The objective is to determine the risks of diseases related to chronic exposures
The studies conducted among the French Cohort of Uranium Miners aim to improve our knowledge of the diseases that could develop in the long term following chronic exposure to ionizing radiations at low doses. They will characterize the possible risk of mortality or morbidity for various diseases, particularly lung cancer, according to exposure to ionizing radiation and taking potential risk factors into account. The studies performed on the cohort are conducted for scientific purposes and are declared to the CNIL (French data protection agency).
Currently, in 2011, the cohort includes more than 5,000 men who have worked in the mining divisions of Crouzille (including Jouac), Forez, Vendée-Bretagne and Hérault for a period of at least one year between 1946 and 2000 (the last mine, Jouac, ceased operating in 2001). Administrative data (period of employment, type of work, place of work), vital status and, when relevant, causes of death are recorded for each miner. The recording of individual dosimetric data, imposed from 1956 onwards since the implementation of radiation protection standards in French mines, gives the annual occupational exposure of miners to radon, a radioactive gas coming from the decay of uranium, which emits alpha radiation. Annual exposure to uranium dust and external gamma radiation emitted by the surrounding ore were also measured. A retrospective reconstruction of radon exposure was performed by a group of experts with regard to miners recruited between 1946 and 1955. Based on this anonymous information, statistical analysis performed by the IRSN’s epidemiology laboratory is used to estimate the risks of mortality according to exposure to ionizing radiations.
The follow-up of the cohort continues, and will allow to collect new risk factors and new health data for the study of non-mortality risks. This extended follow-up will also allow the study to confirm (or not) any excess mortality observed in previous analyses, and allow the diseases that could develop in the long term to be studied.
The first cohort set up in the 1980s included a group of 1785 underground workers who worked prior to 1972 (Tirmarche 1993, Laurier 2004). Since then, the cohort has been extended to all individuals with 'miner' status in the CEA-COGEMA group. The vital status reconstruction performed to date, covering the period to December 31st 1999, has provided mean duration of the follow-up of 30 years and has recorded 1467 deaths.
The analyses carried out on the French cohort have not revealed any increase in overall mortality among uranium miners compared to the general population. An excess of deaths from lung cancer was however observed. This risk of death is associated to cumulative radon exposure (Vacquier 2008), remaining after adjustment for smocking habits (Leuraud 2007) and silicotic status (Amabile 2009), known risk factors for lung cancer. It was shown that the relationship between lung cancer risk and radon exposure was modified by the time since exposure, the exposure period, type of mine, and hard physical activity (Rogel 2002, Vacquier 2009). Excess deaths from kidney cancer were also observed (Vacquier 2008), but no association with the level of exposure to radon was found. An analysis of the cardiovascular risks was also performed (Nusinovici 2010).
The French cohort of uranium miners was also integrated in joint analyses in the context of international collaborations (Lubin 19941, BEIR 19992, Tomasek 2008). The French cohort recently participated in the European Alpha-Risk project coordinated by IRSN in the context of European joint research projects. The pooling of data from the three European cohorts (French, Czech and German) made it possible to conduct analyses on more than 50,000 uranium miners. The initial results can be viewed on the Alpha-Risk project website.
1Lubin JH, Boice JD, Edling C, Hornung R, Howe GK, E. Kusiak R (1994) Radon and lung cancer risk: A joint analysis of 11 underground miners studies. National Institutes of Health, National Cancer Institute ed. Washington,DC: NIH Publication N°94-3644.
2Committee on Health Risks of Exposure to Radon - National Research Council. (1999) Health effects of exposure to radon (BEIR VI): Washington DC: National Academy Press.