Analysis of chromosome aberrations in nuclear-power-plant workers considering the lifetime of lymphocytes

Eurados review of retrospective dosimetry techniques for internal exposures to ionising radiation and their applications

This work presents an overview of the applications of retrospective dosimetry techniques in case of incorporation of radionuclides. The fact that internal exposures are characterized by a spatially inhomogeneous irradiation of the body, which is potentially prolonged over large periods and variable over time, is particularly problematic for biological and electron paramagnetic resonance (EPR) dosimetry methods when compared with external exposures. The paper gives initially specific information about internal dosimetry methods, the most common cytogenetic techniques used in biological dosimetry and EPR dosimetry applied to tooth enamel. Based on real-case scenarios, dose estimates obtained from bioassay data as well as with biological and/or EPR dosimetry are compared and critically discussed. In most of the scenarios presented, concomitant external exposures were responsible for the greater portion of the received dose. As no assay is available which can discriminate between radiation of different types and different LETs on the basis of the type of damage induced, it is not possible to infer from these studies specific conclusions valid for incorporated radionuclides alone. The biological dosimetry assays and EPR techniques proved to be most applicable in cases when the radionuclides are almost homogeneously distributed in the body. No compelling evidence was obtained in other cases of extremely inhomogeneous distribution. Retrospective dosimetry needs to be optimized and further developed in order to be able to deal with real exposure cases, where a mixture of both external and internal exposures will be encountered most of the times.

Dicentric Dose Estimates for Patients Undergoing Radiotherapy in the RTGene Study to Assess Blood Dosimetric Models and the New Bayesian Method for Gradient Exposure

The RTGene study was focused on the development and validation of new transcriptional biomarkers for prediction of individual radiotherapy patient responses to ionizing radiation. In parallel, for validation purposes, this study incorporated conventional biomarkers of radiation exposure, including the dicentric assay. Peripheral blood samples were taken with ethical approval and informed consent from a total of 20 patients undergoing external beam radiotherapy for breast, lung, gastrointestinal or genitourinary tumors. For the dicentric assay, two samples were taken from each patient: prior to radiotherapy and before the final fraction. Blood samples were set up using standard methods for the dicentric assay. All the baseline samples had dicentric frequencies consistent with the expected background for the normal population. For blood taken before the final fraction, all the samples displayed distributions of aberrations, which are indicative of partial-body exposures. Whole-body and partial-body cytogenetic doses were calculated with reference to a 250-kVp X-ray calibration curve and then compared to the dose to blood derived using two newly developed blood dosimetric models. Initial comparisons indicated that the relationship between these measures of dose appear very promising, with a correlation of 0.88 (P = 0.001). A new Bayesian zero-inflated Poisson finite mixture method was applied to the dicentric data, and partial-body dose estimates showed no significant difference (P > 0.999) from those calculated by the contaminated Poisson technique. The next step will be further development and validation in a larger patient group.

Radioactively contaminated areas: Bioindicator species and biomarkers of effect in an early warning scheme for a preliminary risk assessment

Concerns about the impacts on public health and on the natural environment have been raised regarding the full range of operational activities related to uranium mining and the rest of the nuclear fuel cycle (including nuclear accidents), nuclear tests and depleted uranium from military ammunitions. However, the environmental impacts of such activities, as well as their ecotoxicological/toxicological profile, are still poorly studied. Herein, it is discussed if organisms can be used as bioindicators of human health effects, posed by lifetime exposure to radioactively contaminated areas. To do so, information was gathered from several studies performed on vertebrates, invertebrate species and humans, living in these contaminated areas. The retrieved information was compared, to determine which are the most used bioindicators and biomarkers and also the similarities between human and non-human biota responses. The data evaluated are used to support the proposal for an early warning scheme, based on bioindicator species and on the most sensitive and commonly shared biomarkers, to perform a screening evaluation of radioactively contaminated sites. This scheme could be used to support decision-making for a deeper evaluation of risks to human health, making it possible to screen a large number of areas, without disturbing and alarming local populations.

What radiation dose does the FISH translocation assay measure in cases of incorporated radionuclides for the Southern Urals populations?

The fluorescence in situ hybridisation (FISH) technique is now well established for retrospective dosimetry in cases of external radiation exposure that occurred many years ago. However, the question remains as to whether FISH provides valid estimates of cumulative red bone marrow radiation doses in cases of incorporation of radionuclides or combined external and internal exposures. This question has arisen in connection with the interpretation of results of dose assessments for epidemiological studies of plutonium workers at the Russian Mayak plant and of members of the public exposed to strontium radioisotopes and external radiation as a result of discharges from Mayak to the Techa River. Exposures to penetrating external radiation result in fairly uniform irradiation of body tissues, and hence similar doses to all tissues, for which FISH dosimetry can provide a reliable measure of this whole body dose. However, intakes of radionuclides into the body by inhalation or ingestion may result in retention in specific organs and tissues, so that the distribution of dose is highly heterogeneous. For radionuclides emitting short-range radiations (e.g. alpha particles), this heterogeneity can apply to dose delivery within tissues and between cells within tissues. In this paper, an attempt is made to address the question of what FISH measures in such circumstances by considering evidence regarding the origin and lifetime dynamics of lymphocyte subsets in the human body in relation to the localised delivery of dose from the internal emitters (90)Sr and (239)Pu, which are of particular interest for the Southern Urals Mayak and Techa River populations, and for which most evidence is available in these populations. It is concluded that the FISH translocation assay can be usefully applied for detecting internal and combined external gamma and internal doses from internally deposited (90)Sr, albeit with fairly large uncertainties. The same may be true of (239)Pu, as well as other radionuclides, although much work remains to be done to establish dose-response relationships.

Chronic radioisotope effects on residents of the Techa River (Russia) region: cytogenetic analysis more than 50 years after onset of exposure

This paper presents the results of a cytogenetic study conducted among residents of the Techa Riverside communities (Southern Urals, Russia) exposed in the early 1950s as a result of releases of liquid radioactive wastes from the Mayak plutonium-production facility. The study was performed 50-60 years after the beginning of the exposure for those individuals who were predominantly exposed to strontium radioisotopes ((89,90)Sr) through drinking contaminated river water and consumption of local foodstuff. Standard cytogenetic methods were used for evaluation of the frequency of unstable chromosome aberrations in exposed persons as well as in persons from the control group who were of similar age and sex, living in similar socio-economic conditions in non-contaminated territories of the Southern Urals. The exposure doses were reconstructed for the studied donors using the Techa River Dosimetry System developed in 2009. The doses of internal exposure from ingested radionuclides were evaluated using individual or family in vivo measurements of (90)Sr-body burden. Individual cumulative absorbed doses in red bone marrow (RBM) in the studied persons varied in the range of 0.01-4.4Gy. A significantly higher level of unstable chromosome aberrations (UCA) in T-cells was observed in the group of exposed individuals as compared to control group. The highest UCA level was detected in the individuals who were suspected of having chronic radiation syndrome.

Comparison of p53 levels in lymphocytes and in blood plasma of nuclear power plant workers

p53 levels were assessed in lymphocytes and in blood plasma of workers from two Czech nuclear power plants (NPP): 114 subjects working in Temelin and 108 subjects working in Dukovany. Ionizing radiation (IR) exposure data were available for 64 and 59 subjects working in the monitored zones from the NPP in Temelin and Dukovany, respectively. The short-term doses of IR for these subjects were 0.01 and 0.12 mSv, and the long-term doses were 0.46 and 5.68 mSv, in the Temelin and Dukovany NPP, respectively. As a control group, 46 subjects living in Ceske Budejovice, a city nearby the Temelin NPP, were analyzed. The concentration of p53 in lymphocytes was significantly higher in workers from the monitored zone in the Dukovany NPP (median value 6.4 pg/microg protein, P <0.001) than in workers from the Temelin NPP (3.2 pg/microg) as well as in the control group (3.5 pg/microg). In contrast, plasma levels of p53 were comparable in the control group (median value 116 pg/ml plasma) and workers from the monitored zone of Dukovany NPP (102 pg/ml), but lower in workers from Temelin NPP (5 pg/ml). Other factors affecting p53 levels were studied. Smoking resulted in increased p53 lymphocyte levels. The effect of polymorphisms in metabolic and DNA repair genes on p53 levels was analyzed. The correlation was found between p53 levels in lymphocytes and p53 codon 72 polymorphism in subjects working in NPPs, but not in the control group. The results of measurement p53 levels in lymphocytes suggest that this biomarker could reflect the short-term as well as long-term effects of low doses IR. Its impact on human health should be further explored.