Impact of considering non-occupational radiation exposure on the association between occupational dose and solid cancer among French nuclear workers
Résumé
Objectives The French nuclear worker cohort allows for the assessment of cancer risk associated with occupational radiation exposure. But workers are also exposed to medical and environmental radiation which can be of the same order of magnitude. This study intends to examine the impact of non-occupational radiation exposures in the dose-risk analysis between occupational radiation exposure and cancer mortality.
Methods The cohort includes workers employed before 1995 for at least one year by CEA, AREVA NC or EDF and badge-monitored for external radiation exposure. Monitoring results were used to calculate occupational individual doses. Scenarios of work-related X-ray and environmental exposures were simulated. Poisson regression was used to quantify associations between occupational exposure and cancer mortality adjusting on non-occupational radiation exposure.
Results The mean cumulative dose of external occupational radiation was 18.4 mSv among 59,004 workers. Depending on the hypotheses made, the mean cumulative work-related X-ray dose varied between 3.1 and 9.2 mSv and the mean cumulative environmental dose was around 130 mSv. The unadjusted excess relative rate of cancer per Sievert (ERR/Sv) was 0.34 [90%CI: -0.44–1.24]. Adjusting on environmental radiation exposure did not modify substantially this risk coefficient, but it was attenuated by medical exposure (ERR/Sv point estimate between 0.15 and 0.23).
Conclusions Occupational radiation risk estimates were lower when adjusted on work-related X-ray exposures. Environmental exposures had a very slight impact on the occupational exposure risk estimates. In any scenario of non-occupational exposure considered, a positive but not significant excess cancer risk associated to occupational exposure was observed.