During 1957-1981, many civilian workers overhauled and repaired nuclear-propelled US Navy ships and submarines. Among these workers, the radiation workers had exposure to low-level radiation, and the other workers (non-radiation workers) had no exposure to low-level radiation. The cancer mortality rates in the radiation workers and non-radiation workers were compiled and reported in 2005 (Sponsler and Cameron, 2005). Table 4 of the paper shows the standardized mortality ratio (SMR) for cancer for the non-radiation workers and the radiation workers. For the non-nuclear workers, observed deaths due to cancer was 878 as compared to the 784.6 expected deaths, resulting in a SMR of 1.12 (95%CI: 1.06-1.20). For radiation workers, combining the data for the <5 mGy and >5 mGy groups, the observed deaths due to cancer was 846 as compared to the 886.53 expected, resulting in a SMR of 0.95 (95%CI: 0.89, 1.02). Taking the ratio of these two SMRs, the relative risk for cancer mortality following low-dose radiation exposure compared to no radiation exposure is 0.85 (0.79, 0.91). Since the comparison is between radiation workers and non-radiation workers, the healthy worker effect, which has been used to explain other studies of radiation workers showing reduction of cancer rates (Boice et al. , 2011; Boice et al. , 2014; Liu et al. , 2014; Kashcheev et al. , 2015; Zhivin et al. , 2016), would not be applicable for this study. References Boice JD, Jr., Cohen SS, Mumma MT, Ellis ED, Cragle DL, Eckerman KF, Wallace PW, Chadda B, Sonderman JS, Wiggs LD, Richter BS and Leggett RW. 2014. Mortality among mound workers exposed to polonium-210 and other sources of radiation, 1944-1979. Radiat Res 181: 208-28. https://www.ncbi.nlm.nih.gov/pubmed/24527690 Boice JD, Jr., Cohen SS, Mumma MT, Ellis ED, Eckerman KF, Leggett RW, Boecker BB, Brill AB and Henderson BE. 2011. Updated mortality analysis of radiation workers at Rocketdyne (Atomics International), 1948-2008. Radiat Res 176: 244-58. https://www.ncbi.nlm.nih.gov/pubmed/21381866 Kashcheev VV, Chekin SY, Maksioutov MA, Tumanov KA, Kochergina EV, Kashcheeva PV, Shchukina NV and Ivanov VK. 2015. Incidence and mortality of solid cancer among emergency workers of the Chernobyl accident: assessment of radiation risks for the follow-up period of 1992-2009. Radiat Environ Biophys 54: 13-23. https://www.ncbi.nlm.nih.gov/pubmed/25315643 Liu JJ, Freedman DM, Little MP, Doody MM, Alexander BH, Kitahara CM, Lee T, Rajaraman P, Miller JS, Kampa DM, Simon SL, Preston DL and Linet MS. 2014. Work history and mortality risks in 90,268 US radiological technologists. Occup Environ Med 71: 819-35. https://www.ncbi.nlm.nih.gov/pubmed/24852760 Sponsler R and Cameron JR. 2005. Nuclear shipyard worker study (1980-1988): a large cohort exposed to low-dose-rate gamma radiation. Int J Low Radiat 1: 463-478. http://www.inderscience.com/info/inarticle.php?artid=7915 Zhivin S, Guseva Canu I, Samson E, Laurent O, Grellier J, Collomb P, Zablotska LB and Laurier D. 2016. Mortality (1968-2008) in a French cohort of uranium enrichment workers potentially exposed to rapidly soluble uranium compounds. Occup Environ Med 73: 167-74. https://www.ncbi.nlm.nih.gov/pubmed/26655962
