A decline in mortality from prostate cancer in the UK Atomic Energy Authority workforce

Early epidemiological studies of the UKAEA workforce, which followed up the mortality of those who worked to the end of 1979, found a significant excess of prostate cancer deaths in some subsets of the cohort, particularly workers internally monitored for tritium contamination and those employed at the Winfrith laboratories. The excess seemed to be associated with work in heavy-water reactors. We have followed up the mortality in the UKAEA workforce to the end of 1997 and compared the mortality from prostate cancer in the years 1980–97 with the years to 1979. We found a significantly lower mortality from prostate cancer in the later years in many of the subsets of the cohort that were previously identified as high risk. There was no evidence of a continuing raised risk of prostate cancer in any subset. We considered two possible reasons why the observed risk might have declined. There is no evidence that any risk associated with heavy-water reactors would have abated in the later years or that the cohort would be less susceptible to prostate cancer. Our conclusion is that the original observation might have been a chance finding among many significance tests.