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A large excess risk of thyroid cancer was observed among Belarusian/Russian/Baltic Chornobyl cleanup workers. A more recent study of Ukraine cleanup workers found more modest excess risks of thyroid cancer. Dose errors in this data are substantial, associated with model uncertainties and questionnaire response. Regression calibration is often used for dose-error adjustment, but may not adequately account for the full error distribution. We aimed to examine the impact of exposure-assessment uncertainties on thyroid cancer among Ukrainian cleanup workers using Monte Carlo maximum likelihood, and compare with results derived using regression calibration. Analyses assessed the sensitivity of results to various components of internal and external dose. Regression calibration yielded an excess odds ratio per Gy (EOR/Gy) of 0.437 (95% CI - 0.042, 1.577, p = 0.100), compared with the EOR/Gy using Monte Carlo maximum likelihood of 0.517 (95% CI - 0.039, 2.035, p = 0.093). Trend risk estimates for follicular morphology tumors exhibited much more extreme effects of full-likelihood adjustment, the EOR/Gy using regression calibration of 3.224 (95% CI - 0.082, 30.615, p = 0.068) becoming ~ 50% larger, 4.708 (95% CI - 0.075, 85.143, p = 0.066) when using Monte Carlo maximum likelihood. Results were sensitive to omission of external components of dose. In summary, use of Monte Carlo maximum likelihood adjustment for dose error led to increases in trend risks, particularly for follicular morphology thyroid cancers, where risks increased by ~ 50%, and were borderline significant. The unexpected finding for follicular tumors needs to be replicated in other exposed groups.

Genomics of radiation-induced damage The potential adverse effects of exposures to radioactivity from nuclear accidents can include acute consequences such as radiation sickness, as well as long-term sequelae such as increased risk of cancer. There have been a few studies examining transgenerational risks of radiation exposure but the results have been inconclusive. Morton et al. analyzed papillary thyroid tumors, normal thyroid tissue, and blood from hundreds of survivors of the Chernobyl nuclear accident and compared them against those of unexposed patients. The findings offer insight into the process of radiation-induced carcinogenesis and characteristic patterns of DNA damage associated with environmental radiation exposure. In a separate study, Yeager et al. analyzed the genomes of 130 children and parents from families in which one or both parents had experienced gonadal radiation exposure related to the Chernobyl accident and the children were conceived between 1987 and 2002. Reassuringly, the authors did not find an increase in new germline mutations in this population. Science , this issue p. eabg2538 , p. 725

This original study aims to quantify the human factor uncertainties in radiation doses for Chernobyl cleanup workers that are associated with errors in direct or proxy personal interviews due to poor memory recall a long time after exposure. Two types of doses due to external irradiation during cleanup mission were calculated independently. First, a "reference" dose, that was calculated using the historical description of cleanup activities reported by 47 cleanup workers shortly after the completion of the cleanup mission. Second, a "current" dose that was calculated using information reported by 47 cleanup workers and respective 24 proxies (colleagues) nominated by cleanup workers during a personal interview conducted more recently, as part of this study, i.e., 25-30 years after their cleanup missions. The Jaccard similarity coefficient for reference and current doses was moderate: the arithmetic mean ± standard deviation was 0.29 ± 0.18 (median = 0.31) and 0.23 ± 0.18 (median = 0.22) for the cleanup worker's and proxy's interviews, respectively. The agreement between two doses was better if the cleanup worker was interviewed rather than his proxy: the median ratio of current to reference dose was 1.0 and 0.56 for cleanup workers and proxies, respectively. The present study has shown that human factor uncertainties lead to underestimation or overestimation of the "true" reference dose for most cleanup workers up to 3 times. In turn, the potential impact of these errors on radiation-related risk estimates should be assessed.

This article presents a methodology for assessing the radiation doses in an urban environment due to external irradiation from radionuclides deposited on the ground and other surfaces as well as from a passing radioactive cloud. The approach was developed and applied to assess individual doses of residents of the town of Pripyat who were evacuated shortly after the Chernobyl accident. Typically, the so-called location factor is defined as the ratio of the dose rate at a point of exposure and the dose rate at an undisturbed lawn far from any buildings. The present study used a new definition of the location factor as a regular four-dimensional grid of ratios of air kerma rates indoors and outdoors distributed in space and time. The location factors were calculated for two scenarios: outdoor and indoor values for typical apartments and buildings in Pripyat. Indoor location factors varied within two orders of magnitude depending on the floor of residence and place of staying inside the apartment. Values of the indoor location factor differed during the daytime and night by a factor of 30–40 depending on the behaviour of an individual within the apartment. Both, outdoor and indoor location factors decreased with decreasing distances between buildings. It was shown that during the first 4 days after the accident, air kerma rates in Pripyat were governed by the radionuclides deposited on the ground surface, and not by radionuclides in the cloud. Specifically, the contribution of the radioactive cloud to air kerma rate was maximal (i.e., 2.3%) on the morning of 28 April 1986. The methodology and results of this study are currently being used to reconstruct the radiation gonadal dose for the subjects of the American–Ukrainian study of parental irradiation in Chernobyl cleanup workers and evacuees for investigating germline mutations in their offspring.

Thyroid doses were estimated for 607 subjects of the case-control study of thyroid cancer nested in the cohort of 150,813 male Ukrainian cleanup workers, who were exposed to radiation as a result of the 1986 Chernobyl nuclear power plant accident. Individual thyroid doses due to external irradiation, inhalation of (131)I and short-lived radioiodine and radiotellurium isotopes ((132)I, (133)I, (135)I, (131m)Te and (132)Te) during the cleanup mission, and intake of (131)I during residence in contaminated settlements were calculated for all study subjects, along with associated uncertainty distributions. The average thyroid dose due to all exposure pathways combined was estimated to be 199 mGy (median dose of 47 mGy; range: 0.15 mGy to 9.0 Gy), with averages of 140 mGy (median of 20 mGy; range: 0.015 mGy to 3.6 Gy) from external irradiation during the cleanup mission, 44 mGy (median of 12 mGy; range: ~0 mGy to 1.7 Gy) due to (131)I inhalation, 42 mGy (median of 7.3 mGy; range: 0.001 mGy to 3.4 Gy) due to (131)I intake during residence, and 11 mGy (median of 1.6 mGy; range: ~0 mGy to 0.38 Gy) due to inhalation of short-lived radionuclides. Internal exposure of the thyroid gland to (131)I contributed more than 50% of the total thyroid dose in 45% of the study subjects. The uncertainties of the individual stochastic doses were characterized by a mean GSD of 2.0, 1.8, 2.0 and 2.6 for external irradiation, inhalation of (131)I, inhalation of short-lived radionuclides and residential exposure, respectively. The models used for dose calculations were validated against instrumental measurements done shortly after the accident. Results of the validation showed that thyroid doses could be estimated retrospectively for Chernobyl cleanup workers two-three decades after the accident with a reasonable degree of reliability.

Although much is known about the radiation-related risk of thyroid cancer in those exposed at young ages, less is known about the risk due to adult exposure, particularly in men. We aimed to examine the association between thyroid radiation dose received during adulthood and thyroid cancer risk in men. We conducted a nested case-control study (149 cases; 458 controls) of male, Ukrainian cleanup workers who first worked in the Chornobyl zone between ages 18 and 59 years, with cases identified through linkage with the National Cancer Registry of Ukraine from 1988 to 2012. Individual thyroid doses due to external and internal exposure during the cleanup mission and during residence in contaminated settlements were estimated (total dose mean 199 mGy; range 0.15 mGy to 9.0 Gy). The excess odds ratio per gray (EOR/Gy) for overall thyroid cancer was 0.40 (95% CI: - 0.05, 1.48; p-value = 0.118). Time since exposure was borderline significant (p-value = 0.061) in modifying this association so that less time since exposure was associated with a stronger EOR/Gy. An elevated, but nonsignificant association was observed for follicular thyroid cancer (EOR/Gy = 1.72; 95% CI: - 0.25, 13.69; p-value = 0.155) based on a small number of cases (n = 24). Our findings for radiation-related overall thyroid cancer risk are consistent with evidence of increased risks observed in most of the other studies of adult exposure, though the magnitude of the effect in this study is lower than in the previous case-control study of Chornobyl cleanup workers.

Radiation doses of parents exposed from the Chornobyl accident as cleanup workers or evacuees were estimated in the National Cancer Institute-National Research Center for Radiation Medicine trio (i.e. father, mother, offspring) study aimed at investigating the radiation effects on germline de novo mutations in children as well as other outcomes. Paternal (testes) and maternal (ovaries) gonadal doses were calculated along with associated uncertainty distributions for the following exposure pathways: (a) external irradiation during the cleanup mission, (b) external irradiation during residence in Pripyat, and (c) external irradiation and (d) ingestion of radiocesium isotopes, such as 134Cs and 137Cs, during residence in settlements other than Pripyat. Gonadal doses were reconstructed for 298 trios for the periods from the time of the accident on 26 April 1986 to two time points before the child’s date of birth (DOB): 51 (DOB-51) and 38 (DOB-38) weeks. The two doses, DOB-51 and DOB-38 were equal (within 1 mGy) in most instances, except for 35 fathers where the conception of the child occurred within 3 months of exposure or during exposure. The arithmetic mean of gonadal DOB-38 doses was 227 mGy (median: 11 mGy, range 0–4080 mGy) and 8.5 mGy (median: 1.0 mGy, range 0–550 mGy) for fathers and mothers, respectively. Gonadal doses varied considerably depending on the exposure pathway, the highest gonadal DOB-38 doses being received during the cleanup mission (mean doses of 376 and 34 mGy, median of 144 and 7.4 mGy for fathers and mothers, respectively), followed by exposure during residence in Pripyat (7.7 and 13 mGy for mean, 7.2 and 6.2 mGy for median doses) and during residence in other settlements (2.0 and 2.1 mGy for mean, 0.91 and 0.81 mGy for median doses). Monte Carlo simulations were used to estimate the parental gonadal doses and associated uncertainties. The geometric standard deviations (GSDs) in the individual parental stochastic doses due to external irradiation during the cleanup mission varied from 1.2 to 4.7 (mean of 1.8), while during residence in Pripyat they varied from 1.4 to 2.8 (mean of 1.8), while the mean GSD in doses received during residence in settlements other than Pripyat was 1.3 and 1.4 for external irradiation and ingestion of radiocesium isotopes, respectively.

Purpose: To share the experience in regulation of radiation safety and protection of workers involved in management of the spent nuclear fuel (SNF) and radioactive waste (RW), as well as radiation protection of the population and environment in the vicinity of sites for temporary storage at Andreeva Bay on the Kola Peninsula. Material and methods: Spent fuel from Russian nuclear powered submarines has been stored at shore based facilities for more than 20 years, notably at Andreeva Bay. The storage facilities were for some years poorly maintained and a significant fraction of the fuel that is still in store at the site wais damaged. Over the last years, hugemuch work has been done to improve the technical infrastructure and prepare for removal of the SNF from the temporary stores, management of existing RW. Results: This paper presents progress with projects of the FMBA of Russia and NRPA cooperation for regulation of radiation safety and protection. During the researches, the following issues were addressed: radiological threat assessment to identify the priority directions of regulation; detailed analysis of the radiation situation on sites, at the territories and nearby the sites; radiation control and monitoring of the environmental conditions; development of the computer maps and geo-information system; emergency preparedness and response; improvement of radiation safety culture; etc. Based on the received results of monitoring and assessment of the current risks, site-specific regulatory documents have been developed for the bodies and institutions under the FMBA of Russia involved in the activities to control the facility. Those documents include the requirements for: radiation protection of workers and population; personal dose monitoring; the RW management including the very low level RW; implementation of the environmental monitoring; radiation monitoring nearby the Andreeva Bay SevRAO facility; and remediation of the sites as remediation criteria and regulations. The next stage of work is to carry out the regulation of large-scale removal of SNF during 2017–2021 and its subsequent transfer to Mayak PA, and operations to bring the infrastructure of the site into the hsafe conditions, i.e., ecological remediation of the site – by 2025. Lessons learnt from this work are being used in support of improved international recommendations and guidance on how to address legacy issues. Conclusion: The experience accumulated during regulation of the remediation process of the former Naval Coastal Technical Bases, has helped to identify new relevant areas of improvement of the regulatory supervision at nuclear legacy sites. The study of potential hazard of radiation exposure to the personnel during technological operations of SNF and RW management is very important issue. In this light, the regulator in cooperation of the operator should develop some effective and efficient activities for dose monitoring. When dealing with the protection of the population and environment, a methodology of comprehensive radiation and chemical monitoring should be developed and models of radiation and chemical risks should be improved taking into account features of contamination of the site under remediation. An important link of the social focus of the regulator and the operator is to improve strategies of public communications near legacy sites under remediation.

Radiation doses received by workers during their movement within areas contaminated as a result of events and activities, leading to emergency or existing exposure situations, may provide a substantial contribution to total external exposure during remediation work. This paper describes an approach to minimise worker external exposure in these circumstances, based on graph theory. The paper describes several tasks, including: searching for a route with the lowest dose, searching for an optimal bypass with a given set of control points and searching for the optimal road network coverage. Classical graph theory algorithms have been used (Dijkstra's algorithm, Chinese postman problem and travelling salesman problem). Algorithms for solving the above mentioned problems have been developed and were included in the information-analytical system for radiation safety. This software has been applied for optimisation of protection during remediation work at the Andreeva Bay site of temporary storage for spent fuel and radioactive waste in the Kola Peninsula, both in the context of existing exposure situations and improving the preparedness for emergency exposure situations.

This paper deals with classification of dose distributions of nuclear workers based on antikurtosis (Q) and entropy coefficients (K) and their relationship presented in QK-diagrams. It is shown that determination of the most appropriate distribution to adopt, for a specific data set of a wide range of input data, requires building and analysing QK-diagrams for distributions of logarithms of individual doses. Actual dose distributions for emergency and occupational exposure situations were then considered, as well as doses for one day of work during clean-up and routine activities. It is shown that, in all cases, three types of distributions of logarithms of individual doses were present: normal, Weibull and Chapeau. The location of the representation point of a dose distribution reflects the degree of dose control of the group of workers whose individual doses are collectively displayed in the QK-diagram. The more the representation point of the analysed distribution of the logarithms of the individual dose of a given contingent of workers deviates from the point of the lognormal distribution, the more there was intervention in the process of individual dose accumulation. Thus, QK-diagrams could be used to develop a dose control function. It is shown that the hybrid lognormal distribution, which is widely used in the field of radiation safety, for the purpose of approximation of real dose distributions, is unable to satisfactorily describe many dose distributions arising in aftermath operations and occupational exposure.

Although transgenerational effects of exposure to ionizing radiation have long been a concern, human research to date has been confined to studies of disease phenotypes in groups exposed to high doses and high dose rates, such as the Japanese atomic bomb survivors. Transgenerational effects of parental irradiation can be addressed using powerful new genomic technologies. In collaboration with the Ukrainian National Research Center for Radiation Medicine, the US National Cancer Institute, in 2014–2018, initiated a genomic alterations study among children born in selected regions of Ukraine to cleanup workers and/or evacuees exposed to low–dose-rate radiation after the 1986 Chornobyl (Chernobyl) nuclear accident. To investigate whether parental radiation exposure is associated with germline mutations and genomic alterations in the offspring, we are collecting biospecimens from father-mother-offspring constellations to study de novo mutations, minisatellite mutations, copy-number changes, structural variants, genomic insertions and deletions, methylation profiles, and telomere length. Genomic alterations are being examined in relation to parental gonadal dose, reconstructed using questionnaire and measurement data. Subjects are being recruited in exposure categories that will allow examination of parental origin, duration, and timing of exposure in relation to conception. Here we describe the study methodology and recruitment results and provide descriptive information on the first 150 families (mother-father-child(ren)) enrolled.

Several hundred thousand individuals, called ‘cleanup workers’ or ‘liquidators’, who took part in decontamination and recovery activities between 1986 and 1990 within the 30-km zone around the Chernobyl nuclear power plant in Ukraine, were mainly exposed to external irradiation. However, those who were involved in cleanup activities during the 10-day period of atmospheric releases also received doses to the thyroid gland due to internal irradiation resulting essentially from inhalation of (131)I. The paper presents the methodology and results of the calculation of individual thyroid doses for cleanup workers. The model that was used considers several factors, including the ground-level outdoor air concentrations of (131)I at the locations of residence and work of the cleanup workers, the reduction of (131)I activity in inhaled air associated with indoor occupancy, the time spent indoors, the breathing rate, which depends on the type of physical activity, and the possible intake of potassium iodine (KI) for iodine prophylaxis. Thyroid doses were calculated for a group of 594 cleanup workers with individual measurements of exposure rate against the neck, called ‘direct thyroid measurements’, that were performed from 30 April to 5 May 1986. The measured values of exposure rate were corrected to subtract the contribution of short-lived radioiodine isotopes in the thyroid to the detector response. The average thyroid dose due to (131)I inhalation by the cleanup workers was estimated to be 180 mGy, while the median was 110 mGy. Most of the cleanup workers (73%) received thyroid doses ranging from 50 to 500 mGy. The highest individual dose from (131)I inhalation among the cleanup workers with direct thyroid measurements was 4.5 Gy. To validate the model, the (131)I activities in the thyroids that were calculated using the model were compared with those derived from the direct thyroid measurements. The mean of the ratios of measured-to-calculated activities of (131)I in the thyroid was found to be 1.6 while the median of those ratios was 0.8. For 60 cleanup workers with direct thyroid measurements, a detailed description of hour-by-hour whereabouts and work history was available. For these cleanup workers the mean of the ratios of measured-to-calculated activities was found to be 1.2 and the median of those ratios was 1.0. These encouraging results suggest that the thyroid dose due to (131)I inhalation could be estimated for Chernobyl cleanup workers with a reasonable degree of reliability even in the absence of direct thyroid measurements. However, this conclusion assumes that detailed information on whereabouts and work history could be obtained for those cleanup workers who were not measured.

The Coastal Technical Base (CTB) №569 at Andreeva Bay was established in the early 1960s and intended for the refueling of nuclear submarine reactors and temporary storage of spent nuclear fuel (SNF) and radioactive waste (RW). In 2001, the base was transferred to the Russian Ministry for Atomic Energy and the site remediation began. The paper describes in detail the radiation situation change at the technical site in Andreeva Bay from 2002-2016, the period of preparation for the most critical phase of remedial work: removal of spent fuel assemblies. The analysis of aggregated indicators and data mining were used. The article suggests the best number and location of checkpoints needed to ensure sufficient accuracy of the radiation situation description. The fractal properties of the radiation field are studied using the Hurst index. The relationship between checkpoints was assessed using the method of searching for checkpoint communities. The decrease in the integral of the ambient dose equivalent rate (ADER) at the technical site was evaluated by the method of time series decomposition. Three components of time series were identified: trend, seasonal and residual. The trend of the ADER integral over the technical site is a monotonic decreasing function, where the initial and final values differ tenfold. Taking into account that 137Cs dominates the radiation situation on-site, it is clear that the ADER due to the radionuclide decay will have decreased by 1.4 times. It is estimated that only a small proportion of 137Cs has migrated off-site. Therefore, approximately a sevenfold decrease in dose rate is mainly due to remediation activities of personnel. During the year, the seasonal component varies the ADER integral by a factor of two, due to snowfall. The residual component reflects the uncertainty of the ADER integral calculation and phases of active SNF and RW management. The methods developed are used to support the optimization of remediation work as well as regulatory supervision of occupational radiation protection.

Groups of Japanese and American scientists, supported by international collaborators, have worked for many years to ensure the accuracy of the radiation dosimetry used in studies of health effects in the Japanese atomic bomb survivors. Reliable dosimetric models and systems are especially critical to epidemiologic studies of this population because of their importance in the development of worldwide radiation protection standards. While dosimetry systems, such as Dosimetry System 1986 (DS86) and Dosimetry System 2002 (DS02), have improved, the research groups that developed them were unable to propose or confirm an additional contribution by residual radiation to the survivor's total body dose. In recognition of the need for an up-to-date review of residual radiation exposures in Hiroshima and Nagasaki, a half-day technical session was held for reports on newer studies at the 59 th Annual HPS Meeting in 2014 in Baltimore, MD. A day-and-a-half workshop was also held to provide time for detailed discussion of the newer studies and to evaluate their potential use in clarifying the residual radiation exposure to atomic bomb survivors at Hiroshima and Nagasaki. The process also involved a re-examination of very early surveys of radioisotope emissions from ground surfaces at Hiroshima and Nagasaki and early reports of health effects. New insights were reported on the potential contribution to residual radiation from neutron-activated radionuclides in the airburst's dust stem and pedestal and in unlofted soil, as well as from fission products and weapon debris from the nuclear cloud. However, disparate views remain concerning the actual residual radiation doses received by the atomic bomb survivors at different distances from the hypocenter. The workshop discussion indicated that measurements made using thermal luminescence and optically stimulated luminescence, like earlier measurements, especially in very thin layers of the samples, could be expanded to detect possible radiation exposures to beta particles and to determine their significance plus the extent of the various residual radiation areas at Hiroshima and Nagasaki. Other suggestions for future residual radiation studies are included in this workshop report.

In compliance with the fundamentals of the government's policy in the field of nuclear and radiation safety approved by the President of the Russian Federation, Russia has developed a national program for decommissioning of its nuclear legacy. Under this program, the State Atomic Energy Corporation 'Rosatom' is carrying out remediation of a Site for Temporary Storage of spent nuclear fuel (SNF) and radioactive waste (RW) at Andreeva Bay located in Northwest Russia. The short term plan includes implementation of the most critical stage of remediation, which involves the recovery of SNF from what have historically been poorly maintained storage facilities. SNF and RW are stored in non-standard conditions in tanks designed in some cases for other purposes. It is planned to transport recovered SNF to PA 'Mayak' in the southern Urals. This article analyses the current state of the radiation safety supervision of workers and the public in terms of the regulatory preparedness to implement effective supervision of radiation safety during radiation-hazardous operations. It presents the results of long-term radiation monitoring, which serve as informative indicators of the effectiveness of the site remediation and describes the evolving radiation situation. The state of radiation protection and health care service support for emergency preparedness is characterized by the need to further study the issues of the regulator-operator interactions to prevent and mitigate consequences of a radiological accident at the facility. Having in mind the continuing intensification of practical management activities related to SNF and RW in the whole of northwest Russia, it is reasonable to coordinate the activities of the supervision bodies within a strategic master plan. Arrangements for this master plan are discussed, including a proposed programme of actions to enhance the regulatory supervision in order to support accelerated mitigation of threats related to the nuclear legacy in the area.

Andreeva Bay in northwest Russia hosts one of the former coastal technical bases of the Northern Fleet. Currently, this base is designated as the Andreeva Bay branch of Northwest Center for Radioactive Waste Management (SevRAO) and is a site of temporary storage (STS) for spent nuclear fuel (SNF) and other radiological waste generated during the operation and decommissioning of nuclear submarines and ships. According to an integrated expert evaluation, this site is the most dangerous nuclear facility in northwest Russia. Environmental rehabilitation of the site is currently in progress and is supported by strong international collaboration. This paper describes how the optimization principle (ALARA) has been adopted during the planning of remediation work at the Andreeva Bay STS and how Russian-Norwegian collaboration greatly contributed to ensuring the development and maintenance of a high level safety culture during this process. More specifically, this paper describes how integration of a system, specifically designed for improving the radiological safety of workers during the remediation work at Andreeva Bay, was developed in Russia. It also outlines the 3D radiological simulation and virtual reality based systems developed in Norway that have greatly facilitated effective implementation of the ALARA principle, through supporting radiological characterisation, work planning and optimization, decision making, communication between teams and with the authorities and training of field operators.

The increased occupational doses resulting from the Chernobyl nuclear reactor accident that occurred in Ukraine in April 1986, the reactor accident of Fukushima that took place in Japan in March 2011, and the early operations of the Mayak Production Association in Russia in the 1940s and 1950s are presented and discussed. For comparison purposes, the occupational doses due to the other two major reactor accidents (Windscale in the United Kingdom in 1957 and Three Mile Island in the United States in 1979) and to the main plutonium-producing facility in the United States (Hanford Works) are also covered but in less detail. Both for the Chernobyl nuclear reactor accident and the routine operations at Mayak, the considerable efforts made to reconstruct individual doses from external irradiation to a large number of workers revealed that the recorded doses had been overestimated by a factor of about two.Introduction of Increased Occupational Exposures: Nuclear Industry Workers. (Video 1:32, http://links.lww.com/HP/A21).

Background: Risks of most types of leukemia from exposure to acute high doses of ionizing radiation are well known, but risks associated with protracted exposures, as well as associations between radiation and chronic lymphocytic leukemia (CLL), are not clear. Objectives: We estimated relative risks of CLL and non-CLL from protracted exposures to low-dose ionizing radiation. Methods: A nested case–control study was conducted in a cohort of 110,645 Ukrainian cleanup workers of the 1986 Chornobyl nuclear power plant accident. Cases of incident leukemia diagnosed in 1986–2006 were confirmed by a panel of expert hematologists/hematopathologists. Controls were matched to cases on place of residence and year of birth. We estimated individual bone marrow radiation doses by the Realistic Analytical Dose Reconstruction with Uncertainty Estimation (RADRUE) method. We then used a conditional logistic regression model to estimate excess relative risk of leukemia per gray (ERR/Gy) of radiation dose. Results: We found a significant linear dose response for all leukemia [137 cases, ERR/Gy = 1.26 (95% CI: 0.03, 3.58]. There were nonsignificant positive dose responses for both CLL and non-CLL (ERR/Gy = 0.76 and 1.87, respectively). In our primary analysis excluding 20 cases with direct in-person interviews < 2 years from start of chemotherapy with an anomalous finding of ERR/Gy = –0.47 (95% CI: < –0.47, 1.02), the ERR/Gy for the remaining 117 cases was 2.38 (95% CI: 0.49, 5.87). For CLL, the ERR/Gy was 2.58 (95% CI: 0.02, 8.43), and for non-CLL, ERR/Gy was 2.21 (95% CI: 0.05, 7.61). Altogether, 16% of leukemia cases (18% of CLL, 15% of non-CLL) were attributed to radiation exposure. Conclusions: Exposure to low doses and to low dose-rates of radiation from post-Chornobyl cleanup work was associated with a significant increase in risk of leukemia, which was statistically consistent with estimates for the Japanese atomic bomb survivors. Based on the primary analysis, we conclude that CLL and non-CLL are both radiosensitive.

26 April 2006 marks the 20th anniversary of the Chernobyl accident. On this occasion, the World Health Organization (WHO), within the UN Chernobyl Forum initiative, convened an Expert Group to evaluate the health impacts of Chernobyl. This paper summarises the findings relating to cancer. A dramatic increase in the incidence of thyroid cancer has been observed among those exposed to radioactive iodines in childhood and adolescence in the most contaminated territories. Iodine deficiency may have increased the risk of developing thyroid cancer following exposure to radioactive iodines, while prolonged stable iodine supplementation in the years after exposure may reduce this risk. Although increases in rates of other cancers have been reported, much of these increases appear to be due to other factors, including improvements in registration, reporting and diagnosis. Studies are few, however, and have methodological limitations. Further, because most radiation-related solid cancers continue to occur decades after exposure and because only 20 years have passed since the accident, it is too early to evaluate the full radiological impact of the accident. Apart from the large increase in thyroid cancer incidence in young people, there are at present no clearly demonstrated radiation-related increases in cancer risk. This should not, however, be interpreted to mean that no increase has in fact occurred: based on the experience of other populations exposed to ionising radiation, a small increase in the relative risk of cancer is expected, even at the low to moderate doses received. Although it is expected that epidemiological studies will have difficulty identifying such a risk, it may nevertheless translate into a substantial number of radiation-related cancer cases in the future, given the very large number of individuals exposed. © 2006 IOP Publishing Ltd.

Between 1986 and 1990, several hundred thousand workers, called "liquidators" or "clean-up workers," took part in decontamination and recovery activities within the 30-km zone around the Chernobyl nuclear power plant in Ukraine, where a major accident occurred in April 1986. The Chernobyl liquidators were mainly exposed to external ionizing radiation levels that depended primarily on their work locations and the time after the accident when the work was performed. Because individual doses were often monitored inadequately or were not monitored at all for the majority of liquidators, a new method of photon (i.e., gamma and x rays) dose assessment, called "RADRUE" (Realistic Analytical Dose Reconstruction with Uncertainty Estimation), was developed to obtain unbiased and reasonably accurate estimates for use in three epidemiologic studies of hematological malignancies and thyroid cancer among liquidators. The RADRUE program implements a time-and-motion dose-reconstruction method that is flexible and conceptually easy to understand. It includes a large exposure rate database and interpolation and extrapolation techniques to calculate exposure rates at places where liquidators lived and worked within approximately 70 km of the destroyed reactor. The RADRUE technique relies on data collected from subjects' interviews conducted by trained interviewers, and on expert dosimetrists to interpret the information and provide supplementary information, when necessary, based upon their own Chernobyl experience. The RADRUE technique was used to estimate doses from external irradiation, as well as uncertainties, to the bone marrow for 929 subjects and to the thyroid gland for 530 subjects enrolled in epidemiologic studies. Individual bone marrow dose estimates were found to range from less than one muGy to 3,300 mGy, with an arithmetic mean of 71 mGy. Individual thyroid dose estimates were lower and ranged from 20 muGy to 507 mGy, with an arithmetic mean of 29 mGy. The uncertainties, expressed in terms of geometric standard deviations, ranged from 1.1 to 5.8, with an arithmetic mean of 1.9.