Cancer mortality at a Naval Nuclear Shipyard

Area of Science:

• Occupational Health
• Radiation Epidemiology
• Public Health

Background:

• A five-fold increase in leukaemia mortality was reported among workers exposed to ionising radiation at Portsmouth Naval Shipyard (PNS).
• This prompted a retrospective cohort mortality study to investigate potential radiation risks in this occupational setting.

Purpose of the Study:

• To evaluate the reported increase in leukaemia mortality among PNS workers exposed to ionising radiation.
• To compare leukaemia mortality rates between radiation-exposed workers, non-radiation workers, and those with no measurable exposure.

Main Methods:

• A retrospective cohort mortality study of civilian workers employed at PNS between 1952 and 1977.
• Ascertainment of vital status for 96% of workers and comparison of observed mortality with expected rates for US White males.
• Analysis of three subcohorts: radiation-exposed workers, non-radiation workers, and radiation workers with no measurable exposure.

Main Results:

• No excess mortality due to leukaemia or any other cause was observed in radiation-exposed workers.
• The standardized mortality ratio for leukaemia among radiation workers was 84 (95% CI, 34–174), indicating no significant excess.
• No dose-response relationship between radiation exposure and mortality was found, nor increased mortality in radiation over non-radiation workers.

Conclusions:

• The study found no evidence to support the reported increase in leukaemia mortality among workers exposed to ionising radiation at PNS.
• Limitations include a short latency period for a significant portion of the cohort (53% with <15 years).
• Further research with longer latency periods may be warranted to fully assess long-term radiation risks.