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.
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