Search

A profound approach to the analysis of clinical data on the dynamics of major hematopoietic lineages (granulocytopoietic, thrombocytopoietic, and erythrocytopoietic systems) in chronically irradiated humans is proposed. It is based on recently developed mathematical models of these systems in humans, which enable one to study and interpret clinical hematological data. The developed approach is applied to the analysis of statistically processed clinical data, which were obtained under hematological examinations of residents of Techa riverside villages. These people were exposed to chronic irradiation with varying dose rate due to the radioactive contamination of the river basin by the Mayak Production Association. In the course of modeling studies, the relationship between the dynamics of aforementioned systems in examined individuals and the variation of chronic exposure dose rate over the considered period of time is revealed. It is found that the models are capable of reproducing common regularities and peculiarities of the dynamics of systems on hand, including the decreased stationary levels of blood cell concentrations during the period of maximum radiation exposure, the recovery processes during the period of decrease of exposure dose rate, and the prevalence of younger bone marrow granulocytopoietic cells over more mature ones during the entire period. The mechanisms of such effects of chronic irradiation on the hematopoietic lineages are revealed on the basis of modeling studies. All this testifies to the efficiency of employment of the developed models in the analysis, investigation, and prediction of effects of chronic irradiation on human hematopoietic system.

Liquid radioactive waste from the Mayak Production Association (Chelyabinsk Region, Russia) is contained in industrial reservoirs (R-11, R-10, R-4, R-17, and R-9) that have different levels of radioactive contamination, increased from R-11 to R-17. A study of the ecosystems in these reservoirs was performed in 2009 to determine if there was any association with the level of contamination. No significant change in the status of biota was found in the reservoir with the lowest radionuclide concentrations (R-11) in comparison to other reservoirs in the region with a similar geography that are unaffected by radioactive contamination. In reservoir R-10, changes in the zoobenthos indices were registered. In reservoir R-4, changes in the zoobenthos and zooplankton communities were registered. In reservoir R-17, there was no ichthyofauna, but strong changes in the phytoplankton, zooplankton, and zoobenthos communities were registered. In reservoir R-9, under the conditions of the heaviest radioactive contamination of water ecosystems in the biosphere, there was no ichthyofauna, and phytoplankton and zooplankton consisted of almost a monoculture of cyanobacteriae and rotifers.

This research has been conducted to study the activity of apoptosis of peripheral blood lymphocytes (PBLs) and the frequency of CD3-/CD4+ PBLs in people who have suffered chronic low-intensity radiation exposure. An increase in the frequency of apoptotic cells (TUNEL) is demonstrated in the group of exposed individuals relative to the control group. The frequency of mutations in the gene of the T-cell receptor in the exposed individuals is also elevated. Analyses of the mean values of apoptosis and CD3-CD4+ PBLs in different dose subgroups have found an increase in the proportion of cells with mutant T-cell receptors against the background of a decrease in the frequency of apoptotic cells in the range of low and medium radiation doses.

The major goal of this study is to investigate and quantitatively describe the nature of the relationship between the characteristics of chronic exposure to ionizing radiation and specific patterns of hematopoiesis reduction. The study is based on about 3,200 hemograms taken for inhabitants of the Techa riverside villages over the years 1951-1956, i.e., the period characterized by a gradual decrease in dose rates. The mean cumulative red bone marrow dose was 333.6 + or - 4.6 mGy. The approach to statistical analyses involved both empirical methods and modeling (generalized linear models and logistic regressions). The results of the analyses highlighted a gradual increase in the frequency of cytopenias with dose rate. The impact of exposure on hematopoiesis reduction patterns was found to be more substantial than that of age and health status. Dose rates resulting in a two-fold increase in the frequency of cytopenias have been estimated.

A new model of the hematopoietic system for humans chronically exposed to ionizing radiation allows for quantitative description of the initial hematopoiesis inhibition and subsequent increase in the risks of late stochastic effects such as leukemia. This model describes the dynamics of the hematopoietic stem cell compartment as well as the dynamics of each of the three blood cell types (leukocytes, erythrocytes, and platelets). The model parameters are estimated from the results of other experiments. They include the steady-state numbers of hematopoietic stem cells and peripheral blood cell lines for an unexposed organism, amplification parameters for each blood cell line, parameters describing the proliferation and apoptosis, parameters of feedback functions regulating the steady-state numbers, and characteristics of radiosensitivity in respect to cell death and non-lethal cell damages. The dynamic model of hematopoiesis is applied to the data on a subcohort of the Techa River residents with hematological measurements (e.g., blood counts) performed in 1950-1956 (which totals to about 3,500 exposed individuals). Among well-described effects observed in these data are the slope values of the dose-effect curves describing the hematopoietic inhibition and the dose rate patterns of the fractions of cytopenic states (e.g., leukopenia, thrombocytopenia). The model has been further generalized by inclusion of the component describing the risk of late stochastic effects. The risks of the development of late effects (such as leukemia) in population groups with specific patterns of early reactions in hematopoiesis (such as leukopenia induced by ionizing radiation) are investigated using simulation studies and compared to data.

Unlabelled: The present paper focuses on the analysis of data resulting from 50-y studies involving assessment of the hemopoiesis state in Techa riverside residents chronically exposed to radiation and evaluation of the bone tissue status for people with Sr incorporation at late time after the intakes., Conclusions: 1. In the late period after the start of chronic radiation exposure (50 y later) only a few individuals with red bone marrow doses reaching about 1.8 Gy (mean dose of 0.66 Gy) had a marked peripheral blood leucopenia, and the incidence of neutropenia, lymphopenia and thrombocypenia in the exposed group did not exceed that noted in the control group. The results of our observations indicate the spontaneous recovery of the hemopoietic system of residents of the Techa riverside villages. Thus, the adaptation mechanisms of hemopoiesis to the long-term chronic exposure in the range of low to intermediate doses are sufficiently effective; 2. About half of the people with Sr incorporation and the control group have changes in bone tissue expressed by different stages of osteoporosis. Age is a determinative factor of bone tissue involution in women while some tendency of Sr influence on the intensity of osteoporosis is revealed in the male group.

Waterborne releases to the Techa River from the Mayak Production Association in Russia during 1949-1956 resulted in significant doses to persons living downstream; the most contaminated village was Metlino, about 7 km from the site of release. Internal and external doses have been estimated for these residents using the Techa River Dosimetry System-2000 (TRDS-2000); the primary purpose is to support epidemiological studies of the members of the Extended Techa River Cohort. Efforts to validate the calculations of external and internal dose are considered essential. One validation study of the TRDS-2000 system has been performed by the comparison of calculated doses to quartz from bricks in old buildings at Metlino with those measured by luminescence dosimetry. Two additional methods of validation considered here are electron paramagnetic resonance (EPR) measurements of teeth and fluorescence in situ hybridization (FISH) measurements of chromosome translocations in circulating lymphocytes. For electron paramagnetic resonance, 36 measurements on 26 teeth from 16 donors from Metlino were made at the GSF-National Research Center for Environment and Health (16 measurements) and the Institute of Metal Physics (20 measurements); the correlation among measurements made at the two laboratories has been found to be 0.99. Background measurements were also made on 218 teeth (63 molars, 128 premolars, and 27 incisors). Fluorescence in situ hybridization measurements were made for 31 residents of Metlino. These measurements were handicapped by the analysis of a limited number of cells; for several individuals no stable translocations were observed. Fluorescence in situ hybridization measurements were also made for 39 individuals believed to be unexposed. The EPR- and FISH-based estimates agreed well for permanent residents of Metlino: 0.67 +/- 0.21 Gy and 0.48 +/- 0.18 Gy (mean +/- standard error of the mean), respectively. Results of the two experimental methods also agreed well with the estimates derived from the use of the TRDS-2000. For all persons investigated according to each technique, the EPR-measured dose to enamel was 0.55 +/- 0.17 Gy, and the TRDS-2000 prediction for the dose to enamel for these individuals is 0.55 +/- 0.07 Gy. The fluorescence in situ hybridization-based dose, 0.38 +/- 0.10 Gy, compared well to the TRDS-2000 prediction of external dose, 0.31 +/- 0.03 Gy, to red bone marrow for these persons. Validation of external doses at the remaining villages is an active area of investigation.

During the years 1949-1952, the Mayak Production Association (MAYAK), which was processing weapons-grade plutonium, was discharging radioactive wastes into the Techa River. As a result, all components of the river system (water, bottom soils, and flood plains) were exposed to massive radioactive contamination. The protective measures taken in the 1950's resulted in the improvement of the radioecological conditions in the Techa River. After 1952, the radioecological conditions in the area were mostly determined by the long-lived radionuclides 9OSr and 137Cs. This article focuses on the dependencies governing the migration of radionuclides along the vertical and horizontal planes in different components of the river system over a 40-y period. Until the 1990's, a decrease in 90Sr and 137Cs contents was noted in environmental samples and foodstuffs produced in riverside villages. In the subsequent years, the radioecological situation on the Techa stabilized. The sources of the current contamination of the river are represented by the runoffs from by-pass canals and swampy upper reaches.