Does uranium induce circulatory diseases? First results from a French cohort of uranium workers.

OBJECTIVES Increased risk of circulatory system diseases (CSDs) was observed in nuclear workers handling uranium and plutonium in Russia and the UK. This work examines the CSD mortality after chronic intake of uranium among 2897 workers (79,892 person-years) at a uranium processing plant (1960-2006) in France. METHODS Cumulative exposure to different uranium compounds, classified by their isotopic composition and solubility type, was quantified on the basis of a plant-specific job-exposure matrix and individual job histories. HRs and associated 95% CI for CSD (n = 111) and specific CSD categories were estimated using Cox regression models, stratified on sex and birth cohort and adjusted for potential confounders. The effect of smoking was analysed among 260 smokers (42 CSD deaths). RESULTS Compared to unexposed workers, CSD mortality was increased among workers exposed to slowly soluble reprocessed uranium (RPU) (HR = 2.13, 95% CI = 0.96 to 4.70) and natural uranium (HR = 1.73, 95% CI = 1.11 to 2.69). The risk increased with cumulative exposure and exposure duration. In the subgroup of smokers, the risk estimates were higher but with larger CIs: HR=1.91 (95% CI = 0.92 to 3.98) for natural uranium and HR = 4.78 (95% CI = 1.38 to 16.50) for RPU. CONCLUSIONS The authors observed that exposure to slowly soluble uranium, namely RPU, may increase the risk of CSD mortality. However, these results are preliminary since the study is lacking statistical power and many other biological and lifestyle-related factors may cause CSD. More detailed investigations are necessary to confirm these findings and analyse in depth the effects of internal radiation exposure on the circulatory system.