Techa River Cohort Research Articles

Risk of death from hematological malignancies in the South Urals Population Exposed to Radiation cohort

The results of studies of long-term effects of population exposure in the South Urals in the 1950s were based for a long time on studies of the effects of exposure in the Techa River cohort and later in the East Urals Radioactive Trace cohort. After the creation of the South Urals Population Exposed to Radiation cohort, combining all persons exposed in the South Urals in the period from January 1, 1950, to December 31, 1960 the size of the cohort doubled, follow-up period reached 71 years, and the number of person-years at risk increased to 1,964,333. The average dose to red bone marrow for all cohort members was 231mGy. Regression analysis using a simple parametric excess relative risk model was performed using the EPICURE statistical package. The analysis resulted in confirmation of a statistically significant (p <0.001) linear doseresponse relationship of mortality for all hemoblastoses, and leukemia. The excess relative risk and 95% confidence intervals of death at 2-year latency period from all hemoblastoses were 0.71/Gy (0.28;1.31); from all leukemias - 1.28/Gy (0.55-2.39) and from leukemias excluding chronic lymphocytic leukemia -1.52/Gy (0.64-2.94). The quadratic model also significantly described the dose dependence; (the differences between the models were not significant). Increasing the follow-up period to 71 years resulted in a slight decrease in risk estimates. The width of the confidence intervals of the risk estimates decreased by more than a factor of 3 compared to earlier studies in the Techa River cohort, which indicates a decrease in uncertainties of risk estimates. Increasing the size of the cohort made it possible to obtain significant risk values for individual population groups (by sex, age, etc.). Analysis of risk values modification did not reveal significant differences in dose dependence on the studied factors, including attained age and age at exposure. The study will be continued to investigate in more detail the influence of time-dependent factors on dose dependence, as well as to assess the risk of death from different cellular forms of leukemia.

Breast cancer incidence risk in accidentally exposed persons of the Southern Urals

The objective of the paper is to assess the breast cancer incidence risk in the Ural cohort of accidentally exposed population. The cohort of people exposed in the Southern Urals on the Techa River and in the East Ural Radioactive Trace was created in 2018. This is the first time that breast cancer risk analysis in women in this cohort is being carried out. Over the period from 1956 to 2018, 337breast cancer cases and 741,533person-years at risk were reported in the female subcohort in the incidence catchment area. Mean accumulated dose to the mammary gland, calculated using the TRDS-2016 dosimetry system, was 46 mGy, the maximum dose was 1 Gy. Regression analysis was performed using the EPICURE software package. Statistical significance with 95% probability was assessed by the maximum likelihood method. As a result of the analysis, a statistically significant linear dependence of breast cancer parameters on the dose was obtained. Excess relative risk for the follow-up period from 1956 through 2018 for members of the female subcohort with a 5-year latency period was 2.39 / Gy. The paper also discusses the impact of available for analyses non-radiation factors on both baseline rates of breast cancer incidence and those associated with radiation exposure. These results do not contradict those obtained in the previous study in the Techa River Cohort separately, and in the Japanese L SS cohort of atomic bomb survivors.

Cytokine profile in the subjects after long-term <i>in utero</i> and postnatal exposure to chronic irradiation

Persons exposed to ionizing radiation in utero and in early childhood constitute a risk group for the development of long-term stochastic consequences of irradiation. The imbalance of cytokines at the long terms after irradiation could be considered a carcinogenic triggering factor in subjects previously irradiated in utero and in early childhood, thus determining relevance of the study. The aim of the present study was to assess the levels of serum cytokines in native residents of coastal villages at the Techa River, whose chronic irradiation had been begun antenatally and to study probable interrelatirons between the detected changes, radiation and non-radiation factors at long terms after the exposure was begun. The main group included 61 persons from the Techa River Cohort who were born in 1950-1960, whose irradiation was begun in utero, being continued over the early postnatal period. For patients from the main group, the mean dose of antenatal radiation was calculated 74.7 mGy for red bone marrow as of, the mean dose of postnatal irradiation was calculated for red bone marrow as 537.5 mGy, and the median age of patients was 64.0 years. The comparison group (90 nonirradiated persons) was comparable to the main group in terms of age, gender, ethnicity and socio-economic status. The median levels for IL-2 in the main group were 1.37 pg/ml; in the comparison group, 2.70 pg/ml, p = 0.020; for IL-10, 4.53 pg/ml versus 7.58 pg/ml, p = 0.030 respectively; for GM-CSF, 0.39 pg/ml in the subjects who were irradiated in utero and in the early postnatal period versus 0.86 pg/ml in non-irradiated persons, p = 0.040. The median serum concentrations of IL-1β, IL-1α, IL-1(ra), IL-4, IL-6, IL-8, G-CSF, TNFα, IFNα, IFNγ in the study group did not show differences from the values in a group of non-irradiated persons. The decrease of the serum IL-2, IL-10 and GM-CSF levels in the persons of the main group did not depend on the dose of antenatal irradiation to red bone marrow, and on the radiation dose to red bone marrow received during the postnatal period of ontogenesis. In the main group, there was a moderate inverse relationship between the serum IL-10 level and age at the time of examination (SR = -0.53, p 0.001). Serum concentrations of IL-2 and IL-10 in the people from comparison group showed a moderate positive correlation with their present age (SR = 0.47, p 0.001 and SR = 0.42, p 0.001 respectively).

Radiogenic risk of solid cancer incidence in persons exposed to radiation in childhood in the Southern Urals

The aim of this work is to assess the radiogenic risk of solid cancers incidence in the members of the Urals Childhood Exposure Cohort. The cohort includes people exposed under 20 years of age as a result of two radiation accidents at the Mayak Production Association in the Southern Urals (discharges of radioactive waste into the Techa River and the formation of the East Ural radioactive trace). The number of the cohort for solid cancer incidence analysis is 31,578 individuals. All the members were postnatally exposed and some of them – in-utero. Some of their parents were exposed before conception. 2,018 solid cancers were registered on the incidence catchment area during the period 1956-2018, the total amount of person years was 818,083. The analysis was carried out by the Poisson regression method with a simple parametric excess relative risk model. 95% confidence intervals were estimated with maximum likelihood approach. Only a postnatal dose was used in the first solid cancer incidence analysis of this cohort members with due account for preconception exposure of parents. TRDS-2016 mean postnatal dose accumulated over the entire follow-up period in the stomach of cohort members was 0.047 Gy. The analysis showed linear dependence of solid cancer incidence excess relative risk on postnatal dose. Excess relative risk was 0.66/Gy, р=0.006 with a five-year latency period. While estimating excess relative risk in different age groups at the beginning of exposure, a significant risk was present only in the age group under 1 year and amounted to 2.16/Gy; р<0.02 at the onset of exposure. The present results are in agreement with the results of the solid cancer incidence risk analysis both in the Techa River Cohort of exposed In-Utero where a statistically significant excess relative risk from a postnatal dose was revealed, and with the results of risk analysis in the Japanese cohort of people exposed in-utero and in early childhood.

Approaches to the assessment of completeness and quality of the registry of exposed population offspring

Uncertainties of radiation risk of late radiation exposure effects in humans are to a great extent determined by completeness and quality of epidemiological data. The registry of the studied cohort is of fundamental importance for the cohort studies. Particular difficulties appear in the course of development of the exposed population offspring registry as these people in contrast to their parents were not affected by radiation exposure. The formation of the cohort of the exposed population offspring has its peculiarities and requires evaluation of its completeness and quality. The objective of this research is to study the value of the sex ratio as a possible criterion to assess the completeness and quality of the registry of the Techa River Cohort offspring. The register of descendants of the irradiated population at the end of 2019 included information on 25930 persons. The formation of the register of descendants of the population irradiated on the Techa River was started in the mid-1950s. At the same time, various documents were used to confirm the fact of birth of a child in irradiated persons. In the Techa River population the proportion of offspring with exposed mother and unexposed father is 22.2%, those with exposed father and unexposed mother made up 13.9%; the proportion of in utero exposed offspring is 44.6%. In accordance to the widely accepted published data it was to be expected that the number of male 1st-generation offspring in the cohort would be lower. However, the results of the conducted research show no changes in the sex ratio among offspring relative to the population-based control. Moreover, it was stated that the sex ratio in the population of the 1st-generation offspring of the exposed residents of the Techa River settlements should not be viewed as secondary. The assumption about the influence of the pre-conceptional exposure of the parents as well as that of the in utero exposure on changes in the sex ratio was not confirmed. It is shown that the decrease in the value of the sex ratio is associated with misreporting of the male 1st -generation offspring who died in childhood and at young age. The value of the sex ratio in groups formed based on the character and dose of exposure, depended mainly on the source of information used in the course of the offspring registry development.

Solid cancer incidence risk in in the Ural cohort of the accidentally exposed population: 1956–2017

To date, the study of the effects of chronic exposure of the South Ural population has been carried out in two separate cohorts – in the Techa River Cohort and in the East Urals Radioactive Trace Cohort. In 2019, the Ural cohort of accidentally exposed population was formed. It included the population exposed in two radiation situations in the Southern Urals in the 1950s. The number of the combined cohort for the cancer incidence analysis was about 60 thousand people, the follow-up period was extended to 2017, the number of solid cancers was 4537, and the number of person-years was 1283267, which is 3 times more than when analyzing the effects of exposure in each of the two radiation situations separately. In the incidence analysis of all solid cancer types, we used the dose accumulated in the walls of the stomach, which corresponds to the dose accumulated in most organs and tissues with the exception of bone tissue and red bone marrow. The mean dose to the stomach accumulated over the entire follow-up period for cohort members was 38 mGy, the maximum -1.13 Gy. The paper presents the first results of solid cancer incidence risk analysis in the combined cohort, which show a statistically significant dose dependence of the incidence in case of chronic exposure in the range of low and medium doses. The sex and age-averaged excess relative risk value of 0.075/100 mGy (the 95% confidence interval is 0.039–0.113) is comparable to that obtained in the studies of the Japanese cohort of atomic bomb survivors. The statistically significant excess relative risk value of 0.047/100 mGy, obtained separately for men, is in good agreement with that in professional cohorts where men prevail – in the cohort of the Chernobyl NPP accident clean-up workers and in the cohort of professional workers in the three countries (UK, France, USA). The established cohort with a long follow-up period has a great potential for furthermore detailed studies of the effects of radiation and non-radiation factors on public health.

Luminescence dosimetry for evaluation of the external exposure in Metlino, upper Techa River valley, due to the shore of the Metlinsky Pond: A feasibility study

Luminescence dosimetry was performed using bricks from the former settlement of Metlino, Southern Urals, Russia, to investigate the feasibility of validating the Techa River Dosimetry System (TRDS) 2016 for the shore of the Metlinsky Pond, upper Techa River region. TRDS is a code for estimating external and internal doses for members of the Extended Techa River Cohort. Several brick samples were taken from the north-western wall of the granary, facing the Metlinsky Pond. Samples were measured at different heights and at different depths into the bricks. Dating of the granary was performed by analyzing well shielded bricks. Assessment of the gamma dose-rate at the sample positions was done by thermoluminescent dosimeters and the dose-rate in front of the granary mapped with a dose-rate meter. Anthropogenic doses in bricks vary from 0.8 to 1.7 Gy and show an increase with sampling height. A similar height profile is observed for the current gamma dose-rate, which is compatible with the results of the dose-rate mapping. Implications for validating the TRDS are discussed.

Trabecula: A Random Generator of Computational Phantoms for Bone Marrow Dosimetry.

This study was motivated by the efforts to evaluate radiation risk for leukemia incidence in the Techa River cohort, where the main bone marrow dose contributors were Sr (bone-seeking beta emitters). Energy deposition in bone marrow targets was evaluated by simulating radiation particle transport using computational phantoms. The present paper describes the computer program Trabecula implementing an algorithm for parametric generation of computational phantoms, which serve as the basis for calculating bone marrow doses. Trabecula is a user-friendly tool that automatically converts analytical models into voxelized representations that are directly compatible as input to Monte Carlo N Particle code.

Распределение индивидуальных доз в когорте людей в результате радиоактивного загрязнения реки Течи

Purpose: Descriptive analysis of the distributions of organ/tissue doses for individuals exposed to radiation as a result of liquid waste releases into the Techa River by the Mayak Production Association (PA) in 1949–1956. 
 Material and methods: The dosimetry system TRDS-2016D has been used to compute individual doses of external and internal exposures. TRDS-2016D databases include information on radionuclide intakes and dose rates in air for settlements located in the contaminated areas of the Techa River and the East Ural Radioactive Trace (EURT). Combining these village-average data with the residence history and age of a particular person, the system produces an individual scenario of external exposure and individual radionuclide intakes and then calculates corresponding external and internal doses from the Techa River and EURT. Available 90Sr-body-burden measurements and available information on individual household locations relative to the contaminated river have been used for refinement of individual dose estimates. 
 Results: Individual doses have been calculated for 29,647 persons included in the Techa River Cohort (TRC). According to residence history data, 5,280 members of the TRC were additionally exposed due to residency in the EURT villages. The cohort-average dose for the majority of extra-skeletal tissues does not exceed 100 mGy, while for the red bone marrow (RBM) it is equal to 350 mGy. In addition to the doses from the Techa River and EURT, individual thyroid doses for TRC members exposed to the Mayak PA atmospheric 131I releases have been calculated in a separate computer program. The cohort–average thyroid dose is 210 mGy. Maximum doses (about 1 Gy to the majority of extra-skeletal tissues and over 7 Gy to the thyroid and RBM) are observed for the persons who lived in their childhood and adolescence in the upper Techa region at close distance to the Mayak PA.
 Conclusion: The TRC members were exposed to chronic radiation over a wide range of doses, but at low-to-moderate-dose rates. Estimates of absorbed doses can be used to analyze the dose dependences of the incidence of solid cancers and leukemias. This can make it possible to verify risk coefficients of low-dose-rate effects of ionizing radiation which can be used for radiation protection purposes.

Enhancements in the Techa River Dosimetry System: TRDS-2016D Code for Reconstruction of Deterministic Estimates of Dose From Environmental Exposures.

Waterborne releases to the Techa River from the Mayak plutonium facility in Russia during 1949-1956 resulted in significant doses to persons living downstream. The dosimetry system Techa River Dosimetry System-2016D has been developed, which provides individual doses of external and internal exposure for the members of the Techa River cohort and other persons who were exposed to releases of radioactive material to the Southern Urals. The results of computation of individual doses absorbed in red bone marrow and extraskeletal tissues for the Techa River cohort members (29,647 persons) are presented, which are based on residence histories on the contaminated Techa River and the East Urals Radioactive Trace, which was formed in 1957 as a result of the Kyshtym Accident. Available Sr body-burden measurements and available information on individual household locations have been used for refinement of individual dose estimates. Techa River Dosimetry System-2016D-based dose estimates will be used for verification of risk of low-dose-rate effects of ionizing radiation in the Techa River cohort.

Risk analysis of the mortality from the diseases of the circulatory system in the Ural cohort of emergency-irradiated population for the years 1950–2015

The paper describes for the first time the results of the radiation effect study using the example of the analysis of circulatory system disease mortality in newly established cohort combining the population exposed in 1950–1960 due to 2 radiation incidents in the Southern Urals (the Techa River and East-Urals radioactive Trace). The cohort consists of 60,205 people. Over a 65-year follow up period 14,830 deaths from all diseases of the circulatory system were registered. Out of this number 6,163 deaths were from ischemic heart disease, and 4,388 deaths were from cerebrovascular diseases. Analysis was performed on the basis of individualized estimates of dose accumulated in muscle tissue (both internal and external components of the dose), calculated with new Techa River Dosimetry System 2016. As per the latest calculations, mean dose to muscle tissue in members of the combined cohort was 34 mGy, maximum dose was 995 mGy. Simple parametric model of excess relative risk (ERR) was used in the analysis. The number of person-years at risk was 1836,203. The findings of the analysis show linear increase of mortality risk per unit dose from all the disease of circulatory system (ERR/100 mGy was 3%; 95% CI: 0,8%; 5,2%) and from ischemic heart disease (ERR/100 mGy was 9,2%; 95% CI: 5,4%; 13,5%). with 15-year latent period. No statistically significant increase in mortality from the cerebrovascular diseases in the combined cohort of the population exposed in the Southern Urals over a 65-year period received evidence. The obtained results are in good agreement with those received in the analysis of the effect in the Techa River Cohort in 2013. The latter covered a 53-year period (with minimum latent period of 15 years) and revealed statistically significant linear dose response for all diseases of the circulatory system (ERR/100 mGy – 0.036) and ischemic heart disease (ERR/100 mGy – 0.056).

RESULTS OF RADON INSPECTION OF SETTLEMENTS COMPROMISED DUE TO DISPOSAL OF RADIOACTIVE WASTE INTO THE TECHA RIVER

During past decades, specialists perform an epidemiological observation of the population exposed to the impact of radioactive discharges into the Techa River. The Techa River cohort studies have identified excess cases of leukemia and solid cancers associated with radiation exposure. At the same time natural sources of radiation, such as radon and its decay products, known to be significant human radiation exposure factor, are not sufficiently studied on this territory. The purpose of the study is to assess the mean value and the distribution indices of radon concentration in 14 settlements affected by radioactive contamination. Radon inspection in settlements located on the Techa River (Chelyabinsk and Kurgan regions) was executed. The measurements were performed in 511 dwellings. For radon inspection there were applied detectors based on LR-115 Kodak Track. The analysis shows the sample both to be representative and allow to estimate radon exposure for inhabitants. The average radon concentration in dwellings is 150 Bq/m3, which results in an annual effective dose of 11 mSv. The estimated number of dwellings with radon concentrations above ECC radon action level 200 Bq/m3 is 19. The factors affecting indoor radon accumulation were established. The radiation dose due to the inhalation of radon, accumulated over a long period of time, seems to be generally comparable to doses associated with the radioactive discharges into the Techa River during the 1949-1956.

Calculations of individual doses for Techa River Cohort members exposed to atmospheric radioiodine from Mayak releases

Time-dependent thyroid doses were reconstructed for over 29,000 Techa River Cohort members living near the Mayak production facilities from 131I released to the atmosphere for all relevant exposure pathways. The calculational approach uses four general steps: 1) construct estimates of releases of 131I to the air from production facilities; 2) model the transport of 131I in the air and subsequent deposition on the ground and vegetation; 3) model the accumulation of 131I in environmental media; and 4) calculate individualized doses. The dose calculations are implemented in a Monte Carlo framework that produces best estimates and confidence intervals of dose time-histories. Other radionuclide contributors to thyroid dose were evaluated. The 131I contribution was 75–99% of the thyroid dose. The mean total thyroid dose for cohort members was 193 mGy and the median was 53 mGy. Thyroid doses for about 3% of cohort members were larger than 1 Gy. About 7% of children born in 1940–1950 had doses larger than 1 Gy. The uncertainty in the 131I dose estimates is low enough for this approach to be used in regional epidemiological studies.

External dose reconstruction for the former village of Metlino (Techa River, Russia) based on environmental surveys, luminescence measurements, and radiation transport modelling.

In the first years of its operation, the Mayak Production Association, a facility part of the Soviet nuclear weapons program in the Southern Urals, Russia, discharged large amounts of radioactively contaminated effluent into the nearby Techa River, thus exposing the people living at this river to external and internal radiations. The Techa River Cohort is a cohort intensely studied in epidemiology to investigate the correlation between low-dose radiation and health effects on humans. For the individuals in the cohort, the Techa River Dosimetry System describes the accumulated dose in human organs and tissues. In particular, organ doses from external exposure are derived from estimates of dose rate in air on the Techa River banks which were estimated from measurements and Monte Carlo modelling. Individual doses are calculated in accordance with historical records of individuals' residence histories, observational data of typical lifestyles for different age groups, and age-dependent conversion factors from air kerma to organ dose. The work here describes an experimentally independent assessment of the key input parameter of the dosimetry system, the integral air kerma, for the former village of Metlino, upper Techa River region. The aim of this work was thus to validate the Techa River Dosimetry System for the location of Metlino in an independent approach. Dose reconstruction based on dose measurements in bricks from a church tower and Monte Carlo calculations was used to model the historic air kerma accumulated in the time from 1949 to 1956 at the shoreline of the Techa River in Metlino. Main issues are caused by a change in the landscape after the evacuation of the village in 1956. Based on measurements and published information and data, two separate models for the historic pre-evacuation geometry and for the current geometry of Metlino were created. Using both models, a value for the air kerma was reconstructed, which agrees with that obtained in the Techa River Dosimetry System within a factor of two.

Estimates of Radiation Effects on Cancer Risks in the Mayak Worker, Techa River and Atomic Bomb Survivor Studies.

For almost 50 y, the Life Span Study cohort of atomic bomb survivor studies has been the primary source of the quantitative estimates of cancer and non-cancer risks that form the basis of international radiation protection standards. However, the long-term follow-up and extensive individual dose reconstruction for the Russian Mayak worker cohort (MWC) and Techa River cohort (TRC) are providing quantitative information about radiation effects on cancer risks that complement the atomic bomb survivor-based risk estimates. The MWC, which includes ~26 000 men and women who began working at Mayak between 1948 and 1982, is the primary source for estimates of the effects of plutonium on cancer risks and also provides information on the effects of low-dose rate external gamma exposures. The TRC consists of ~30 000 men and women of all ages who received low-dose-rate, low-dose exposures as a consequence of Mayak's release of radioactive material into the Techa River. The TRC data are of interest because the exposures are broadly similar to those experienced by populations exposed as a consequence of nuclear accidents such as Chernobyl. In this presentation, it is described the strengths and limitations of these three cohorts, outline and compare recent solid cancer and leukemia risk estimates and discussed why information from the Mayak and Techa River studies might play a role in the development and refinement of the radiation risk estimates that form the basis for radiation protection standards.

The linear no-threshold theory: Readers weigh in

The linear no-threshold theory: Readers weigh in

Solid Cancer Incidence in the Techa River Incidence Cohort: 1956-2007.

Previously reported studies of the Techa River Cohort have established associations between radiation dose and the occurrence of solid cancers and leukemia (non-CLL) that appear to be linear in dose response. These analyses include 17,435 cohort members alive and not known to have had cancer prior to January 1, 1956 who lived in areas near the river or Chelyabinsk City at some time between 1956 and the end of 2007, utilized individualized dose estimates computed using the Techa River Dosimetry System 2009 and included five more years of follow-up. The median and mean dose estimates based on these doses are consistently higher than those based on earlier Techa River Dosimetry System 2000 dose estimates. This article includes new site-specific cancer risk estimates and risk estimates adjusted for available information on smoking. There is a statistically significant (P = 0.02) linear trend in the smoking-adjusted all-solid cancer incidence risks with an excess relative risk (ERR) after exposure to 100 mGy of 0.077 with a 95% confidence interval of 0.013-0.15. Examination of site-specific risks revealed statistically significant radiation dose effects only for cancers of the esophagus and uterus with an ERR per 100 mGy estimates in excess of 0.10. Esophageal cancer risk estimates were modified by ethnicity and sex, but not smoking. While the solid cancer rates are attenuated when esophageal cancer is removed (ERR = 0.063 per 100 mGy), a dose-response relationship is present and it remains likely that radiation exposure has increased the risks for most solid cancers in the cohort despite the lack of power to detect statistically significant risks for specific sites.

Focused review of mathematical modeling of radiation-related abnormalities in the Techa River cohort

Mathematical models describe relationships between numerical values. Adequate models can make testable extrapolations. A requirement to a mathematical model is its validity: once construed, a model and the region of validity should be tested. Here is reviewed a series of studies of the Techa river cohort, where mathematical models were claimed to reveal relationships between the dynamics of the hemato- and lymphopoiesis and the evolution of radiation dose rate over time. However, mathematical models describe rather than reveal relationships. The use of mathematical models without adequate verification may be conductive to the overestimation of biological effects of the low-dose low-rate ionizing radiation. Possible mechanisms of such overestimation are discussed.

FISH analysis of translocations induced by chronic exposure to Sr radioisotopes: second set of analysis of the Techa River Cohort.

Fluorescent in situ hybridisation analysis of stable translocations was performed for 26 residents living along the Techa River (Russia), who were predominantly (95%) exposed to ingested strontium radioisotopes ((89)Sr and (90)Sr) resulting in exposure of their red bone marrow (RBM). Analysis was conducted at the Urals Research Center for Radiation Medicine, Public Health England and Leiden University Medical Center. Each laboratory scored 1000 cells per donor, which resulted in ∼1000 genome equivalents (GE) per donor. The age-dependent spontaneous level of translocations for each donor was evaluated on the basis of data published by Sigurdson et al. (International study of factors affecting human chromosome. Mutat. Res. 2008;652: :112-121). Reconstruction of doses was performed with the 'Techa River Dosimetry System' developed in 2009. In the studied donors, the range of individual cumulated RBM dose was from 0.3 to 3.7 Gy. Analysis of the yield of stable translocations dependent on the individual RBM dose from (89,90)Sr showed a linear dose-response relationship of 0.007 ± 0.002 translocation/GE cell/Gy (R = 0.61, p = 0.001). This set of results was in a good agreement with the previous data reported for 18 donors by Vozilova et al. (Preliminary FISH-based assessment of external dose for residents exposed on the Techa River.

Joint U.S./Russian Studies of Population Exposures Resulting From Nuclear Production Activities in the Southern Urals

Beginning in 1948, the Soviet Union initiated a program for production of nuclear materials for a weapons program. The first facility for production of plutonium was constructed in the central portion of the country east of the southern Ural Mountains, about halfway between the major industrial cities of Ekaterinburg and Chelyabinsk. The facility, now known as the Mayak Production Association, and its associated town, now known as Ozersk, were built to irradiate uranium in reactors, separate the resulting plutonium in reprocessing plants, and prepare plutonium metal in the metallurgical plant. The rush to production, coupled with inexperience in handling radioactive materials, led to large radiation exposures, not only to the workers in the facilities, but also to the surrounding public. Fuel processing started with no controls on releases, and fuel dissolution and accidents in reactors resulted in release of ~37 PBq of I between 1948 and 1967. Designed disposals of low- and intermediate-level liquid radioactive wastes, and accidental releases via cooling water from tank farms of high-level liquid radioactive wastes into the small Techa River, caused significant contamination and exposures to residents of numerous small riverside villages downstream of the site. Discovery of the magnitude of the aquatic contamination in late 1951 caused revisions to the waste handling regimes, but not before over 200 PBq of radionuclides (with large contributions of Sr and Cs) were released. Liquid wastes were diverted to tiny Lake Karachay (which today holds over 4 EBq); cooling water was stopped in the tank farms. In 1957, one of the tanks in the tank farm overheated and exploded; over 70 PBq, disproportionately Sr, was blown over a large area to the northeast of the site. A large area was contaminated and many villages evacuated. This area today is known as the East Urals Radioactive Trace (EURT). Each of these releases was significant; together they have created a unique group of cohorts with their chronic, low dose-rate radiation exposure. The 26,000 workers at Mayak were highly exposed to external gamma and inhaled plutonium. A cohort of individuals raised as children in Ozersk is under evaluation for their exposures to radioiodine. The Techa River Cohort consists of over 30,000 people who were born before the start of exposure in 1949 and lived along the Techa River. The Techa River Offspring Cohort consists of ~21,000 persons born to one or more exposed parents of this group, many who also lived along the contaminated river. The EURT Cohort consists of ~18,000 people who were evacuated from the EURT soon after the 1957 explosion and another 8,000 who remained. These groups together are the focus of dose reconstruction and epidemiological studies funded by the United States, Russia, and the European Union to address the question, "Are doses delivered at low dose rates as effective in producing health effects as the same doses delivered at high dose rates?"Introduction of Joint U.S. and Russian Studies of Population Exposures (Video 2:13, http://links.lww.com/HP/A28).