Incomplete data on the Canadian cohort may have affected the results of the study by theInternational Agency for Research on Cancer on the radiogenic cancer risk among nuclearindustry workers in 15 countries

Abstract

In 1995 the International Agency for Research on Cancer (IARC) completed a studythat involved nuclear workers from facilities in the USA, UK and Canada. Theonly significant, though weak, dose-related associations found were for leukaemiaand multiple myeloma. The results for the Canadian cohort, which comprisedworkers from the facilities of Atomic Energy of Canada Limited (AECL), werecompatible with those for the other national cohorts. In 2005, IARC completed afurther study, involving nuclear workers from 15 countries, including Canada.In these results, the dose-related risk for leukaemia was not significant but theprominent finding was a statistically significant excess relative risk per sievert (ERRSv − 1) for ‘all cancers excluding leukaemia’. Surprisingly, the risk ascribed to the Canadiancohort for all cancers excluding leukaemia, driven by the AECL sub-cohort, wassignificantly higher than the risk estimate for the 15-country cohort as a whole. We haveattempted to identify why the results for the AECL cohort were so discrepant and had sucha remarkable influence on the 15-country risk estimate. When considering the issuesassociated with data on the AECL cohorts and their handling, we noted a striking feature:a major change in outcome of studies that involved Canadian nuclear workers occurredconcomitantly with the shift to when data from the National Dose Registry (NDR) ofCanada were used directly rather than data from records at AECL. We concluded thatan important contributor to the considerable upward shift in apparent risk inthe 15-country and other Canadian studies that have been based on the NDRprobably relates to pre-1971 data and, in particular, the absence from the NDR ofthe person-years of workers who had zero doses in the calendar years 1956 to1970. Our recommendation was for there to be a comprehensive evaluation ofthe risks from radiation in nuclear industry workers in Canada, organisation byorganisation, in which some of the anomalies that we have identified might beaddressed.