovascular disease is the shape of the dose response relationship, which is unclear in the Japanese data. The analysis of the present paper suggests that linear extrapolation would be appropriate for this endpoint. [ABSTRACT FROM AUTHOR]

The International Commission on Radiological Protection (ICRP) has considered for over 60 years that the lens of the eye is among the most radiosensitive tissues, and has recommended dose limits for the lens to prevent occurrence of vision impairing cataracts (VICs). Epidemiological evidence that doses much lower than previously thought produce cataracts led ICRP to recommend reducing dose threshold for VICs and reducing an occupational equivalent dose limit for the lens in 2011, when only a single threshold of 0.5 Gy was recommended. On the basis of epidemiological evidence, ICRP assumed progression of minor opacities into VICs and no dose rate effect. This contrasts with previously recommended separate thresholds for minor opacities and VICs, and for different exposure scenarios. Progression was assumed based on similar risks of cataracts and cataract surgery in Japanese atomic bomb survivors. The absence of dose rate effect derived from the observed similar thresholds for protracted exposures in Chernobyl cleanup workers and in atomic bomb survivors. Since 2011, there has been an increasing body of epidemiological evidence relating to cataracts and other ocular diseases (i.e. glaucoma and macular degeneration), particularly at low doses and low dose rates. This review paper gives an overview of the scientific basis of the 2011 ICRP recommendation, discusses the plausibility of these two assumptions in the light of emerging scientific evidence, and considers the radiosensitivity of the lens among ocular structures. [ABSTRACT FROM AUTHOR]

Several letters to the editor and a reply are presented in response to article "Radiation exposure from CT scans in childhood and subsequent risk in leukemia and brain tumours: a restrospective cohort study," by M.S. Pearce, J.A. Salotti, and M.P. Little in the 2012 issue.