Physical dosimetry of chernobyl cleanup workers

Primary care clinic visits in formerly evacuated areas due to radiation disaster following the Great East Japan Earthquake: A retrospective descriptive study

Radiation disasters pose distinctive medical challenges, requiring diverse care approaches. Beyond radiation exposure assessment, addressing health impacts due to lifestyle changes, especially among vulnerable populations, is vital. Evacuation orders issued in radiation-affected areas introduce unique healthcare dynamics, with their duration significantly influencing the recovery process. Understanding evolving patient demographics and medical needs after lifting evacuation orders is crucial for post-disaster care planning. Minamisoma Municipal Odaka Hospital, located 13 to 20 km from Fukushima Daiichi Nuclear power plant in a post-evacuation zone, was greatly affected by the Great East Japan Earthquake and subsequent radiation disaster. Data were retrospectively collected from patient records, including age, gender, visit date, diagnoses, and addresses. Patient records from April 2014 to March 2020 were analyzed, comparing data before and after the July 2016 evacuation order lift. Data was categorized into pre and post-evacuation order lifting periods, using International Classification of Diseases, Tenth Edition codes, to identify the top diseases. Statistical analyses, including χ-square tests, assessed changes in disease distributions. Population data for Odaka Ward and Minamisoma City fluctuated after lifting evacuation orders. As of March 11, 2011, Odaka Ward had 12,842 residents (27.8% aged 65+ years), dropping to 8406 registered residents and 2732 actual residents by April 30, 2018 (49.7%). Minamisoma City also saw declines, with registered residents decreasing from 71,561 (25.9%) to 61,049 (34.1%). The study analyzed 11,100 patients, mostly older patients (75.1%), between 2014 and 2020. Post-lifting, monthly patient numbers surged from an average of 55.2 to 213.5, with female patients increasing from 33.8% to 51.7%. Disease patterns shifted, with musculoskeletal cases declining from 23.8% to 13.0%, psychiatric disorders increasing from 9.3% to 15.4%, and trauma-related cases decreasing from 14.3% to 3.9%. Hypertension (57.1%) and dyslipidemia (29.2%) prevailed post-lifting. Urgent cases decreased from 1.3% to 0.1%. This study emphasizes the importance of primary care in post-evacuation zones, addressing diverse medical needs, including trauma, noncommunicable diseases, and psychiatric disorders. Changing patient demographics require adaptable healthcare strategies and resource allocation to meet growing demands. Establishing a comprehensive health maintenance system tailored to these areas' unique challenges is crucial for future disaster recovery efforts.

Reliability of Questionnaire-Based Dose Reconstruction: Human factor uncertainties in the Radiation Dosimetry of Chernobyl Cleanup Workers

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.

Risk of thyroid cancer in Ukrainian cleanup workers following the Chornobyl accident

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.

Lithuanian cohort of Chernobyl cleanup workers: Cancer incidence follow-up 1986-2012

BACKGROUND

Cancer risks following radiation exposure in adulthood after Chernobyl are less studied compared to those after exposure in childhood. We aimed to evaluate cancer risk in the Lithuanian cohort of Chernobyl cleanup workers 26 years after their exposure in Chernobyl.

METHODS

Study population (6707 men) was followed for cancer incidence upon return from Chernobyl till the end of 2012 by linkage procedure with the Lithuanian Cancer Registry and for migration and death - with Central Population Registry. The site-specific cancer risk in the cohort was estimated by calculating the standardised incidence ratio (SIR) with 95 % confidence interval (CI).

RESULTS

A total of 596 cancer cases was observed in the cohort, against 584 expected (SIR 1.02; 95 % CI 0.94, 1.11). Only incidence of mouth and pharynx cancers was increased compared to the expected (SIR 1.41; 95 % CI 1.07, 1.86). Nevertheless, an increased risk of thyroid cancer was observed among cleanup workers who were younger than 30 years when entering the Chernobyl zone (SIR 2.90; 95 % CI 1.09, 7.72), whose radiation dose was above 100 milisievert (mSv) (SIR 3.13; 95 % CI 1.30, 7.52) and who had shorter duration of stay (SIR 2.30; 95 % CI 1.03, 5.13).

CONCLUSIONS

Our findings are consistent with those observed in other cohorts of workers, namely, the increased risk of cancer sites related to behavioural factors. The increased risk of thyroid cancer among cleanup workers who were younger than 30 years when entering Chernobyl and whose radiation dose was above 100 mSv cannot exclude the association with the radiation exposure in Chernobyl.

Consequences of atmospheric contamination by radioiodine: the Chernobyl and Fukushima accidents

PURPOSE

After the accidents of nuclear power plants at Chernobyl and at Fukushima, huge amounts of radioactive iodine were released into the atmosphere.

METHODS

We reviewed data on the health consequences of these accidents with a focus on thyroid consequences.

RESULTS

Among the 2 million children who were living in highly contaminated regions in Belarus, Ukraine and Russia, 7000 cases of thyroid cancer had occurred in 2005. This is the most significant radiation-induced consequence of the Chernobyl accident. The increased incidence of thyroid cancer observed in adult population who lived in these highly contaminated regions is at least in major part related to screening and it is not possible to individualize among these thyroid cancers those that are potentially caused by radiation exposure. For populations who lived outside these regions at the time of the accident, there is no detectable consequence of the radiation exposure on the thyroid gland. Among children who lived nearby the Fukushima power plant in 2011, there is currently no evidence of an increased incidence of thyroid cancer. Ultrasonography screening in these individuals detected a number of thyroid cancers that are probably not related to the accident. Because thyroid cancer is frequent, studies have been carried out to distinguish radiation-induced from their sporadic counterparts, and genomic signatures might be helpful.

CONCLUSIONS

The consequences of the Chernobyl accident clearly demonstrate that populations living nearby a nuclear power plant should be protected in case of accident by sheltering, food restrictions and prophylaxis of thyroid irradiation by potassium iodine administration, if the predicted estimated dose to the thyroid gland of children might be >50 mGy. These countermeasures should be applied in priority to children, adolescents and pregnant women; they are safe and effective.

Strengths and Weaknesses of Dosimetry Used in Studies of Low-Dose Radiation Exposure and Cancer

BACKGROUND

A monograph systematically evaluating recent evidence on the dose-response relationship between low-dose ionizing radiation exposure and cancer risk required a critical appraisal of dosimetry methods in 26 potentially informative studies.

METHODS

The relevant literature included studies published in 2006-2017. Studies comprised case-control and cohort designs examining populations predominantly exposed to sparsely ionizing radiation, mostly from external sources, resulting in average doses of no more than 100 mGy. At least two dosimetrists reviewed each study and appraised the strengths and weaknesses of the dosimetry systems used, including assessment of sources and effects of dose estimation error. An overarching concern was whether dose error might cause the spurious appearance of a dose-response where none was present.

RESULTS

The review included 8 environmental, 4 medical, and 14 occupational studies that varied in properties relative to evaluation criteria. Treatment of dose estimation error also varied among studies, although few conducted a comprehensive evaluation. Six studies appeared to have known or suspected biases in dose estimates. The potential for these biases to cause a spurious dose-response association was constrained to three case-control studies that relied extensively on information gathered in interviews conducted after case ascertainment.

CONCLUSIONS

The potential for spurious dose-response associations from dose information appeared limited to case-control studies vulnerable to recall errors that may be differential by case status. Otherwise, risk estimates appeared reasonably free of a substantial bias from dose estimation error. Future studies would benefit from a comprehensive evaluation of dose estimation errors, including methods accounting for their potential effects on dose-response associations.

Estimation of Radiation Doses for a Case-control Study of Thyroid Cancer Among Ukrainian Chernobyl Cleanup Workers

Thyroid doses were estimated for 607 subjects of a 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 I and short-lived radioiodine and radiotellurium isotopes (I, I, I, Te, and Te) during the cleanup mission, and intake of 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: 47 mGy; range: 0.15 mGy to 9.0 Gy), with averages of 140 mGy (median: 20 mGy; range: 0.015 mGy to 3.6 Gy) from external irradiation during the cleanup mission, 44 mGy (median: 12 mGy; range: ~0 mGy to 1.7 Gy) due to I inhalation, 42 mGy (median: 7.3 mGy; range: 0.001 mGy to 3.4 Gy) due to I intake during residence, and 11 mGy (median: 1.6 mGy; range: ~0 mGy to 0.38 Gy) due to inhalation of short-lived radionuclides. Internal exposure of the thyroid gland to I contributed more than 50% of the total thyroid dose in 45% of the study subjects. The uncertainties in the individual stochastic doses were characterized by a mean geometric standard deviation of 2.0, 1.8, 2.0, and 2.6 for external irradiation, inhalation of I, inhalation of short-lived radionuclides, and residential exposure, respectively. The models used for dose calculations were validated against instrument measurements done shortly after the accident. Results of the validation showed that thyroid doses could be estimated retrospectively for Chernobyl cleanup workers two to three decades after the accident with a reasonable degree of reliability.

Radiation Exposure to the Thyroid After the Chernobyl Accident

INTRODUCTION

The Chernobyl accident resulted in a considerable release of radioactivity to the atmosphere, particularly of Iodine-131 (¹³¹I), with the greatest contamination occurring in Belarus, Ukraine, and western part of Russia.

MATERIAL AND METHODS

Increase in thyroid cancer and other thyroid diseases incidence in population exposed to Chernobyl fallout in these counties was the major health effect of the accident. Therefore, a lot of attention was paid to the thyroid doses, mainly, the ¹³¹I intake during two months after the accident. This paper reviews thyroid doses, both the individual for the subjects of radiation epidemiological studies and population-average doses. Exposure to ¹³¹I intake and other exposure pathways to population of affected regions and the Chernobyl cleanup workers (liquidators) are considered.

RESULTS

Individual thyroid doses due to ¹³¹I intake varied up to 42 Gy and depended on the age of the person, the region where a person was exposed, and their cow's milk consumption habits. Population-average thyroid doses among children of youngest age reached up to 0.75 Gy in the most contaminated area, the Gomel Oblast, in Belarus. Intake of ¹³¹I was the main pathway of exposure to the thyroid gland; its mean contribution to the thyroid dose in affected regions was more than 90%. The mean thyroid dose from inhalation of ¹³¹I for early Chernobyl cleanup workers was estimated to be 0.18 Gy. Individual thyroid doses due to different exposure pathways varied among 1,137 cleanup workers included in the epidemiological studies up to 9 Gy. Uncertainties associated with dose estimates, in terms of mean geometric standard deviation of individual stochastic doses, varied in range from 1.6 for doses based on individual-radiation measurements to 2.6 for "modelled" doses.

CONCLUSION

The ¹³¹I was the most radiologically important radionuclide that resulted in radiation exposure to the thyroid gland and cause an increase in the of rate of thyroid cancer and other thyroid diseases in population exposed after the Chernobyl accident.

Cancers after Chornobyl: From Epidemiology to Molecular Quantification

An overview and new data are presented from cancer studies of the most exposed groups of the population after the Chornobyl accident, performed at the National Research Center for Radiation Medicine (NRCRM). Incidence rates of solid cancers were analyzed for the 1990-2016 period in cleanup workers, evacuees, and the general population from the contaminated areas. In male cleanup workers, the significant increase in rates was demonstrated for cancers in total, leukemia, lymphoma, and thyroid cancer, as well as breast cancer rates were increased in females. Significantly elevated thyroid cancer incidence was identified in the male cleanup workers cohort (150,813) in 1986-2012 with an overall standardized incidence ratio (SIR) of 3.35 (95% CI: 2.91-3.80). A slight decrease in incidence rates was registered starting at 25 years after exposure. In total, 32 of 57 deaths in a group of cleanup workers with confirmed acute radiation syndrome (ARS) or not confirmed ARS (ARS NC) were due to blood malignancies or cancer. Molecular studies in cohort members included gene expression and polymorphism, FISH, relative telomere length, immunophenotype, micronuclei test, histone H2AX, and TORCH infections. Analysis of chronic lymphocytic leukemia (CLL) cases from the cohort showed more frequent mutations in telomere maintenance pathway genes as compared with unexposed CLL patients.

Thyroid doses due to Iodine-131 inhalation among Chernobyl cleanup workers

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 ¹³¹I. 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 ¹³¹I at the locations of residence and work of the cleanup workers, the reduction of ¹³¹I 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 ¹³¹I 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 ¹³¹I inhalation among the cleanup workers with direct thyroid measurements was 4.5 Gy. To validate the model, the ¹³¹I 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 ¹³¹I 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 ¹³¹I 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.

Doses for post-Chernobyl epidemiological studies: are they reliable?

On 26 April 2016, thirty years will have elapsed since the occurrence of the Chernobyl accident, which has so far been the most severe in the history of the nuclear reactor industry. Numerous epidemiological studies were conducted to evaluate the possible health consequences of the accident. Since the credibility of the association between the radiation exposure and health outcome is highly dependent on the adequacy of the dosimetric quantities used in these studies, this paper makes an effort to overview the methods used to estimate individual doses and the associated uncertainties in the main analytical epidemiological studies (i.e. cohort or case-control) related to the Chernobyl accident. Based on the thorough analysis and comparison with other radiation studies, the authors conclude that individual doses for the Chernobyl analytical epidemiological studies have been calculated with a relatively high degree of reliability and well-characterized uncertainties, and that they compare favorably with many other non-Chernobyl studies. The major strengths of the Chernobyl studies are: (1) they are grounded on a large number of measurements, either performed on humans or made in the environment; and (2) extensive effort has been invested to evaluate the uncertainties associated with the dose estimates. Nevertheless, gaps in the methodology are identified and suggestions for the possible improvement of the current dose estimates are made.

Dosimetry Support of the Ukrainian-American Case-control Study of Leukemia and Related Disorders Among Chornobyl Cleanup Workers

This paper describes dose reconstruction for a joint Ukrainian-American case-control study of leukemia that was conducted in a cohort of 110,645 male Ukrainian cleanup workers of the Chornobyl (Chernobyl) accident who were exposed to various radiation doses over the 1986-1990 time period. Individual bone-marrow doses due to external irradiation along with respective uncertainty distributions were calculated for 1,000 study subjects using the RADRUE method, which employed personal cleanup history data collected in the course of an interview with the subject himself if he was alive or with two proxies if he was deceased. The central estimates of the bone-marrow dose distributions range from 3.7 × 10(-5) to 3,260 mGy, with an arithmetic mean of 92 mGy. The uncertainties in the individual stochastic dose estimates can be approximated by lognormal distributions; the average geometric standard deviation is 2.0.

Non-cancer morbidity among Estonian Chernobyl cleanup workers: a register-based cohort study

OBJECTIVE

To examine non-cancer morbidity in the Estonian Chernobyl cleanup workers cohort compared with the population sample with special attention to radiation-related diseases and mental health disorders.

DESIGN

Register-based cohort study.

SETTING

Estonia.

PARTICIPANTS

An exposed cohort of 3680 men (cleanup workers) and an unexposed cohort of 7631 men (population sample) were followed from 2004 to 2012 through the Population Registry and Health Insurance Fund database.

METHODS

Morbidity in the exposed cohort compared with the unexposed controls was estimated in terms of rate ratio (RR) with 95% CIs using Poisson regression models.

RESULTS

Elevated morbidity in the exposed cohort was found for diseases of the nervous system, digestive system, musculoskeletal system, ischaemic heart disease and for external causes. The most salient excess risk was observed for thyroid diseases (RR=1.69; 95% CI 1.38 to 2.07), intentional self-harm (RR=1.47; 95% CI 1.04 to 2.09) and selected alcohol-related diagnoses (RR=1.25; 95% CI 1.12 to 1.39). No increase in morbidity for stress reactions, depression, headaches or sleep disorders was detected.

CONCLUSIONS

No obvious excess morbidity consistent with biological effects of radiation was seen in the exposed cohort, with the possible exception of benign thyroid diseases. Increased alcohol-induced morbidity may reflect alcohol abuse, and could underlie some of the higher morbidity rates. Mental disorders in the exposed cohort were probably under-reported. The future challenge will be to study mental and physical comorbidities in the Chernobyl cleanup workers cohort.

Increased occupational radiation doses: nuclear fuel cycle

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).

Risk of thyroid cancer among chernobyl liquidators

After the Chernobyl accident in 1986, the "liquidators" or clean-up workers were among those who received the highest radiation doses to the thyroid from external radiation. Some were also exposed to radioiodines through inhalation or ingestion. A collaborative case-control study nested within cohorts of Belarusian, Russian and Baltic liquidators was conducted to evaluate the radiation-induced risk of thyroid cancer. The study included 107 cases and 423 controls. Individual doses to the thyroid from external radiation and from iodine-131 ((131)I) were estimated for each subject. Most subjects received low doses (median 69 mGy). A statistically significant dose-response relationship was found with total thyroid dose. The Excess Relative Risk (ERR) per 100 mGy was 0.38 [95% confidence interval (CI): 0.10, 1.09]. The risk estimates were similar when doses from (131)I and external radiation were considered separately, although for external radiation the ERR was not statistically significantly elevated. The ERR was similar for micro carcinomas and larger size tumors, and for tumors with and without lymph node involvement. Although recall bias and uncertainties in doses could have affected the magnitude of the risk estimates, the findings of this study contribute to a better characterization the risk of thyroid cancer after radiation exposure in adulthood.

The Chernobyl experience in the area of retrospective dosimetry

The Chernobyl accident, which occurred on 26 April 1986 at a nuclear power plant located less than 150 km north of Kiev, was the largest nuclear accident to date. The unprecedented scale of the accident was determined not only by the amount of released activity, but also by the number of workers and of the general public involved, and therefore exposed to increased doses of ionising radiation. Due to the unexpected and large scale of the accident, dosimetry techniques and practices were far from the optimum; personal dosimetry of cleanup workers (liquidators) was not complete, and there were no direct measurements of the exposures of members of the public. As a result, an acute need for retrospective dose assessment was dictated by radiation protection and research considerations. In response, substantial efforts have been made to reconstruct doses for the main exposed cohorts, using a broad variety of newly developed methods: analytical, biological and physical (electron paramagnetic resonance spectroscopy of teeth, thermoluminescence of quartz) and modelling. This paper reviews the extensive experience gained by the National Research Center for Radiation Medicine, Academy of Medical Sciences, Ukraine in the field of retrospective dosimetry of large cohorts of exposed population and professionals. These dose reconstruction projects were implemented, in particular, in the framework of epidemiological studies, designed to follow-up the medical consequences of the Chernobyl accident and study health effects of ionizing radiation, particularly Ukrainian-American studies of cataracts and leukaemia among liquidators.

The role of mass spectrometry-based metabolomics in medical countermeasures against radiation

Radiation metabolomics can be defined as the global profiling of biological fluids to uncover latent, endogenous small molecules whose concentrations change in a dose-response manner following exposure to ionizing radiation. In response to the potential threat of nuclear or radiological terrorism, the Center for High-Throughput Minimally Invasive Radiation Biodosimetry was established to develop field-deployable biodosimeters based, in part, on rapid analysis by mass spectrometry of readily and easily obtainable biofluids. In this review, we briefly summarize radiation biology and key events related to actual and potential nuclear disasters, discuss the important contributions the field of mass spectrometry has made to the field of radiation metabolomics, and summarize current discovery efforts to use mass spectrometry-based metabolomics to identify dose-responsive urinary constituents, and ultimately to build and deploy a noninvasive high-throughput biodosimeter.

Radrue method for reconstruction of external photon doses for Chernobyl liquidators in epidemiological studies

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.

The Ukrainian-American study of leukemia and related disorders among Chornobyl cleanup workers from Ukraine: II. Estimation of bone marrow doses

After the accident that took place on 26 April 1986 at the Chornobyl nuclear power plant, hundreds of thousands of cleanup workers were involved in emergency measures and decontamination activities. In the framework of an epidemiological study of leukemia and other related blood diseases among Ukrainian cleanup workers, individual bone marrow doses have been estimated for 572 cases and controls. Because dose records were available for only about half of the study subjects, a time-and-motion method of dose reconstruction that would be applicable to all study subjects, whether dead or alive, was developed. The doses were calculated in a stochastic mode, thus providing estimates of uncertainties. The arithmetic mean individual bone marrow doses were found to range from 0.00004 to 3,300 mGy, with an average value of 87 mGy over the 572 study subjects. The uncertainties, characterized by the geometric standard deviation of the probability distribution of the individual dose, varied from subject to subject and had a median value of about 2. These results should be treated as preliminary; it is likely that the dose calculations and particularly the uncertainty estimates will be improved in the follow-up of this effort.