Relationship between occupational exposure to ionizing radiation and mortality at the French electricity company, period 1961-2003

Epidemiological studies in nuclear industry workers can produce relevant information to better appreciate the health risks related to chronic external exposure to low doses of ionizing radiation (IR). This work examined the relations between exposure to IR and mortality in workers at the French Electricity Company (EDF), followed up to year 2003. Permanent staff who had worked for at least 1 year at EDF during period 1961-1994 and who had been monitored for exposure to IR were included (n = 22,393). One-sided trend tests for mortality according to cumulative dose and relative risks at 100 mSv were estimated using Poisson regression. Main analyses were stratified on age, sex, calendar time and education. A total of 874 deaths occurred, and 66 workers were lost to follow-up. Median age at end of follow-up was 48. None of the causes of death investigated increased significantly according to dose, except cerebrovascular diseases (p = 0.01), but this last observation was based on only 22 cases. These results do not allow dismissing a possible influence of IR on cancer risk in this population. The cohort is still relatively young and therefore confidence intervals for estimated relative risks remain wide, although they have considerably narrowed since a previous analysis. Chance is a possible explanation for the association between IR and cerebrovascular mortality, due to the low number of cases on which it is based. These results thus need to be stabilized by conducting joint analyses with similar cohorts.