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ATSDR Releases Health Assessment on Oak Ridge Iodine 131 Releases
Releases occurred during manufacturing of radioactive lanthanum from 1944-1956

For Immediate Release:
May 23, 2008

ATLANTA - The Agency for Toxic Substances and Disease Registry (ATSDR) announced that recently discovered evidence suggests Iodine-131 (I-131) releases occurring between 1944 and 1956 from the X-10 Site at the Oak Ridge National Laboratory (ORNL) did not extend beyond the facility boundary at levels that would constitute a public health hazard.

Iodine 131 is a radioactive isotope with an eight-day half-life released into the air during the manufacture of radioactive lanthanum at ORNL during the period in question. 

Historical air monitoring data from the 1950s and deer thyroid data collected between 1979 and 1989 were supplied to ATSDR during Public Health Assessment research of I-131 releases from the X-10 Site.  This finding differs from earlier computer modeling indicating the towns of Gallaher Bend and Bradbury may have been affected by releases.

While I-131 can contaminate soil, water, plants and animals, the most likely method of human ingestion of 1-131 would be from milk – particularly from cows and goats raised in backyards or pastures closest to the X-10 site. Individuals living near the X-10 site between 1944 and 1956 may have come in contact with I-131 primarily from drinking milk. 

The study also found that persons 21 years or older during the active release period were not exposed to I-131 at levels that would induce thyroid disease or thyroid cancer.  Individuals age 18 and under who consumed milk from local or backyard-grazed animals during the active period may have an increased risk of thyroid disease.  However, scientists cannot state with any degree of certainty what this risk might be – if any.

Because of the limitations with the currently available data and the large uncertainties associated with the previously modeled I-131 release estimates, the extent to which nearby off-site communities were affected by the I-131 releases in the past can not be determined at this time. Therefore, ATSDR cannot reach a definitive conclusion whether residential exposure to I-131 occurred at levels sufficient to cause harmful health effects.

ATSDR Recommendations

For more information about I-131 releases and the ATSDR Oak Ridge public health assessment visit or contact Jack Hanley at 770/ 488-0736 or call 1-800-CDC-INFO.


ATSDR, a federal public health agency of the U.S. Department of Health and Human Services, evaluates the human health effects of exposure to hazardous substances.

Members of the news media can request an interview by calling the NCEH/ATSDR Office of Communication at 770-488-0700.

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Updated May 23, 2008
For more information, contact ATSDR at:
770-488-0700 or e-mail (news media)

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