United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Las Vegas NV89114
Research and Development
EPA-600/S4-82-069 Mar. 1983
Project Summary
Plutonium Burdens in People
Living Around the Rocky Flats
Plant
John C. Cobb, B. Charles Eversole, Philip G. Archer, Roxanna Taggart, and
Deward W. Efurd*
A study was conducted to find out
whether the tissue of people who had
lived near to or downwind from Rocky
Flats Nuclear Weapons Facility in Colo-
rado contained more plutonium (Pu)
than the tissue of people living farther
away. In addition to tissue analyses,
investigators obtained information on
age; sex; smoking, occupational, and
residence history, and causes of death.
The tissue samples were collected from
autopsy cases during the period 1976-
1979. The purpose of the study was to
measure levels of Pu-236, Pu-238, Pu-
239 and Pu-240, and the Pu-240/239
ratio in the tissue of people who had not
been occupationally exposed and who
died in Colorado over that three-year
period.
Samples were collected from human
autopsies in each of three collection
areas: Area A -- up to 25 km from Rocky
Flats; Area B ~ between 25 and 50 km
from Rocky Flats; and Area C - all of
Colorado outside a 50 km radius of
Rocky Flats and east of the Continental
Divide.
With plutonium concentrations in lung
and liver tissue as the dependent vari-
able, a stepwise, multiple regression
analysis was used to test the data with
independent variables of age, packyears
of cigarette smoking, and distance of
residence from Rocky Flats, analyzed
separately by sex and for selected areas.
The Pu-240/239 ratios in the liver
were significantly higher than in the
lung, and the total amount of plutonium
burden in the liver was about 10 times
'McClellan Central Laboratory, currently at Los
Alamos National Laboratory.
greater than in the lung. These observa-
tions reflect the longer retention time of
plutonium in the liver.
Results indicated that sex, age, and
smoking history were all more strongly
related to plutonium burden in the liver
than distance from Rocky Flats. Addi-
tionally, results show that a male at the
average age of 65.4 years, as in this
study, would have 1.5 times more pluto-
nium in his liver if he had been an 80-
packyear smoker than if he had been a
nonsmoker. For a 50-packyear smoker
at the average age. the ratio would have
been 1.3 times more plutonium.
The data on concentration and total
lung burden and on the Pu-240/239
ratio in lung and liver suggest that
releases of plutonium from Rocky Flats
contributed only a small amount to
plutonium burdens in humans east and
southeast of the site, as the total amount
of plutonium in human tissues was small
and not very different from that ob-
served by other researchers who have
studied people from other locations in
the nation.
This Project Summary was devel-
oped by EPA's Environmental Moni-
toring Systems Laboratory, Las Vegas,
NV, to announce key findings of the
research project that is fully document-
ed in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Background
At the request of Senator Haskell of
Colorado, a study was conducted to find
out whether the tissue of people who had
lived near to or downwind from Rocky
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Flats contained more plutonium than the
tissue of people living farther away. For
those deceased who were autopsied and
who had lived in eastern Colorado at least
five years, information was collected on
age; sex; smoking, residential, and occu-
pational history; cause of death; and
presence of pulmonary or liver disease.
Samples of lung, liver, gonads, adrenals
and rib were collected for plutonium
analysis. The isotopes for which the
samples were analyzed were Pu-236, Pu-
238, Pu-239, Pu-240 and the ratio of Pu-
240 to Pu-239. Plutonium in tissue from
Colorado residents can arise from both
worldwide fallout and from local sources
such as the Rocky Flats plant near
Boulder, Colorado.
The amount of global atmospheric
plutonium varies from year to year,
depending on the types of atomic bombs
being tested; however, the bulk of pluto-
nium from American and Russian nuclear
test programs fell from the atmosphere by
1968. Subsequent measurements show
that the amount of plutonium has been
declining ever since.
A possible source of plutonium in
Colorado was a September 1957 fire at
the Rocky Flats plant, which released
plutonium-seeded smoke that was swept
southward by a prevailing wind (Hammond,
1971). Another release occurred be-
tween January and June of 1968 and
during 1969, when drums containing oil
contaminated with plutonium were being
moved. Several were damaged, releasing
into the soil plutonium particles that were
then resuspended in the air during high
winds (Seed, 1971). These are two
known acute releases from Rocky Flats;
others could have occurred, and a con-
tinual, very low level was probably re-
leased from normal operations.
Several other possible sources of pluto-
nium exist in Colorado. Until September
1980, there had been 565 tests at the
nuclear test site in Nevada, of which 140
tests produced measurable amounts of
radiation outside site boundaries (Hicks,
1981). Also, since 1968, the Peoples'
Republic of China has conducted about
20 nuclear weapons tests that added to
the global plutonium inventory. Since the
Chinese tests were relatively recent and
the retention half-time of plutonium in
lung tissue is 500 days, a related contri-
bution of plutonium to the lungs of people
recently living in Colorado could exist.
Atmospheric transport and diffusion
processes would have dispersed the
nuclear test site and Chinese debris
clouds before they reached Colorado, so
that plutonium loads would have been
randomly distributed in the soil of the
state. By contrast, weapons-grade pluto-
nium released by the Rocky Flats plant
would be concentrated near the facility.
In addition. Rocky Flats plutonium has an
isotope ratio (240/239) of 0.06 com-
pared to a worldwide fallout isotope ratio
of 0.18, so that measurement of the Pu-
240/239 ratio in a sample permits an
estimate of the Rocky Flats contribution
to the sample.
The highest known concentration of
plutonium in the air in Colorado occurred
during the 1957 fire. The relatively high
level at that time was probably of short
duration as compared to the lower, more
sustained levels associated with the oil
drum spills during 1968 and 1969.
Many measurements of soil plutonium
concentration levels have been made
around the perimeter of Rocky Flats. They
show a much higher concentration of
plutonium east and southeast of the site
than at distant locations. This is probably
due to prevailing winds that blow from
west to east Relatively little soil contam-
ination was found south, west north-
west, or northeast of the site.
If the fire and spills at Rocky Flats
between 1957 and 1968-1969 caused
plutonium exposure to local residents
that was excessive in comparison to
plutonium exposure from worldwide fall-
out, then an increased concentration of
plutonium in tissue could be expected
now among those who lived downwind
from Rocky Flats during that period. This
could be detected by a low ratio of Pu-
240 to Pu-239 in lung tissue, where the
retention half-time of plutonium is rela-
tively short.
The usefulness of the study was not
limited to the questions about Rocky
Flats but included inquiry into the rela-
tionship between smoking history, age,
sex, cause of death, and plutonium con-
centrations in liver and lung.
Methods and Procedures
The study was coordinated by the U.S.
Environmental Protection Agency (EPA),
Environmental Monitoring Systems Lab-
oratory, Las Vegas, Nevada, and con-
ducted by the University of Colorado
Medical Center and the Colorado State
Health Department Fifteen hospitals in
Denver, Pueblo, and Colorado Springs
collected tissue samples for the study.
Samples were collected from human
autopsies in each of three collection
areas: Area A -- up to 25 km from Rocky
Flats; Area B ~ between 25 and 50 km
from Rocky Flats; and Area C —all of
Colorado outside a 50 km radius of Rocky
Flats and east of the Continental Divide. A
total of 519 samples were coJIected, 147
from Area A, 182 from Area B, and 190
from Area C. (See Figure 1.) Samples
came mostly from heavily populated
areas around Denver, Colorado Springs,
and Pueblo, with scattered cases from all
of eastern Colorado. Only three samples
came from places within 10 km of Rocky
Flats, because the area was very sparsely
settled.
Each set of samples generally included
one whole lung, 750 grams of liver, both
gonads, if available, both adrenals, if
available, and a sample of rib. Interviews
with next of kin yielded places of resi-
dence of the deceased, any possible
occupational plutonium exposure, smok-
ing history in packyears, age, sex, and
cause of death.
In lung tissue, the plutonium is less
evenly distributed than in the liver, and
much of it is deposited in the lymph
nodes. Hence, only samples that included
more than 90 percent of eitherthe right or
left lung were used.
The U.S. Air Force McClellan Central
Laboratory of Sacramento, California,
analyzed the lung and liver samples by
both alpha pulse height analysis (APHA)
and mass spectrometry. In addition,
standards were checked by the Lawrence
Livermore Laboratory, Knolls Atomic
Power Laboratory, and Los Alamos Scien-
tific Laboratory. The EPA, in consultation
with the Health Departments of Colo-
rado and Jefferson County and with the
University of Colorado, decided which
tissue and how many would be collected,
based on what was then known about
plutonium distribution in the body from
inhaled plutonium oxide particles. Be-
cause pulmonary lymph nodes tend to
concentrate plutonium particles from the
lungs, lymph nodes were included in all
lung specimens.
During preparation of samples at au-
topsy, organs are removed from the body
and sliced in such a way that blood or
other fluids seep out and are washed
away. Measurements indicated that if the
liver lost about 10 percent of its weight in
fluid seepage, only about 1.5 percent of
resident plutonium was lost By far the
largest part of the plutonium burden is
evidently rather firmly fixed to the tissue
and does not drain off with the fluid.
Consequently, due to changes in tissue
fluids at time of death, total organ burden ^
of plutonium is more meaningful than the fl
organ tissue concentration alone and
therefore was measured in the study.
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Only individuals who lived in eastern
Colorado for at least five years since
1968, who neither worked at Rocky Flats
nor had been otherwise occupationally
exposed to plutonium, were included in
the study. Distance from Rocky Flats was
noted for three time periods: the last five
years of life; the period from 1968 to
1970; and the time of the fire in 1957.
The distribution of the causes of death
was compared to the distribution of
causes of death for the entire state for the
same period of years to determine the
degree to which the samples were repre-
sentative of the population who died in
Colorado during those same years.
Alpha Spectrometry
Plutonium samples were analyzed by
alpha spectroscopy for the presence of
Pu-236, Pu-238, and Pu-239+240. Each
sample was counted on either a Frisch
Grid detector for approximately 2000
minutes or on a silicon solid state detec-
tor for approximately 3000 minutes.
Mass Spectrometry
Plutonium samples were loaded by
evaporation on rhenium filaments, placed
in the source of the mass spectrometer
and ionized by heating to 1900°C. From
this, the Pu-240/239 atom ratio and dpm
were determined.
With plutonium concentrations, organ
burdens, and isotope ratios in lung and
liver tissue as the dependent variable, a
stepwise, multiple regression analysis
was used to test the data with inde-
pendent variables of age, packyears of
cigarette smoking, and distance from
Rocky Flats. Samples were analyzed
separately by sex and for selected areas.
Results
Of the 519 sample sets obtained for
the study, those from 41 control area
residents have not been analyzed for
plutonium because of budget constraints.
Ten were excluded from analysis because
of various problems (See Figure 1.). For
the 468 with interviews, 19 were ex-
cluded from the study because the indi-
vidual might have been occupationally
exposed to plutonium or had lived in an
area where other plutonium exposure
could have occurred.
The remaining 449 sets of samples
included in the study represented an
aged population with females slightly
older than males. The males were much
heavier smokers. Almost two thirds of
the females were nonsmokers. People
who resided within 50 km east and south
of Rocky Flats during the 1957 fire had a
minutely lower average ratio of Pu-240/
239 in their livers than did those living in
the other study areas, but distance from
Rocky Flats did not show any consistent
relationship for this group.
Males had a slightly but significantly
higher average liver burden of plutonium
than females, but they also smoked signif-
icantly more. Liver burden appears to be
low and weakly related to any of the
variables in females; however, in males,
both age and packyears of smoking were
519 Autopsies
22 = Possibly
Otherwise Exposed
to Weapons-
Grade Plutonium
2 = Tissue
Not Yet
Analysed
3 = Occupationally
Exposed, Ruled
Out of This Study
46 Not Included in
Data of Tables
5 = Tissue
Analysed for
Plutonium
19 Tissue
Analysed for
Plutonium
512 = Completed
Interviews
490-"ANOE."
Autopsied, Not
Otherwise Exposed
to Weapons-
Grade Plutonium
41 - "EXTRA-C."
Extras from Area C,
Tissue not yet Analysed
449 = "Study Population.
Tissue Analysed for
Plutonium
473 - Pu 239+240 Analysis
Reported for Liver and/or Lung.
Figure 1. Breakdown of 519 autopsied individuals.
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usually positively and significantly related
to liver burden. Nonsmokers and light
smokers were more likely to have no
Plutonium in their lungs than were heavy
smokers. The data on Pu-240/239 ratio
in lungs tended toward the ratio found in
soil, as a function of distance from Rocky
Flats, but was statistically weak.
The mean value for concentration of
Plutonium in the lungs of people who had
lived in eastern Colorado was very similar
to the median value estimated by Mclnroy
(1979) for the Colorado population and is
only slightly higherthan the median value
estimated by Fisenne (1979) for a much
younger and healthier population in New
York City. For liver plutonium concen-
tration, the mean for eastern Colorado
was only slightly higher than the esti-
mated median of both Mclnroy and
Fisenne, which could be accounted for by
differences in age, sex, and smoking
habits.
Results indicated that sex, age, and
smoking history were all more strongly
related to plutonium burden in the liver
than distance from Rocky Flats. Differ-
ences between mean liver burdens for
male heavy versus light smokers, be-
tween males and females of each group,
and between older and younger males
were all significant Females did not
show an age difference in liver burden
and smoking did not seem to have an
influence in women.
Discussion
There are several possible explana-
tions for finding that older people have
larger plutonium burdens than do younger
people. First, the peak of plutonium
pollution from worldwide fallout occurred
in 1963, after which it dropped during the
next four years by a factor of 15 (Efurd,
1977). Young people born since then
would therefore have had considerably
less exposure.
Second, young people have healthier
lungs in general and are better able to
eliminate inhaled participates than older
people. Third, from 1950 to 1970, older
people were still smoking more than
younger people. Only in recent years
have teenagers begun to smoke so much
(Last, 1980). Fourth, since plutonium
was first used in 1945, an older person
would generally have been exposed to
more plutonium than a younger person.
Finally, for growing children, the amount
of air inhaled per unit time increases with
increasing lung size, which increases
with age. All of these factors would tend
to give older people a larger plutonium
burden.
Pu-240/239 ratios in the liver were
significantly higher than in the lung.
Additionally, the total amount of pluto-
nium burden in the liver was about 10
times greater than in the lung. Both of
these observations are explained by the
fact that retention half-time of plutonium
in the liver is 30 times longer than in the
lung. Thus, the liver would reflect the
accumulation of plutonium over a person's
whole lifetime and consequently have a
much greater plutonium burden and a
higher Pu-240/ 239 ratio.
The results of the study suggest that a
male at the average age of 65.4 years, as
in this study, would have 1.5 times more
plutonium in his liver if he had been an
80-packyearsmokerthan if he had been a
nonsmoker. For a 50-packyear smoker at
the average age, the ratio would be 1.3
times more plutonium. The higher pluto-
nium levels probably do not result from a
higher intake of plutonium among smokers
but from the toxic and irritating sub-
stances in cigarette smoke that damage
the clearing mechanisms of the lungs,
thereby preventing the natural elimina-
tion of particles.
Regarding the question of the Rocky
Flats facility as a source of plutonium, the
results of the study were not conclusive.
The data suggest that releases of pluto-
nium from Rocky Flats have contributed
to human plutonium burdens east and
southeast of the site, but the total amount
of plutonium in human tissue is small and
not very different from that observed by
other researchers who have studied
people from other locations in the nation.
References
Efurd, D. W., G. L Merrill Jr., J. T. Phelps,
and K. D. Rosenlof, 1977. Measure-
ments of Americium and Plutonium in
the Atmosphere, Published in Transur-
ancis in Natural Environments, NVO-
178, Edited by M. G. White and P. B.
Puna way, pg. 249.
Fisenne, I. M., M. E. Wrenn and N. Cohen,
Progress Report to US Dept. of Energy
on Contract EY-76-S-02-2968 entitled:
"Determination of Pu 239, 249 Tissue
Concentrations in Nonoccupationally
Exposed Residents of New York City."
(Ph.D. Thesis of Isabel M. Fisenne,
N.Y. Univ. Medical Center.)
Hammond, S.E. 1971. "Industrial-type
Operations as a Source of Environ-
mental Plutonium" LA 4756, Proceed-
ings of Environmental Plutonium Sym-
posium held at LASL, 4-5 August
1971, pp. 25-35.
Hicks, H. G. 1981. Radiochemical Data
Collected on Events from which Radio-
activity Escaped Beyond the Borders of
the Nevada Test Range Complex,
Lawrence Livermore Laboratory Report
UCRL-52934.
Last J. M., 1980. Textbook from "Public
Health and Preventive Medicine" by
M. Rosenau. Appleton-Century-Croft
1980.
Mclnroy, J. F., era/. 1979. Plutonium in
Autopsy Tissue: A Revision and Up-
dating of Data Reported in LA-4875.
Health Physics Vol. 37, pp. 1-136.
Seed, J. R., K. W. Calkins, C. T. Illsley, F.
J. Miner, and J. B. Owen, July9,1971.
RFP-INV-10 Committee Evaluation of
Plutonium Levels in Soil Within and
Surrounding USAEC Installation at
Rocky Flats, Colorado. Prepared under
Contract AT (29-1 )-1106 for the Albu-
querque Operations Office U.S. Atomic
Energy Commission.
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John C. Cobb. B. Charles Eversole, Philip G. Archer, andRoxanna Taggartare with
the University of Colorado Health Sciences Center. Denver, CO 80262; Deward
W. Efurd is currently with Los Alamos National Laboratory.
Stuart C. Black is the EPA Project Officer (see below).
The complete report, entitled "Plutonium Burdens in People Living Around the
Rocky Flats Plant." (Order No. PB 83-137 372; Cost: $22.00, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
P.O. Box 15027
Las Vegas, NV 89114
. S. GOVERNMENT PRINTING OFFICE: 1983/6W-095/1920
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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