A reanalysis of cancer mortality in Canadian nuclear energy workers
(1957–1994) based on revised exposure and cohort data
Abstract of the journal article published in British Journal of Cancer: November 2013
Lydia B. Zablotska, Rachel S.D. Lane (CNSC), Patsy A. Thompson (CNSC)
Background: A 15-country study of nuclear workers reported significantly increased radiation-related risks of all cancers excluding leukemia, with Canadian data a major factor behind the pooled results. We analyzed mortality (1957–1994) in the updated Canadian cohort and provided revised risk estimates.
Methods: Employment records were searched to verify and revise exposure data and to restore missing socioeconomic status. Excess relative risks per sievert (ERR/Sv) of recorded radiation dose and 95% confidence intervals (CIs) were estimated using Poisson regression.
Results: A significant heterogeneity of the dose-response for solid cancer was identified (p=0.02), with 3,088 early (1956–1964) Atomic Energy of Canada Limited (AECL) workers having a significant increase (ERR/Sv=7.87, 95%CI:1.88, 19.5), and no evidence of radiation risk for 42,228 workers employed by three nuclear power plant companies and post-1964 AECL (ERR/Sv=-1.20, 95%CI:<-1.47, 2.39). Radiation risks of leukemia were negative in early AECL workers and non-significantly increased in other workers. In analyses with separate terms for tritium and gamma doses, there was no evidence of increased risk from tritium exposure. All workers had mortality lower than the general population.
Conclusion: Significantly increased risks for early AECL workers are most likely due to missing dose data. Analyses of the remainder of the Canadian nuclear workers (93.2%) provided no evidence of increased risk, but the risk estimate was compatible with estimates that form the basis of radiation protection standards.
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