C. Metz-Flamant

External radiation exposure and mortality in a cohort of French nuclear workers

Objective: To analyse the effect of external radiation exposure on the mortality of French nuclear workers. Methods: A cohort of 29 204 workers employed between 1950 and 1994 at the French Atomic Energy Commission (Commissariat à l’Energie Atomique (CEA)) or at the General Company of Nuclear Fuel (COmpagnie GEnérale des MAtières nucléaires (Cogema, now Areva NC)) was followed up for an average of 17.8 years. Standardised mortality ratios (SMRs) were computed with reference to French mortality rates. Dose-effect relationship were analysed through trend tests and Poisson regression, with linear and log-linear models. Results: The mean exposure to X and gamma radiation was 8.3 mSv (16.9 mSv for exposed worker population). A total of 1842 deaths occurred between 1968 and 1994. A healthy worker effect was observed, the number of deaths in the cohort being 59% of the number expected from national mortality statistics. Among the 21 main cancer sites studied, a statistically significant excess was observed only for skin melanoma, and an excess of borderline statistical significance was observed for multiple myeloma. A dose-effect relationship was observed for leukaemia after exclusion of chronic lymphoid leukaemia (CLL). The relative risk observed for non-CLL leukaemia, n = 20, was 4.1 per 100 mSv (90% CI 1.4 to 12.2), linear model and 2.2 per 100 mSv (90% CI 1.2 to 3.3), log-linear model. Significant dose-effect relationship were also observed for causes of deaths associated with alcohol consumption: mouth and pharynx cancer, cirrhosis and alcoholic psychosis and external causes of death. Conclusion: The risk of leukaemia increases with increasing exposure to external radiation; this is consistent with published results on other nuclear workers cohorts.

Malignant pleural mesothelioma risk among nuclear workers: a review

Exposure to ionising radiation has been suggested as a causal risk factor for malignant pleural mesothelioma (MPM). Studies of patients treated by radiotherapy for primary cancers have suggested that radiation contributes to the development of secondary MPM. Here we examined the risk to nuclear workers of MPM related to exposure to low doses of occupational radiation at low dose rates. All results concerning MPM risk in published studies of nuclear workers were examined for their association with radiation exposure and potential confounders. We found 19 relevant studies. Elevated risks of pleural cancer were reported in most (15/17) of these studies. Eight reported risks higher for radiation monitored workers than for other workers. However, of 12 studies that looked at associations with ionising radiation, only one reported a significant dose-risk association. Asbestos was an important confounder in most studies. We conclude that studies of nuclear workers have not detected an association between ionising radiation exposure and MPM. Further investigations should improve the consideration of asbestos exposure at the same time as they address the risk of MPM related to occupational exposure of nuclear workers to low doses of ionising radiation at low dose rates.

Irradiations à faibles doses et risque de pathologie cardiovasculaire : revue des études épidémiologiques

BACKGROUND While cardiovascular risks associated with high level of ionizing radiation are well-established, long-term effects of low and medium levels of exposure, between 0 and 5 gray (Gy), on the cardiovascular system are debated. METHODS Available literature was reviewed considering various populations, such as survivors of atomic bombs, nuclear workers, Chernobyl liquidators, radiologists and radiological technologists and patients exposed for medical reasons. RESULTS A significant increased risk of cardiovascular diseases associated with low doses of ionizing radiation was observed in 13 studies among the 27 analyzed. The ischemic heart diseases risk was detailed in 16 studies and seven of them showed a significant increase. The cerebrovascular risk was significantly increased in five studies among the 12 considered. CONCLUSION Some epidemiological and experimental data are clearly in favour of an increased cardiovascular risk associated with exposure to low doses. However, given the multifactorial origin of cardiovascular diseases and the lack of a clear pathophysiologic mechanism, epidemiological results have to be carefully interpreted. Further research should be conducted in this area.

Revue généraleIrradiations à faibles doses et risque de pathologie cardiovasculaire : revue des études épidémiologiquesLow doses of ionizing radiation and risk of cardiovascular disease: A review of epidemiological studies

BACKGROUND While cardiovascular risks associated with high level of ionizing radiation are well-established, long-term effects of low and medium levels of exposure, between 0 and 5 gray (Gy), on the cardiovascular system are debated. METHODS Available literature was reviewed considering various populations, such as survivors of atomic bombs, nuclear workers, Chernobyl liquidators, radiologists and radiological technologists and patients exposed for medical reasons. RESULTS A significant increased risk of cardiovascular diseases associated with low doses of ionizing radiation was observed in 13 studies among the 27 analyzed. The ischemic heart diseases risk was detailed in 16 studies and seven of them showed a significant increase. The cerebrovascular risk was significantly increased in five studies among the 12 considered. CONCLUSION Some epidemiological and experimental data are clearly in favour of an increased cardiovascular risk associated with exposure to low doses. However, given the multifactorial origin of cardiovascular diseases and the lack of a clear pathophysiologic mechanism, epidemiological results have to be carefully interpreted. Further research should be conducted in this area.

Mortality Among Workers Monitored for Radiation Exposure at the French Nuclear Fuel Company

ABSTRACT A cohort of 9,285 nuclear workers employed at the French company AREVA NC specializing in the nuclear fuel cycle was established. Vital status, causes of death, employment characteristics and annual exposure to ionizing radiation were reconstructed for each individual over the time period 1977–2004. Standardized mortality ratios (SMRs) were computed using national mortality rates as an external reference. Tests for trends in mortality with duration of employment and cumulative external dose were performed. The all-cause and all-cancer mortality was significantly lower than expected from the French population. No significant excess among cancer sites studied was observed. Significant positive trends with cumulative dose were observed for colon and liver cancer and for respiratory diseases. Isolated significant trends should be carefully interpreted and considered in line with the large number of trend tests performed.

Cohorte des travailleurs du nucléaire à Électricité de France : mortalité des agents statutaires sur la période 1968–2003

BACKGROUND We conducted a mortality study on a cohort of French nuclear workers employed at Electricité de France (EDF). A first cancer mortality analysis had covered the period 1968-1994. This paper presents results from a mortality analysis including nine additional years of follow-up to cover workers employed from 1968 to 2003. METHODS The cohort includes 22393 workers, 97% of whom are males. Employment data were updated using the EDF personnel file. Vital status was ascertained using the French National Registry of Population, and further completed using EDF personnel and pension files. Causes of death were obtained from the National registry of causes of death. Standardised Mortality Ratios (SMR) were computed using national rates as references. Variations of all causes and all cancers SMRs were studied according to demographic and occupational characteristics. RESULTS At the study end point (31/12/2003), 74% of workers are still in active employment. Only 0.3% of workers are lost to follow-up. The median duration of follow-up is 20 years. Causes are ascertained for 96% of deaths. The total number of deaths is 874, 307 of which are cancer deaths. SMRs for all causes and cancers show a significant deficit compared to the French national mortality. No significant excess was observed for any of the cancer sites studied. Non-significant excesses are observed for pancreatic, pleural, kidney and brain cancer. Significant variations of all causes SMRs according to age at study entry and attained age are observed. Significant variations of all causes and all cancers SMRs according to diploma at employment are observed, with a reduced SMR for a higher level of diploma. CONCLUSION There is a significant deficit of mortality compared to the general population, reflecting a strong Healthy Worker Effect. Although nine years of follow-up were added, this cohort is made up of young workers, most of whom are still in active service. Regular updating of the follow up of this cohort is planned, aiming for an occupational health surveillance of workers occupationally exposed to ionizing radiation in France.

Exposition aux rayonnements ionisants et mortalité des travailleurs du CEA et de la Cogema

Resume Objectif Analyser les effets de l’exposition aux rayonnements ionisants sur la mortalite des travailleurs de l’industrie nucleaire. Methode Une cohorte de 29 204 travailleurs employes entre 1950 et 1994 au Commissariat a l’energie atomique (CEA) ou a la Compagnie Generale des Matieres nucleaires (Cogema, devenue Areva NC) a ete suivie pendant 17,8 ans en moyenne. La mortalite de la population a ete comparee a celle de la population francaise par la methode des rapports de mortalite standardises (SMR : Standardized Mortality Ratio). L’association entre l’exposition aux rayonnements ionisants et le risque de deces a ete analysee par des tests de tendance et par des regressions de Poisson. Resultats L’exposition moyenne cumulee aux rayons X et gamma a ete de 8,3 mSv sur la periode (16,9 mSv pour la population exposee). Un total de 1 842 deces est survenu entre 1968 et 1994, pour 3 117 deces attendus d’apres les statistiques de mortalite nationales. Parmi les 21 localisations de cancer etudiees, il a ete observe un exces statistiquement significatif de melanome malin et un exces de myelome multiple a la limite de la significativite. Une association entre l’exposition aux rayons X et gamma et le risque de leucemie (hors leucemie lymphoide chronique) a ete observee sur la base de 20 deces par leucemie. Le risque relatif estime pour une exposition de 100 mSv compare a une exposition nulle etait de 2,2, IC90 % = [1,2 ;3,3]. Des relations dose-effet statistiquement significatives ont egalement ete observees pour des causes de deces associees a la consommation d’alcool : cancer de la cavite buccale et du pharynx, cirrhose et psychose alcoolique, et causes externes de deces. Conclusion Le risque de leucemie croit avec la dose de rayons X et gamma au sein de la cohorte. Ceci est coherent avec les resultats deja publies sur l’epidemiologie des travailleurs du nucleaire.

Modelling leukemia risk associated to chronic external radiation exposure in a French cohort of nuclear workers

Objectives Leukemia is one of the first long term health effects to be noted after acute exposure to relatively high doses of ionising radiation. Leukemia mortality after external exposure at low doses and low-dose rates has been investigated at the French atomic energy commission (CEA) and nuclear fuel company (Areva NC). Methods The cohort includes monitored workers employed more than 1 year between 1950 and 1994 at CEA or Areva NC companies. Leukemia mortality after X and γ rays exposure was estimated using excess relative risk (ERR) models and time dependent modifying factors were investigated using time windows. Results More than 36 700 workers, followed-up for an average of 28 years, are included into the cohort. A total of 73 leukemia deaths occurred between 1968 and 2004. Among exposed workers, mean cumulative external dose per worker was 21.7 milliSievert (mSv). A significant association between leukemia mortality and dose has been observed with a 2-year lag time. The association was of larger magnitude for myeloid leukemia. ERR per Sv was larger between 2 and 15 years after exposure and no association was observed for doses received at exposure-rates lower than 10 mSv per year. Conclusions Analyses show a risk of leukemia after chronic external ionising radiation exposure in the French CEA-AREVA NC cohort. Results are consistent with those found in other nuclear workers studies. Further analyses of modifying factors should be conducted on the bases of pooled nuclear worker cohorts.