Thesis: Studies of workers exposed to ionizing radiation enable the characterization of health effects resulting from chronic low-dose exposure. Although extensive research has been carried out on the subject, there are still uncertainties surrounding the quantification of these effects. To date, medical workers represents the largest group of workers occupationally exposed to artificial sources of ionizing radiation. Their subsequent risk of various pathologies is therefore an important subject of study. Nevertheless, the conclusions of these studies are uncertain and debated, particularly regarding the risk of developing tumors of the central nervous system (CNS).Based on literature reviews supported by meta-analyses and on statistical analyses of data collected as part of the epidemiological follow-up of the ORICAMs (Occupational Radiation Induced Cancer in Medical staff) cohort, this thesis aims to improve knowledge of the effects of ionizing radiation on health in the context of low-dose exposure.A mortality analysis was carried out on the ORICAMs cohort, including 164 015 medical workers occupationally exposed to ionizing radiation in France, presenting at least one dosimetric record between 2002 and 2012. Mortality was significantly lower in the ORICAMs cohort than in the general population. However, these results based on a comparative analysis with national rates may be influenced by the healthy worker effect, and do not allow to conclude on the existence or not of a potential relationship between occupational exposure and the risk of death. To address this issue, a case-control study nested within the ORICAMs cohort was set up, including 33 cases and 160 controls. However, conditional logistic regression analyses showed no dose-response relationship between occupational exposure to ionizing radiation and death from CNS tumors. An extension of the cohort follow-up and the inclusion of the case-control study in the international BECOME project will increase the statistical power of the analyses, allowing the assessment of the long-term effects of chronic exposure to low doses of ionizing radiation.