8291190 Occupational exposure to ionizing radiation and cardiovascular disease mortality among nuclear power plant workers in the Canadian national dose registry

<h3>Objective</h3> Findings from epidemiological studies suggest that low- to moderate ionizing radiation doses increase the risk of cardiovascular disease (CVD). However, the effects of lower doses, experienced in occupational settings, and of chronic exposures on CVD risks require further investigation. We examined the association between occupational exposure to ionizing radiation and the risk of CVD mortality among Canadian nuclear power plant (NPP) workers. <h3>Methods</h3> We assembled a retrospective cohort of 98,735 NPP workers from the Canadian National Dose Registry employed from 1961 onwards. Mortality was ascertained via record linkage to national vital statistics data through 2020. International Classification of Disease rubrics were used to classify CVD deaths based on the underlying cause of death. Whole-body dose measurements came from workplace personal monitoring. Standardized mortality ratios (SMRs) were estimated to compare the mortality experience of the NPP workers to the age-, sex- and calendar year-specific Canadian general population. Poisson regression and linear excess relative risk (ERR) models, adjusted for attained age, sex, and calendar period, were used for internal dose-response analyses. <h3>Results</h3> The mean whole-body lifetime accumulated exposure was 9.63mSv (SD=28.5). A total of 2,345 deaths from circulatory disease were identified during the follow-up, and of these, 1,440 and 340 were from ischemic heart disease and cerebrovascular disease, respectively. Compared to the general population, NPP workers had lower mortality rates with SMRs of 0.76 (95%CI: 0.73, 0.80), 0.78 (95%CI: 0.74, 0.82), and 0.79 (95%CI: 0.71, 0.88) for circulatory, ischemic heart disease, and cerebrovascular disease mortality, respectively. For cardiovascular disease (circulatory diseases excluding cerebrovascular disease), the ERR/100mSv was -0.16 (95%CI: -0.28, -0.04). <h3>Conclusion</h3> Our findings suggest that contemporary levels of occupational exposure to ionizing radiation do not increase the risk of cardiovascular mortality, but our results should be interpreted cautiously due to possible biases related to uncontrolled confounding and under-ascertainment of mortality. <h3>Funding</h3> This project was funded by Conexus Nuclear Inc.