To complicate matters further, there was no central listing of participants by name.
A study cohort was finally identified from research by the
Armed Forces Radiobiology Research Institute (AFRRI), an element of the
Defense Nuclear Agency.
The list named 3,153 military personnel* who had been
issued film badges at the Nevada Test Site (NTS) for the period that included
31 August 1957, the date of Shot SMOKY. Seventy-one names were added from
other sources, thereby making a total cohort of 3,224 individuals.
This
number of individuals was used in the study.
Several sources were then explored to identify the cases of leukemia and
other cancers among this cohort.
Four leukemia cases were identified from a
list of more than 3,000 individuals who made inquiries regarding the publicity
surrounding the index case.
31 August 1957.
Of these personnel, 447 had been at the NTS on
The AFRRI list was also compared with various clinical files,
including those of the Armed Forces Institute of Pathology (AFIP), the
Veterans Administration (VA) death benefit file, and personnel records at the
National Personnel Records Center. Four more cases were identified from these
records, which made a total of nine (including the index case).
Each case was confirmed by CDC, and the total exceeded the expected
incidence of 3.5 leukemia cases in this cohort.
The expected incidence was
calculated by applying age- and sex-specific incidence rates published by the
National Cancer Institute to the person-years accumulated by the SMOKY cohort
from 1957 through mid-1977.
the study.
Eight of the nine cases had died by the time of
This exceeded the expected mortality of 2.9 calculated from U.S.
rates for the 1970s.
Both comparisons were considered statistically signif-
icant, even if two of the cases that could be questioned with regard to
inclusion in the cohort were dropped.
Radiation exposure was considered as a possible cause of this increased
incidence.
The available dosimetry (film badge results) and radiological
analyses of tissue from two patients did not, however, support this hypothesis.
Therefore, CDC tentatively concluded that if the apparent excess of
*Primarily U.S. Army personnel who were assigned to Exercise Desert Rock and
wore film badges provided by the U.S. Army Signal Depot, Lexington, KY.
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