Mortality among male workers at a thorium-processing plant

Area of Science:

• Occupational Health
• Environmental Health
• Radiological Health

Background:

• Thorium's potential as an energy source necessitates understanding its long-term health impacts.
• Workers in thorium and rare earth chemical production may face unique occupational exposures.

Purpose of the Study:

• To evaluate the long-term mortality and morbidity associated with occupational exposure to thorium and related chemicals.
• To assess cancer and respiratory disease risks in a cohort of thorium chemical production workers.

Main Methods:

• A cohort of 3039 male workers employed between 1940-1973 was studied.
• Mortality data were ascertained via the Social Security Administration and compared to U.S. white male rates.
• A subgroup with potentially higher exposure received more intensive follow-up.

Main Results:

• Overall standardized mortality ratio (SMR) was 1.05; excess mortality noted for motor vehicle accidents, lung cancer (SMR=1.44), pancreatic cancer (SMR=2.01), and respiratory diseases (SMR=1.31).
• In a high-exposure subgroup, pancreatic cancer SMR was significantly elevated (4.13).
• Smoking habits may explain some excess lung and pancreatic cancer and respiratory disease mortality.

Conclusions:

• Occupational exposure to thorium and associated chemicals may increase risks for certain cancers and respiratory diseases.
• Smoking is a significant confounding factor requiring further investigation.
• Continued follow-up is crucial to fully elucidate long-term health effects.