Cancer mortality in relation to monitoring for radionuclide exposure in three UK nuclear industry workforces

Our plain-English summary of Cancer mortality in relation to monitoring for radionuclide exposure in three UK nuclear industry workforces, by L.M. Carpenter, C.D. Higgins, A.J. Douglas, et al (British Journal of Cancer, 1998).

The study

• Authors: L.M. Carpenter, C.D. Higgins, A.J. Douglas, N.E. Maconochie, R.Z. Omar, P. Fraser, V. Beral, P.G. Smith
• Journal: British Journal of Cancer
• Published: 1998;78(9):1224-32
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Cancer mortality in 40,761 employees of three UK nuclear industry facilities who had been monitored for external radiation exposure was examined according to whether they had also been monitored for possible internal exposure to tritium, plutonium or other radionuclides (uranium, polonium, actinium or other unspecified). Death rates from cancer were compared both with national rates and with rates in radiation workers not monitored for exposure to any radionuclides. Among workers monitored for tritium exposure, overall cancer mortality was significantly below national rates [standardized mortality ratio (SMR) = 83, 165 deaths; 2P = 0.02] and none of the cancer-specific death rates was significantly above either the national average or rates in non-monitored workers. Although the overall death rate from cancer in workers monitored for plutonium exposure was also significantly low relative to national rates (SMR = 89, 581 deaths; 2P = 0.005), mortality from pleural cancer was significantly raised (SMR = 357, nine deaths; 2P = 0.002); none of the rates differed significantly from those of non-monitored workers. Workers monitored for radionuclides other than tritium or plutonium also had a death rate from all cancers combined that was below the national average (SMR = 86, 418 deaths; 2P = 0.002) but prostatic cancer mortality was raised both in relation to death rates in the general population (SMR = 153, 37 deaths; 2P = 0.02) and to death rates in radiation workers who had not been monitored for exposure to any radionuclide [rate ratio (RR) = 1.65; 2P = 0.03]. Mortality from cancer of the lung was also significantly increased in workers monitored for other 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 in monitored workers were examined according to the timing and duration of monitoring for radionuclide exposure, with rates of radiation workers not monitored for any radionuclide forming the comparison group. In tritium-monitored workers, RRs for prostatic cancer varied significantly according to the number of years in which they were monitored (2P = 0.03). In workers monitored for plutonium exposure, RRs for all cancers combined increased with the number of years in which they were monitored (2P = 0.04) and with the number of years since first monitoring (2P = 0.0003). There was little suggestion of systematic variation in 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 radiation dose. These analyses of cancer mortality in relation to monitoring 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 of the lung, pleura, prostate and all cancers combined. Some of these findings may be due to chance. Moreover, because of the paucity of related 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 investigations of the relationship between radionuclide exposure and cancer in nuclear industry workers are needed.

In plain English

This study examined cancer deaths to the end of 1988 among 40,761 radiation workers at the UK Atomic Energy Authority, the Atomic Weapons Establishment and British Nuclear Fuels' Sellafield plant. Workers monitored for internal intake of tritium, plutonium or other radionuclides were compared with national rates and with workers not monitored for any radionuclide, including later-monitored workers' time before first monitoring. Each monitored group had lower overall cancer death rates than national rates. Plutonium-monitored workers had raised pleural cancer death rates versus national rates (standardized mortality ratio 357, nine deaths; 100 equals the national rate), but no cancer death rate in this group was significantly higher than in comparison workers. All pleural cancer deaths were mesotheliomas. Lacking asbestos exposure data, the authors found this result difficult to interpret. Workers monitored for other radionuclides had higher lung cancer (rate ratio 1.31, 95% confidence interval 1.06 to 1.61) and prostate cancer (rate ratio 1.65, 1.03 to 2.65) death rates than comparison workers. The authors concluded that some findings may be due to chance and that firm conclusions cannot be drawn at this stage.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Cohort study of mortality in nuclear industry radiation workers. Radionuclide monitoring status was treated as time-dependent. The not-monitored comparison group included workers never monitored for any radionuclide and the time before first monitoring of workers who were monitored later. Death rates were compared with national rates (SMRs) and with this not-monitored group (rate ratios).
• Who was studied: 40,761 workers (37,395 male, 3,366 female) monitored for external radiation. They had worked at AEA establishments (Harwell with Culham and London, Dounreay, Winfrith) before 1980, at the AWE before 1983, or at the Sellafield plant of British Nuclear Fuels Limited before 1976. Deaths were followed up to the end of 1988.
• Exposure: Being monitored for possible internal exposure to tritium, plutonium, or other radionuclides (uranium, polonium, actinium or other unspecified; AEA and AWE workers only), alongside cumulative external radiation dose. Monitoring did not necessarily mean actual exposure. Asbestos exposure was not measured.
• Main results:
  • Plutonium-monitored workers had significantly raised pleural cancer mortality relative to national rates (SMR 357, nine deaths, 2P = 0.002). Their all-cancer SMR was 89 (581 deaths).
  • Plutonium-monitored workers had no specific cancers with death rates above those of workers not monitored for any radionuclide. They had significantly lower rates for cancers of the buccal cavity and pharynx and for thyroid cancer.
  • All pleural cancer deaths observed were mesotheliomas.
  • The study showed no suggestion of a relationship between pleural cancer and external radiation dose.
  • Workers monitored for other radionuclides had higher death rates than non-monitored workers for lung cancer (RR 1.31, 95% CI 1.06-1.61; 164 deaths) and prostate cancer (RR 1.65, 95% CI 1.03-2.65; 37 deaths). Their prostate cancer SMR versus national rates was 153 (95% CI 108-211).
  • In plutonium-monitored workers, rate ratios for all cancers combined rose with time since first monitoring: 0.79 under 10 years, 0.95 at 10-19 years and 1.20 at 20 years or more (trend 2P = 0.0003).
  • Tritium-monitored workers had overall cancer mortality below national rates (SMR 83, 165 deaths). Their three testicular cancer deaths were a significant excess relative to non-monitored workers (RR 8.37, 95% CI 1.48-43.14).
• The authors' conclusion: The authors concluded that certain patterns of monitoring for some radionuclides may be associated with higher death rates from cancers of the lung, pleura, prostate and all cancers combined. They added that some findings may be due to chance, that firm conclusions cannot be drawn at this stage, and that further investigation is needed.
• Limitations the authors state:
  • There were no data on asbestos exposure, which makes the excess of pleural cancer in plutonium-monitored workers difficult to interpret.
  • The analyses relied only on whether workers were monitored, not on estimated internal doses.
  • Testing 30 specific cancers across three monitoring categories raises multiple-testing problems.
  • Some findings rest on small numbers of deaths and may have arisen by chance.
  • For Sellafield workers, monitoring information covered only plutonium and tritium, and only the year of first monitoring.

Topics

Medical terms in this study, explained in our Lexicon: standardized mortality ratio (SMR), rate ratio, Pleura.

Related studies

• Malignant pleural mesothelioma risk among nuclear workers: a review — C. Metz-Flamant, I. Guseva Canu, et al. (2011)
• Cancer risks and low-level radiation in U.S. shipyard workers — G.M. Matanoski, J.A. Tonascia, et al. (2008)
• Mortality and cancer incidence of Australian participants in the British nuclear tests in Australia — R.T. Gun, J. Parsons, et al. (2008)
• Solid cancer mortality associated with chronic external radiation exposure at the French atomic energy commission and nuclear fuel company — C. Metz-Flamant, E. Samson, et al. (2011)
• Mortality rates among nuclear industry workers at Lucas Heights Science and Technology Centre — R.R. Habib, S.M. Abdallah, et al. (2005)
• Lung cancer in relation to employment in the electrical utility industry and exposure to magnetic fields — D.A. Savitz, V. Dufort, et al. (1997)

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