CANCER MORTALITY IN RELATION TO MONITORING FOR RADIONUCLIDE EXPOSURE IN 3 UK NUCLEAR INDUSTRY WORKFORCES

Cancer mortality in 40 761 employees of three UK nuclear industry faci lities who had been monitored for external radiation exposure was exam ined according to whether they had also been monitored for possible in ternal exposure to tritium, plutonium or other radionuclides (uranium, polonium, actinium or other unspecified). Death rates from cancer wer e compared both with national rates and with rates in radiation worker s not monitored for exposure to any radionuclides, Among workers monit ored for tritium exposure, overall cancer mortality was significantly below national rates [standardized mortality ratio (SMR) = 83, 165 dea ths; 2P = 0.02] and none of the cancer-specific death rates was signif icantly above either the national average or rates in non-monitored wo rkers. Although the overall death rate from cancer in workers monitore d for plutonium exposure was also significantly low relative to nation al rates (SMR = 89, 581 deaths; 2P = 0.005), mortality from pleural ca ncer was significantly raised (SMR = 357, nine deaths; 2P = 0.002); no ne of the rates differed significantly from those of non-monitored wor kers. Workers monitored for radionuclides other than tritium or pluton ium also had a death rate from all cancers combined that was below the national average (SMR = 86, 418 deaths; 2P = 0.002) but prostatic can cer mortality was raised both in relation to death rates in the genera l population (SMR = 153, 37 deaths; 2P = 0.02) and to death rates in r adiation workers who had not been monitored for exposure to any radion uclide [rate ratio (RR) = 1.65; 2P = 0.03], Mortality from cancer of t he lung was also significantly increased in workers monitored for othe r radionuclides compared with those of radiation workers not monitored for exposure to radionuclides (RR = 1.31, 164 deaths; 2P = 0.01). For cancers of the lung, prostate and all cancers combined, death rates i n monitored workers were examined according to the timing and duration of monitoring for radionuclide exposure, with rates of radiation work ers not monitored for any radionuclide forming the comparison group. I n tritium-monitored workers, RRs for prostatic cancer varied significa ntly according to the number of years in which they were monitored (2P = 0.03). In workers monitored for plutonium exposure, RRs for all can cers combined increased with the number of years in which they were mo nitored (2P = 0.04) and with the number of years since first monitorin g (2P = 0.0003), There was little suggestion of systematic variation i n RRs for workers monitored for other radionuclides in relation to the timing or duration of monitoring, nor did it appear that their raised rates of cancer of the lung and prostate were explained by external r adiation dose. These analyses of cancer mortality in relation to monit oring for radionuclide exposure reported in a large cohort of nuclear industry workers suggest that certain patterns of monitoring for some radionuclides may be associated with higher death rates from cancers o f the lung, pleura, prostate and all cancers combined. Some of these f indings may be due to chance. Moreover, because of the paucity of rela ted data and lack of information about other possible exposures, such as whether plutonium workers are more likely to be exposed to asbestos , firm conclusions cannot be drawn at this stage. Further investigatio ns of the relationship between radionuclide exposure and cancer in nuc lear industry workers are needed.