Mortality Study of Los Alamos Workers With Higher Exposures to Plutonium

In 1974 the authors searched Los Alamos health physics records to find every worker carrying the largest amounts of plutonium inside the body. The search turned up 241 workers whose estimated internal deposit was 10 nanocuries or more. Deposits were calculated from plutonium in urine samples using a computer code called PUQFUA. This report follows the 224 white male workers in that group, tracks who died and of what, and extends an earlier report through April 1980. Follow-up on the group was 100 percent complete.

Deaths in the group were fewer than expected for United States white males of the same age and year of death. The standardized mortality ratio, a figure where 100 means the same death rate as the comparison population, was 56 for all causes, with a 95 percent confidence interval of 40 to 75. For all malignant neoplasms, meaning cancers, the ratio was 54, with a confidence interval of 23 to 106. The cancers most watched after plutonium exposure, in bone, lung, liver and the bone marrow and lymphatic systems, were rare or absent.

The authors credit the low rates mainly to selection effects rather than to any protection, including the healthier profile of employed people and the screening that came with security clearances and military service for some of the earliest workers. Current deposits in the male group ranged from under 1 nanocurie to 243 nanocuries, taken in mostly by breathing plutonium particles. Smoking histories came from living workers and from next of kin. The report says its data do not support the theory of a much higher lung cancer risk from smoking combined with insoluble plutonium.