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.

[Causes of death of COGEMA active workers, 1980-1995]. / Causes de décès des travailleurs actifs de la COGEMA, 1980-1995.

BACKGROUND: Populations exposed to risks at work show a deficit in deaths in comparison with the national population, the "healthy worker effect". This effect has been observed among former nuclear workers. The aim of our cross-sectional study was to evaluate the mortality in a metallurgy worker population, and to study the impact of the choice of the reference population on the estimation of the Standardized Mortality Ratio (SMR). METHODS: The studied population was the COGEMA Metallurgy Department workers, aged 25 years to 64, during the period 1980-1995 in two regions of France (North--La Hague; South--Cadarache, Marcoule, Miramas and Pierrelatte). In order to account for geographical variability and the difference in mortality between the working population and the non-working population, we used several reference populations: national population, regional population, "working" national population (farmers not present in COGEMA and non-workers excluded), and "working" regional population. RESULTS: All SMRs were increased when we used a "working" regional reference compared with the national reference population. Among men, eight pathologies presented a significant deficit with a national reference, whereas only two pathologies showed a deficit with the "working" regional reference. CONCLUSION: The use of a reference population close to the study population enabled us to reduce the Healthy Worker Effect among metallurgy workers at COGEMA plants.