The News Flag
Wednesday, July 9, 1997

Death rates consistent with U.S.

Last modified at 12:00 p.m.
on Friday, July 11, 1997

by Mark Newbold Neal
Oak Ridger staff

A study led by two Oak Ridge researchers revealed that mortality rates for people employed on the Oak Ridge Reservation between 1943 and 1985 were consistent with national averages.

Donna Cragle, an epidemiologist at Oak Ridge Associated Universities and one of the researchers for the study, says the similarity between mortality rates of the Oak Ridge workers and national averages for this period is a "little bit unusual."

"We would expect the rates for Oak Ridge workers to be lower than the national standard because of the 'healthy worker effect,' " Cragle said. She said the standardized mortality analysis for the nation includes those who cannot work, such as the sick and disabled, and should thus be higher than those for Oak Ridge workers.

The study continues a mission that the Department of Energy started years ago to examine the effects of radiation exposure on the nuclear workers compared to national averages. The study was picked up in 1994 by the National Institute of Occupational Safety and Health, which then contracted with ORAU to conduct the research.

Cragle and Ed Frome, a statistician at DOE's Oak Ridge National Laboratory, collaborated with epidemiologists from the University of North Carolina to study 106,020 workers who worked for at least 30 days at one of the Oak Ridge facilities (ORNL, the Oak Ridge K-25 Site and the Oak Ridge Y-12 Plant). Nearly 28,000 of these workers died before the end of 1984, the cutoff for statistical records.

Cragle said the study was the first of its kind to compare mortality patterns among a number of facilities. However, she said, this was only one of the study's objectives; the study included minorities for the first time and also focused on changes in mortality relative to increasing radiation dose.

In the comparison of mortality at the various Oak Ridge facilities, the researchers studied only the white male workers. The results showed that workers at K-25 had the highest death rate from both cancer and non-cancer causes.

Cragle said the most noticeable difference, however, was in the non-cancer deaths at K-25, which were much higher than at the other Oak Ridge facilities. In response to questioning, she said the increase at K-25 could be due to chemical exposures, which were not considered in the study. She suggested that further studies including workers from 1984 and beyond would be necessary to draw such conclusions.

In her conclusions, Cragle stated that this study was most important as a benchmark for further studies of how diseases and death patterns compare at DOE facilities.

Robert Rinsky, senior research epidemiologist with NIOSH, said that more facility-wide studies of disease patterns in DOE workers will follow in the coming years.

Other findings from the study include:


* The death rates among all Oak Ridge workers from diseases of the digestive system (both malignant and non-malignant) and diseases of the circulatory system were substantially lower than the national rates.


* Among white males, lung cancer deaths were 18 percent higher than national averages, and deaths from respiratory diseases were 12 percent higher. Frome said the study did not include data on workers' smoking habits, which could be a cause of death from lung cancer.


* Nonwhite males showed a 73-percent higher death rate from cancer of the large intestine.


* Both white and non-white females were found to have mortality patterns consistent with national averages.


* Lung cancer death rates were higher among Y-12 and K-25 workers than ORNL workers.


* Leukemia death rates were higher for ORNL workers than those at Y-12 and K-25.


* A specific study of the white males at ORNL and Y-12 revealed a correlation between radiation dose and cancer death rate. As cumulative external dose increased, so did the cancer death rate.

Copyright 1997 The Oak Ridger


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