Most dose-response analyses were based on unadjusted doses with a ten year lag. There was no evidence for an association between leukemia deaths (based on a two year lag) and external radiation dose. Except for those born after 1930, leukemia mortality rates at X-10 were higher than those for U. S. white males and higher than those for similar Y-12 and multiple facility workers (see Table VII). See the next to last paragraph of this section for further discussion of leukemia rates. Prostate cancer rates were elevated relative to the U. S. rates and are about two times higher in workers with any amount of recorded external doses relative to those who received no occupational dose (see Fig. 2D). There was, however, no evidence for a smoothly increasing dose-response for prostate cancer. Two studies of UK workers have reported statistical associations between radiation dose and mortality from cancer of the prostate [31,27]. Cardis and colleagues , however, note that more recent studies indicate that the association with external dose was largely a result of correlation between external radiation and radionuclide contamination.