Search

International audience; This article aims at comparing reference methods for the assessment of cancer risk from exposure to genotoxic carcinogen chemical substances and to ionizing radiation. For chemicals, cancer potency is expressed as a toxicological reference value (TRV) based on the most sensitive type of cancer generally observed in animal experiment of oral or inhalation exposure. A dose-response curve is established by modelling experimental data adjusted to apply to human exposure. This leads to a point of departure from which the TRV is derived as the slope of a linear extrapolation to zero dose. Human lifetime cancer risk can then be assessed as the product of dose by TRV and it is generally considered to be acceptable below 10-5 for public in normal situation. Radiation exposure is assessed as effective dose corresponding to a weighted average of energy deposition in body organs. Cancer risk models were derived from the epidemiological follow-up of atomic bombing survivors. Considering a linear-no-threshold dose-risk relationship and average baseline risks, lifetime nominal risk coefficients were established for 13 types of cancers. Those are adjusted according to the severity of each cancer type and combined into an overall indicator denominated radiation detriment. Exposure to radiation is subject to dose limits proscribing unacceptable health detriment. The differences between chemical and radiological cancer risk assessments are discussed and concern data sources, extrapolation to low doses, definition of dose, considered health effects and level of conservatism. Despite these differences, opportunities exist to bring closer the two types of risk assessment.

International audience; Procedures using iodine-131 represent more than 90% of all therapies in nuclear medicine in Algeria. It is important to evaluate the long-term biological effects of iodine treatment on non-target organs to improve patient radiation protection. This experimental radiotoxicology study aims to determine the biokinetic models of iodine contamination. For this purpose, two Wistar rat models, with and without a thyroid, have been used to evaluate the biological half-life of iodine and then to perform a biodistribution study of iodine activity in 15 organs and tissues. For the most relevant organs, the respective absorbed doses have been calculated using RODES software. © 2019 Society for Radiological Protection. Published on behalf of SRP by IOP Publishing Limited. All rights reserved.

International audience; Nowadays, protection standards against ionizing radiation health effects are mainly derived from the results of the epidemiological study of atomic bomb survivors in Hiroshima and Nagasaki, who were exposed externally to radiation, at high dose rate. However, exposure to ionizing radiation in the general population and in workers generally occurs as a cumulation of low doses over years (therefore, at low dose rates), and as a result of external, but also internal, exposure. Epidemiological studies in radiation workers allow studying the long-term health effects of such exposures, and are precious to assess the adequacy of current radiation protection standards against cancer. In addition, they also allow for the study of new priority research questions in radiation protection, such as potential non-cancer effects of low dose radiation. Finally, they also provide a general picture of health in populations of radiation workers, which is useful for occupational and public health expertise. This article provides an overview of epidemiological research conducted in workers of the nuclear cycle by the French Institute for Radiological Protection and Nuclear Safety (IRSN), and discusses perspectives for its future developments. © EDP Sciences 2018; À ce jour, les normes internationales de radioprotection sont essentiellement basées sur les connaissances des effets sanitaires des rayonnements ionisants issues des études de cohortes de survivants des bombardements atomiques d’Hiroshima et de Nagasaki, qui ont subi des irradiations par voie externe à forts débits de doses. Or, les expositions aux rayonnements ionisants survenant en population générale et chez certains travailleurs correspondent généralement à de faibles doses, cumulées de manière prolongée dans le temps. Ces expositions peuvent avoir lieu par irradiation externe mais aussi par contamination interne. Les études épidémiologiques chez les travailleurs du nucléaire permettent notamment de mieux caractériser les effets de ces conditions d’expositions. Elles permettent ainsi d’évaluer l’adéquation des normes de radioprotection pour protéger les travailleurs, mais également la population générale adulte, contre les risques de cancer. Par ailleurs, elles permettent d’aborder de nouveaux questionnements de recherche en radioprotection, comme les potentiels effets non cancéreux. Enfin, ces études fournissent un bilan de santé général des populations de travailleurs du nucléaire. Cet article propose une vue d’ensemble des recherches épidémiologiques menées par l’Institut de Radioprotection et de Sûreté Nucléaire (IRSN) chez les travailleurs du cycle électronucléaire en France. Il dresse également quelques perspectives de développements possibles de ces recherches.

– The 2007 Recommendations of the International Commission on Radiological Protection (ICRP, 2007) introduced changes that affect the calculation of effective dose, and implied a revision of the dose coefficients for internal exposure, published previously in the Publication 30 series (ICRP, 1979, 1980, 1981, 1988) and Publication 68 (ICRP, 1994). In addition, new data are now available that support an update of the radionuclide-specific information given in Publications 54 and 78 (ICRP, 1988a, 1997b) for the design of monitoring programmes and retrospective assessment of occupational internal doses. Provision of new biokinetic models, dose coefficients, monitoring methods, and bioassay data was performed by Committee 2, Task Group 21 on Internal Dosimetry, and Task Group 4 on Dose Calculations. A new series, the Occupational Intakes of Radionuclides (OIR) series, will replace the Publication 30 series and Publications 54, 68, and 78. OIR Part 1 has been issued (ICRP, 2015), and describes the assessment of internal occupational exposure to radionuclides, biokinetic and dosimetric models, methods of individual and workplace monitoring, and general aspects of retrospective dose assessment. OIR Part 2 (ICRP, 2016), this current publication and upcoming publications in the OIR series (Parts 4 and 5) provide data on individual elements and their radioisotopes, including information on chemical forms encountered in the workplace; a list of principal radioisotopes and their physical half-lives and decay modes; the parameter values of the reference biokinetic model; and data on monitoring techniques for the radioisotopes encountered most commonly in workplaces. Reviews of data on inhalation, ingestion, and systemic biokinetics are also provided for most of the elements. Dosimetric data provided in the printed publications of the OIR series include tables of committed effective dose per intake (Sv Bq−1 intake) for inhalation and ingestion, tables of committed effective dose per content (Sv Bq−1 measurement) for inhalation, and graphs of retention and excretion data per Bq intake for inhalation. These data are provided for all absorption types and for the most common isotope(s) of each element. The electronic annex that accompanies the OIR series of publications contains a comprehensive set of committed effective and equivalent dose coefficients, committed effective dose per content functions, and reference bioassay functions. Data are provided for inhalation, ingestion, and direct input to blood. This third publication in the series provides the above data for the following elements: ruthenium (Ru), antimony (Sb), tellurium (Te), iodine (I), caesium (Cs), barium (Ba), iridium (Ir), lead (Pb), bismuth (Bi), polonium (Po), radon (Rn), radium (Ra), thorium (Th), and uranium (U).

ObjectivesThere is growing evidence of an association between low-dose external γ-radiation and circulatory system diseases (CSDs), yet sparse data exist about an association with chronic internal uranium exposure and the role of non-radiation risk factors. We conducted a nested case–control study of French AREVA NC Pierrelatte nuclear workers employed between 1960 and 2005 to estimate CSD risks adjusting for major CSD risk factors (smoking, blood pressure, body mass index, total cholesterol and glycaemia) and external γ-radiation dose.MethodsThe study included 102 cases of death from CSD and 416 controls individually matched on age, gender, birth cohort and socio-professional status. Information on CSD risk factors was collected from occupational medical records. Organ-specific absorbed doses were estimated using biomonitoring data, taking into account exposure regime and uranium physicochemical properties. External γ-radiation was measured by individual dosimeter badges. Analysis was conducted with conditional logistic regression.ResultsWorkers were exposed to very low radiation doses (mean γ-radiation dose 2 and lung uranium dose 1 mGy). A positive but imprecise association was observed (excess OR per mGy 0.2, 95% CI 0.004 to 0.5). Results obtained after adjustment suggest that uranium exposure might be an independent CSD risk factor.ConclusionsOur results suggest that a positive association might exist between internal uranium exposure and CSD mortality, not confounded by CSD risk factors. Future work should focus on numerous uncertainties associated with internal uranium dose estimation and on understanding biological pathway of CSD after protracted low-dose internal radiation exposure.

The 2007 Recommendations (ICRP, 2007) introduced changes that affect the calculation of effective dose, and implied a revision of the dose coefficients for internal exposure, published previously in the Publication 30 series (ICRP, 1979a,b, 1980a, 1981, 1988) and Publication 68 (ICRP, 1994b). In addition, new data are now available that support an update of the radionuclide-specific information given in Publications 54 and 78 (ICRP, 1989a, 1997) for the design of monitoring programmes and retrospective assessment of occupational internal doses. Provision of new biokinetic models, dose coefficients, monitoring methods, and bioassay data was performed by Committee 2 and its task groups. A new series, the Occupational Intakes of Radionuclides (OIR) series, will replace the Publication 30 series and Publications 54, 68, and 78. OIR Part 1 (ICRP, 2015) describes the assessment of internal occupational exposure to radionuclides, biokinetic and dosimetric models, methods of individual and workplace monitoring, and general aspects of retrospective dose assessment. OIR Part 2 (ICRP, 2016), OIR Part 3 (ICRP, 2017), this current publication, and the final publication in the OIR series (OIR Part 5) provide data on individual elements and their radioisotopes, including information on chemical forms encountered in the workplace; a list of principal radioisotopes and their physical half-lives and decay modes; the parameter values of the reference biokinetic models; and data on monitoring techniques for the radioisotopes most commonly encountered in workplaces. Reviews of data on inhalation, ingestion, and systemic biokinetics are also provided for most of the elements. Dosimetric data provided in the printed publications of the OIR series include tables of committed effective dose per intake (Sv per Bq intake) for inhalation and ingestion, tables of committed effective dose per content (Sv per Bq measurement) for inhalation, and graphs of retention and excretion data per Bq intake for inhalation. These data are provided for all absorption types and for the most common isotope(s) of each element. The online electronic files that accompany the OIR series of publications contains a comprehensive set of committed effective and equivalent dose coefficients, committed effective dose per content functions, and reference bioassay functions. Data are provided for inhalation, ingestion, and direct input to blood. This fourth publication in the OIR series provides the above data for the following elements: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), actinium (Ac), protactinium (Pa), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), and fermium (Fm).

International audience; The biokinetic model for systemic americium (Am) currently recommended by the International Commission on Radiological Protection (ICRP) for application to occupational intake of Am is based on information available through the early 1990s. Much additional information on Am biokinetics has been developed in the past 25 y, including measurements of retention and excretion of 241Am in many workers with 241Am burdens and post mortem measurements of 241Am in tissues of some of those workers. The ICRP's current Am model is reasonably consistent with the updated information, with the main exception that the current model apparently overestimates 24-hour urinary Am as a fraction of skeletal or systemic Am at late times after intake. This paper provides an overview of current information on the systemic kinetics of Am in adult human subjects and laboratory animals and presents an updated biokinetic model for systemic Am that addresses the discrepancies between the current database and current ICRP systemic model for Am. This model is applied in Part 4 (to appear) of an ICRP series of reports on intake of radionuclides by workers called the OIR (Occupational Intake of Radionuclides) series. © 2019 Not subject to copyright in the USA. Contribution of Oak Ridge National Laboratory.

International audience; European Radiation Dosimetry Group (EURADOS) Working Group 7 is a network on internal dosimetry that brings together researchers from more than 60 institutions in 21 countries. The work of the group is organised into task groups that focus on different aspects, such as development and implementation of biokinetic models (e.g. for diethylenetriamine penta-acetic acid decorporation therapy), individual monitoring and the dose assessment process, Monte Carlo simulations for internal dosimetry, uncertainties in internal dosimetry, and internal microdosimetry. Several intercomparison exercises and training courses have been organised. The IDEAS guidelines, which describe – based on the International Commission on Radiological Protection’s (ICRP) biokinetic models and dose coefficients – a structured approach to the assessment of internal doses from monitoring data, are maintained and updated by the group. In addition, Technical Recommendations for Monitoring Individuals for Occupational Intakes of Radionuclides have been elaborated on behalf of the European Commission, DG-ENER (TECHREC Project, 2014–2016, coordinated by EURADOS). Quality assurance of the ICRP biokinetic models by calculation of retention and excretion functions for different scenarios has been performed and feedback was provided to ICRP. An uncertainty study of the recent caesium biokinetic model quantified the overall uncertainties, and identified the sensitive parameters of the model. A report with guidance on the application of ICRP biokinetic models and dose coefficients is being drafted at present. These and other examples of the group’s activities, which complement the work of ICRP, are presented. © 2018, The International Society for Prosthetics and Orthotics.

International audience; In the early phase of a nuclear reactor accident, in-vivo monitoring of impacted population would be highly useful to detect potential contamination during the passage of the cloud and to estimate the dose from inhalation of measured radionuclides. However, it would be important to take into account other exposure components (1) inhalation of unmeasured radionuclides and (2) external irradiation from the plume and from the radionuclides deposited on the soil. This article presents a methodology to calculate coefficients used to convert in-vivo measurement results directly into doses, not only from the measured radionuclides but from all sources of exposure according to model-based projected doses. This early interpretation of in-vivo measurements will provide an initial indication of individual exposure levels. As an illustration, the methodology is applied to two scenarios of accidents affecting a nuclear power plant a loss-of-coolant accident leading to core meltdown and a steam generator tube rupture accident. © The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email journals.permissions@oup.com.

International audience; PURPOSE: The aim is to investigate associations between mortality and exposure to ionizing radiation in a cohort of uranium workers with potential for internal and external radiation exposures.METHODS: Workers employed for at least 6 months between 1958 and 2006 in five plants involved in the French nuclear fuel cycle were included and followed up between 1968 and 2013. Cause-specific standardized mortality ratios were calculated. Analyses of associations between individual cumulative radiation dose (both internal and external, lagged by 5-15 years) and mortality were conducted using Poisson regression.RESULTS: The cohort includes 4541 workers. The mean cumulative external dose was 11.12 mGy. Mean cumulative internal doses ranged, depending on modelling hypotheses, from 0.05 to 0.09 mGy (liver) and from 4.22 to 10.90 mGy (lung). At the end of the follow-up, 838 workers were deceased and 28 lost to follow-up. A healthy worker effect was observed. The risk of prostate and lung cancers mortality was significantly higher for workers exposed to cumulative external dose above 50 mGy compared to non-exposed, but these associations were based only on three cases and became non-significant, although of similar magnitude, after adjustment for smoking. Associations with internal dose showed no consistent pattern.CONCLUSIONS: For the first time, a study was conducted in a French cohort of uranium workers with a complete reconstruction of internal dose. Results are preliminary and must be interpreted with caution because of the limited cohort size and significant sources of uncertainty. Future steps of this study will overcome these limitations.

International audience; H Miloudi, M Locatelli, G Autret, D Balvay, A Desbrée, E Blanchardon, J M Bertho application of RODES software to experimental biokinetic data for dose assessment in mice and rats. In support of experimental studies of chronic, long-term contamination in rodents, voxel-based computer models were built representing adult mice and juvenile, adult and elderly rats of both sexes. RODES software was created to calculate absorbed radiation doses to organs with these specific anatomical models. Absorbed doses were then calculated starting from previously published biokinetic data. Whole body doses showed less than 5% differences between calculation with RODES and calculation with the ICRP Publication 108 model for long term exposure to 90Sr of mice. Similar results were obtained for long term exposure to 137Cs. Dose distribution for 90Sr internal contamination also showed that the dose to the skeleton is six fold more as compared to the whole body dose while radiation dose to other organs is less than the mean whole body dose. These results underline the importance of using specific anatomical models according to the age and the sex of experimental animals. © 2017 IOP Publishing Ltd.

Supplemental Digital Content is available in the text., Background: Carcinogenic risks of internal exposures to alpha-emitters (except radon) are poorly understood. Since exposure to alpha particles—particularly through inhalation—occurs in a range of settings, understanding consequent risks is a public health priority. We aimed to quantify dose–response relationships between lung dose from alpha-emitters and lung cancer in nuclear workers. Methods: We conducted a case–control study, nested within Belgian, French, and UK cohorts of uranium and plutonium workers. Cases were workers who died from lung cancer; one to three controls were matched to each. Lung doses from alpha-emitters were assessed using bioassay data. We estimated excess odds ratio (OR) of lung cancer per gray (Gy) of lung dose. Results: The study comprised 553 cases and 1,333 controls. Median positive total alpha lung dose was 2.42 mGy (mean: 8.13 mGy; maximum: 316 mGy); for plutonium the median was 1.27 mGy and for uranium 2.17 mGy. Excess OR/Gy (90% confidence interval)—adjusted for external radiation, socioeconomic status, and smoking—was 11 (2.6, 24) for total alpha dose, 50 (17, 106) for plutonium, and 5.3 (−1.9, 18) for uranium. Conclusions: We found strong evidence for associations between low doses from alpha-emitters and lung cancer risk. The excess OR/Gy was greater for plutonium than uranium, though confidence intervals overlap. Risk estimates were similar to those estimated previously in plutonium workers, and in uranium miners exposed to radon and its progeny. Expressed as risk/equivalent dose in sieverts (Sv), our estimates are somewhat larger than but consistent with those for atomic bomb survivors. See video abstract at, http://links.lww.com/EDE/B232.

International audience; In order to support animal experiments of chronic radionuclides intake with realistic dosimetry, voxel-based three-dimensional computer models of mice and rats of both sexes and three ages were built from magnetic resonance imaging. Radiation transport of mono-energetic photons of 11 energies and electrons of 7 energies was simulated with MCNPX 2.6c to assess specific absorbed fractions (SAFs) of energy emitted from 13 source regions and absorbed in 28 target regions. RODES software was developed to combine SAF with radiation emission spectra and user-supplied biokinetic data to calculate organ absorbed doses per nuclear transformation of radionuclides in source regions (S-factors) and for specific animal experiments with radionuclides. This article presents the design of RODES software including the simulation of the particles in the created rodent voxel phantoms. SAF and S-factor values were compared favourably with published results from similar studies. The results are discussed for rodents of different ages and sexes. © 2017 IOP Publishing Ltd.

The fourth workshop of the Multidisciplinary European Low Dose Initiative (MELODI) was organised by STUK—Radiation and Nuclear Safety Authority of Finland. It took place from 12 to 14 September 2012 in Helsinki, Finland. The meeting was attended by 179 scientists and professionals engaged in radiation research and radiation protection. We summarise the major scientific findings of the workshop and the recommendations for updating the MELODI Strategic Research Agenda and Road Map for future low dose research activities.

Recent epidemiology studies highlighted the detrimental health effects of exposure to low dose and low dose rate ionizing radiation (IR): nuclear industry workers studies have shown increased leukaemia and solid tumour risks following cumulative doses of

International audience; The assessment and management of risks associated with exposures to ionising radiation are defined by the general radiological protection system, proposed by the International Commission on Radiological Protection (ICRP). This system is regarded by a large majority of users as a robust system although there are a number of dissenting voices, claiming that it is not suitable for estimating the risks resulting from internal exposures. One of the specific issues of internal exposure involves short-range radiations such as Auger and beta particles. Auger- and beta-emitting radionuclides can be distributed preferentially in certain tissue structures and even in certain cellular organelles, according to their chemical nature and the vector with which they are associated. Given the limited range of the low-energy electrons in biological matter, this heterogeneous distribution can generate highly localised energy depositions and exacerbate radiotoxic responses at cellular level. These particularities in energy distribution and cellular responses are not taken into account by the conventional methods for the assessment of risk. Alternative systems have been proposed, based on dosimetry conducted at the cellular or even molecular level, whose purpose is to determine the energy deposition occurring within the DNA molecule. However, calculation of absorbed doses at the molecular level is not sufficient to ensure a better assessment of the risks incurred. Favouring such a microdosimetric approach for the risk assessments would require a comprehensive knowledge of the biological targets of radiation, the dose-response relationships at the various levels of organisation, and the mechanisms leading from cellular energy deposition to the appearance of a health detriment. The required knowledge is not fully available today and it is not yet possible to link an intracellular energy deposition to a probability of occurrence of health effects or to use methods based on cellular dosimetry directly. The imperfections of the alternative approaches proposed so far should not discourage efforts. Protection against exposure to Auger and low-energy beta emitters would benefit from mechanistic studies, dedicated to the study of energy depositions of the radionuclides in various cellular structures, but also from radiotoxicological studies to define the relative biological effectiveness of the various Auger emitters used in medicine and of certain low-energy beta emitters, whose behaviour may depend greatly on their chemical form during intake. The scientific expertise, as well as the human and physical resources needed to conduct these studies, is available. They could be now mobilised into international low-dose research programmes, in order to ultimately improve the protection of people exposed to these specific radionuclides. © 2013 IOP Publishing Ltd.

International audience; Dose assessment after intakes of radionuclides requires application of biokinetic and dosimetric models and assumptions about factors influencing the final result. In 2006, a document giving guidance for such assessment was published, commonly referred to as the IDEAS Guidelines. Following its publication, a working group within the European networks CONRAD and EURADOS was established to improve and update the IDEAS Guidelines. This work resulted in Version 2 of the IDEAS Guidelines, which was published in 2013 in the form of a EURADOS report. The general structure of the original document was maintained; however, new procedures were included, e.g. the direct dose assessment method for 3H or special procedure for wound cases applying the NCRP wound model. In addition, information was updated and expanded, e.g. data on dietary excretion of U, Th, Ra and Po for urine and faeces or typical and achievable values for detection limits for different bioassay measurement techniques. © The Author 2015. Published by Oxford University Press. All rights reserved.

International audience; The TECHREC project, funded by the European Commission, will provide Technical Recommendations for Monitoring Individuals for Occupational Intakes of Radionuclides. It is expected that the document will be published by the European Commission as a report in its Radiation Protection Series during 2016. The project is coordinated by the European Radiation Dosimetry Group (EURADOS) and is being carried out by members of EURADOS Working Group 7 (Internal Dosimetry). This paper describes the aims and purpose of the Technical Recommendations, and explains how the project is organised. © Crown copyright 2015.

The potential health impacts of chronic exposures to uranium, as they occur in occupational settings, are not well characterized. Most epidemiological studies have been limited by small sample sizes, and a lack of harmonization of methods used to quantify radiation doses resulting from uranium exposure. Experimental studies have shown that uranium has biological effects, but their implications for human health are not clear. New studies that would combine the strengths of large, well-designed epidemiological datasets with those of state-of-the-art biological methods would help improve the characterization of the biological and health effects of occupational uranium exposure. The aim of the European Commission concerted action CURE (Concerted Uranium Research in Europe) was to develop protocols for such a future collaborative research project, in which dosimetry, epidemiology and biology would be integrated to better characterize the effects of occupational uranium exposure. These protocols were developed from existing European cohorts of workers exposed to uranium together with expertise in epidemiology, biology and dosimetry of CURE partner institutions. The preparatory work of CURE should allow a large scale collaborative project to be launched, in order to better characterize the effects of uranium exposure and more generally of alpha particles and low doses of ionizing radiation. © 2016 IOP Publishing Ltd.

International audience; In case of internal contamination with plutonium materials, a treatment with diethylene triamine pentaacetic acid (DTPA) can be administered in order to reduce plutonium body burden and consequently avoid some radiation dose. DTPA intravenous injections or inhalation can start almost immediately after intake, in parallel with urinary and fecal bioassay sampling for dosimetric follow-up. However, urine and feces excretion will be significantly enhanced by the DTPA treatment. As internal dose is calculated from bioassay results, the DTPA effect on excretion has to be taken into account. A common method to correct bioassay data is to divide it by a factor representing the excretion enhancement under DTPA treatment by intravenous injection. Its value may be based on a nominal reference or observed after a break in the treatment. The aim of this study was to estimate the influence of this factor on internal dose by comparing the dose estimated using default or upper and lower values of the enhancement factor for 11 contamination cases. The observed upper and lower values of the enhancement factor were 18.7 and 63.0 for plutonium and 24.9 and 28.8 for americium. For americium, a default factor of 25 is proposed. This work demonstrates that the use of a default DTPA enhancement factor allows the determination of the magnitude of the contamination because dose estimated could vary by a factor of 2 depending on the value of the individual DTPA enhancement factor. In case of significant intake, an individual enhancement factor should be determined to obtain a more reliable dose assessment. © 2016 Health Physics Society.

International audience; The knowledge of the absorbed radiation dose is essential in order to interpret the results of animal experiments with chronic ingestion of radionuclides by rodents. In order to evaluate this absorbed dose, we applied the dose conversion factors proposed by ICRP publication 108 to mouse chronic ingestion experiments with 20 kBq.L-1 137Cs- or 90Sr-contaminated water. The results indicated that whole-body absorbed doses were 9 mGy and 10 mGy by the end of 20 weeks of 137Cs or 90Sr ingestion, respectively. These results of dose calculations were compared with results obtained with a more refined method using published organ-specific absorbed fractions of energy. There was good agreement between the two methods, indicating that, despite the simple hypotheses used to apply the ICRP 108 dose conversion factors to our mouse model, this method allows one to calculate in a simple and reliable way the absorbed radiation dose received by the rodents during long-term experiments on chronic ingestion of radionuclides. © 2012 EDP Sciences.

A workshop dedicated to cancer risks associated with low-dose internal contamination was organised in March 2011, in Paris, in the framework of the DoReMi (Low Dose Research towards Multidisciplinary Integration) European Network of Excellence. The aim was to identify the best epidemiological studies that provide an opportunity to develop a multidisciplinary approach to improve the evaluation of the cancer risk associated with internal contamination. This workshop provided an opportunity for in-depth discussions between researchers working in different fields including (but not limited to) epidemiology, dosimetry, biology and toxicology. Discussions confirmed the importance of research on the health effects of internal contamination. Several existing epidemiological studies provide a real possibility to improve the quantification of cancer risk associated with internal emitters. Areas for future multidisciplinary collaborations were identified, that should allow feasibility studies to be carried out in the near future. The goal of this paper is to present an overview of the presentations and discussions that took place during this workshop.

cited By 3; Lung cancer risk following radon inhalation is strongly established. On the contrary, much less is known about the possible health effects of radon ingestion via drinking water. This article summarizes the current knowledge of dosimetry following radon ingestion. Results from epidemiological studies of radon in drinking water are also presented and discussed. © 2010 EDP Sciences.; Si le risque de cancer du poumon lié à l’inhalation de radon est aujourd’hui largement reconnu, les possibles conséquences sanitaires de l’ingestion d’eau contenant du radon apparaissent moins bien documentées. Cet article synthétise les connaissances actuelles sur la dosimétrie correspondant à l’ingestion de radon. Les résultats des études épidémiologiques sur les effets sanitaires du radon dans l’eau de boisson sont également présentés et discutés.

The individual monitoring of internal exposure of workers comprises two steps: measurement and measurement interpretation. The latter consists in reconstructing the intake of a radionuclide from the activity measurement and calculating the dose using a biokinetic model of the radionuclide behavior in the human body. Mathematically, reconstructing the intake is solving an inverse problem described by a measurement-model equation. The aim of this paper is to propose a solution to this inverse problem when the measurement-model parameters are considered as uncertain. For that, an analysis of the uncertainty on the intake calculation is performed taking into account the dispersion of the measured quantity and the uncertainties of the measurement-model parameters. It is shown that both frequentist and Bayesian approaches can be used to solve the problem according to the measurement-model formulation. A common calculation algorithm is proposed to support both approaches and applied to the examples of tritiated water intake and plutonium inhalation by a worker. © 2009 Health Physics Society.

Modelling Pu/Am decorporation by DTPA. A new tool has been developed to optimize DTPA efficacy as concerns reduction of effective dose after 239 Pu wound. For example, the simulations show, for moderately soluble compounds (type M), a 1/3 decrease of effective dose is obtained after repeated early treatment (24 i.v. for 4 months), whereas a decrease by a factor 5 can be reached if treatments continue for 5 years at 2 week interval. By contrast, for poorly soluble compounds (type S), negligible efficacy is observed after early treatments, and a 3 time decrease of dose is obtained for treatments performed at 2 week interval for 50 years. Some of the hypotheses retained for modelling DTPA decorporation are validated from new experimental data published recently, and structure of a new model which can be applied both to Pu and Am is reported, taking into account urinary and faecal excretion, structure being suitable for different doses of DTPA and using various galenic forms.

To improve calibration methods of in vivo counting, our laboratory has developed a computer tool to model internal contamination and assess in vivo activity and corresponding organ absorbed doses. The aim of the recent work was to define a more realistic source based on biokinetic models. The influence of the biokinetic parameters on the in vivo counting was studied through the simulation of an acute inhalation intake of Am. The tissue distribution of activity predicted by the biokinetic model was visualized. Two equivalent methods for determination of the efficiency related to the total activity distributed in the body were used. The comparison between the efficiency taking the biokinetics into account and the classically estimated efficiency quantifies the influence of the activity distribution in the body and provides conversion factors for correcting the classical efficiency to account for biokinetics. ©2009Health Physics Society.

La conversion en dose d’une exposition au radon fait l’objet de debats. L’UNSCEAR a defini un coefficient de conversion de la concentration en radon vers la dose efficace a partir de modeles dosimetriques et d’informations epidemiologiques. La CIPR recommande d’evaluer le risque lie au radon a partir des etudes epidemiologiques. Pour permettre la prise en compte d’une exposition combinee a d’autres sources de rayonnements ionisants, elle a adopte des conventions de conversion en dose efficace inferieures de 10 a 30 % au coefficient de l’UNSCEAR, sur la base du suivi epidemiologique des mineurs d’uranium. Ainsi, des niveaux de reference differents pour la concentration en radon peuvent etre deduits d’un meme niveau de dose efficace suivant que l’on applique l’un ou l’autre facteur de conversion. Cependant, il convient de rappeler que ces differences sont negligeables par rapport aux incertitudes associees aux etudes tant dosimetriques qu’epidemiologiques et que les niveaux de reference ne sont que des outils pour aider a reduire aussi bas que raisonnablement possible l’exposition au radon et le risque qui en resulte.

Recent developments in the software package OEDIPE - enabling the simulation of in vivo counting - to use the biokinetic data in the modelling of the internal contamination. As part of the improvement of calibration techniques of in vivo counting, the Labo- ratory of Internal Dose Assessment of IRSN has developed a computer tool, "OEDIPE", to model internal contamination, to simulate in vivo counting and to cal- culate internal dose. The previous version of this software enabled to easily model sources made of a single radionuclide and located in a single organ but could not repre- sent a mixture of radionuclides which distribution evolves from the time of intake according to the biokinetics of the radionuclides. The purpose of this article is to des- cribe a new facility developed in the software to allow the modelling of sources heterogeneous in composition and in distribution and optionally to automatically inte- grate the distribution of the activity in different tissues estimated by biokinetic calculation at any time since the intake. These new developments give the opportunity to study much more complex contamination cases and the influence of the biokinetics on the in vivo counting, leading to a better assessment of the calibration coefficients and of the corresponding uncertainties.

L’estimation des doses absorbee, equivalente et efficace resultant d’une contamination interne se base sur la mesure de l’activite par anthroporadiametrie (in vivo ) ou par analyse radiotoxicologique in vitro. La valeur d’activite mesuree est interpretee en termes de dose a l’aide de modeles biocinetiques et dosimetriques qui decrivent le devenir des radionucleides dans le corps d’un individu de reference et permettent de calculer l’energie qu’ils y deposent. Pour s’assurer du respect des limites reglementaires de dose, des programmes de surveillance sont mis en place. Les mesures d’activite peuvent etre interpretees suivant une procedure standard comme celle proposee par le groupe IDEAS. Cependant, une incertitude significative est introduite dans le calcul de la dose par les incertitudes de mesure, par la meconnaissance partielle des conditions d’exposition et par le realisme imparfait des modeles. En plus de cette incertitude, l’extrapolation aux faibles doses d’effets biologiques observes apres une irradiation plus intense, la toxicite chimique des radionucleides et l’heterogeneite du depot d’energie rendent difficile l’estimation du risque resultant d’une contamination interne. En conclusion, il convient de garder a l’esprit que la dose efficace est un outil de gestion de la radioprotection mais pas un indicateur quantitatif du risque individuel.

The IDEAS Guidelines for the assessment of internal doses from monitoring data suggest default measurement uncertainties (i.e. scattering factors, SFs) to be used for different types of monitoring data. However, these default values were mainly based upon expert judgement. In this paper, SF values have been calculated for different radionuclides and types of monitoring data using real data contained in the IDEAS Internal Contamination Database. Results are presented. © The Author 2007. Published by Oxford University Press. All rights reserved.

Some beaches in the south of France present high levels of natural radioactivity mainly due to thorium (Th) and uranium (U) present in the sand. Risk assessment after internal exposure of members of the public by either inhalation or ingestion of black sand of Camargue was performed. This evaluation required some information on the human bioavailability of U and Th from this sand. In vitro assays to determine the solubility of U, Th and their progeny were performed either in simulated lung fluid, with the inhalable fraction of sand, or in both simulated gastric and intestinal fluids with a sample of the whole sand. The experimental data show that the bioavailability of these radionuclides from Camargue sand is low in the conditions of the study. Prospective dose assessment for both routes of intake show low risk after internal exposure to this sand. © The Author 2007. Published by Oxford University Press. All rights reserved.

The EUropean RAdiation DOSimetry Group (EURADOS) initiated in 2005 the CONRAD Project, a Coordinated Network for Radiation Dosimetry funded by the European Commission (EC), within the 6th Framework Programme (FP). The main purpose of CONRAD is to generate a European Network in the field of Radiation Dosimetry and to promote both research activities and dissemination of knowledge. The objective of CONRAD Work Package 5 (WP5) is the coordination of research on assessment and evaluation of internal exposures. Nineteen institutes from 14 countries participate in this action. Some of the activities to be developed are continuations of former European projects supported by the EC in the 5th FP (OMINEX and IDEAS). Other tasks are linked with ICRP activities, and there are new actions never considered before. A collaboration is established with CONRAD Work Package 4, dealing with Computational Dosimetry, to organise an intercomparison on Monte Carlo modelling for in vivo measurements of 241Am deposited in a knee phantom. Preliminary results associated with CONRAD WP5 tasks are presented here. © The Author 2007. Published by Oxford University Press. All rights reserved.

International audience; In case of incidental confinement failure, mixed oxide (MOX) fuel preparation may expose workers to plutonium aerosols. Due to its potential toxicity, occupational exposure to plutonium compounds should be kept as low as reasonably achievable. To ensure the absence of significant intake of radionuclides, workers at risk of internal contamination are monitored by periodic bioassay planned in a routine monitoring programme. From bioassay results, internal dose may be estimated. However, accurate dose calculation relies on known exposure conditions, which are rarely available when the exposure is demonstrated by routine monitoring only. Therefore, internal dose calculation is subject to uncertainty from unknown exposure conditions and from activity measurement variability. The present study calculates the minimum detectable dose (MDD) for a routine monitoring programme by considering all plausible conditions of exposure and measurement uncertainty. The MDD evaluates the monitoring quality and can be used for optimization. Here, MDDs were calculated for the monitoring of workers preparing MOX fuel. Uncertain parameters were modelled by probability distributions defined according to information provided by experts of routine monitoring, of workplace radiological protection and of bioassay analysis. Results show that the current monitoring is well adapted to potential exposure. A sensitivity study of MDD highlights high dependence on exposure condition modelling. Integrating all expert knowledge is therefore crucial to obtain reliable MDD estimates, stressing the value of a holistic approach to worker monitoring. © 2016 The Author.

The evaluation of uncertainties in doses from intakes of radionuclides is one of the most difficult problems in internal dosimetry. In this paper, the process of assessing internal doses from monitoring measurements is reviewed and the major sources of uncertainty are discussed. Methods developed independently at HPA and at IRSN for the determination of uncertainties in internal doses assessed from monitoring measurements are described. Both use a Monte Carlo simulation approach. Results are described for three illustrative examples. An alternative method developed at the Los Alamos National Laboratory that uses Bayesian statistical methods is also described briefly. Copyright © 2006 Oxford University Press.

For the assessment of doses after inhalation of airborne uranium compounds by workers, the International Commission on Radiological Protection (ICRP) developed compartmental models that are used to calculate reference dose coefficients and retention and excretion functions. It is assumed that each acute intake has no effect on the biokinetics of later intakes. Consequently, retention and excretion after multiple or chronic exposure are predicted using the same models as after acute exposure. This assumption was tested here on rats exposed to repeated inhalation of uranium dioxide (UO 2 ). First, excretion and organ retention were determined after a single inhalation of UO 2 . The follow-up of incorporated activity was used to design a biokinetic model for uranium inhaled by rats. Second, the biokinetics of uranium were monitored in two experiments of repeated inhalations of uranium dioxide under different intake patterns. For these two experiments, the organs' retention and excretion after repeated UO 2 inhalation were predicted using the biokinetic model and compared to the experimental measurement. Under the two sets of experimental conditions considered, the prediction of the biokinetic model based on acute exposure data was consistent with the biokinetics observed after repeated UO 2 inhalations, with the possible exception of retention in the skeleton. Copyright© Taylor & Francis Group, LLC.

International audience; Parameter uncertainties for the biokinetic model of caesium (Cs) developed by Leggett et al. were inventoried and evaluated. The methods of parameter uncertainty analysis were used to assess the uncertainties of model predictions with the assumptions of model parameter uncertainties and distributions. Furthermore, the importance of individual model parameters was assessed by means of sensitivity analysis. The calculated uncertainties of model predictions were compared with human data of Cs measured in blood and in the whole body. It was found that propagating the derived uncertainties in model parameter values reproduced the range of bioassay data observed in human subjects at different times after intake. The maximum ranges, expressed as uncertainty factors (UFs) (defined as a square root of ratio between 97.5th and 2.5th percentiles) of blood clearance, whole-body retention and urinary excretion of Cs predicted at earlier time after intake were, respectively 1.5, 1.0 and 2.5 at the first day; 1.8, 1.1 and 2.4 at Day 10 and 1.8, 2.0 and 1.8 at Day 100; for the late times (1000 d) after intake, the UFs were increased to 43, 24 and 31, respectively. The model parameters of transfer rates between kidneys and blood, muscle and blood and the rate of transfer from kidneys to urinary bladder content are most influential to the blood clearance and to the whole-body retention of Cs. For the urinary excretion, the parameters of transfer rates from urinary bladder content to urine and from kidneys to urinary bladder content impact mostly. The implication and effect on the estimated equivalent and effective doses of the larger uncertainty of 43 in whole-body retention in the later time, say, after Day 500 will be explored in a successive work in the framework of EURADOS. © The Author 2014.

International audience; To facilitate the estimation of radiation doses from intake of radionuclides, the International Commission on Radiological Protection (ICRP) publishes dose coefficients (dose per unit intake) based on reference biokinetic and dosimetric models. The ICRP generally has not provided biokinetic models or dose coefficients for intake of noble gases, but plans to provide such information for 222Rn and other important radioisotopes of noble gases in a forthcoming series of reports on occupational intake of radionuclides (OIR). This paper proposes a generic biokinetic model framework for noble gases and develops parameter values for radon. The framework is tailored to applications in radiation protection and is consistent with a physiologically based biokinetic modelling scheme adopted for the OIR series. Parameter values for a noble gas are based largely on a blood flow model and physical laws governing transfer of a non-reactive and soluble gas between materials. Model predictions for radon are shown to be consistent with results of controlled studies of its biokinetics in human subjects. © 2013 IOP Publishing Ltd.

The International Commission on Radiological Protection (ICRP) recently estimated the risk of lung cancer associated with radon exposure, and a statement was issued in ICRP Publication 115. This was based on recent epidemiological studies and the results from a joint analysis of cohorts of Czech, French, and German uranium miners, and indicated that the excess relative risk of lung cancer per unit of exposure should be expressed with consideration of chronic exposure over more than 10 years, by modelling time since median exposure, age attained or age at exposure, and taking in account, if possible, interaction between radon and tobacco. The lifetime excess absolute risk (LEAR) calculated from occupational exposure studies is close to 5 × 10−4 per working level month (WLM) (14 × 10−5 per hm J/m3). LEAR values estimated using risk models derived from both miners and domestic exposure studies are in good agreement after accounting for factors such as sex, attained age, and exposure scenario. A sensitivity analysis highlighted the high dependence of background mortality rates on LEAR estimates. Using lung cancer rates among Euro-American males instead of the ICRP reference rates (males and females, and Euro-American and Asian populations), the estimated LEAR is close to 7 × 10−4 per WLM (20 × 10−5 per hm J/m3).

International audience; Epidemiological studies on uranium miners are being carried out to quantify the risk of cancer based on organ dose calculations. Mathematical models have been applied to calculate the annual absorbed doses to regions of the lung, red bone marrow, liver, kidney and stomach for each individual miner arising from exposure to radon gas, radon progeny and long-lived radionuclides (LLR) present in the uranium ore dust and to external gamma radiation. The methodology and dosimetric models used to calculate these organ doses are described and the resulting doses for unit exposure to each source (radon gas, radon progeny and LLR) are presented. The results of dosimetric calculations for a typical German miner are also given. For this miner, the absorbed dose to the central regions of the lung is dominated by the dose arising from exposure to radon progeny, whereas the absorbed dose to the red bone marrow is dominated by the external gamma dose. The uncertainties in the absorbed dose to regions of the lung arising from unit exposure to radon progeny are also discussed. These dose estimates are being used in epidemiological studies of cancer in uranium miners. Published by Oxford University Press.

International audience; Ionizing radiation is a known human carcinogen that can induce a variety of biological effects depending on the physical nature, duration, doses and dose-rates of exposure. However, the magnitude of health risks at low doses and dose-rates (below 100mSv and/or 0.1mSvmin-1) remains controversial due to a lack of direct human evidence. It is anticipated that significant insights will emerge from the integration of epidemiological and biological research, made possible by molecular epidemiology studies incorporating biomarkers and bioassays. A number of these have been used to investigate exposure, effects and susceptibility to ionizing radiation, albeit often at higher doses and dose rates, with each reflecting time-limited cellular or physiological alterations. This review summarises the multidisciplinary work undertaken in the framework of the European project DoReMi (Low Dose Research towards Multidisciplinary Integration) to identify the most appropriate biomarkers for use in population studies. In addition to logistical and ethical considerations for conducting large-scale epidemiological studies, we discuss the relevance of their use for assessing the effects of low dose ionizing radiation exposure at the cellular and physiological level. We also propose a temporal classification of biomarkers that may be relevant for molecular epidemiology studies which need to take into account the time elapsed since exposure. Finally, the integration of biology with epidemiology requires careful planning and enhanced discussions between the epidemiology, biology and dosimetry communities in order to determine the most important questions to be addressed in light of pragmatic considerations including the appropriate population to be investigated (occupationally, environmentally or medically exposed), and study design. The consideration of the logistics of biological sample collection, processing and storing and the choice of biomarker or bioassay, as well as awareness of potential confounding factors, are also essential. © 2012 Elsevier B.V.

International audience; Reports have described apparent biological effects of Cs-137 (the most persistent dispersed radionuclide) irradiation in people living in Chernobyl-contaminated territory. The sensitive analytical technology described here should now help assess the relation of this contamination to the observed effects. A rat model chronically exposed to Cs-137 through drinking water was developed to identify biomarkers of radiation-induced metabolic disorders, and the biological impact was evaluated by a metabolomic approach that allowed us to detect several hundred metabolites in biofluids and assess their association with disease states. After collection of plasma and urine from contaminated and non-contaminated rats at the end of the 9-months contamination period, analysis with a LC-MS system detected 742 features in urine and 1309 in plasma. Biostatistical discriminant analysis extracted a subset of 26 metabolite signals (2 urinary, 4 plasma non-polar, and 19 plasma polar metabolites) that in combination were able to predict from 68 up to 94% of the contaminated rats, depending on the prediction method used, with a misclassification rate as low as 5.3%. The difference in this metabolic score between the contaminated and non-contaminated rats was highly significant (P = 0.019 after ANOVA cross-validation). In conclusion, our proof-of-principle study demonstrated for the first time the usefulness of a metabolomic approach for addressing biological effects of chronic low-dose contamination. We can conclude that a metabolomic signature discriminated Cs-137-contaminated from control animals in our model. Further validation is nevertheless required together with full annotation of the metabolic indicators.

International audience; The aim of this study was to assess the risk of lung cancer death associated with cumulative lung doses from exposure to α-particle emitters, including radon gas, radon short-lived progeny, and long-lived radionuclides, and to external γ rays among French uranium miners. The French "post-55" sub-cohort included 3,377 uranium miners hired from 1956, followed up through the end of 1999, and contributing to 89,405 person-years. Lung doses were calculated with the ICRP Human Respiratory Tract Model (Publication 66) for 3,271 exposed miners. The mean "absorbed lung dose" due to α-particle radiation was 78 mGy, and that due to the contribution from other types of radiation (γ and β-particle radiation) was 56 mGy. Radon short-lived progeny accounted for 97 of the α-particle absorbed dose. Out of the 627 deaths, the cause of death was identified for 97.4, and 66 cases were due to lung cancer. A significant excess relative risk (ERR) of lung cancer death was associated with the total absorbed lung dose (ERR/Gy 2.94, 95 CI 0.80, 7.53) and the α-particle absorbed dose (4.48, 95 CI 1.27, 10.89). Assuming a value of 20 for the relative biological effectiveness (RBE) of α particles for lung cancer induction, the ERR/Gy-Eq for the total weighted lung dose was 0.22 (95 CI 0.06, 0.53). © 2012 by Radiation Research Society.

Potential internal contamination of workers is monitored by periodic bioassay measurements interpreted in terms of intake and committed effective dose by the use of biokinetic and dosimetric models. After a prospective evaluation of exposure at a workplace, a suitable monitoring programme can be defined by choosing adequate measurement techniques and frequency. In this study, the sensitivity of a programme is evaluated by the minimum intake and dose, which may be detected with a given level of confidence by taking into account uncertainties on exposure conditions and measurements. This is made for programme optimisation, which is performed by comparing the sensitivities of different alternative programmes. These methods were applied at the AREVA NC reprocessing plant and support the current monitoring programme as the best compromise between the cost of the measurements and the sensitivity of the programme. © The Author 2010. Published by Oxford University Press. All rights reserved.

cited By 12; Diethylene Triamine Pentaacetic Acid (DTPA) is used for decorporation of plutonium because it is known to be able to enhance its urinary excretion for several days after treatment by forming stable Pu-DTPA complexes. The decorporation prevents accumulation in organs and results in a dosimetric benefit, which is difficult to quantify from bioassay data using existing models. The development of a biokinetic model describing the mechanisms of actinide decorporation by administration of DTPA was initiated as a task in the European COordinated Network on RAdiation Dosimetry (CONRAD). The systemic biokinetic model from Leggett et al. and the biokinetic model for DTPA compounds of International Commission on Radiological Protection Publication 53 were the starting points. A new model for biokinetics of administered DTPA based on physiological interpretation of C-labeled DTPA studies from literature was proposed by the group. Plutonium and DTPA biokinetics were modeled separately. The systems were connected by means of a second order kinetics process describing the chelation process of plutonium atoms and DTPA molecules to Pu-DTPA complexes. It was assumed that chelation only occurs in the blood and in systemic compartment ST0 (representing rapid turnover soft tissues), and that Pu-DTPA complexes and administered forms of DTPA share the same biokinetic behavior. First applications of the CONRAD approach showed that the enhancement of plutonium urinary excretion after administration of DTPA was strongly influenced by the chelation rate constant. Setting it to a high value resulted in a good fit to the observed data. However, the model was not yet satisfactory since the effects of repeated DTPA administration in a short time period cannot be predicted in a realistic way. In order to introduce more physiological knowledge into the model several questions still have to be answered. Further detailed studies of human contamination cases and experimental data will be needed in order to address these issues. The work is now continued within the European Radiation Dosimetry Group, EURADOS. Copyright © 2010 Health Physics Society.

cited By 2; Potential internal contaminations of workers are monitored by periodic bioassays interpreted in terms of intake and committed effective dose through biokinetic and dosimetric models. After a prospective evaluation of exposure at a workplace, a suitable monitoring program can be defined by the choice of measurement techniques and frequency of measurements. However, the actual conditions of exposure are usually not well defined and the measurements are subject to errors. In this study we took into consideration the uncertainties associated with a routine monitoring program in order to evaluate the minimum intake and dose detectable for a given level of confidence. Major sources of uncertainty are the contamination time, the size distribution and absorption into blood of the incorporated particles, and the measurement errors. Different assumptions may be applied to model uncertain knowledge, which lead to different statistical approaches. The available information is modeled here by classical or Bayesian probability distributions. These techniques are implemented in the OPSCI software under development. This methodology was applied to the monitoring program of workers in charge of plutonium purification at the AREVA NC reprocessing facility (La Hague, France). A sensitivity analysis was carried out to determine the important parameters for the minimum detectable dose. The methods presented here may be used for assessment of any other routine monitoring program through the comparison of the minimum detectable dose for a given confidence level with dose constraints. Copyright © 2010 Health Physics Society.

The emission of radiation from a contaminated body region is connected with the dose received by radiosensitive tissue through the specific absorbed fractions (SAFs) of emitted energy, which is therefore an essential quantity for internal dose assessment. A set of SAFs were calculated using the new adult reference computational phantoms, released by the International Commission on Radiological Protection (ICRP) together with the International Commission on Radiation Units and Measurements (ICRU). Part of these results has been recently published in ICRP Publication 110 (2009 Adult reference computational phantoms (Oxford: Elsevier)). In this paper, we mainly discuss the results and also present them in numeric form. The emission of monoenergetic photons and electrons with energies ranging from 10 keV to 10 MeV was simulated for three source organs: lungs, thyroid and liver. SAFs were calculated for four target regions in the body: lungs, colon wall, breasts and stomach wall. For quality assurance purposes, the simulations were performed simultaneously at the Helmholtz Zentrum München (HMGU, Germany) and at the Institute for Radiological Protection and Nuclear Safety (IRSN, France), using the Monte Carlo transport codes EGSnrc and MCNPX, respectively. The comparison of results shows overall agreement for photons and high-energy electrons with differences lower than 8%. Nevertheless, significant differences were found for electrons at lower energy for distant source/target organ pairs. Finally, the results for photons were compared to the SAF values derived using mathematical phantoms. Significant variations that can amount to 200% were found. The main reason for these differences is the change of geometry in the more realistic voxel body models. For electrons, no SAFs have been computed with the mathematical phantoms; instead, approximate formulae have been used by both the Medical Internal Radiation Dose committee (MIRD) and the ICRP due to the limitations imposed by the computing power available at this time. These approximations are mainly based on the assumption that electrons are absorbed locally in the source organ itself. When electron SAFs are calculated explicitly, discrepancies with this simplifying assumption are notable, especially at high energies and for neighboring organs where the differences can reach the same order of magnitude as for photon SAFs. © 2010 Institute of Physics and Engineering in Medicine.

In order to optimise the monitoring of potentially exposed workers, it is desirable to determine specific values of absorption for the compounds handled. This study derives specific values of absorption rates for different chemical forms of plutonium from in vitro and animal (monkeys, dogs, mice, rats) experiments, and from human contamination cases. Different published experimental data have been reinterpreted here to derive values for the absorption parameters, fr, sr and ss, used in the human respiratory tract model currently adopted by the International Commission on Radiological Protection (ICRP). The consequences of the use of these values were investigated by calculating related committed effective doses per unit intake. Average and median estimates were calculated for fr, sr, and ss for each plutonium compound, that can be used as default values for specific chemical forms instead of the current reference types. Nevertheless, it was shown that the use of the current ICRP reference absorption types provides reasonable approximations. Moreover, this work provides estimates of the variability in pulmonary absorption and, therefore, facilitates analyses of the uncertainties associated with assessments, either from bioassay measurements or from prospective calculations, of intake and dose. © IOP Publishing Ltd.

The Chernobyl accident released many radionuclides in the environment. Some are still contaminating the ground and thus the people through dietary intake. The long-term sanitary consequences of this disaster are still unclear and several biological systems remain to be investigated. Cholesterol metabolism is of particular interest, with regard to the link established between atherosclerosis and exposure to high-dose ionizing radiations. This study assesses the effect of cesium-137 on cholesterol metabolism in rats, after a chronic exposure since fetal life. To achieve this, rat dams were contaminated with cesium-137-supplemented water from two weeks before mating until the weaning of the pups. Thereafter, the weaned rats were given direct access to the contaminated drinking water until the age of 9 months. After the sacrifice, cholesterol metabolism was investigated in the liver at gene expression and protein level. The cholesterolemia was preserved, as well as the cholesterol concentration in the liver. At molecular level, the gene expressions of ACAT 2 (a cholesterol storage enzyme), of Apolipoprotein A-I and of RXR (a nuclear receptor involved in cholesterol metabolism) were significantly decreased. In addition, the enzymatic activity of CYP27A1, which catabolizes cholesterol, was increased. The results indicate that the rats seem to adapt to the cesium-137 contamination and display modifications of hepatic cholesterol metabolism only at molecular level and within physiological range.

Retrospective estimates of internal doses received by workers in the nuclear industry following intake of radionuclides, based on bioassay data, are a benchmark method in epidemiological studies. Nonetheless, full information relative to thousands of people included in an epidemiological cohort is rarely available, thus implying difficulties to estimate exposure precisely. To evaluate the cumulative exposure to uranium in a cohort of the AREVA NC Pierrelatte plant workers, we compared the epidemiological Job Exposure Matrix (JEM) method with the dosimetric method based on biological monitoring of exposure for 30 workers randomly selected within the cohort. A moderate to strong correlation was observed between the estimators resulting from the two approaches, thereby validating the JEM as a tool that can be used to characterise cumulative exposure to uranium in the cohort. In addition, this study showed that the JEM is a valuable complement to the interpretation of bioassy, (1) in providing information on exposure periods as well as on physical and chemical form of the radionuclides and (2) in compensating for the lack of exposure data regarding the very earliest periods. Combining the two methods may improve the precision in reconstructing cumulative exposure for epidemiological studies. © 2010 Elsevier GmbH.

Administration of diethylene triamine pentaacetic acid (DTPA) can enhance the urinary excretion rate of plutonium (Pu) for several days, but most of this Pu decorporation occurs on the first day after treatment. The development of a biokinetic model describing the mechanisms of decorporation of actinides by administration of DTPA was initiated as a task of the coordinated network for radiation dosimetry project. The modelling process was started by using the systemic biokinetic model for Pu from Leggett et al. and the biokinetic model for DTPA compounds of International Commission on Radiation Protection Publication 53. The chelation of Pu and DTPA to Pu-DTPA was treated explicitly and is assumed to follow a second-order process. It was assumed that the chelation takes place in the blood and in the rapid turnover soft tissues compartments of the Pu model, and that Pu-DTPA behaves in the same way as administered DTPA. First applications of this draft model showed that the height of the peak of urinary excretion after administration of DTPA was determined by the chelation rate. However, repetitions of DTPA administration shortly after the first one showed no effect in the application of the draft model in contrast to data from real cases. The present draft model is thus not yet realistic. Therefore several questions still have to be answered, notably about where the Pu-DTPA complexes are formed, which biological ligands of Pu are dissociated, if Pu-DTPA is stable and if the biokinetics of Pu-DTPA excretion is similar to that of DTPA. Further detailed studies of human contamination cases and experimental data about Pu-DTPA kinetics will be needed in order to address these issues. The work will now be continued within a working group of EURADOS. © The Author 2009. Published by Oxford University Press. All rights reserved.