The association between prostate cancer and exposure to65Zn in UKAEA employees

In a recent case-control study among UKAEA employees an elevated incidence of prostate cancer was associated with potential exposure to 51 Cr, 65 Zn, 60 Co, 59 Fe and 3 H. The authors highlighted 65 Zn as the most likely carcinogen because zinc is concentrated in the prostate gland and the effective doses from its Auger electrons may be very high at short range. However, predictions from BEIR V models are that a radiation dose to the prostate of at least 17 Sv would be required to account for the observed risk of cancer. The authors calculate that the maximum conceivable intakes of 65 Zn over a 10 year period would only produce a dose of 216 mSv to the prostate gland even if they exaggerate the degree of concentration and the damaging effects of Auger electrons. Using more realistic assumptions, the authors arrive at a dose of only 7.2 mSv which is a factor of over 1000 too low. Similar calculations for the other radionuclides again leave the dose well short of that required to explain the observed risk. It is concluded that 65 Zn and the other activation products are merely markers for a working environment in which the risk is raised for other unidentified reasons.