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News from the National Academies
Date: Oct. 20, 1999
Contacts: Neil Tickner, Media Relations Officer
Megan O'Neill, Media Relations Assistant
(202) 334-2138; e-mail <news@nas.edu>

[ EMBARGOED: NOT FOR PUBLIC RELEASE BEFORE 11 A.M. EDT WEDNESDAY, OCT. 20 ]

Publication Announcement

Interpretation of 'Atomic Vets' Death Rates Limited by Challenges
Of Conducting Retrospective Epidemiological Studies

Ever since 1976, when a veteran of a 1957 nuclear test in Nevada claimed that he developed leukemia as a result of his exposure to the radiation, veterans and their families, scientists, and the public have struggled to determine if there is a connection between participation in the tests and adverse health effects. In a new study, one of the largest of its kind, the Institute of Medicine (IOM) of the National Academies looked into the causes and rates of death among the nearly 70,000 soldiers, sailors, airmen, and marines who participated during the 1950s in at least one of five groups of atmospheric nuclear tests chosen for examination. These servicemen were present at tests conducted in the Nevada desert or in the South Pacific; some 30 percent have since died. The question that remains is whether some number of deaths may have been attributable to radiation exposure.

The researchers at the Medical Follow-up Agency of the IOM looked at whether participants' death rates were higher than those of a comparison group of nearly 65,000 military personnel serving at the same time but not involved in the tests. They did not examine differences in nonfatal disease or injury.

The difficulties in doing such a retrospective epidemiologic study are manifold: Many years have passed since the tests, and the extent to which each serviceman was exposed is extraordinarily hard to determine because of the limited amount of exposure data collected at the time.

By beginning with the most complete lists of participants to date, identifying a comparable group of servicemen who did not participate in nuclear bomb blasts, and tracking death certificates through various sources, the researchers were able to draw this general conclusion: There is no difference between the two groups in overall death rates or in total deaths from cancer.

The researchers also investigated specific causes of death. When looking at leukemia, participants in the nuclear tests had a 14 percent higher death rate than those in the comparison group. But the study report points out that this difference is not statistically significant, meaning that the results may be due to chance.

Because leukemia was originally singled out as a primary target for investigation, the researchers also looked at subcategories of participants. For example, land-based participants -- those in the Nevada desert -- had a death rate from leukemia that was 50 percent higher than military personnel in similar units who did not take part in atomic tests. Sea-based test participants in the South Pacific, however, did not differ from their comparison group in leukemia deaths.

The leukemia findings are consistent with those of other studies of atomic test participants, the study group said. That is, the handful of other studies conducted have found slightly increased rates of leukemia.

The study report also points out some unanticipated results regarding two other kinds of cancer -- prostate and nasal. Deaths from prostate cancer were 20 percent higher among test participants than the comparison group, and even higher for nasal cancer. The prostate cancer findings have not been consistently seen in other studies of people exposed to radiation and are therefore difficult to interpret. The nasal cancer finding is even harder to interpret, in part because this is the first study of atomic test participants to look specifically for that cause of death. To date, nasal cancer has not been among the cancers considered to be caused by radiation.

To improve understanding of the associations observed, researchers would need a crucial set of missing data -- information on the size of the radiation dose received by each veteran. At the time of the tests, dose data were not being collected specifically for medical research; dose measurement and records maintenance was neither complete nor consistent. In the ensuing decades, the federal government has used the available information to reconstruct doses -- not for research purposes, but to support veterans' claims for compensation. After a review of available data, the IOM did not use the dose information, finding it unsuitable for research of this kind.

This latest report supersedes an IOM report published in 1985. Several years after completion of the first study, substantial inaccuracies were discovered in the data provided to the researchers. Not all the veterans listed as test participants had actually been present at nuclear tests, while some who were present were omitted. The new study uses corrected and validated participant lists, as well as an enhanced study design. The IOM also assembled a volunteer panel of experts in the fields of biostatistics, epidemiology, radiation effects, and archival sources to advise the research staff in its work.

The study was funded by the Defense Threat Reduction Agency of the U.S. Department of Defense. The Institute of Medicine is a private, nonprofit organization that provides health policy advice under a congressional charter granted to the National Academy of Sciences.

Read the full text of The Five Series Study: Mortality of Military Participants in U.S. Nuclear Weapons Testsfor free on the Web, as well as more than 1,800 other publications from the National Academies. Printed copies are available for purchase from the National Academy Press Web site or at the mailing address in the letterhead; tel. (202) 334-3313 or 1-800-624-6242. Reporters may obtain a pre-publication copy from the Office of News and Public Information at the letterhead address (contacts listed above).


INSTITUTE OF MEDICINE
Medical Follow-up Agency

Authors of
The Five Series Study:
Mortality of Military Participants in U.S. Nuclear Weapons Tests


Susan Thaul, Ph.D. (study director)
Epidemiologist

Harriet Crawford, B.S.
Operations Director

Heather O'Maonaigh, M.A.
Research Associate

William F. Page, Ph.D.
Statistician