Fetal dose assessment for the offspring of the Techa Riverside residents

Massive releases of fission products from the plutonium facility Mayak (Southern Urals, Russia) resulted in the contamination of the Techa river and its floodlands (1949–1956). The results of long-term studies of exposure populations have been used for different purposes of retrospective dosimetry. The riverside residents were exposed via various pathways and their progeny were exposed in utero both to external radiation and to internal radiation from radionuclides ingested by the mothers prior to conception and during pregnancy. Fetal doses due to ⁹⁰Sr from the maternal skeleton were estimated and compared with doses from other pathways. Individual red bone marrow (RBM) doses to the late fetuses were calculated on the basis of ⁹⁰Sr contents measured in the maternal skeleton and the ⁹⁰Sr transfer coefficients (TC) to the fetal skeleton were determined on the basis of the Techa river data. Two values of TC were assumed depending on the mothers’ maturation status in the period of maximum releases: TC=0.2 for group 1 (adulthood of mothers in 1950) and TC=0.02 for group 2 (mothers not yet in menarche age in 1950). Fetal doses in both groups that resulted from the different TC values varied by a factor of about 5–8. Furthermore, the fetal RBM doses due to ⁹⁰Sr from the maternal skeleton were found to depend on the distances from the site of release and the time after major ⁹⁰Sr intake. The average fetal RBM doses in the population of the upper, middle and lower Techa riverside regions were close to the ratio 3:2:1 and 20 years after the onset of contamination, the fetal doses have decreased by a factor of about 3–5. The distance from the site of release determined the relative contribution of different pathways to the fetal dose. For the settlements that are located closest to the site of release, the external exposure was of major concern up to the date of evacuation. For the non-evacuated settlements, the contribution of internal doses was higher and after 1956, external exposure is assumed to be negligible. From 1956 on, ⁹⁰Sr that has been transferred from the maternal skeleton was practically the single source of in utero exposure. Received: 8 December 2000 / Accepted: 1 July 2001     

A reconsideration of the external dose assessment for the Techa river population

A new methodology is employed to infer the time course of the external dose rate that affected the Techa riverside population. This was accomplished using information on the radionuclide composition of released radioactive waste and from earlier and current data on the degree of the river floodplain contamination with (137)Cs. The new approach is proposed for use in the dose reconstruction. Compared to current assumptions it indicates a considerably higher dose contribution due to short-lived fission products from the predominant peak of contamination in 1951. Relative to the present Techa river dosimetry system (TRDS-2000) this information may increase the external dose estimates several fold and correspondingly reduce the solid cancer risk estimate.     

Cataract in the chronically exposed residents of the Techa riverside villages

The present study is based on a retrospective analysis of archive data of the Clinical Department of the Urals Research Center for Radiation Medicine that has been established to examine and treat accidentally exposed residents of the Urals Region. All individuals included in this study were examined by an ophthalmologist. The study of cataract incidence has been conducted retrospectively for the period from 1951 till 2000 among chronically exposed residents of the Techa riverside villages (6343 persons). Individual accumulated absorbed doses to soft tissues (analogue of eye dose) reached 1.18 Gy (mean 0.12 Gy) while for 88.9% of the study group the dose did not exceed 0.1 Gy. There was no evidence of the influence of low-dose and low-dose rate on cataract incidence. Excess relative risk of cataract formation per 1 Gy was 0.40 (95% CI ?0.43; 1.47). It is noted that 15% of all excess cases were registered in persons with soft tissue dose above 0.3 Gy, though their fraction among all examined persons was only 4.1%. Risk of cataract development significantly increased in exposed individuals with retinal angiosclerosis, diabetes and arterial hypertension.     

On an evaluation of external dose values in the Techa River Dosimetry System (TRDS) 2000

Absorbed doses were determined by thermoluminescence (TL) measurements for bricks from a height of 6 m from the south-western wall of the former mill in Metlino that faced the Techa river. Measurements of the internal beta-radiation and alpha-radiation in the brick samples and of radionuclide activities in soil samples from the Techa river valley were performed. The absorbed dose in bricks due to the natural radiation was derived and subtracted from the total dose in order to obtain the absorbed dose in the bricks caused by anthropogenic sources. The results were combined with results from two previous studies. The absorbed dose in the bricks due to the radiation field after relocation of the Metlino population in 1956 was derived from dose rates in air measured in front of the sampling locations in 1996/1997. Based on these dose rates the dose to bricks was calculated by means of conversion factors from the literature. The absorbed dose accumulated in the bricks in the period 1949–1956 was nearly 80% of the total dose that had been determined by TL measurements. Previously derived conversion factors were applied to obtain an estimate of the gamma dose in air at the former shore of the Techa river. An uncertainty and sensitivity analysis was performed with the program package Crystal Ball. Care was taken to treat statistical and systematic uncertainties separately and to take parameter correlations into account. The resulting distribution for the gamma dose accumulated in the period 1949–1956 at the Techa river shore has a median value of 32 Gy with a 95% confidence interval of 21–45 Gy. This study confirms the corresponding value of 26.6 Gy that is used in the Techa River Dosimetry System (TRDS) 2000.     

Characterization of immunity status in exposed residents of the Techa riverside villages 50 years after the onset of radiation exposure

The goal of the study was to assess the state of immunity in exposed residents of the Techa riverside villages 50 years, or more, after the onset of radiation exposure. 127 chronically exposed persons and 55 unexposed persons were studied. The mean dose to red bone marrow (RBM) was 0.69 Sv in exposed subjects, the mean dose to soft tissue was 0.07 Sv, the mean dose rate amounted to 0.10 Sv/yr to RBM and 0.02 Sv/yr to soft tissues in 1950. The state of the basic links of the immunity system (cellular, humoral, mononuclear phagocyte system, cytokine spectrum, etc.) was assessed using conventional methods. Exposed persons manifested a significant reduction in the absolute counts of CD3+, CD4+, CD 11b+, CD16+ lymphocytes in the peripheral blood, as well as an increase in the relative counts of CD8+. The group comprised of the Techa riverside residents demonstrated an increased immunoregulatory index (exposed individuals: 1.47; controls: 1.71, p = 0.001). An increased production of Immunoglobulin A and increased proportions of CD25+ lymphocytes were revealed in exposed individuals. Changes in the phagocytic activity of neutrophils and monocytes were insignificant, and were primarily associated with changes in the proportions of pagocytes in the peripheral blood stream. The state of the immunity in chronically exposed individuals at late time after the begin of exposure is characterized by a number of specific features reflected primarily on the cellular immunity. No relationship between immunity changes and accumulated exposure dose and dose rate were noted over the period of maximum radiation exposures (1950).     

Strontium metabolism in teeth and enamel dose assessment: analysis of the Techa river data

People living on the banks of the Techa river were exposed to ⁹⁰Sr in the early 1950s. Data obtained by radiochemical measurements of extracted permanent teeth, ⁹⁰Sr autopsy measurements in bone and tooth samples, in vivo measurements of surface beta activity of the anterior teeth and whole-body counter (WBC) measurements of ⁹⁰Sr in the skeleton have been analyzed. Surface beta activity measurements indicate a biological half-life of ⁹⁰Sr of about 35 years in enamel. The WBC measurements have been performed since 1974 and a model for the age-dependent strontium retention in human bone has been used to extrapolate to previous time periods when the other measurement results were obtained. For the first decade after the intake, the ratio of the ⁹⁰Sr concentrations in teeth and bones were found to decrease with age at the time of major intake, from about 10 for 1-year-old children to about 0.3 for adults. There was a considerable variability of individual data within each age group. For adults, the correlation between ⁹⁰Sr in skeleton and teeth was not high at 0.47 according to radiochemical data for posterior teeth (molars and premolars) and 0.43 according to measurements of surface beta activity for anterior teeth. For children and adolescents there was no correlation between individual measurements in the skeleton and teeth. The absorbed dose in enamel due to ⁹⁰Sr in dentine has been calculated by Monte Carlo simulations of the electron transport. The results are in agreement with EPR measurements of the absorbed dose in the enamel of persons exposed, mainly due to ⁹⁰Sr ingestion. Received: 19 July 1999 / Accepted: 5 May 2000     

Verification of external exposure assessment for the upper Techa riverside by luminescence measurements and Monte Carlo photon transport modeling

An area located in the Southern Urals was contaminated in 1949–1956 as a result of radioactive waste releases into the Techa river by the Mayak Production Association. The external dose reconstruction of the Techa river dosimetry system (TRDS-2000) for the exposed population is based on an assessment of dose rates in air (DRA) obtained by modeling transport and deposition of radionuclides along the river for the time before 1952 and by gamma dose rate measurements since 1952. The aim of this paper is to contribute to a verification of the TRDS-2000 external dose assessment. Absorbed doses in bricks from a 130-year-old building in the heavily exposed Metlino settlement were measured by a luminescence technique. By the autumn of 1956 the population of Metlino had been evacuated, and then a water reservoir was created at the village location, which led to a change in the radioactive source geometry. Radiation transport calculations for assumed environmental sources before and since 1957 were performed with the MCNP Monte Carlo code. In combination with TRDS-2000 estimates for annual dose rates in air at the shore of the Techa river for the period 1949–1956 and contemporary dose rate in air measurements, absorbed doses in bricks were calculated. These calculations were performed deterministically with best estimates of the modeling parameters and stochastically by propagating uncertainty distributions through the calculation scheme. Assessed doses in bricks were found to be consistent with measured values within the uncertainty bounds, while their best estimates were approximately 15% lower than the luminescence measurements.An erratum to this article can be found at     

Leukemia incidence among people exposed to chronic radiation from the contaminated Techa River, 1953–2005

Beginning in 1950, people living on the banks of the Techa River received chronic low-dose-rate internal and external radiation exposures as a result of releases from the Mayak nuclear weapons plutonium production facility in the Southern Urals region of the Russian Federation. The Techa River cohort includes about 30,000 people who resided in riverside villages sometime between 1950 and 1960. Cumulative red bone marrow doses range up to 2 Gy with a mean of 0.3 Gy and a median of 0.2 Gy. Between 1953 and 2005, 93 first primary cases of leukemia, including 23 cases of chronic lymphatic leukemia (CLL), were ascertained among the cohort members. A significant linear dose–response relationship was seen for leukemias other than CLL (P < 0.001), but not for CLL. The estimated excess relative risk per Gy is 4.9 (95% confidence interval (CI): 1.6; 14.3) for leukemias other than CLL and less than 0 (95% upper bound 1.4) for CLL.     

Evaluation of anthropogenic dose distribution amongst building walls at the Metlino area of the upper Techa River region

This paper presents the results of an effort to evaluate anthropogenic doses in bricks from old buildings located on the banks of the Techa River. The river area was contaminated in 1949–1956 as a result of radioactive waste releases by the Mayak plutonium facility (Southern Urals, Russia). Absorbed doses were determined by luminescence measurements of quartz extracted from the near-surface layers of bricks sampled in 1991–1997 from three remained buildings (a mill, a granary and a church). These buildings are located in the former residence area of Metlino, which was the settlement located closest to the release site (residents of Metlino were relocated from the contaminated river in 1956). The measured anthropogenic dose in the three buildings was found to be comparable: minimum values were equal to 0.5–0.9 Gy and maximum values amounted to about 3–4 Gy. Unfortunately, the geometry of gamma-exposure of the brick samples changed significantly in 1956 as a result of creation of an artificial reservoir downstream of the Metlinsky pond. Since luminescence data provide absorbed dose in the investigated samples accumulated over the whole period of irradiation, for interpretation of the data obtained it is important to know the exposure geometry for the period of maximal exposure, which was in the early 1950s. In 2005, archival data describing configuration of contaminated water streams and shorelines (which were the main sources of gamma-irradiation) were published. Comparison of these data with the results of the luminescence study presented here showed that the bricks with the highest thermoluminescence (TL)-based doses faced contaminated shores and were located close to them. In contrast, the bricks with lower values of measured dose were opposite to contaminated shores and/or being shielded. This demonstrates that the luminescence method allowed reconstruction of the anthropogenic dose distribution in the former settlement center. The obtained results suggest new options for further luminescence studies in Metlino aimed at the reconstruction of the external exposures of the affected population.     

Minisatellite germline mutation rate in the Techa River population

Germline mutation at eight minisatellite loci has been studied among the irradiated families from the Techa River population and non-exposed families from the rural area of the Chelyabinsk and Kurgan Oblasts. The groups were matched by ethnicity, parental age, occupation and smoking habit. A statistically significant 1.7-fold increase in mutation rate was found in the germline of irradiated fathers, whereas maternal germline mutation rate in the exposed families was not elevated. Most of the minisatellite loci showed an elevated paternal mutation rate in the exposed group, indicating a generalised increase in minisatellite germline mutation rate in the Techa River population. These data suggest that the elevated minisatellite mutation rate can be attributed to radioactive exposure. The spectra of paternal mutation seen in the unexposed and exposed families were indistinguishable.     

Modeling analysis of the lymphocytopoiesis dynamics in chronically irradiated residents of Techa riverside villages

A biologically motivated dynamical model of the lymphocytopoietic system in irradiated humans is applied here to analyze the data obtained under hematological examinations of residents of Techa riverside villages. Those people were exposed to chronic irradiation with varying dose rates, due to the radioactive contamination of the river basin by the Mayak Production Association. Modeling studies revealed the relationship between the dynamics of the lymphocytopoietic system in the examined individuals and the variation of dose rate over the considered period of time. It is found that the developed model is capable of reproducing the decreased level of blood lymphocyte concentration observed during the period of maximum radiation exposure, the recovery processes in the system observed during the period of decreasing dose rate, as well as the enhanced mitotic activity of bone marrow precursor cells in this hematopoietic lineage observed during the entire period under consideration. Mechanisms of these effects of chronic irradiation on the human lymphocytopoietic system are elucidated based on the applied model. The results obtained demonstrate the efficiency of the developed model in the analysis, investigation, and prediction of effects of chronic irradiation with varying dose rate on the human lymphocytopoietic system. In particular, the developed model can be used for predicting any radiation injury of this vital system in people exposed to chronic irradiation due to environmental radiological events, such as anthropogenic radiation accidents or radiological terroristic attacks.     

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.     

Protracted radiation exposure and cancer mortality in the Techa River Cohort

In the 1950s many thousands of people living in rural villages on the Techa River received protracted internal and external exposures to ionizing radiation from the release of radioactive material from the Mayak plutonium production complex. The Extended Techa River Cohort includes 29,873 people born before 1950 who lived near the river sometime between 1950 and 1960. Vital status and cause of death are known for most cohort members. Individualized dose estimates have been computed using the Techa River Dosimetry System 2000. The analyses provide strong evidence of long-term carcinogenic effects of protracted low-dose-rate exposures; however, the risk estimates must be interpreted with caution because of uncertainties in the dose estimates. We provide preliminary radiation risk estimates for cancer mortality based on 1,842 solid cancer deaths (excluding bone cancer) and 61 deaths from leukemia. The excess relative risk per gray for solid cancer is 0.92 (95% CI 0.2; 1.7), while those for leukemia, including and excluding chronic lymphocytic leukemia, are 4.2 (CI 95% 1.2; 13) and 6.5 (CI 95% 1.8; 24), respectively. It is estimated that about 2.5% of the solid cancer deaths and 63% of the leukemia deaths are associated with the radiation exposure.     

Ecotoxicological study of bottom sediments from reservoir 11 of the Techa River cascade

The ecotoxicological properties of sediments from reservoir R-11 of the Techa River cascade are studied in comparison to the Shershni reservoir. Radiochemical analysis of sediment and water samples from R-11 show that the radioactivity of the sediments ranges from 240 to 360 kBq/dm³ dry weight for ⁹⁰Sr and from 10 to 161 kBq/dm³ dry weight for ¹³⁷Cs. The absorbed doses for Oligochaeta from R-11 are calculated on the basis of radiochemical data. The hydrobiological studies include (1) study of the population density and diversity of Oligochaeta species in the reservoirs and (2) laboratory bioassay of sediments with Tubifex tubifex as a biomonitor species. The results indicate that the Oligochaeta population density in R-11 is less than in the Shershni reservoir. No significant effects of the absorbed dose rate on population density, survival rate, or fertility are found in a laboratory Tubificidae bioassay of R-11 sediments. However, a decrease in fertility is noted in experiments at a higher absorbed dose.     

Electron paramagnetic resonance radiation dose assessment in fingernails of the victim exposed to high dose as result of an accident

In this paper, we report results of radiation dose measurements in fingernails of a worker who sustained a radiation injury to his right thumb while using 130 kVp X-ray for nondestructive testing. Clinically estimated absorbed dose was about 20–25 Gy. Electron paramagnetic resonance (EPR) dose assessment was independently carried out by two laboratories, the Naval Dosimetry Center (NDC) and French Institut de Radioprotection et de Sûreté Nucléaire (IRSN). The laboratories used different equipments and protocols to estimate doses in the same fingernail samples. NDC used an X-band transportable EPR spectrometer, e-scan produced by Bruker BioSpin, and a universal dose calibration curve. In contrast, IRSN used a more sensitive Q-band stationary spectrometer (EMXplus) with a new approach for the dose assessment (dose saturation method), derived by additional dose irradiation to known doses. The protocol used by NDC is significantly faster than that used by IRSN, nondestructive, and could be done in field conditions, but it is probably less accurate and requires more sample for the measurements. The IRSN protocol, on the other hand, potentially is more accurate and requires very small amount of sample but requires more time and labor. In both EPR laboratories, the intense radiation-induced signal was measured in the accidentally irradiated fingernails and the resulting dose assessments were different. The dose on the fingernails from the right thumb was estimated as 14 ± 3 Gy at NDC and as 19 ± 6 Gy at IRSN. Both EPR dose assessments are given in terms of tissue kerma. This paper discusses the experience gained by using EPR for dose assessment in fingernails with a stationary spectrometer versus a portable one, the reasons for the observed discrepancies in dose, and potential advantages and disadvantages of each approach for EPR measurements in fingernails.     

The state of hemopoiesis under conditions of long-term bone marrow irradiation in residents of the Techa riverside villages

The paper presents the results of a 50-year study on the state of hemopoiesis in the Techa riverside residents chronically exposed to radiation in the range from low to intermediate doses. The highest bone marrow doses were attributable to intakes of osteotropic 9OSr with drinking water and local food products. During the period of maximum radiation exposures (1951-1953) exposed residents were manifesting decreased counts of peripheral blood leukocytes (neutrophils and lymphocytes) and thrombocytes. Normal counts of erythrocytes were maintained owing to the effect of sufficient compensatory mechanisms, including accelerated rates of erythrocaryocyte proliferation and maturation. The development of peripheral blood granulocytopenia was influenced by the delay in the differentiation of neutrophilic bone-marrow granulocytes at the myelocyte phase, a marked increase in the frequency of lethal abnormalities in bone-marrow neutrophils, and pathological mitoses. The period of normalization of the blood cell composition was significantly variable for different blood cell series, and was noted to depend on exposure dose rate, extent of the primary hemopoiesis inhibition and specific physiological characteristics of exposed individuals.