Researchers assessing fallout of pre-'56 X-rays at K-25

[Susan Gawarecki <loc@ICX.NET>]

Researchers assessing fallout of pre-'56 X-rays at K-25 

July 2, 2001

By Frank Munger News-Sentinel

                    

While conducting a study of deaths from multiple myeloma among workers

at the K-25 plant in Oak  Ridge, researchers identified a source of

radiation not considered in earlier projects that looked at occupational

illness -- medical X-rays. 



In particular, the research team from NIOSH (National Institute for

Occupational Safety and Health) became interested in K-25's use of

photofluorography for chest X-rays of workers until 1956, when an

equipment switch was made to the conventional technique still in use. 



The photofluorographic technique, which produced an image of the chest

on a fluorescent screen, reportedly delivered a radiation dose to the

bone marrow that was about 100 times greater than today's X-ray method

(800 millirads vs. 8 millirads). 



Dr. John Cardarelli, the principal investigator for NIOSH, said

researchers raised questions when they came across X-ray films at Oak

Ridge that were a different size (4-by-10 inches) than the conventional

film size (14-by-17). The smaller images are associated with

photofluorography. 



The health implications of the discovery are not clear, but the NIOSH

team felt the information was potentially significant enough to alter

risk estimates for K-25 employees whose work records showed relatively

low-dose radiation histories. Indeed, based on a limited study of 45

workers, the exposures from the work-related chest X-rays dwarfed the

amount of radiation received from occupational activities at the

uranium-enrichment plant. 



"This is a very small study," Cardarelli cautioned. 



Nonetheless, NIOSH determined that if this information were excluded

from an epidemiological study, many of those nuclear workers at K-25

would have been placed in "inappropriate" dose categories. 



That's why the team went ahead and reported this issue in a separate

paper, even though the major study of mortality rates from multiple

myeloma at K-25 won't be completed for at least another year. 



Cardarelli said NIOSH researchers planned to use the medical X-ray

information in current epidemiological studies and address questions

about the historical use of photofluorography in upcoming projects. 



All the government's World War II-era nuclear facilities, including Y-12

and X-10 in Oak Ridge, used the photofluorographic technique because it

was an economical way to get chest images in large quantity, Cardarelli

said. He said he didn't know when the other facilities abandoned the use

of photofluorography. 



"It all depends on when they purchased new X-ray equipment, which is not

something that is purchased very often," he said. 



The NIOSH researcher said the photofluorographic technique was widely

used in the general population for tuberculosis screening. 



Cardarelli said the dose information from medical X-ray records would

probably have more impact on  studies of workers at relatively low-level

radiation facilities, such as K-25, than at facilities in Hanford,

Wash., where workers historically received higher radiation exposures. 



Of course, this new information also raises questions about previous

studies done at K-25 and the other Oak Ridge facilities. How much would

this have changed the radiation-dose profiles of Oak  Ridge workers?

Would it alter risk estimates? 



According to the NIOSH report, previous studies of nuclear workers have

not included radiation exposures from work-related X-rays for several

reasons. For instance, there was a "perception" that the contribution

from chest X-rays would be low compared to other sources of radiation at

the plant, and "epidemiologists have traditionally assumed that

exposures from work-related X-rays would be randomly distributed

throughout the working population, so that effects associated with this

exposure would not influence the analysis." 



The research team discounted both of those assumptions. 



The chest X-rays actually turned out to be the biggest radiation source

for some workers, and documents indicated that radiation workers

typically received more chest X-rays than other, nonexposed workers,

NIOSH said. 

-- 

.....................................................

Susan L. Gawarecki, Ph.D., Executive Director

Oak Ridge Reservation Local Oversight Committee

                       -----                       

A schedule of meetings on DOE issues is posted on our Web site

http://www.local-oversight.org/meetings.html - E-mail loc@icx.net

.....................................................

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