People and Ionizing Radiation

People and ionizing 3radiation

140 2008 Scientific and Technical Report - IRSN 3 People and ionizing radiation...... 142

3.1 lessons learned from assessments on radiotherapy accidents and research on radiotherapy complications...... 144.

newsflashnewsflashnewsflashnewsflashnewsflashnews 3.2 New bioindicators set to work in studying the Dakar accident....... 151

3.3 radionuclides microdistribution in biological tissue using analytical ion microscopy...... 154. 3.4 ePIdemiological studies of leukemia incidence in children and young adults living around nuclear facilities: a critical review...... 165. 3.5 New approach to epidemiological follow-up of workers exposed to internal contamination risks: applying the Job Exposure Matrix ...... 171.

newsflashnewsflashnewsflashnewsflashnewsflashnews 3.6 development of an instrumented phantom to measure effective dose at workstations...... 177. 3.7 New personal dosimeters to monitor workers...... 179

3.8 Key events and dates...... 182.

IRSN - 2008 Scientific and Technical Report 141 People and ionizing radiation

Patrick GOURMELON Human Radiation Protection Division

uman radiation protection is a field that calls on to employ innovative techniques to improve risk assessment in this complementary and multidisciplinary skills. Recent type of exposure situation. The article on analytical ion micros- H radiological incidents and accidents have demonstrated copy highlights research work that has determined the most com- the essential role of IRSN's advanced technical platform in conducting mon sites of uranium accumulation in tissue and cells. In assessments. Feedback from these events shows that a high-quality experimental models set up in the Human Health and Environmental assessment can only be achieved quickly and efficiently in a cutting- areas of the ENVIRHOM program, high-precision maps indicating edge technological environment based on dynamic research uranium micro-locations in various sensitive organs were obtained programs. for the first time using analytical ion microscopy. This type of study should lead to a better understanding of the biological mechanisms Throughout the years IRSN has gained national and international involved, as well as the physiological, or even pathological, conse- renown for its work in managing the medical aspects of irradiation quences of radionuclide bioaccumulation phenomena. accidents. In several real-world situations, multidisciplinary teams have conducted assessments to establish the causes of accidents and their The impact of nuclear facilities on human health and the environ- impact on human health. The first article in this chapter recalls the ment inevitably leads to the recurrent question on the effects of latest accidents occurring in radiotherapy and radiosurgery, and pres- low-dose exposure. While all categories of the population are ents the Institute's research on the biological mechanisms of compli- concerned, special focus has been placed on children. A German cations encountered in radiotherapy treatments. Lessons learned from study published in late 2007 put forward that there was a greater these assessments have stressed the importance of supporting active risk of leukemia in children (aged from 0 to 4) living within 5 kilo research in this area. In the coming years, radiopathology research is meters of nuclear facilities. At the request of the ASN, the French expected to reinforce knowledge on the risks inherent to radiotherapy nuclear safety authority, IRSN conducted a critical review of stud- and the use of cell therapy in treating radiological burns. ies published on the subject. The results report that numerous studies have sought to explain the exceptionally high incidence of Estimating the dose absorbed by the body or a targeted organ leukemia observed around certain nuclear sites by focusing on still remains a difficult task today in situations involving internal multiple potential risk factors. In most of the studies, quite varied contamination. It is therefore essential to have an exact idea of the in their approach, researchers come up against methodological location and residence time of radionuclides in the body. For sev- limitations that make it difficult to demonstrate the chain of eral years now, the Institute has been conducting research on how causality. Although the most widely supported hypothesis points

142 2008 Scientific and Technical Report - IRSN to an infectious cause linked to the mixing of populations around nuclear sites, it is still difficult to determine why the incidence of leukemia observed is higher there than elsewhere, due to insufficient knowledge on the risk factors contributing to childhood leukemia. Large-scale national or international epidemiological studies should therefore be initiated on this subject.

Monitoring worker exposure is one of the Institute's major concerns. Through its various activities, IRSN continuously seeks to improve its skills in absorbed-dose assessment. Recent implementation of new risk assessment tools is the result of this policy. The last article in this chapter describes the methods used to improve assessment of the potential cancerous effects of internal contamination in workers from the nuclear industry (Areva) in France. New investigations were conducted to retrospectively assess exposure to uranium and the related chemical products at various workstations. A database on exposure according to the jobs performed was created to reconstruct individual exposure cases. In a context where no data is available on individual internal exposure, this database provides an alternative for assessing exposure retrospectively. It can easily be applied to other facilities in the nuclear industry. This approach can serve as a basis for further epidemiological studies aiming to improve quantification of the risks associated with worker exposure to ionizing radiation.

IRSN - 2008 Scientific and Technical Report 143 3.1 Lessons learned from assessments on radiotherapy accidents and research on radiotherapy complications

Marc BENDERITTER, Fabien MILLIAT, Agnès FRANçOIS Radiopathology and Experimental Therapy Laboratory

In the last few years the Institute has been asked to apply its expertise to studying the causes of radiotherapy overdoses and their medical consequences. Having had the foresight to unite multidisciplinary skills in this field several years ago, it was well prepared for this task.

Lessons learned from this experience emphasize the need to develop new research programs to study the medical complications of radiotherapy, in preparation for risk assessments entailed by changes in this discipline.

Radiotherapy and radiation protection Justification consists of providing support to confirm the technical applied to patients: benefits and risks choice made. Optimization aims to reduce the dose received by healthy tissue "as much as possible", while ensuring treatment Several hundreds of thousands of patients suffer from cancer every efficacy. year and more than half of these patients are treated, or have been treated, by radiotherapy applied alone or combined with other treatments such as surgery or chemotherapy. In France, the number of Accidental overexposure in radiotherapy people treated each year by radiotherapy is estimated at 200,000, while in Europe this figure reaches 1.5 million, and 1 million in the In France, since 2005, any event occurring in a radiotherapy facility United States. Eradication of tumors through radiotherapy is increas- that could impact human health must be declared to the nuclear ingly effective, but the medical world is still confronted with toxic safety authority, the ASN. After investigation, the event may be side effects that affect healthy tissue in 5 to 10% of these qualified as an incident, or even a severe accident. Since that date, patients. about twenty radiotherapy incidents or accidents have been declared. These overdose accidents in radiotherapy vary in their degree of Radiotherapy regulations in France are based on the European Council severity, and are often associated with new radiotherapy procedures, directive 97/43/Euratom of June 30, 1997, which is specific to the such as conformational radiotherapy (as in the accidents at the radiation protection of patients and has been transposed to the university medical center in Grenoble and the hospital in Épinal) or public health code. The two basic principles stipulate that the thera- stereotactic radiotherapy (as was the case at the university medical peutic act must be justified, and protection must be "optimized". centers in Lyon and Toulouse) (Figure 1).

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lines of action to the ad hoc medical committee in charge of 2005 handling the medical treatment of these patients. 5,000 2006

Amiens 1 2007 The stereotactic radiosurgery accident at the Toulouse university Univ. Med. Center hospital center involved a cohort of 145 patients, treated for benign Saint-Antoine Paris 1 397 Univ. Med. Center tumors of the central nervous system (neuromas, meningiomas, Clinic in 1 1 pituitary adenomas), malignant tumors (metastatic tumors of the La Garenne-Colombes IGR 24 brain, gliomas), and vascular lesions (artery and vein malformations). 2 Épinal Cancer 1 Hospital Institute Tours Univ. The ASN called on IRSN to analyze the health risk resulting from in Angers Med. Center patients' overexposure to radiation, subsequent to inadequate Lyon Univ. calibration of the accelerator. The circumstances were analyzed in 2 1 Med. Center Saintes Hospital 1 (South & East) 1 the first assessment report submitted by the Institute on Cancer Institute 1 in Saint-Étienne October 16, 2007. Although it involved a large number of patients Grenoble Univ. Med. Center treated over a period of several months, the radiosurgery accident Toulouse Univ. 8 at the Toulouse medical center was quite different from the radio- Med. Center 1 145 1 Clinic in Cancer therapy accidents that occurred in Épinal. The Toulouse accident Clinic in Marseille Institute Tarbes in Nice was caused by an initial error in accelerator calibration. This error induced deviations in the doses delivered to patients, variable from one patient to another, depending on the targeted volume to be

Figure 1 Radiotherapy incidents and accidents requiring an treated and the pathology in question. It was therefore particu- Institute assessment. The number of patients involved in these radiotherapy incidents or accidents is shown inside larly complicated to ascertain the health impact of this accident the circles. in terms of radiation-induced secondary neurological complications. Assessment of these consequences required a special scientific approach, conducted in several phases, some at the Toulouse hos- Contribution of the Institute's assessment pital, which at times mobilized twenty to thirty people from IRSN of radiotherapy overdose accidents over certain periods. This assessment determined the state of health as well as the psychological state of the patients, and classified Between May 2004 and May 2005, at the Jean Monnet Hospital them according to the severity of their complications. Individual in Épinal, 24 patients were significantly overexposed during pros- dosimetry data was reconstructed for each of the 145 patients. The trate cancer treatments based on conformational radiotherapy. recommendations issued by IRSN were for the most part followed On October 12, 2006, the Minister for Health referred the case to by the ASN in implementing the measures required to manage this the Institute, who was to apply its knowledge in radiopathology accident. "to determine the recommended treatment for each victim of the The collective assessments provided by IRSN called on the skills of Épinal radiotherapy accident, providing each person with the best the Institute's hospital physicists, dosimetry specialists, and radio- possible health care". The Minister called on IRSN again in March pathologists. They contributed to creating a greater awareness of 2007 regarding the potential overexposure of 423 patients at the the risks inherent to these medical practices. A certain number of Jean Monnet Hospital between 2001 and 2006. lessons were learned through these different assessments, many of which were inspired by experience acquired in the field of nuclear More recently, a third case was referred to the Institute involving safety. patients treated by radiotherapy between 1987 and 2001 in the same hospital. The conclusions of these various assessments revealed deviations from procedure in setting up treatments and Reinforcing equipment inspections before providing patient follow-up, as well as certain cases of system- setting into operation atic overexposure. The knowledge and competence acquired by IRSN on the toxic effects of cancer radiotherapy on healthy tissues The latest radiotherapy devices can deliver doses more accurately in the abdominal and pelvic area contributed significantly to calculated according to the volume of the tumor to be irradiated, assessing the patients' state of health, classifying the cases accord- sparing the healthy tissue surrounding the tumor. In this way, ing to the severity of complications, and proposing therapeutic higher doses can, in theory, be used safely for improved therapeu-

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tic effect. These increasingly complex devices feature very sophis- A better understanding of clinical data on ticated systems providing automatic adjustment of the radiation radiotherapy side effects beam, driven by embedded software that also ensures safety functions. However, most of these devices do not allow the radiothera- Several studies conducted in various countries have been published pist to directly check the dose actually delivered and its spatial on the frequency of radiotherapy-related complications for different geometry during treatment sessions. Consequently, the human- types of pathology, and an international classification system exists machine interface and, more generally, designed-in operating to "grade" the severity of these side effects. Certain radiotherapy safety features on this equipment are critical parameters that clinics provide in-depth, long-term clinical follow-up for their determine the quality and safety of treatments. patients. On the national scale, however, the assessments that IRSN has conducted at the request of public authorities following radio- IRSN observed that regulations relative to operation of this equip- therapy incidents or accidents have brought to light differences in ment are based on a European directive that primarily aims to achieve clinical follow-up protocols, which vary depending on the clinic or "free circulation" of medical devices on the European market, based hospital in question. on compliance with harmonized standards. Yet the conditions for implementation of this directive do not allow for in-depth examina- In the case of the accident in Épinal, the fact that there was practi- tion of safety design on equipment as complex and innovative as, cally no patient follow-up was the main reason that explained why for example, the Cyberknife, which features a linear particle accel- malfunctions remained undetected, which, in the long run, was erator mounted on a robot arm, a technology that has the advantage seriously detrimental to the health of several patients. IRSN consid- of performing stereotactic irradiation while avoiding sensitive organs. ers that there is still room for progress: professional organizations The same applies to the process of setting the equipment into should initiate action to set up a standard and systematic approach operation, which does not always provide all the necessary safeguards, to clinical follow-up of patients that would facilitate comparison especially with regards to calibration. IRSN considers that inspection of professional practices, and research should be conducted to move of these devices, which intrinsically constitute a significant radio- forward in radiotherapy protocols. Standard practices in clinical logical hazard for patients, should be reinforced, so that applicable follow-up would provide an additional safeguard in treatment methods approach those practiced in nuclear facilities. safety, since it would also allow alert signals to be passed on to the radiotherapist.

Developing a nuclear safety culture in radiotherapy clinics Amplify research efforts on irradiation side effects Implementation of the Cancer Plan led to an acceleration in the acquisition of sophisticated equipment in radiotherapy clinics. In France, every year 60% of cancer patients receive external radio- Applying these devices implied more widespread use of high-per- therapy treatments, for 3.8 million sessions. This technique shows by formance treatments to the benefit of patients, as shown by nation- far the best cost-efficiency ratio, since 50% of the curative treat- wide statistics. However, in spite of the quality assurance techniques ments represent only 12% of the costs of cancerology. But the implemented systematically to ensure compliance with operating drawback to this efficiency is the side effects that appear, which procedures, IRSN considers that in several clinics the insufficient are variable depending on the organ treated. Some of them disap- number of radiophysicists, added to the lack of an adequate safety pear spontaneously, while others occur inevitably. Unfortunately, culture in the radiotherapy teams, leaves too much room open for 5 to 10% of patients develop more or less serious complications undetected malfunctions, especially with regards to equipment late in their radiotherapy program. In France, there is no record adjustments, which could entail serious consequences for of the percentage of cases showing complications late in radio- patients. therapy treatment, making it extremely difficult to conduct epidemiological studies in this area. The gradual introduction of systematic in vivo dosimetry, the rein- forcement and recognition of the radiophysicist as a profession, in IRSN therefore considers that there is a knowledge deficit in risk terms of both numbers and academic education, and their place in assessment and quantification with regards to this type of compli- the organization of radiotherapy departments, are all factors of cation. Creating a national register to record radiotherapy complica- progress. tions, and launching epidemiological studies conducted by both

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radiotherapists and physicians from the various medical specializa- the chronic nature of the lesions, and the associated morbidity and tions involved (gastroenterologists, pulmonologists, dermatologists, mortality rates. IRSN developed its research programs based on the neurologists, etc.) should contribute to better risk assessment of assumption that ionizing radiation has a toxic effect resulting from radiotherapy complications. a pathological scarring process in irradiated tissue. The early effects are due to the impact of ionizing radiation on highly proliferating While funds allocated to cancer research are significant and have tissue compartments, such as the epithelium, and on micro-vascu- led to considerable progress, no specific financing has been ded- larization. Early effects participating in the development of late icated to research on radiotherapy side effects. The Institut Gustave effects are referred to as "consequential fibrosis". Late effects Roussy, one of the most renown clinics for cancer treatment in resulting from consequences on the vascular and mesenchymal Europe, and IRSN have been forerunners in this area for several compartments are referred to as "primary fibrosis". Different types years. Research conducted through this partnership has started of local irradiation are now available for animal experimentation, to reveal the biological mechanisms involved in the development capable of producing lesions comparable to those observed on of radiotherapy complications. Results have also led to the iden- different human organs (intestine, skin, lungs). tification of biomarkers and proposals for new treatments. The first transfers of research results to clinical studies are now under In this context, IRSN research has set out to achieve the following way. goals: understand the mechanisms involved in the cell and tissue response IRSN considers that if patients are to reap the full benefits of this of healthy tissue located in the irradiated field; work, translational research programs must be developed to trans- propose new tools for diagnosis and prognosis of radiotherapy fer scientific knowledge on radiotherapy complications to the side effects during the clinically silent phase; clinical sphere, a major challenge for today and the future. Multi- propose new radiation protection treatments for healthy tissue institutional research programs should unite complementary skills that do not have a protective effect on the tumor. in radiobiology, radiopathology, radiotherapy, and dosimetry to Research programs that have been conducted approach these create operational synergy around risk assessment for optimal use questions at different phases, ranging from studies on new thera- of radiation treatments in the medical field. peutic targets to implementation of second-phase clinical development studies. Even today, the most severe cases of radiotherapy complications cannot be treated through conventional therapeutic programs. IRSN Developing experimental models to study radiotherapy considers that the development of translational research programs complications in the abdominal and pelvic area aiming to validate the use of new therapeutic approaches, such as The analysis of intestinal radiological complications in humans cell therapy, in treating severe radiotherapy complications, and requires working on a large number of surgical resections, which securing their transfer to the clinical environment is necessary to are relatively difficult to obtain. By working in cooperation with a ensure the best possible health care for patients in these critical hospital structure, IRSN can obtain these surgical specimens (such situations. as a resection of irradiated small intestine) and gain access to the "tissue library" of the pathology department. This valuable biological material is used to study the pathological physiology of The Institute's position concerning R&D radiation enteritis in the patient. on radiotherapy side effects An accurate description of the cascade of events occurring in tissue Research on the biological mechanisms involved in after irradiation requires kinetic studies that cannot be conducted radiotherapy complications on humans. Experimental models of radiation fibrosis were therefore Special focus has been given to intestinal complications, which are set up for the rat and mouse to describe morphological changes in part of a change process classically defined in terms of early and the intestine after irradiation. In spite of their limits, these animal late effects. Early effects, or acute radiation-induced enteritis, affect models contribute useful information on the processes involved in 80% of patients receiving radiotherapy in the abdominal and lesions and scarring of digestive tissue. One of the models calls on pelvic area, and may evolve gradually into radiation-induced fibro- surgery to permanently attach a loop of small intestine in the sis, or chronic radiation-induced enteritis (in 5 to 10% of patients). scrotum after castration. In this way, fractionated radiation can be These complications can have a significant clinical impact due to applied to the loop to model primary fibrosis. Another model

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Top view Side view fibrosis processes. It is produced in large quantities by special cells (fibroblasts) after activation by TGFβ.

Vascular lesions are considered to be a determining event in the initiation and progression of radiation-induced tissue damage, since they generate ischemia and tissular hypoxia phenomena, which contribute to the noxious effects observed in radiation fibroses. Researchers have sought out the physiological, pathological, and molecular mechanisms involved in the pathogenesis of radiation-induced vascular damage to define therapeutic strategies capable of protecting healthy tissue Figure 2 Irradiation experimental model simulating radiotherapy after irradiation. complications in the abdominal and pelvic area in animals. To begin, vascular lesions were characterized on the basis of rectum samples from 38 patients subjected to pre-operative radiotherapy to treat adenocarcinoma of the rectum. This work was conducted developed at IRSN consists of applying single-dose irradiation to a in cooperation with Dr. E. Deutsch (radiotherapist at the Institut loop of small intestine externalized for radiation purposes only. This Gustave Roussy in Villejuif) and Pr. J.-C. Sabourin (pathologist at the model is used to develop consequential fibrosis (Figure 2). university medical center in Rouen). The vascular lesions observed were characterized by their focal nature and the absence of sys- Models using cell cultures to characterize pathological scarring in temization. Immuno-histochemical markers revealed vascular the intestine have also been developed. Mesenchyme cells, name- fibrosis in these patients, characterized by significant proliferation ly sub-epithelial myofibroblasts, smooth muscle cells, and endothe- and migration of the vascular smooth muscle cells and a fibro- lial cells, are the most frequently used in IRSN's radiopathology genic phenotype (Figure 3). In a later phase, researchers set out to laboratory, since they contribute to the toxic effects of radiother- discover some of the physiological and pathological mechanisms apy in tissue. Based on samples taken from patients, primary cultures that cause radiation-induced vascular fibroses. are obtained and are used to specifically study the response of a certain type of cell, or the interaction between two cell partners The possibility of an integrated response of the entire vessel after through co-culture techniques. irradiation has not yet been explored. Radiation-induced distur- The purpose is to use these various models to acquire knowledge bances in vascular matrix remodeling could therefore be the result on the mechanisms associated with the initiation and progression of dysfunctioning between endothelial cells (EC) and smooth of radiotherapy complications and their treatment. This new knowl- muscle cells (SMC). edge can then be correlated with clinical observations on patients, Co-culture models were developed for in vitro study of communica- and new therapeutic targets can be validated in clinical studies tion between these two types of cell. Results showed that prolif- carried out with hospital partners. eration of SMCs was stimulated in the presence of irradiated ECs. They also revealed that SMCs had a greater tendency to migrate Characterizing initiation and progression mechanisms within a lesion area in the presence of irradiated ECs. As concerns of radiotherapy side effects the fibrogenic phenotype, it was shown that several proteins (CTGF, Part of the general development mechanisms of fibrosis in a radiation- PAI-1, COL1A2 and COL3A1) involved in the cellular mechanisms induced intestinal fibrosis model were recently characterized in the stimulated after irradiation increase in SMCs in the presence of IRSN radiopathology laboratory. Two biological factors involved in irradiated ECs. To characterize the soluble factors that may be the initiation and progression of radiation enteritis were studied: the involved in the induction of this fibrogenic differentiation, secretion Transforming Growth Factor β (TGFβ) and the Connective Tissue of the growth factor TGFβ1 was measured after EC irradiation. This Growth Factor (CTGF). secretion was stimulated in the irradiated ECs. Results suggest that the TGFβ1 from the ECs could activate signaling pathway in SMCs TGFβ is a ubiquitously secreted cytokine. It plays a role in regulating through paracrine effects. The molecular cascade of TGF signaling differentiation and proliferation mechanisms in several types of cells. was characterized. Various techniques from molecular biology The three isoforms (β1, 2 and 3) bind to the same receptor, but have (transfection, antisense Smad3 siRNA, gene reporter), pharmacol- different cellular expressions. CTGF is a growth factor involved in ogy (anti-TGFβ-RII neutralizing antibody), and immunocytochem-

148 2008 Scientific and Technical Report - IRSN People and ionizing radiation 3.1

This work developed new knowledge on the molecular mechanisms at work in vascular lesions after irradiation. It demonstrates the CE importance of relationships between the different types of vessel cells, and the role of the TGFβ biological factor. TGFb1

Another example from the study on the role of CTGF also illustrates TGF-RII TGF-RI p smad 7 the Institute's approach in research on the biological mechanisms p

p involved in radiotherapy complications. The IRSN radiopathology smad 2/3smad 4

p p p CMLv laboratory recently characterized part of the general radiation-induced p p TF TF fibrogenesis mechanisms in a model of radiation-induced intestinal fibrosis, radiation enteritis. In genomics experiments (using a DNA COL1A2, COL3A1, CTGF, PAI -1 chip) conducted on human fibrosis biopsies, researchers revealed the

Figure 3 Molecular cascade involved in the development of role of a molecular cascade that depends on small GTPases from the vascular fibrosis. TGFβ 1 binds to Type II receptors, which then recruit Type I receptors. Following this Rho family and their effectors, ROCK proteins. These intracellular recruitment, Type II receptors phosphorylize the Type I signaling proteins intervene in the organization of the cytoskeleton receptors, activating their kinase activity. The activated Type I receptors, in turn, recruit and phosphorylize the of myofibroblasts by controlling actin polymerization. In vitro intracellular mediators of the TGFβ 1 cascade, referred to as the "SMAD proteins". Activation of the SMAD research specified that the Rho/ROCK cascade is involved in maintain- transcription factors is characterized by their nuclear ing intestinal radiation-induced fibrosis through its role in regulating translocation, followed by binding to DNA sequences and other transcription factors (TF) located in promoter the expression of pro-fibrosis genes such as CTGF and extracellular sequences of the target genes, thereby activating their matrix molecules (collagen, fibronectin, MMP, etc.) (Figure 4). transcription.

In other work carried out by the radiopathology laboratory, results showed that inhibition of the Rho pathway makes it possible to Isoprenylation regulate the radiation-induced thrombogenic and pro-inflamma- tory phenotype in endothelial cells. This cellular and molecular G RhoA-B characterization work led to an in vivo assessment on the efficacy of Pravastatine, a pharmacological inhibitor of the Rho/ROCK GTP pathway. This molecule was chosen because it has been used Rho Kinase clinically in treating cardiovascular pathologies for over ten years, simplifying transfer to a clinical environment. CTGF Stress fibers Proposing new therapeutic alternatives for treating Collagen Scarring radiotherapy side effects contraction Studies began by evaluating the preventive effect of Pravastatine

Fibrosis on the development of late radiation-induced intestinal fibroses in the rat. Histopathological analysis of the tissue showed that this treatment controlled radiation-induced intestinal toxicity in the Figure 4 Molecular cascade involved in the development of medium term (15 weeks) by restoring the structure of the external intestinal fibrosis. CTGF plays a predominant role in the progression of fibrosis. This pro-fibrosis growth factor is muscle tunic, while at the same time reducing the extent of fibrone- controlled by the Rho pathway and can be modulated crosis areas. The most significant result was observed 26 weeks pharmacologically, particularly by using statins. after irradiation. The tissue was almost completely restored in the treated group. In other experiments conducted in cooperation with the group led by Pr. J. Bourhis from the Institut Gustave Roussy, istry (nuclear translocation of SMAD3 and 4) were used to explore Pravastatine did not result in protection of the tumor in vivo and the molecular mechanisms that result in vascular fibrosis. Results even increased the tumor's sensitivity to radiation in vitro. The showed that through paracrine effects, ECs stimulated the fibro- difference in the effect observed on healthy tissue and on the tumor genic differentiation of SMCs after irradiation by means of a TGFβ/ in pre-clinical experiments encouraged researchers to investigate SMAD3-dependent mechanism. the protective effect of Pravastatine on patients treated for cervi-

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cal cancer by pelvic radiotherapy. The effect was compared to that Radiopathology research perspectives obtained through placebo treatment of digestive tract, bladder, and Lessons learned from assessment of radiotherapy accidents empha- vagina symptomatology observed 18 months after radiotherapy. size the importance of supporting active research in radiopathology. Research and assessment activities concerning high-dose In a later phase, the effect of Pravastatine on acute radiation-induced irradiation in the coming years will be built around two major toxicity, its impact on patient comfort, and it effectiveness against programs at the Institute: an experimental research program on the fibrosis will be tested. This protocol was assessed by the ethics risks involved in using ionizing radiation to treat cancer (ROSIRIS), committee of the Institut Gustave Roussy and received a favorable conducted in association with Inserm, and a cell-therapy program opinion. An application has been submitted for authorization to that aims to promote innovative treatment of irradiated tissue by begin clinical research. transferring cell therapy to the clinical environment, performed in cooperation with the Armed Forces health service.

References C. Bourgier, V. Haydont, F. Milliat, A. François, V. Holler, P. Lasser, J. Bourhis, D. Mathe, M.C. Vozenin-Brotons (2005). Inhibition of Rho-kinase-modulated radiation- induced fibrogenic phenotype in intestinal smooth muscle cells through alteration of the cytoskeleton and connective tissue growth factor expression. Gut 54(3), 336-43. F. Milliat, A. Francois, M. Isoir, E. Deutsch, R. Tamarat, G. Tarlet, A. Atfi, P. Validire, J. Bourhis, J.C. Sabourin, M. Benderitter (2006). Influence of endothelial cells on vascular smooth muscle cells phenotype after irradiation: implication in radiation-induced vascular damages. Am. J. Pathol. 169(4), 1,484-95. F. Milliat, J.C. Sabourin, G. Tarlet, V. Holler, E. Deutsch, V. Buard, R. Tamarat, A. Atfi, M. Benderitter, A. François (2008). Essential role of plasminogen activator inhibitor type-1 in radiation enteropathy. Am. J. Pathol. 172(3),691-701. M.C. Vozenin-Brotons, A. Mauviel (2006). How to model the events in cutaneous fibrosis? Med. Sci. (Paris), 22(2), 172-7. Rapport DRPH/2006-08. Accident de radiothérapie d’Épinal : mission d’évaluation des pathologies radio-induites et proposition d’actions thérapeutiques, rapport d’avancement n° 1, 6 novembre 2006 (saisine du ministère de la Santé). Rapport DRPH/2006-08 bis. Accident de radiothérapie d’Épinal : mission d’évaluation des pathologies radio-induites et proposition d’actions thérapeutiques, rapport d’avancement n° 2, 13 novembre 2006 (saisine du ministère de la Santé). Rapport DRPH/2007-02. Expertise d’évaluation des pratiques de radiothérapie au centre hospitalier Jean Monnet d’Épinal, mars 2007 (saisine du ministère de la Santé). Rapport DRPH/2007-05. Expertise d’évaluation des pratiques de radiothérapie au centre hospitalier Jean Monnet d’Épinal entre 1987 et 2000, novembre 2007 (saisine du ministère de la Santé). Rapport DRPH/2008-03. L’accident de radiochirurgie stéréotaxique au centre hospitalier universitaire de Toulouse : évaluation dosimétrique et clinique, analyse de risque (saisine ASN).

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NEW bioindicators set to work 3.2 in studying the Dakar accident

Philippe VOISIN On June 3, 2006, after taking a gamma-ray Assessment of the absorbed dose was con- Radiobiology and Epidemiology Department image on a worksite in Dakar, Senegal, an ducted on all victims using biological dosim- iridium-192 source came loose from its etry. Dicentric chromosomal aberrations in guide tube and remained trapped in the blood lymphocytes were counted in two ejection duct. The duct and guide tube were phases: a quick classification phase based on then stored in an office for several weeks 50 cells observed per person, followed by a until July 31, 2006, when the equipment much longer, but more accurate phase based was packaged and sent by express delivery on the study of 250 to 500 cells per to Abidjan in the Ivory Coast. The first time person. the gamma ray projector was used at Abidjan, the technician realized that an New methods tested object was jammed in the ejection tube, Other methods for assessing radiation- keeping the source from moving, and dis- induced damage were also used to analyze covered that the iridium source had been this accident. The purpose was to determine removed from its holder. whether it was possible to classify a large population into three or four categories IRSN was called on to conduct a dosimetric based on simple criteria. and biological assessment on the 65 people potentially irradiated (either during the For the first time, dicentric aberrations were storage period, in preparation and handling systematically detected through an auto- of the package at Dakar, in air transport, or mated process based on analyzing micros- while attempting to shoot images at Abid copy images of irradiated lymphocyte jan) and to issue an opinion on the sever- cultures. ity of radiation-induced damage on the most affected victims. Four of these people Of the 46 individuals tested in this manner, presented localized radiation-induced automatic detection proved to be more lesions and were taken to the Percy Military efficient than the manual observation of 50 Hospital in Clamart, France beginning on cells adopted in the sorting phase. August 30, 2006. It was less efficient, however, than the con- In a large-scale accident, the main problem ventional assessment method applied to is sorting the victims, based on the absorbed 500 cells. dose of radiation or the severity of radiation-induced damage. In the Dakar accident, Development of this approach should it was difficult to sort the victims because nonetheless be pursued, especially since it of the time that had elapsed between the could also be used to assess irradiation date of irradiation and the moment that heterogeneity. people became aware of the accident, resulting in a period that could have reached Another technique explored, based on oli- several weeks in certain cases. gonucleotide chips (Figure 1), consists of

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Chip with 26,000 oligonucleotides measuring the expression of over 18,000 human genes simultaneously

Relative measurement of the Irradiated condition difference in gene expression Non-irradiated conditions marked with red fluorochrome between the two conditions marked with green fluorochrome

Gene that does not change expression with irradiation

Gene overexpressed in Gene underexpressed the irradiated condition in the irradiated condition

Figure 1 Principle of competitive hybridization on an oligonucleotide chip.

analyzing the levels of expression of certain count, which provides information on the genes after irradiation. For example, the state of the blood (red blood cells, white level of expression of 25,000 genes was blood cells, platelets), thereby reflecting the measured on victims of the Dakar accident state of the bone marrow, which may be using blood lymphocytes from 20 individu- destroyed by irradiation, affecting the per- als subjected to varying degrees of exposure. son's vital prognosis. Dosing the plasma After analyzing the results, 22 candidate concentration of a specific growth factor, genes were selected, whose levels of expres- Flt3-ligand, also provides an indication that sion seemed to indicate a level of exposure. bone marrow activity has resumed. These Unfortunately, technical problems related two measurements were taken simultane- to sample transport made it impossible to ously on all potentially irradiated individuals. completely validate these results. Combined analysis of the complete blood count and Flt3-ligand values resulted in a An initial assessment of irradiation after an unique severity score, which showed good accident is classically obtained by a full blood agreement with the irradiation dose esti-

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CBC/Flt3-ligand score 12

4 r 2 = 0.614 n = 63 p < 0.001

0 0 0.5 1 1.5 22.5 3 Irradiation dose (Gy)

Figure 2 Linear regression analysis between the complete blood count/Flt3-ligand score and the irradiation dose defined by cytogenetic biological dosimetry. Results show that the score can be used to identify patients who have received an irradiation dose greater than 0.5 Gy.

mated using dicentric chromosomal aberra- In conclusion, the Dakar accident provided tion analysis (Figure 2). the opportunity to implement and demonstrate the validity of a certain number This correlation also made it possible to of innovative experimental approaches quickly identify those victims who were at resulting from research conducted by IRSN the greatest risk. Nonetheless, for the Dakar throughout the years on radiation accident, the significant interval between accidents. exposure and analysis limited the validity of the approach. It will require confirmation through retrospective studies on other irradiation accidents.

IRSN - 2008 Scientific and Technical Report 153 3.3 radionuclides microdistribution in biological tissue using analytical ion microscopy

Christine TESSIER, David SUHARD, François REBIÈRE Radiochemistry Laboratory Jean-René JOURDAIN Human Radiation Protection Division

To understand how radionuclides are transferred and transported into ecosystems and humans through chronic exposure, maps must be established showing the distribution of contaminants in the biological structures targeted by bioaccumulation phenomena. Among the various techniques used for analysis and imaging, ion microscopy, or the SIMS technique, based on coupling secondary ion emission with a mass spectrometer, represents a powerful tool capable of recognizing the locations of radioelement accumulation in tissue and cells.

The fate of uranium through gill respiration and food capture [Simon et al, 2004 and 2005; Fournier et al, 2005]. Initiated in 2001 at IRSN, the ENVIRHOM research program seeks to broaden knowledge on the risks that prevail when humans and This discussion focuses on the study of the uranium distribution ecosystems are chronically exposed to low-dose ionizing radiation. profiles in the targeted organs after internal contamination through One of the main subjects of study in the program is the biokinetics chronic exposure to this radioelement. The biological matrices analyzed of radionuclides in organisms and their biological impact under were the renal cortex in the rat, and the gills of Corbicula fluminea. exposure conditions of this type. The program has therefore placed Various analysis techniques were used, including SIMS (Secondary Ion particular focus on cell and tissue structures capable of accumulat- Mass Spectrometry) and EFTEM (Energy Filtered Transmission Electron ing the incorporated radionuclide(s), thereby contributing new Microscopy), along with spectroscopic methods such as EELS (Electron knowledge towards a better understanding of the mechanisms at Energy Loss Spectroscopy) and ESI (Electron Spectroscopic work and the biological and clinical consequences of these bioac- Imaging). cumulation phenomena. This research set out to examine the hypothesis postulating that To study radionuclide accumulation processes in living organisms, uranium incorporated through chronic contamination modifies iron various experiments were conducted on rodents contaminated by metabolism [Donnadieu-Claraz et al, 2007], since uranium uses the adding uranyl nitrate to their drinking water [Paquet et al, 2006; same transporters as iron. A comparative study of the retention Donnadieu-Claraz et al, 2007], and on the fresh-water bivalve sites of these two elements was therefore conducted using the Corbicula fluminea, invertebrate mollusks exposed to uranium above-mentioned analytical methods.

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Lense Cesium gun Slit diaphragm 1-12 kV Electrostatic sector Duoplasmatron Magnetic sector 2-17.5 kV Deflector Cesium gun Stigmator isolating valve

Electrostatic Energy analyzer slit Focusing magnet

Primary beam magnet

Isolating valve

Field aperture Entrance slit Non-evaporable Contrast diaphragm getter Exit slit Primary beam Faraday cup Spectrometer isolating valve Electron multiplier

Secondary beam Faraday cup Isolating valve Sample -10 to +10 kV Multi-channel ion image detector Fluorescent screen

Figure 1 Schematic representation of the Caméca SIMS 4F-E7 instrument.

Complementary analysis techniques A primary ion source generates the incident beam, which is then steered, focused and rastered over the surface to be analyzed using The SIMS technique a system based on electrostatic lenses and raster steering deflectors. The purpose of SIMS (secondary ion mass spectrometry), or ana- The sputtered secondary ions are accelerated and focused in the lytical ion microscopy, is to obtain an elemental and isotopic secondary ion column, and directed towards the entrance slit to analysis of a solid surface using an ion beam coupled with a mass the mass spectrometer. The latter consists of an electrostatic sec- spectrometer. The principle consists of bombarding the sample tor, which sorts the ions according to a given energy, and a mag- using a charged particle beam set to an accelerating voltage of netic sector, which selects the ions according to their mass-to-charge roughly 10 KeV. The primary ion beam impacts the target particles, ratio. At the spectrometer exit, the resulting secondary ion beam ejecting those located on the free surface, a portion of which is is directed towards an electron multiplier connected to an elec- ionized spontaneously. These "secondary ions" are then acceler- tronic system. The result provides the mass spectra, isotopic ratio ated and analyzed using a mass spectrometer to reconstruct the measurements, and concentration profiles as a function of the chemical and isotopic composition of the sample surface. profile depth.

The SIMS instrument used in this study (the Caméca IMS 4F-E7), The lenses located in the secondary ion transfer column before the conceived by Castaing and Slodzian [Castaing et al, 1962; Slodzian, mass spectrometer are used to form an image of the location from 1964], is represented schematically in Figure 1. which the particles were sputtered from the solid surface. Ion imaging is used to represent the spatial distribution of the various elements under study in the selected matrix.

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All the sources, the beam transfer components and the sample The technique is based on analyzing the energy distribution of fast chamber are placed under a "secondary vacuum" of approximate- incident electrons, initially almost monochromatic, once they have ly 10-13 bar. crossed through the sample. Multiple physical processes can cause Two primary ion sources may be used, the choice depending on the electrons to lose energy as they penetrate through a solid. High type of element to be analyzed. To detect positive secondary ions, electron energy loss analysis focuses on the excitation states of + - a negative primary ion beam is selected (O2 , O ions from an electrons produced by the target particles, based on atomic orbit- oxygen source). Conversely, sputtering negative secondary ions als as they approach the Bloch state and ionization. The ionization requires a positive primary ion beam (Cs+ ions from a cesium thresholds are set to the core electron binding energy of the source). sample and are superimposed on a permanent decreasing field. When coupled with energy-filtered imaging, this technique can be used to map the various elements to be found in the structure. This Performance and limitations of the sims technique examination, conducted in cooperation with the Inra Nurelice Labo SIMS can detect and measure almost all elements in the ratory in Jouy-en-Josas, was performed on a EFTEM Zeiss EM 902. periodic table, including their isotopes.

Sensitivity is approximately 1 atomic ppm for most ele- Experiment protocols and preparation of ments, but may reach up to 1 atomic ppb for some. This biological samples technique can be used to detect trace elements, and even ultra-trace elements. Animal experiments involving contamination of Corbicula fluminea Elemental distributions for a given surface can be deter- bivalves were carried out in the IRSN radioecology laboratory [Simon mined using a lateral resolution of approximately 1 µm, et al, 2004 and 2005]. Collected in the Gironde region, from Lac with concentration profiles that depend on the profiling depth in the matrix, at a resolution of approximately Sanguinet, the mollusks were contaminated with a uranyl nitrate 1 nm. solution introduced in the aquarium, at a uranium content of 500 µg/l

The instrument has high mass resolution (up to approx. and 20 µg/l. Exposure time was 10 days for the higher concentration, 104). Mass resolution is defined by the expression R = M/ and 10, 40, and 90 days for the lower concentration. The bivalve gills ΔM, where M is the molecular mass of the detected ion. It can discriminate the molecular mass of two very close were then sampled, prepared for observation under an optical micro- elements, separated by a distance of ΔM = 10-4 M. scope and analysed with SIMS and EFTEM techniques. Preparation of a biological sample for study under a charged particle beam must meet several requirements: SIMS is a destructive analysis method: the sample is eroded during the experiment. for SIMS, the surface of the sample must be perfectly flat and polished. Otherwise, the ion beam produced from the sample surface It is difficult to determine the absolute concentration of is not isotropic and the resulting image is always out of focus, regard- an element, which is one of the major drawbacks of this technique. The secondary ion emission process is too less of how finely the instrument has been tuned; complex to establish a global model of the analysis pro- biological samples are not good conductors, and may even be cess, not to mention analytical quantification [Wittmaack, 1980; Benninghoven, 1987]. isolating. Obtaining an absolute concentration can only be Bombarding the sample with ions or electrons may produce charge achieved by taking measurements on standard samples from the same matrix as the sample to be analyzed, effects, a phenomenon that results in charge accumulation on the at known concentrations of the element, distributed sample surface. homogeneously throughout the matrix. In the case of this study, it would have been very difficult to prepare To correct this problem, the slices are placed on a conducting plate standard biological samples. (gold plate finished to a mirror surface) for SIMS analyses, or a gold grid is laid on the sample for transmission electron microscopy. Gills of control bivalves not exposed to uranium were also prepared The EFTEM technique for examination using these various analysis techniques. This instrument offers the possibility of using electron energy loss Animal experiments involving contamination of rats were carried spectroscopy (EELS) and electron spectroscopic imaging (ESI) to out by IRSN at the radiotoxicology laboratory [Paquet et al., 2006]. characterize and map the chemical elements in the sample at very Adult Sprague-Dawley rats were subjected to chronic contamination high sensitivity and high lateral resolution, i.e. approximately 10 for periods of nine and 18 months through uranium ingestion by nanometers [Bordat et al, 2000; Lechaire et al, 2008]. drinking mineral water containing enriched and spent uranyl nitrate,

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250 eV. The incident electron beam energy was 120 KeV. 238U+ 56Fe+ Experimental conditions detection detection

+ + Primary ion beam O2 O2 Uranium distribution in gills of Corbicula fluminea Primary ion beam accelerating 12.5 KeV 12.5 KeV voltage The gill is an organ located on both sides of the mollusk's body, in Primary ion beam intensity 7.10-9A 2.10-9A the form of inner and outer demibranches. Each demibranch consists of an ascending limb and descending limb, connected to the gill Secondary ion beam accelerating 4.5 KeV 4.5 KeV voltage axis (Figure 2).

Primary ion beam raster pattern 200 × 200 µm2 100 × 100 µm2 The basic element of the gill is the filament (Figure 3). All filaments are arranged in series, parallel to each other. Gills fulfill several Mass resolution M/ΔM = 300 M/ΔM = 3,000 functions. They are responsible for respiration and capturing food particles through cilia surrounding the filaments. Lateral cilia circu- Table 1 Experimental conditions for analyses based on the SIMS technique (Caméca 4F-E7). late water through the gill tissue, lateralfrontal cilia collect food particles, and frontal cilia carry food to the body of the bivalve. respectively. The uranium content in the mineral water was 40 mg/l, Results obtained using SIMS corresponding to a daily ingestion of approximately 1 mg of ura- The mass spectra obtained on control samples and contaminated nium per animal. The renal cortex samples were prepared for SIMS samples (Figure 4) reveal the presence of uranium in the tissue in analyses. Rat kidneys that had not been contaminated by uranium ten days exposure period. The fact that there is no peak at mass were also examined. 238 in the control sample mass spectrum (< 1 count per second) indicates that the uranium detected in the contaminated sample Stringent experimental conditions for SIMS and EFTEM comes only from the contaminant and confirms that the SIMS analyses technique is appropriate for detecting trace amounts of uranium SIMS analysis experimental conditions (choice of primary ion beam, in the Corbicula fluminea samples. Ion images of 40Ca+ show gill primary ion beam intensity, primary and secondary ion beam accel- morphology (Figure 5). Ion images of 238U+, representing con- erating voltage, raster pattern, etc.) are shown in Table 1. A prelimi- tamination ingested at 20 µg/l for 90 days, reveal uranium distribu- nary study was carried out to determine the optimum experimental tion within the gills. conditions, since a compromise must be found between sputtering speed, which must not be too high, and detection sensitivity, which Distribution is heterogeneous (forming clusters greater than 1 µm) must be as high as possible. and is located mainly in the filaments and on the periphery of the interlamellar junctions. This result holds for all types of contamina- Analysis were conducted in several steps. For uranium detection, the tion studied. mass spectra were obtained around the mass of isotope 258 of Table 2 gives all the results obtained. A greater accumulation of uranium, then, in the same analysed aera, elemental ion images were uranium appeared in the gills when contamination was ingested captured at a calcium mass of 40, to visualize the tissue morphol- at 500 µg/l, but uptake in this case occurred soon after exposure ogy, and 238 for uranium. These analyses were carried out at low began. The exposure time did not seem to significantly increase mass resolution (M/ΔM = 300). To detect the main iron isotope at the level of uranium retained in the gill structure. mass 56, it was necessary to operate at high mass resolution (M/ ΔM = 3,000) to separate detection of the very close 40Ca16O+ group, Comparative study of retention areas between also present in biological tissue. For each range studied, mass spec- uranium and iron using SIMS tra and ion images were recorded for 40Ca+, 56Fe+, and 238U+. The analysis results on iron detected in the contaminated mollusk gills were comparable to those obtained from the control samples In studies carried out using EFTEM, iron and uranium were identified (Figure 6), where iron was retained in large aggregates (a few using characteristic rays Fe-L2,3 (708 eV) and U-O4,5 (96 eV). The filtered micrometers in diameter) in the gill matrix. image showing the tissue structure was obtained at an energy loss of For bivalves exposed to uranium, ion images of 56Fe+ and 238U+

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Mantle Gill axis

Interlamellar Descending cavity limb Interlamellar Ascending septum limb

Food groove

Inner Outer demibranch demibranch

Figure 3 Optical image of a cross-section through the gill of Figure 2 Schematic representation of the gill structure of Corbicula fluminea. Corbicula fluminea.

a b c C/s C/s C/s 101 102 102 238U Peak

1 1 Background 10 10

10 10

10-1 10-1 10-1 235 237 239 241 235 237 239 241 235 237 239 241 Mass: (u) Mass: (u) Mass: (u)

Figure 4 Mass spectra from the gills of Corbicula fluminea. a) Control samples. b) Contaminated at 20 µg/l, 10 days. c) Contaminated at 20 µg/l, 40 days.

were compared. Superimposing the SIMS images (Figure 7) shows Comparison of results obtained using other analysis that uptake of these two elements does not occur at the same and imaging techniques locations. The results obtained in this study were compared with those achieved using other analysis techniques, namely the NanoSIMS 50 (Laboratoire Léon Latarjet/Institut Curie-Orsay) and energy-filtered transmission 20 µg/l 20 µg/l 20 µg/l 500 µg/l electron microscopy (Laboratoire Nurélice/Inra, Jouy-en-Josas). Control 10 days 40 days 90 days 10 days The Caméca NanoSIMS 50 is a new-generation instrument. It features a smaller primary ion beam (which can reach roughly 20-30 238U+ < 1 70 - 90 50 - 80 90 400 (counts/s) nanometers) than the SIMS instrument in our laboratory (measuring about one micrometer), providing ion images with better lat-

Table 2 238U+ results according to bivalve exposure conditions. eral resolution.

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a b c

Ca+ U+ Ca+ /U+

+ + Ca+ U+ Ca /U

200 x 200 mm2 200 x 200 mm2 200 x 200 mm2

Figure 5 Ion imaging of cross-sections through the gill of Corbicula fluminea. a) 40Ca+. b) 238U+. c) 238U+ (red) overlaid on 40Ca+ (blue).

Another advantage is that this instrument can detect five elements Uranium distribution in the renal cortex in parallel, meaning it can produce several elemental distribution of the rat profiles from the same microvolume [Guerquin-Kern et al, 2005]. The ion images obtained using the NanoSIMS are absolutely com- Results obtained using ion microscopy parable to those achieved in our laboratory, thereby validating our The renal cortex consists of glomeruli, proximal kidney tubules results. Figure 8 represents overlaid images of 238U+ (green), 56Fe+ (PKT), Henlé's loop, distal kidney tubules (DKT), and collecting ducts (blue), and 40Ca+ (red). (Figure 10).

Results obtained using EFTEM (Figure 9) show distributions for These various areas can be distinguished on both cross-sectional uranium (red) and iron (blue) on the image of the contaminated gill views observed under an optical microscope and on the SIMS imag- structure (gray). These chemical images, taken at a lateral resolution es shown in Figure 11. Ion images of 40Ca+ are representative of the of roughly 20-30 nanometers, demonstrated that, aside from ura- tissue structure that can be observed through an optical microscope. nium accumulation in vessels located inside gill filaments (confirm- These points of interest were studied for two contamination periods, ing SIMS results), uranium was also present inside the frontal and one lasting nine months, and the other 18 months. lateral cilia located around the outside of the filaments, with cilia thickness measured at about 200 nm. It is also interesting to note The comparison of mass spectra (Figure 12) performed on a control that iron accumulates in different locations than the contaminant. sample and a contaminated sample for 18 months revealed uranium in the tissues subsequent to contamination. After a con- Analysis of the EELS spectrum produced by the primary electron tamination period of nine months, spectral analyses only showed beam, carried out on cross-sections through control gill samples, uranium retention in the proximal kidney tubules. Overlaid ion did not detect any uranium, thereby demonstrating that any nat- images of 40Ca+ and 238U+ (represented in gray and red, respec- urally-occurring trace of this radionuclide present in the samples tively) obtained from this structure reveal a heterogeneous distri- did not influence the measurement results. bution of uranium in the form of clusters from one to two

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a b

C/s Control 10 3

40Ca16 O+ 10 2 56Fe+

101 Fe+

10-1 100 x 100 μm 2 Ca+ Fe+ 55.9 56 Mass: (u)

Figure 6 Control sample of Corbicula gill. a) Mass spectrum. b) Ion images of 40Ca+ and 56Fe+ (100 x 100 µm2).

Fe+ clusters 238U+ locations Gill filaments

Figure 7 Overlaid images of Corbicula fluminea gills contaminated with uranium (500 µg/l, 10 days); 40Ca+ (blue), 238U+ (pink), 56Fe+ (green).

Filaments

238U+ clusters

Figure 8 Overlaid ion images of 40Ca+ (red), 238U+ (green), 56Fe+ (blue) obtained using a NanoSIMS 50 on a gill contaminated at a rate of 500 µg/l over a period of 10 days.

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Figure 9 Overlaid electron images showing uranium distribution (in red) on the structural image of the gill (gray) and the EELS spectrum.

Glomerular Distal capsule kidney tubule

Glomerulus Proximal kidney tubule Collecting duct

Henlé’s loop Renal pelvis

Figure 10 Schematic representation of the renal cortex structure. Figure 11 Optical and ion images of various structures in the renal cortex.

micrometers in diameter (Figure 13). However, the results shown causing a functional deficiency of the kidney. To confirm this hypoth- in the mass spectra and elemental images obtained from exposed esis, it would be prudent to envisage conducting animal experimen- rodents over an 18-month period indicate that the radionuclide tation where the rat is contaminated over at least nine months, accumulated in all the cortex structures: glomeruli, proximal kidney then not exposed to uranium for a few months before being sacri- tubules, Henlé's loop, distal kidney tubules, and the collector ducts ficed to observe whether the uranium is eliminated after uptake in (Figure 14). Uranium was not distributed homogeneously through- the proximal kidney tubulures. out the various structures, and the amount retained appears greater for the concentration ingested over 18 months than for the Comparative study of retention areas between 9-month contamination period. uranium and iron using SIMS technique SIMS data (mass spectra and ion images) obtained from the renal These significant results suggest that the uranium uptake kinetics cortex of the control rats indicate that iron was distributed in a large depend on the period of exposure of the rat. Accumulation in all number of sizeable clusters throughout all structures (Figure 15). the renal cortex structures of the animals exposed for 18 months Analysis results on the contaminated rats are comparable to may perhaps be related simply to the long lifetime of the rats, those obtained on the unexposed animals. Overlaid ion images

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a C/s 101

Background

10-1 235 237 239 241 Mass: (u)

b C/s 101

Presence of 238U+

10-1 235 237 239 241 Mass: (u)

Figure 12 Mass spectra. a) Control kidney. b) Contaminated kidney. Figure 13 Overlaid ion images of rat kidneys, 238U+ (red) and 40Ca+ (gray). Contamination at 9 months.

Figure 14 Overlaid ion images of rat kidneys, 238U+ (red) and 40Ca+ (gray). Contamination at 18 months.

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a b c

C/s 10 3

40 16 + 10 2 Ca O 56Fe+

101

10-1 56 56,1 Mass: (u)

Figure 15 Kidney from control rat. a) Mass spectrum. b) Ion image of 56Fe+ (100 x 100 µm2). c) Ion image of 40Ca+ (100 x 100 µm2).

+ + + + Fe (gray)/ U (red) Fe+ (gray)/ U+ (red) Fe (gray)/ U (red)

Figure 16 Overlaid ion images of 56Fe+ (gray) and 238U+ (red) from contaminated rat kidneys at 18 months (100 x 100 µm2).

of 56Fe+ et 238U+ suggest that, as in the case of the bivalves, ated with a mass spectrometer revealed, for the first time, there is no interaction between iron and uranium (Figure 16). heterogeneous distributions of this radionuclide in two biological matrices. In the gills of the Corbicula fluminea bivalve, the experiment results (mass spectra and ion images) showed Conclusions and outlook that uranium accumulated in clusters in the gill structure, just 10 days after exposure to a very low concentration of this ele- Conducted within IRSN's ENVIRHOM research program, this ment in water (20 µg/l). study showed that analytical ion microscopy, or SIMS, in the laboratory is completely adequate to study distribution profiles In rats contaminated over periods of nine and 18 months of radionuclides present in low concentrations in biological through ingestion of 40 mg/l of uranium in their drinking water, matrices after internal contamination. SIMS data suggested uranium retention kinetics in the renal cortex that depend on the contamination period. In animals In the case of uranium contamination resulting from chronic exposed for nine months, only the proximal kidney tubes exposure, the ion beam analysis and imaging technique associ- showed any accumulation of uranium, whereas in rodents

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exposed for 18 months, all the structures in the renal cortex This research also demonstrated that these techniques are contained clusters of the contaminant. capable of providing complementary information. In the context of studies conducted on ecosystems, this experimental The study also showed that, for both biological matrices, there contribution will be pursued on another biological matrix: the was no correlation between iron and uranium uptake points. Danio fish, focusing on the reproductive system and larvae.

All these results were confirmed and validated with results With regards to studies on the rat, SIMS analyses will continue, achieved using other analysis techniques: ion microscopy with but will focus on another radionuclide, 137Cs. Rat organs such as the Caméca NanoSIMS 50, and the EFTEM technique, combin- the liver, kidney, thyroid gland, skeletal muscle, and the heart ing electron energy loss spectroscopy (EELS) with electron will be examined. spectroscopic imaging (ESI). Study of uranium distribution on the scale of the cell is also envisaged. Preliminary analyses carried out on cell cultures appear promising.

References A. Benninghoven, F.G. Rüdenauer, H.W. Werner (1987). Secondary Ion Mass Spectrometry. Chemical analysis, vol. 86 (Ed. John Wiley, New York). C. Bordat, M. Sich, F. Réty, O. Bouet, G. Gournot, C.A. Cuénod, O. Clément (2000). Distribution of iron oxide nanoparticles in rat lymph nodes studied using electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI). J. Magnet. Res. Imaging 12,505-509. R. Castaing, G. Slodzian (1962). Microanalyse par émission ionique secondaire. J. Microscopie 1, 394-410. M. Donnadieu-Claraz, M. Bonnehorgue, B. Dhieux, C. Maubert, F. Cheney, F. Paquet, P. Gourmelon (2007). Chronic exposure to uranium leads to iron accumulation in rat kidney cells. Radiation Research 167, 454-464. E. Fournier, D. Tran, F. Denison, J.C. Massabuau, J. Garnier-Laplace (2005). Valve closure response to uranium exposure for a freshwater bivalve (Corbicula fluminea): quantification of the influence pH. Environ. Toxicol. and Chem. 23(5), 1,108-1,114. J.L. Guerquin-Kern, T.D. Wu, C. Quintana, A. Croisy (2005). Progress in analytical imaging of the cell dynamic secondary ion mass spectrometry (SIMS microscopy). Biochim. And Biophys. Acta 1724, 228-238. S. Halpern (1983). Méthodes chimiques de préparation des échantillons. Microanalyse en biologie (Ed : C. Qintana et S. Halpern), SFME, Paris, 93-104. P.J. Lechaire, G. Frébourg, F. Gaill, O. Gros (2008). In situ characterization of sulphur in gill-endosymbionts of the shallow water lucinid Codakia orbicularis (Linné, 1758) by high-pressure cryofixation and EFTEM microanalysis. Marine Biology, 1-8, in press. F. Paquet, P. Houpert, E. Blanchardon, O. Delissen, C. Maubert, B. Dhieux, A.M. Moreels, S. Frelon, P. Voisin, P. Gourmelon (2006). Accumulation and distribution of uranium in rats after chronic exposure by ingestion. Health Physics 190(2), 139-147. O. Simon, J. Garnier-Laplace (2004). Kinetic analysis of uranium accumulation in the bivalve Corbicula fluminea: effect of pH and direct exposure levels. Aquatic toxicology 68, 95-108. O. Simon, J. Garnier-Laplace (2005). Laboratory and field assessment of uranium accumulation trophic transfer efficiency in the crayfish Orconectes limosus fed on the bivalve C. fluminea. Aquatic Toxicology 74, 372-383. G. Slodzian (1964). Étude d’une méthode d’analyse locale chimique et isotopique utilisant l’émission ionique secondaire. A. Phys. 9, 594-648. K. Wittmaack (1980). Aspects of quantitative secondary ion mass spectrometry. Nucl. Inst. Methods 168, 343-356.

164 2008 Scientific and Technical Report - IRSN 3.4 Epidemiological studies of leukemia incidence in children and young adults living around nuclear facilities: a critical review

Dominique LAURIER, Marie-Odile BERNIER, Sophie JACOB, Klervi LEURAUD, Camille METZ, Éric SAMSON Epidemiology Laboratory Patrick LALOI Radiobiology and Epidemiology Department

An epidemiological study published at the beginning of 2008, concerning the entire fleet of nuclear power plants in Germany, showed that there was an increased risk of developing leukemia in children under five years of age living less than five kilometers from a nuclear power plant [Kaatschet al, 2008]. A great deal of research has been carried out on this subject since the early 1980s [Laurier, 1999; Laurier, 2002]. To situate the results of the German study in the context of available epidemiological knowledge, the epidemiology laboratory at IRSN compiled data on this subject and conducted a critical analysis of results relative to the risk of leukemia in children and young adults below the age of 25 living in the vicinity of nuclear facilities. The conclusions of this study were published in a report in April 2008 [Bernier et al, 2008]. It is based on the most exhaustive as possible review of epidemiological studies published in the international literature describing the frequency of leukemia in areas close to nuclear facilities located in different countries around the world. The published results were then submitted to critical review. Discussions on the results also took into consideration conclusions from studies that did not focus on nuclear facilities, within the methodological limits associated with descriptive epidemiological studies. The potential causes of childhood leukemia and the main hypotheses explored to explain the localized incidence clusters observed in the vicinity of certain nuclear facilities were also discussed.

Background information and methods of the alkylating drugs used in chemotherapy. Other factors that are suspected but whose role has not yet been confirmed include low-dose Leukemia is not a frequent pathology in children: every year in France exposure to ionizing radiation, electromagnetic fields, pesticides, benzene, there are about 470 new cases and 75 deaths from childhood leukemia infectious agents, and others. According to estimations by some authors, for a population of about 12 million children (aged 0 to 14) [Clavel et for example, natural radiation could be responsible for nearly 20% of al, 2004]. Acute lymphoblastic leukemia accounts for nearly 80% of cases of childhood leukemia in Great Britain [Wakeford, 2004]. leukemia incidence in children. A peak appears in the frequency of this type of leukemia between the ages of 1 and 6. The few recognized risk Although several potential risk factors have been put forward, today factors of childhood leukemia include trisomy 21, Fanconi anemia, there is little information available to explain the causes of leukemia, external exposure to high-dose ionizing radiation, and administration and 90% of leukemia cases remains unexplained.

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The method used for this review is based on bibliographical research 20 15 compiled from the Scopus and PubMed databases. Other documents 10 5 were obtained from IRSN archives and through direct contact with 1 Definition of concentric zones according to researchers in France and abroad. In total, several hundreds documents distance from site (reports, articles in scientific journals) on the risk of leukemia in young people aged under 25 living around nuclear sites were collected. Several types of study of varying quality have been conducted, such as local Observed Σ 2 Cases count and multi-site cluster studies, control and cohort case studies, for each zone radioecological studies, and dosimetry work, to name a few. The review made a distinction between two types of research: descriptive studies, which aim to estimate the frequency of leuke- Observed Σ mia incidence and detect any excess risk within a given population; RR = Expected Σ 3 Assessment of relative analytical studies, that seek to determine the factors that could risk (RR) in each zone explain any excess risk of leukemia incidence within a population. RR Review of descriptive studies 4 Trend test for risk as a Descriptive studies try to answer the question: "Is the frequency of function of distance leukemia in the vicinity of a particular site higher than elsewhere?". It is important to emphasize that these studies are not designed to search for the factors that explain cases clusters. The methods Figure 1 Principle of a cluster study. employed are generally quite simple and are based on counting the number of cases in the surrounding areas, most often defined by concentric circles (Figure 1). (near the Kruemmel plant in Germany) [Grosche, 1992; Wichmann, 2004; Hoffmann, 2007]. Other clusters were well documented, In total, results from descriptive studies are available for 198 nucle- especially in Great Britain, near the Aldermaston and Burghfield ar sites, located in ten different countries: Great Britain, Germany, sites [COMARE, 2005; Roman et al, 1987] and in France, near the France, Sweden, Spain, the USA, Canada, Japan, Switzerland, and Israel. reprocessing plant at La Hague [Viel, 1995; Guizard et al, 1997], The results of all these studies were reviewed, making a distinction but the data currently available is not sufficient to confirm excess between local studies focused on a specific site, and multi-site stud- risk (Figure 3). ies simultaneously covering a group of sites within a given country, thereby covering a larger population. Evaluation criteria were applied Among the multi-site studies surveyed (25 studies in eight differ- in order to assess the reliability of collected results. ent countries), those that best met the assessment criteria were the recent studies conducted in Great Britain [COMARE, 2005], in Criteria were defined according to the type of data in question Germany [Kaatsch, 2008] and in France [White-Koning et al, 2004] (morbidity/mortality), the geographical area studied (relevance of (Figure 4). These studies do not indicate, across all the sites exam- the size and boundaries of the areas considered), the power of the ined, an increased risk of leukemia in children (aged 0 to 14) or study (ability to reveal a low excess risk) and the statistical significance young adults (aged 0 to 24) near nuclear facilities. Few studies of any observed excess, the validity of the statistical methodology, provide results specific to the age group ranging from 0 to 4 years. the reproducibility of results (excess revealed by different methods), Given the current state of knowledge, however, the results of the and lastly, the persistence of excess over time (Figure 2). German study are not supported by studies conducted in other countries. In particular, recent geographic studies conducted in Among the 198 sites reported, three excesses met the stated Great Britain [Bithell, 2008] and France [Laurier et al, 2008] do not evaluation criteria and were considered as confirmed clusters. reveal any increase in the risk of leukemia incidence in children These sites were Seascale (near the Sellafield plant in England) aged 0 to 4 in the vicinity of nuclear power plants. [Black, 1984; COMARE, 1996], Thurso (near the Dounreay plant Other studies have shown local excess of childhood leukemia in areas in Scotland) [Heasman et al, 1986; COMARE, 2005] and Elbmarsch where there are no nuclear facilities. Furthermore, several studies

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Collected information Assessment criteria Classification

Over 100 studies Incidence > Mortality No excess reported United Kingdom, Germany, USA, Appropriate zoning Canada, Israel, Switzerland, Spain, Power Not confirmed excess Statistical validity Sweden, Japan, and France. Possible excess Reproducibility Persistence over time Confirmed excess

Figure 2 Analytical approach.

CANADA Ottawa

USA GREAT BRITAIN PACIFIC Stockholm OCEAN ATLANTIC SWEDEN OCEAN 500 km NORTH SEA

London Berlin

GERMANY Prague Paris ATLANTIC CZECH Washington OCEAN REP. Berne SWITZERLAND FRANCE 250 km SPAIN

Tel Aviv Madrid SEA OF JAPAN ISRAEL MEDITERRANEAN SEA 500 km JAPAN

Tokyo

Results of epidemiological studies: PACIFIC OCEAN NPP No excess reported Possible excess EAST Others Not confirmed excess Confirmed excess CHINA SEA 500 km

Figure 3 Results per site: 198 sites, 10 countries.

show spatial and temporal clusters of leukemia incidence in children ent to descriptive studies, which make it difficult to interpret results. that are not related to the presence of any potential sources of risk Studies on the risks of leukemia around nuclear sites are numerous [Bernier et al, 2008]. and diverse, making it necessary to examine each new result in the Lastly, it is important to point out the significant limitations inher- light of available scientific knowledge.

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GREAT BRITAIN Stockholm CANADA Ontario SWEDEN Ottawa

NORTH SEA Iowa

USA Pennsylvania Connecticut Berlin PACIFIC London OCEAN GERMANY Washington ATLANTIC OCEAN Paris ATLANTIC OCEAN FRANCE

SEA OF JAPAN

SPAIN JAPAN

Madrid Tokyo

PACIFIC MEDITERRANEAN SEA OCEAN EAST CHINA SEA Mortality Incidence Mortality + incidence

Figure 4 Multi-site studies: 25 studies, 8 countries.

Review of analytic studies on the an infectious cause related to the population mixing with large- potential causes of observed local excess scale construction sites, such as that of a nuclear power plant.

Subsequent to descriptive studies in which leukemia clusters were Some research focused on a possible connection to environmental observed close to certain nuclear facilities, several investigations exposure caused by radioactive or chemical discharges from nucle- were launched to identify factors that might explain these excess- ar facilities, as in Great Britain [COMARE, 1988; COMARE, 1989; es, in particular close to the sites at Sellafield, Dounreay, COMARE, 1996] or in France, in work by the Nord-Cotentin Aldermaston, and Burghfield in the United Kingdom, La Hague in Radioecology Group [GRNC, 1999; GRNC, 2002]. Results indicate France and Kruemmel in Germany. that doses received due to discharges from nuclear facilities are These works were based on various approaches and protocols, low and cannot explain the excess risk observed at specific loca- including epidemiological studies (type of geography, control groups, tions. cohorts), measurement of doses received by the population, and The hypothesis based on a relationship with the father's occupa- radioecological assessments. Three main hypotheses were put tional exposure to external ionizing radiation before child conception forward to try to explain why the observed risk was higher in the was proposed for the Sellafield site [Gardner et al,1990], but was vicinity of certain nuclear facilities: not confirmed later, and today seems to have been rejected [Doll a link with environmental exposure due to radioactive or chemi- et al, 1994]. cal discharges from nuclear facilities; a link with fathers' exposure to ionizing radiation before children The hypothesis on an infectious cause related to population mixing were conceived; around nuclear sites was put forward by Kinlen [Kinlen, 1988] and

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was confirmed by several epidemiological results [Kinlen, 2004]. German nuclear power plants. To date, no similar observations According to some authors, this hypothesis could partly explain the have been made in other countries, including France. The pub- excesses observed close to certain sites (in particular Sellafield and lished German study cannot explain the observed excess. Dounreay) [Kinlen, 1988; Kinlen, 2004]. So far, however, it has not been possible to identify or isolate the infectious agent(s) involved. Furthermore, several studies have attempted to explain the local Moreover, this hypothesis can only be applied to specific sites where excess of leukemia around certain nuclear sites by focusing on significant displacement of the population has occurred, and cannot multiple potential risk factors. Among the different areas be applied to all the sites in a country or a region. explored, the hypothesis based on an infectious cause related to population mixing around the nuclear sites seems to be the The implication of other environmental factors was considered in most well-founded. However, to date, the infectious agent(s) some publications, such as electromagnetic fields due to high- involved have not been found. voltage power lines, pesticide use in gardens or fields, the presence of other industrial sites, or high exposure to naturally-occurring Determining the causes of the local excess of leukemia observed radioactivity. But these factors are not specific to nuclear facilities, close to certain nuclear sites is limited by lack of knowledge on and so far none of them have been confirmed as a recognized risk the risk factors of childhood leukemia. Development of broader factor of childhood leukemia. analytical studies, reaching a national or international scale is necessary to clarify leukemia aetiology. Even today, although several suggestions have been proposed, the origin of the clusters observed close to certain nuclear sites has not been established. However, it should be noted that most of these studies present methodological limitations (geographical case studies or studies of small populations), making it difficult to detect any causal link. In addition to this problem, there is no available knowledge on the risk factors associated with childhood leukemia. Large-scale analytical studies such as those under way in France, based on the national register of malignant hemopathy in children, could provide a better understanding of the causes behind clusters of childhood leukemia.

Conclusion

Since the 1980s, many descriptive studies have estimated the frequency of leukemia in young people living close to nuclear facilities. These studies were conducted in answer to a demand for information on the part of local populations, and also contribute to the discussion on the effects of low environmental doses. The bibliographical review showed great diversity in the approaches taken and methods used.

Local excess of childhood leukemia exist in the United Kingdom close to the reprocessing plants at Sellafield and Dounreay, and in Germany close to the Kruemmel nuclear power plant. Nevertheless none of the multi-site studies currently available, including in France, show an overall increase in the frequency of leukemia in children and young people aged 0 to 14 or 0 to 24 in the vicinity of nuclear sites. A recent epidemiological study described an excess of leukemia in children aged 0 to 4 around

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References M.-O. Bernier, E. Gregoire, S. Jacob, P. Laloi, D. Laurier, K. Leuraud et al. (2008). Les études épidémiologiques des leucémies autour des installations nucléaires chez l’enfant et le jeune adulte : Revue critique. Fontenay-aux-Roses : IRSN ; Mars 2008. Report No.: DRPH/SRBE 2008-01. J. Bithell (2008). Childhood leukemia near British nuclear installations: methodological issues and recent results. Rad Prot Dosim. 2008 Oct. 20. [Epub ahead of print] D. Black (1984). Investigation of the possible increased incidences of cancer in West Cumbria. London: HMSO. J. Clavel, A. Goubin, M.-F. Auclerc, A. Auvrignon, C. Waterkeyn, C. Patte et al. (2004). Incidence of childhood leukaemia and non-Hodgkin’s lymphoma in France: National Registry of Childhood Leukaemia and Lymphoma, 1990-1999. Eur. J. Cancer Prev. 2004 Apr.; 13(2):97-103. COMARE (1988). Committee on Medical Aspects of Radiation in the Environment, Second Report. Investigation of the possible increased incidence of childhood cancer in young persons near the Dounreay nuclear establishment, Caithness, Scotland. United Kingdom, London: HMSO. COMARE (1989). Committee on Medical Aspects of Radiation in the Environment, Third Report. Report on the Incidence of Childhood Cancer in the West Berkshire and North Hampshire area, in which are situated the Atomic Weapons Research Establishment, Aldermaston and the Royal Ordnance Factory. United Kingdom, London: HMSO. COMARE (1996). Committee on Medical Aspects of Radiation in the Environment, Fourth Report. The incidence of cancer and leukaemia in young people in the vicinity of the Sellafield site, West Cumbria: Further studies and an update of the situation since the publication of the report of the Black Advisory Group in 1984. United Kingdom, London: Department of Health. COMARE (2005). Committee on Medical Aspects of Radiation in the Environment, Tenth Report. The incidence of childhood cancer around nuclear installations in Great Britain. United Kingdom, London: Health Protection Agency. H.-O. Dickinson, L. Parker (1999). Quantifying the effect of population mixing on childhood leukaemia risk: the Seascale cluster. Br. J. Cancer. 81(1):144-51. R. Doll, H.-J. Evans, S.-C. Darby (1994). Paternal exposure not to blame. Nature. 367(6465):678-80. M.-J. Gardner, M.-P. Snee, A.-J. Hall, C.-A. Powell, S. Downes, J.-D. Terrell (1990). Results of case-control study of leukaemia and lymphoma among young people near Sellafield nuclear plant in West Cumbria. BMJ. 300(6722):423-9. GRNC (1999). Estimation des niveaux d’exposition aux rayonnements ionisants et des risques de leucémies associés de populations du Nord-Cotentin – Rapport de synthèse. Fontenay-aux-Roses, France : Groupe radioécologie Nord-Cotentin, Institut de protection et de sûreté nucléaires. GRNC 2e mission (2002). Évaluation des risques associés aux rejets chimiques des installations nucléaires du Nord-Cotentin – Volume 2 : risques pour la santé. Fontenay-aux-Roses, Paris : Groupe radioécologie Nord-Cotentin, Institut de protection et de sûreté nucléaires. B. Grosche (1992). Leucémies infantiles dans le voisinage des centrales nucléaires en Allemagne. Symposium sur les agrégats de leucémie ; Canada, Ottawa : Atomic Energy Control Board. p.19-25. A.-V. Guizard, A. Spira, X. Troussard, A. Collignon, ARKM (1997). Incidence des leucémies de 0 à 24 ans dans le Nord Cotentin. Rev. Epidemiol. Santé Publ. 45:530-5. M.-A. Heasman, I.-W. Kemp, J.-D. Urquhart, R. Black (1986). Childhood leukaemia in northern Scotland. Lancet. 1(8475): 266. W. Hoffmann, C. Terschueren, D.-B. Richardson (2007). Childhood leukemia in the vicinity of the Geesthacht nuclear establishments near Hamburg, Germany. Environ Health Perspect. 2007 Jun.; 115(6):947-52. P. Kaatsch, C. Spix, R. Schulze-Rath, S. Schmiedel, M. Blettner (2008). Leukaemia in young children living in the vicinity of German nuclear power plants. Int. J. Cancer. 2008 Dec. 7; 122(4):721-6. L. Kinlen (1988). Evidence for an infective cause of childhood leukaemia: comparison of a Scottish new town with nuclear reprocessing sites in Britain. Lancet. 2(8624):1323-7. L.-J. Kinlen (2004). Childhood leukemia and population mixing. Pediatrics. 2004 Jul.; 114(1):330-1. D. Laurier (1999). Leucémies chez les moins de 25 ans autour d’installations nucléaires en France et à l’étranger : revue des études épidémiologiques descriptives. Radioprotection. 34(2):149-76. D. Laurier, C. Rommens, C. Drombry-Ringeard, A. Merle-Szeremeta, J.-P. Degrange (2000). Assessment of the risk of radiation-induced leukaemia in the vicinity of nuclear installations: The Nord-Cotentin radio-ecological study. Rev. Epidemiol. Santé Publ. 48:2S24-36. D. Laurier, B. Grosche, P. Hall (2002). Risk of childhood leukaemia in the vicinity of nuclear installations – Findings and recent controversies. Acta Oncol. 41(1):14-24. D. Laurier, D. Hémon, J. Clavel (2008). Childhood leukaemia incidence below the age of 5 years near French nuclear power plants. J. Radiol. Prot. 2008 Sep. ; 28:401-3. E. Roman, V. Beral, L. Carpenter, A. Watson, C. Barton, H. Ryder et al. (1987). Childhood leukaemia in the West Berkshire and Basingstoke and North Hampshire District Health Authorities in relation to nuclear establishments in the vicinity. BMJ. 294(6572):597-602. J.-F. Viel, D. Pobel, A. Carre (1995). Incidence of leukaemia in young people around the La Hague nuclear waste reprocessing plant: a sensitivity analysis. Stat Med. 14(21-22):2459-72. R. Wakeford (2004). The cancer epidemiology of radiation. Oncogen; 23: 6404-28. M.-L. White-Koning, D. Hemon, D. Laurier, M. Tirmarche, E. Jougla, A. Goubin et al. (2004). Incidence of childhood leukaemia in the vicinity of nuclear sites in France, 1990-1998. Br. J. Cancer. 91(5):916-22. H.-E. Wichmann, E. Greiser (2004). Untersuchungsprogramm Leukämie in der Samtgemeinde Elbmarsch: Fragestellungen, Ergebnisse, Beurteilungen. Hannover: Niedersächsischen Ministeriums für Soziales, Frauen, Familie und Gesundheit; Novembre 2004.

170 2008 Scientific and Technical Report - IRSN 3.5 New approach to epidemiological follow-up of workers exposed to internal contamination risks: applying the Job Exposure Matrix

Irina GUSEVA CANU, Éric SAMSON Epidemiology Laboratory

Workers in the nuclear industry may be exposed to ionizing radiation through external radiation, internal radiation, or a combination of both. For over ten years, the IRSN epidemiology laboratory (Lepid) has conducted studies on workers in the nuclear field (at CEA, Areva NC, and EDF), to assess the cancer mortality risk associated with external radiation exposure [Guseva Canu et al, 2008; Rogel et al, 2005; Telle-Lamberton et al, 2004; Telle-Lamberton et al, 2007]. In the last three years, Lepid has initiated other studies that also take into account internal radiation risks, through the European ALPHA-RISK Program and a common-interest program carried out with Areva. These studies have led to two doctoral theses in epidemiology.

Internal radiation occurs when radioactive particles are inhaled or Moreover, exposure to certain substances (chemical products, asbes- ingested, or taken up through a wound. While the effects of exter- tos, tobacco, alcohol), which could contribute to cancer risk, quite nal radiation (from X-rays and gamma rays) have been extensively often are not systematically taken into account [Guseva Canu et al, explored in large-scale epidemiological studies [Cardis et al, 2005], 2008]. It is therefore difficult to draw conclusions on the relationship the effects due to incorporation of uranium particles and other between cancer mortality and internal exposure to uranium based alpha-emitting elements remain relatively unknown [Cardis et al, on available epidemiological studies. This highlights the need to 2007]. develop alternative approaches to internal dosimetry that are capable of reconstructing exposure to multiple risk factors. Calculating the organ dose caused by internal radiation requires reconstructing the particle exposure situation. Doses assessed in The Job Exposure Matrix, which establishes a correspondence this way can present significant uncertainty due to incomplete data between a list of jobs and exposure indicators [Goldberg et al, 1993], on the history of worker exposure, heterogeneity in the methods is one of the possible alternatives. and indicators used to measure exposure, difficulty in interpreting individual biological data (worker monitoring in radiotoxicology), The purpose of this article is to demonstrate how the job exposure and the numerous hypotheses used to assess internal exposure matrix approach can be used to characterize exposure in the French [Guseva Canu et al, 2008 ; Boice et al, 2006]. nuclear industry, based on the pilot study conducted by IRSN at the Areva NC plant in Pierrelatte.

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Method used to build the job exposure matrix Exposure agents Details

1 The Areva NC plant (former Cogema) in Pierrelatte is involved in 1 - F natural U compounds UF6, UF4, UO2(NO3)2, (UO4, nH2O) several phases of the nuclear fuel cycle. From 1960 to 1990 the main 1 activities in the plant focused on uranium enrichment, and the 2 - M natural U compounds (U2O7)(NH4)2, U3O8, UO2F2, UO3 chemical conversion of uranium since the 1980's. Workers may 1 therefore have been exposed to uranium particles and aerosols, as 3 - S natural U compounds UO2 well as the chemical products used in the process. Most workers have 4 - F1 U compounds UF , UF , UO (NO ) , (UO , nH O) held steady jobs in the plant, and consequently have received regular from reprocessing 6 4 2 3 2 4 2

medical follow-up throughout their career. That is why Lepid, in 5 - M1 U compounds (U O )(NH ) , U O , UO F , UO agreement with Areva physicians, chose the Pierrelatte plant for its from reprocessing 2 7 4 2 3 8 2 2 3

first epidemiological study on workers that risk uranium 6 - S1 U compounds UO2 contamination. from reprocessing Perchloroethylene, tetrachloroethyl- ene, trichloroethylene, dichlo- 7 - Chlorinated substances The structure of the job exposure matrix [Guseva Canu et al, 2008] romethane, polychlorinated covered three dimensions – job description, exposure, and time biphenyls (PCBs) period – to take into account changes over time in the processing Hydrofluoric acid, tungsten hexafluo- 8 - Fluorinated substances and exposure conditions in the plant. ride, fluorite, potassium fluoride

Ammonia, ammonia anhydride, nitric 9 - Nitrogenous substances The list of jobs and workstations for the different periods and the list acid, nitrous vapors of exposure agents (uranium-containing products and other carci-

nogenic, mutagenic, or toxic chemical products) to which workers 10 - Solvents containing aromatic Benzene, toluene, xylene, styrene may have been exposed were defined by an expert committee hydrocarbons composed of 23 members familiar with the history of the processes 11- Welding fumes. 12 - Rock wool and fiberglass. and products used in the plant and their chemical and radiotoxic 13 - Asbestos. 14 - Refractory ceramic fibers. 15 - Chromates. 16 - Chlorine etrifluoride. 17 - Trichloroethylene. 18 - Lead. effects, as well as safety engineers, radiation protection specialists, 19 - Mercury. 20 - Silica. 21 - Hydrazine and other fuels. chemical engineers, occupational physicians, toxicologists, dosimetry 22 - Heat. Uranium-bearing compounds have been classified in three categories (F, M, and specialists, and epidemiologists. S) according to their solubility in biological tissues (fast, moderate, and slow) [ICRP, 1994].

The frequency of exposure and the amount of product that work- Table 1 Exposure conditions assessed in the job exposure matrix. ers were potentially exposed to in the course of their career were defined as exposure indices. A committee of assessors estimated these indices on a relative scale from 0 to 3. The assessors were selected from three populations: "A" for workers active in the plant for participating (on an anonymous, volunteer basis), assessment with considerable seniority and thorough knowledge of their work- instructions, and the assessment grid to be completed. ing environment; "R" for retired workers; and "AR" for plant retirees belonging to ARGCEA (an association of CEA-Cogema retirees). The grids filled in by the active workers were collected at the plant by the safety engineers, and those completed by retired workers For the latter worker population, a computer file of updated were sent in by mail. All the assessor responses were centralized, addresses was available, making it easy to contact the relevant input, and processed statistically using the technique derived from persons. Nonetheless, since this population could have had a life the Delphi method [Dalkey and Helmer, 1963]. This technique was style significantly different from the other retirees due to its par- used to statistically examine the distributions resulting from the ticipation in an association, the survey also included the other assessors' answers, in order to obtain a Frequency score and a retiree population, classified in the "R" group. Assessment work was Quantity score representative of each job/period combination for standardized using an assessment guide, common to all three each exposure agent. The final matrix was validated by experts after populations, that explained the purpose of the study, the conditions examining the internal coherence of the matrix, as well as its

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Number of surveys Number of surveys Assessor population Participation rate (%) distributed completed

A (active workers) 182 182 100

R (retired workers) 197 85 43

AR (retired workers belonging 353 86 25 to the association)

Total 732 353 56

Table 2 Composition of assessment committee and participation rate according to type of assessor.

Generic worksta- Period Unat_1_Freq Unat_1_Quant Unat_2_Freq Unat_2_Quant Unat_3_Freq Unat_3_Quant tion

1_CME2 1966 - 1976 2 1 0 0 0 0

1_CME2 1976 - 1986 1 1 0 0 0 0

1_CME2 1986 - 1996 1 1 0 0 0 0

1_CME2 1996 - 2006 1 1 1 1 1 1

1_CME3 1966 - 1976 0 0 0 0 0 0

1_CME3 1976 - 1986 2 1 0 0 0 0

1_CME3 1986 - 1996 2 1 0 0 0 0

1_CME3 1996 - 2006 0 0 2 2 1 1

1_CME4 1966 - 1976 3 3 1 3 0 0

1_CME4 1976 - 1986 1 1 1 1 0 0

1_CME4 1986 - 1996 2 1 0 0 0 0

1_CME4 1996 - 2006 3 3 3 3 2 1

1_CME5 1966 - 1976 3 2 3 2 3 2

1_CME5 1976 - 1986 3 2 3 2 3 2

1_CME5 1986 - 1996 3 2 3 2 3 2

1_CME5 1996 - 2006 3 3 3 3 3 3

1_CME6 1966 - 1976 3 3 0 0 0 0

Table 3 Final job exposure matrix (excerpt from the exposure index table)

external coherence with respect to exposure in other comparable Results nuclear facilities. In addition, for a representative sample of workers (1% of the study population), the exposure results provided by Internal radiation exposure was represented by several exposure the matrix were compared with those in medical files, which served agents, according to two criteria: uranium purity, used to distinguish as the reference source for exposure data. Consistency, sensitivity, naturally-occurring uranium components from those coming from and specificity of the assessment were evaluated [Bouyer and reprocessed uranium, containing traces of activation and/or fission Hémon, 1994]. products; and transferability (high, medium, low) of uranium par-

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Observed Degree of Exposure agent Kappa (%) Sensitivity Specificity agreement (%) agreement

Uranium-bearing substances from 85 66 Good 0.81 0.96 natural uranium

Uranium-bearing substances from 92 83 Excellent 0.82 0.98 reprocessed uranium

Asbestos 61 9 Poor 1.00 0.60

Fiberglass and rock wool 74 27 Mediocre 0.50 0.80

Chlorinated substances 71 42 Moderate 0.77 0.67

Fluorinated substances 58 15 Mediocre 0,57 0.60

Nitrogenous substances 68 36 Mediocre 0.59 0.79

Total 78 56 Moderate 0.72 0.83

Table 4 Results from comparison between exposure data taken from the matrix and exposure data from worker medical files, used as reference data.

ticles to biological tissues after incorporation. The exposure agents tive judgements on exposure provided from medical files, taking for which exposure was assessed are given in Table 1. Exposure to into account random factors). According to the interpretation cri- each of the 22 exposure agents was assessed for 73 generic work- teria for the Kappa values proposed by Landis and Koch [Landis and stations. In addition, the generic workstations were divided into Koch, 1977], as regards uranium-containing products, the matrix several periods (1960-1975, 1976-1983, 1984-1995, 1996-2006), data showed very good agreement with the medical file data. with exposure considered as stable within each one, but variable from one period to another. Agreement was not as good for chemical products, and was even In total 353 workers were included in the assessment committee poor for asbestos exposure. Sensitivity and specificity demon- and submitted acceptable assessment grids. Distribution of the strated the matrix's ability to detect exposure to an exposure agent assessors according to their source population is shown in Table 2. when it was present, or to exclude it when it was not [Last, 1995]. The overall sensitivity and specificity values, close to one, showed At the end of the first statistical review, 84% of the scores attrib- that the matrix performed well. uted by the assessors during the assessment procedure were accepted. The second review and the score arbitration session with the experts gave way to a satisfactory Quantity score and Frequency The Job Exposure Matrix: a high- score for each generic workstation/period pair. These scores were performance tool then recorded in the exposure index table presented in Table 3. The job exposure matrix was used for retrospective assessment of In-house specialists at Areva NC Pierrelatte (safety engineers, uranium exposure and the associated chemical products, in a supervisor in charge of chemical product and asbestos surveillance, context where there was no useable measurement data on indi- and radiation protection specialists) examined the internal coher- vidual exposure. The method used to prepare the job exposure ence of the final matrix, judged satisfactory, to establish internal matrix guarantees the reliability and reproducibility of the result- validation. The exposure data produced by the matrix was compared ing exposure data in several ways. with data from the workers' medical files (the data reference), to establish external validation. The results of this validation process To start, many studies have reviewed the job exposure matrix are shown in Table 4. In comparing the two data sources, the degree method, formalized in the 1980's [Goldberg, 1993 ; Hoar, 1983], of agreement was estimated based on observed agreement and the and it has been applied widely in epidemiological studies, espe- Kappa coefficient (used to estimate agreement among the qualita- cially in occupational studies.

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Furthermore, in this study, the aspects listed below actually improved the observed sensitivity and specificity values, the established job the method: exposure matrix is a useful tool with a satisfactory performance. a large number of assessors (n = 353) and experts participated in preparation, giving a solid estimation of the chronological changes in exposure conditions and minimizing memory bias; The Job Exposure Matrix: a useful tool with information collection was standardized, limiting bias related to a satisfactory performance the interviewee and improving reproducibility; applying the Delphi method reduced the influence of assessor The job exposure matrix presented in this study was established to subjectivity in the answers, resulting in a statistical response rep- retrospectively assess exposure of fuel cycle workers to uranium resentative of the group; and the associated chemical products. The matrix was validated discrimination covered a large number of jobs (74 generic work- and today constitutes a source of data on specific exposure at the stations), improving accuracy of the job exposure matrix; Areva NC plant in Pierrelatte. exposure was assessed before conducting the epidemiological studies, avoiding bias related to the assessor as concerns the vital It is used to study the relationship between internal exposure to status and cause of death of the subjects under study. uranium and cancer mortality in the plant workers. Designed in a relatively simply format (Microsoft® Access database), it can serve Nonetheless, the absence of useable data obtained through instru- to establish epidemiological surveillance of exposure over time, both ment measurements to characterize exposure represented a sig- retrospectively and for predictive purposes. The job exposure matrix nificant limitation for the resulting job exposure matrix. Only the is also a tool that the plant can use for risk management: exposure relative levels of exposure frequency and quantity were established, agents listed in the plant's regulatory occupational risk assessment which was not sufficient to infer any precise physical significance. document [Areva Report, 2005] and also featured in the job exposure These levels represented the "mean exposure levels for the period in matrix are notified in real time by occupational health and safety question". By multiplying the exposure frequency and quantity by specialists and safety engineers. The flexibility of the matrix makes the period of exposure at a given workstation, it was nonetheless it easy to update exposure levels for products that are already possible to obtain a cumulative exposure score, a known quantita- listed, and to add new exposure agents. New exposure indices can tive variable, reflecting exposure to each of the 22 exposure agents be incorporated any time, and even better, current exposure data in "dose years" for the entire career of each worker. This method can be replaced by actual measured values. This will become more has been used in other studies [Rice and Heineman, 2003; Ritz et common as instrumented measurement of the various contaminants al, 2006; Seidler et al, 1998] and has proven reliable in demonstrat- used in the plant becomes more widespread. ing the relationship between exposure and the pathology under study. The worker cohort from the Areva NC plant in Pierrelatte is The method developed to build the job exposure matrix can be used currently being studied [Guseva Canu et al, in press]. as a prototype for other fuel cycle plants. In the European ALPHA- RISK program, coordinated by IRSN's epidemiology laboratory, a Agreement between the job exposure matrix data and the medical cohort study was set up, including workers from Comurhex and Areva file data was satisfactory. Agreement was particularly good for ura- NC (uranium chemical processing), Eurodif (uranium enrichment), nium-containing products, which are subject to stringent medical FBFC (fuel manufacture), Socatri (uranium treatment and recovery), surveillance regulations. As regards asbestos, fiberglass, and certain and CEA (research). The study aims to quantify the mortality risk chemical products, however, since their noxious effects were unknown related to internal radiation of workers, as a function of exposure. It at the time, exposure to these substances was not monitored regu- therefore requires reconstruction of individual exposure to radiation larly by occupational medicine in the past. Agreement observed for (both internal and external), chemical substances, and other indi- chemical products was therefore mediocre, and for asbestos was vidual risk factors such as smoking, based on different sources of practically null (Kappa = 9%). information (medical files, etc.). The job exposure matrix approach can be used to supplement available data and assess exposure for This validated the initial hypothesis postulating that the medical past periods where data is often lacking or unusable. files did not provide enough data to reliably assess exposure to chemical products. The job exposure matrix provides a more accurate reflection of chronic low-dose exposure to substances, especially when it is specific to the facility under study. According to

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References J.D. Boice Jr., D.E. Marano, S.S. Cohen, M.T. Mumma, W.J. Blot, A.B. Brill et al. (2006). Mortality among Rocketdyne workers who tested rocket engines, 1948-1999. J. Occup. Environ. Med. 48:1070-92. J. Bouyer, D. Hémon (1994). Les matrices emploi-exposition. Rev. épidém. Santé Publ. 42:235-245. E. Cardis, M. Vrijheid, M. Blettner, E. Gilbert, M. Hakama, C. Hill et al. (2005). Risk of cancer after low doses of ionising radiation: retrospective cohort study in 15 countries. Br. Med. J. 331:77-80. E. Cardis, M. Vrijheid, M. Blettner, E. Gilbert, M. Hakama, C. Hill et al. (2007). The 15-Country Collaborative Study of Cancer Risk Among Radiation Workers in the Nuclear Industry: Estimates of Radiation-Related Cancer Risk, Radiat. Res. 167:396-416. N. Dalkey, O. Helmer (1963). An experimental application of the DELPHI method to use of experts. Management Science. 9:458-67. M. Goldberg, H. Kromhout, P. Guenel, A.C. Fletcher, M. Gerin, D.C. Glass et al. (1993). Job exposure matrices in industry. International Journal of Epidemiology. 22:S10-5. I. Guseva Canu, E.D. Ellis , M. Tirmarche (2008). Cancer risk in nuclear workers occupationally exposed to uranium with emphasis on internal exposure. Health Phys. 94:1-17. I. Guseva Canu, A. Rogel, E. Samson, S. Benhamou, A. Laplanche, M. Tirmarche (2008). Cancer mortality risk among biology research workers in France: first results of two retrospective cohort studies. Int. Arch. Occup. Environ. Health. 81:777-85. I. Guseva Canu, G. Molina, M. Goldberg, P. Collomb, J.C. David, P. Perez et al. (2008). Development of a job exposure matrix for the epidemiological follow-up of workers in the French nuclear industry. Results of a pilot study. Rev. Epidem. Santé. Publ. 56:21-29. I. Guseva Canu, F. Paquet, M. Goldberg, B. Auriol, P. Bérard, P. Collomb et al. Comparative assessing for radiological, chemical, and physical exposures at the French uranium conversion plant: Is uranium the only stressor? Int. J. Hygiene. Environ. Health. (in press). S. Hoar (1983). Job exposure matrix methodology. Journal of Toxicology – Clinical Toxicology. 21:9-26. ICRP (1994). Publication 66. Human respiratory tract model for radiological protection. ICRP; Ann. ICRP. Vol. 26, No. 1. Oxford: Pergamon Press 1994. J.R. Landis, G.G. Koch (1977). The measurement of observer agreement for categorical data. Biometrics. 33:159-174. J.M. Last (1995). A dictionary of epidemiology. Oxford: Oxford University Press. Rapport Areva (2005). Procédure d’identification des dangers de l’évaluation et de la maîtrise des risques pour la santé et la sécurité au travail. Service Sécurité du travail et Radioprotection Areva NC établissement de Pierrelatte. Rapport Q03112AB. C. Rice, E.F. Heineman (2003). An asbestos job exposure matrix to characterize fiber type, length, and relative exposure intensity. Appl. Occup. Environ. Hyg. 18:506-12. B. Ritz, Y. Zhao, A. Krishnadasan, N. Kennedy, H. Morgenstern (2006). Estimated effects of hydrazine exposure on cancer incidence and mortality in aerospace workers. Epidemiology. 17:154-61. A. Rogel, N. Carre, E. Amoros, M. Bonnet-Belfais, M. Goldberg, E. Imbernon et al.(2005). Mortality of workers exposed to ionizing radiation at the French National Electricity Company. Am. J. Ind. Med. 47:72-82. A. Seidler, H. Heiskel, R. Bickeboller, G. Elsner (1998). Association between diesel exposure at work and prostate cancer. Scand. J. Work. Environ. Health. 24:486-94. M. Telle-Lamberton, D. Bergot, M. Gagneau, E. Samson, J.M. Giraud, M.O. Neron et al. (2004). Cancer mortality among French Atomic Energy Commission workers. Am. J. Ind. Med. 45:34-44. M. Telle-Lamberton, E. Samson, S. Caer, D. Bergot, D. Bard, F. Bermann et al. (2007). External radiation exposure and mortality in a cohort of French nuclear workers. Occup. Environ. Med. 64:694-700.

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Development of an instrumented phantom 3.6 to measure effective dose at workstations

Carmen VILLAGRASA, Julien DARRÉON, Radiological risk is assessed based on the A numerical feasibility study to determine Isabelle CLAIRAND, effective dose, E, a value used in radiation photon irradiation fields(1) demonstrated Ionizing Radiation Dosimetry Laboratory François QUÉINNEC protection to define the maximum limits the advantage of this type of instrument, External Dosimetry Department of individual exposure. To determine this based on calculations of effective dose

value, the dose absorbed by organs must be and individual dose equivalent Hp(10) for known, which implies that in theory it is the various types of radiation (that are not possible to measure effective dose standard and realistic for a given worksta- directly at workstations. Measurable quan- tion). 24 detection positions were defined tities, such as the individual dose equivalent inside the phantom to assess effective

Hp(10), were therefore defined in Report 51 dose within a 30% tolerance for energy by the International Commission on incident photons between 40 KeV and 4 Radiation Units and Measurements (Icru), MeV. to obtain accurate estimates of effective dose. Construction of the human-like phantom was part of new thesis work begun in This is the magnitude that is measured at November 2006. The first phase involved workstations using dosimeters worn on developing the detectors to be fitted inside the chest. The individual dose equivalent, the dummy. These detectors had to meet however, was defined for "standard", usu- specific requirements: compact in size ally simplified, exposure conditions. Given (a few cubic centimeters), a very low dose the characteristics in dosimeter response, rate detection threshold (on the order of it may, in certain situations, significantly 1 µSv/h), a linear energy response under- or overestimate effective dose, and (from 40 KeV to 4 MeV), and immediate thereby the radiological risk to the work- readout. Fiber optical sensors were selected er. A measuring instrument capable of for their ability to provide practically instant directly assessing the effective dose, E, remote readouts. A detector prototype was would make it possible to evaluate these developed (Figure 1) in cooperation with deviations. the particle physics laboratory in Caen (CNRS – IN2P3). The solution adopted by IRSN's Ionizing Radiation Dosimetry Laboratory consisted The detector consists of a 6 cm3 plastic of designing a human-like dummy equipped scintillator that emits a visible light propor- with detectors to measure the dose absorbed tional to the received dose. These photons by organs. The purpose was to build an are sent through a strand of optical fibers instrument that would directly measure to a photomultiplier tube, which converts effective dose, and in the final outcome them into an electrical signal. A program ensure that personal dosimeters were was developed using LabWindows-CVI to adequate for the exposure conditions manage the detection system, and record (1) Thesis by C. Furstoss, 2003-2006. encountered by exposed workers. and analyze data.

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Optical fiber Photocathode

Scintillator Photomultiplier tube Output signal

Figure 1 Diagram of dosimetry system prototype built into the dummy used to determine effective dose at workstations.

The prototype was characterized. The detec- that are a function of the incident photon tor was capable of measuring a dose rate of energy, so that the scintillator can be tuned approximately 1 µSv.h-1. Its response was to a degree of response equivalent to that stable, showing about 5% reproducibility, of human tissue. with background noise measured systematically before each measurement. Since a The second phase of this project, involving sub-response was observed for low-energy complete construction of the dosimeter- photons (less than 100 KeV), characteriza- equipped dummy, and running tests under tion under metrological conditions has been real-life conditions, is expected to be com- planned in order to define correction factors pleted at the end of 2009.

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New personal dosimeters 3.7 to monitor workers

Patrice FRABOULET French regulations require dosimetric ing the Institute's choice included the Dosimetric Monitoring Laboratory monitoring of workers exposed to ionizing extremely high-precision measurements radiation. External dosimetry involves achieved by RPL technology, as well as the assessing the individual dose received by wide range of dosimetry functions proposed: people who have been exposed to a field of readout capability, dose imaging, and pre- radiation (X-rays, gamma, beta, neutrons) cise information provided on the type of produced by an external radioactive source. radiation. This can be accomplished by wearing a personal dosimeter, which indicates the Comparative tests were conducted on the dose absorbed by the entire body or part various available dosimetry techniques. of the body, either in real time, using elec- Dosimetry based on the RPL technique tronic instruments (referred to as active or (Figure1) achieved greater performance for operational dosimetry), or at a later time, all criteria defined in the standards, i.e. by reading the dosimeter in a specially measurement accuracy, result reproduc- equipped laboratory. Regardless of the ibility, angular response, energy and dose system used, the dosimeter must be cho- response (Table 1). sen according to the type of radiation to which personnel will be exposed. The RPL dosimeter demonstrated certain metrological advantages. It can measure IRSN provides dosimetric follow-up for very low doses of just a few microsieverts nearly 151,000 workers in France, located (µSv), or very high doses (10 Sv or more), at roughly 17,000 sites, covering all sectors which makes this dosimeter appropriate for of activity: hospitals, clinics, research labo- both individual dosimetric follow-up and ratories, industrial plants, etc. The IRSN radiation monitoring in a work area or in dosimetric monitoring laboratory provides the environment, under both normal and and operates nearly 1,500,000 dosimeters accident exposure conditions. RPL technol- every year to fulfill this mission. ogy also offers high-precision measurements regardless of the radiation incident A new RPL dosimeter angle, a characteristic that is essential to After using radiographic film dosimetry for cover all the different geometric situations several years, and in response to new tech- in which dosimeter wearers may find them- nical and regulatory requirements, in 2006 selves. The possibility of creating an actual IRSN initiated a project to replace the film- digital image of the dose can provide infor- based instrument by a more powerful mation on worker exposure conditions, for dosimeter. Radiophotoluminescent (RPL) example whether exposure occurred just dosimeter technology was chosen, based once or repeatedly, or whether external on a technical study conducted by IRSN in contamination occurred via radioactive ele- preparing its technical specifications, and ments or objects (such as a pen) that may proposals submitted by the world's leading have been placed in front of the dosimeter, dosimeter suppliers. The main criteria guid- thereby interfering with measurement.

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TLD OSL RPL (thermo- (optically (radiophoto Film luminescent detection) stimulated luminescence) luminescence)

Detected energy range

Detection limit

Angular response

Repeat readings (Thermogram)

Dose imaging

Data on low-energy X- and gamma radiation

Data on b energy

* Test results on passive dosimeters available in France.

Table 1 Comparison of different dosimeters*.

Information on the type of radiation and Monitoring exposure to neutrons is techni- its energy level can also be obtained through cally difficult due to their specific nature. a special analysis performed on the detec- These particles are neutral with a very wide tor, in the event of confirmed exposure. All energy range, and the biological effects they this information can be read as many times produce are a function of their energy. as necessary. Improving metrology and dosimetry tech- A new laboratory was created to manufac- niques used to ensure radiation protection ture and operate the new dosimeter system. in the workplace is therefore a major chal- Located in Le Vésinet, it employs over 50 lenge, both in France and around the world. people and features a production line with Moreover, regulatory changes lowering a high degree of automation. With millions detection thresholds have made it necessary of the new RPL dosimeter already operating to implement a new generation of neutron in Japan, this instrument is obviously an ideal dosimeters. choice for any organization concerned by radiation protection .

Neutron dosimetry Every year in Europe, tens of thousands of workers are exposed to neutron radiation, often combined with gamma radiation. They operate in the nuclear industry (power plants, fuel manufacturing, transport and recycling), in military nuclear applications, research, radiotherapy and industrial use of certain radioactive sources.

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Electron Conduction band

RPL RPL Excitation Excitation

Irradiation Ag0 Ag++ luminescence luminescence UV Valence band

Electron trap

Figure 1 Luminescence refers to all physical light-emitting processes that occur spontaneously or in response to stimulation. In the dosimeter selected by IRSN, radiophotoluminescence is induced by silver-activated glass. Ionizing radiation (β, γ, or X) strips away electrons from the structure of the glass detector. These electrons are then trapped by impurities contained in the glass (silver ions). When placed under an ultraviolet beam, the trapped electrons emit an orange luminescence as they return to a lower energy level. The brightness of this luminescence is proportional to the dose received.

IRSN's passive neutron dosimeter is based tion technique. The PN3+ has measuring on a PN3-type trace detector. Work con- capabilities that meet regulatory require- ducted by the Institute to improve perfor- ments and offers features that can assess mance on this type of dosimeter was worker exposure conditions. This new dosim- completed in 2008. The outcome was a new eter was set into operation in January design, the "PN3+", capable of detecting 2009. thermal, intermediate, and fast neutrons, achieved by adding lithium-6 converting filters and cadmium screens (Figure 2).

The proposed result is a more sensitive dosimeter featuring expertise capability, designed for the neutron spectra commonly found in the nuclear industry or medical sector. Like the RPL, traces observed on the surface of the detector can be represented by images. They can also provide + information on the spectrum of the incident Figure 2 IRSN's PN3 , a more sensitive dosimeter featuring expertise neutron radiation and, in certain cases, on capability, designed for the neutron spectra commonly the angle of incidence. found in the nuclear industry or medical sector. The new PN3+ neutron dosimeter proposed by IRSN incorporates innovative functions that significantly enhance the conventional performance levels achieved using this detec-

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Key EVENTS and dates

Dissertations June 16, 2008 October 13, 2008 defended Céline Bourgier submitted a thesis on Stéphanie Lamart submitted a thesis "Study of the mechanisms involved in radiation- entitled "Study on the influence of radionuclide March 27, 2008 induced fibrogenic differentiation and anti- biokinetics on whole-body counts using voxel- Odile Carvahlo submitted a thesis on "Using fibrosis therapeutics" in Villejuif (Paris ized digital phantoms" in Saclay (Paris concepts from physical optics and image process- region). region). ing techniques to study acute radiation syndrome of the skin: correlation with results from biological September 29, 2008 October 15, 2008 and biophysical analyses" at the University of Irina Canu submitted a thesis entitled Blandine Vacquier submitted a thesis on Paris XII. "Epidemiological study on workers exposed to the "Analysis of mortality in a cohort of French the risk of absorbing uranium" at the University uranium miners" at the Paul Brousse Hospital May 16, 2008 of Paris VI. (Paris region). Moubarak Mouisedine submitted a thesis entitled "Use of human mesenchymal stem cells to treat radiation-induced tissue damage" in Paris.

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OTHER June 2008 December 2008 KEY events The 2008 Laurent EXMELIN scientific award Patent application filed for use of a calix- was attributed on June 20, 2008 to an IRSN arene-based nano-emulsion to decontaminate January 2008 thesis submitted by Noëlle Pierrat for research skin (healthy skin and wounds) contaminated Organization of the AM2008 EURADOS work conducted at the IRSN Internal Dose by actinides. Annual Meeting in Paris including the Winter Assessment Laboratory (LEDI), entitled "Vox School on "Retrospective dosimetry" and the elized digital phantoms associated with the workshop on "Dosimetric issues in the medical MCNP Monte Carlo code applied to realistic in use of ionizing radiation". vivo measurement of actinides in lungs and contaminated wounds". This award is attrib- February 2008 uted every year in recognition of a significant Publication of the second assessment report scientific contribution to radiotoxicology. on the stereotactic radiosurgery accident at the university medical center in Toulouse: October 2008 "Dosimetric and clinical assessment, risk anal- A five-year research project was initiated ysis". This report was submitted to the French between SDI and FMBC in Moscow (the former nuclear safety authority, the ASN. IBPh), which aims to improve methods for treating wounds after plutonium or americium April 2008 contamination, and to assess the associated Publication of a critical review of epidemio- dose. The main topics of study will include logical studies on leukemia incidence in children measuring contaminated wounds, the biokinet- and young adults living in the vicinity of nucle- ics involved, and treatment using DTPA. ar facilities.

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