Key Issues
Radiation Safety at Nuclear Power Plants: Studies Look at Public, Workers
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Oak Ridge Study. A study conducted for the Oak Ridge Associated Universities by Steven Wing of the University of North Carolina was published in 1991. The study looked at the 1,524 deaths from all causes among the 8,318 white males hired at Oak Ridge National Laboratory between 1943 and 1972. When compared with all U.S. white males, the Oak Ridge workers had lower than average mortality risks for most causes of death. The study identified 346 cancer deaths among the workers, whereas 438 normally would be expected. The exception was leukemia: Oak Ridge workers were at a 63 percent higher risk of death than all white males. There were 28 deaths from leukemia, whereas 17 normally would be expected.
The same workers had been the subject of an earlier study, which found no increased leukemia risks and no association between cancer mortality and occupational exposures to radiation and other substances. The researchers had no explanation for the difference between the studies. The study does observe an apparent statistical association, but there was insufficient data to conclude that low-level radiation exposure caused the higher than anticipated deaths from leukemia. The study did not take into account possible exposures to hazardous materials, smoking habits or lifestyles.
Navy Shipyard Workers. A study by researchers at The Johns Hopkins University, released in 1991, found no evidence that the workers who serviced nuclear-powered ships for the U.S. Navy between 1957 and 1981 were harmed by their on-the-job exposure to low levels of radiation.
Commissioned by the U.S. Department of Energy, the study examined the records of 70,000 civilian male workers employed at two private and six naval shipyards. The group included 38,220 workers who were exposed to low levels of radiation while on the job, and 32,510 nonexposed workers. The cancer death rate among the radiation-exposed shipyard workers (most of whom accumulated exposures of greater than 500 rem) was lower than among the nonexposed workers and slightly lower than the rate for the U.S. white male population.
The rate for leukemia, specifically, was slightly lower than expected—both among the exposed and nonexposed shipyard workers. In addition, the overall death rate among radiation-exposed shipyard workers was significantly lower than the rate for U.S. white males.
The last finding is not unexpected, since worker populations in general tend to have below-average mortality rates. This is because workers must be healthy to be hired, and they must remain healthy to continue their employment.
Stewart-Kneale Studies. British epidemiologists Alice Stewart and George Kneale published 1977, 1981 and 1993 studies on the effects of low radiation doses on workers at DOE’s Hanford, Wash., nuclear complex. The 1981 analysis covered workers who died no later than 1977. The 1993 analysis included deaths from 1944 through 1986.
Among the questionable 1993 findings: 200 of the workers died or will die from radiation-induced cancer; older workers were at greater risk than younger workers; and doses as low as that from natural background radiation may be more harmful than implied in current radiation exposure standards for workers and the public.
Questions raised about the study’s validity include:
Oak Ridge Study. A study conducted for the Oak Ridge Associated Universities by Steven Wing of the University of North Carolina was published in 1991. The study looked at the 1,524 deaths from all causes among the 8,318 white males hired at Oak Ridge National Laboratory between 1943 and 1972. When compared with all U.S. white males, the Oak Ridge workers had lower than average mortality risks for most causes of death. The study identified 346 cancer deaths among the workers, whereas 438 normally would be expected. The exception was leukemia: Oak Ridge workers were at a 63 percent higher risk of death than all white males. There were 28 deaths from leukemia, whereas 17 normally would be expected.
The same workers had been the subject of an earlier study, which found no increased leukemia risks and no association between cancer mortality and occupational exposures to radiation and other substances. The researchers had no explanation for the difference between the studies. The study does observe an apparent statistical association, but there was insufficient data to conclude that low-level radiation exposure caused the higher than anticipated deaths from leukemia. The study did not take into account possible exposures to hazardous materials, smoking habits or lifestyles.
Navy Shipyard Workers. A study by researchers at The Johns Hopkins University, released in 1991, found no evidence that the workers who serviced nuclear-powered ships for the U.S. Navy between 1957 and 1981 were harmed by their on-the-job exposure to low levels of radiation.
Commissioned by the U.S. Department of Energy, the study examined the records of 70,000 civilian male workers employed at two private and six naval shipyards. The group included 38,220 workers who were exposed to low levels of radiation while on the job, and 32,510 nonexposed workers. The cancer death rate among the radiation-exposed shipyard workers (most of whom accumulated exposures of greater than 500 rem) was lower than among the nonexposed workers and slightly lower than the rate for the U.S. white male population.
The rate for leukemia, specifically, was slightly lower than expected—both among the exposed and nonexposed shipyard workers. In addition, the overall death rate among radiation-exposed shipyard workers was significantly lower than the rate for U.S. white males.
The last finding is not unexpected, since worker populations in general tend to have below-average mortality rates. This is because workers must be healthy to be hired, and they must remain healthy to continue their employment.
Stewart-Kneale Studies. British epidemiologists Alice Stewart and George Kneale published 1977, 1981 and 1993 studies on the effects of low radiation doses on workers at DOE’s Hanford, Wash., nuclear complex. The 1981 analysis covered workers who died no later than 1977. The 1993 analysis included deaths from 1944 through 1986.
Among the questionable 1993 findings: 200 of the workers died or will die from radiation-induced cancer; older workers were at greater risk than younger workers; and doses as low as that from natural background radiation may be more harmful than implied in current radiation exposure standards for workers and the public.
Questions raised about the study’s validity include:
- First, a 1992 study by the U.K. Radiological Protection Board of 95,000 nuclear power plant workers—who had received greater occupational doses than the Hanford employees—showed no excess cancers whatever.
- Second, Stewart and Kneale’s results could have been marred by a flaw in their previous studies, in which they ignored exposures of workers to potential carcinogens besides radiation.
- Third, if doses as small as those in the Stewart study affected cancer rates, then 5 million residents of Colorado, where the natural radiation level is high because of the altitude, should show 50,000 excess cancer deaths over their lifetime. But between 1950 and 1988, Colorado residents experienced fewer—not more—leukemia deaths than people at sea level.
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