Cancer risks and low-level radiation in U.S. shipyard workers

Area of Science:

• Occupational Health
• Radiation Epidemiology
• Cancer Research

Background:

• Shipyard workers involved in nuclear ship overhauls face potential occupational hazards.
• Previous studies suggest links between radiation exposure and cancer, but data on low-level, protracted exposures are less clear.

Purpose of the Study:

• To investigate cancer risks, including leukemia, lymphopoietic cancers (LHC), lung cancer, and mesothelioma, in nuclear shipyard workers.
• To analyze the dose-dependent relationship between radiation exposure and cancer incidence in this cohort.

Main Methods:

• A cohort study of 28,000 workers with >= 5.0 mSv, 10,462 workers with < 5.0 mSv, and 33,353 non-nuclear workers.
• Dose-dependent risk analyses were performed, comparing high exposure groups to lower exposure groups.
• Relative risks were calculated for specific cancers based on radiation dose.

Main Results:

• Nuclear workers had lower leukemia and LHC mortality than US white males but higher lung cancer and a five-fold excess of mesothelioma.
• Cancer risk increased with exposure above 10.0 mSv.
• While most increased risks were not statistically significant, a trend of increasing risk with higher radiation exposure was observed for leukemia, LHC, lung cancer, and mesothelioma.

Conclusions:

• Low-level, protracted gamma-ray exposure may be associated with increased risks of certain cancers in nuclear shipyard workers.
• Asbestos exposure is a significant co-factor, particularly for mesothelioma risk.
• Further follow-up is needed to refine risk estimates for this population and for comparison with other cohorts.