{Reprinted from Nature, Vol. 262, No. 5571, pp. 745-748, August 26, 1976)
407901
Re
Plutonium levels in Kwajalein Lagoon
V. E. Noshkin, R. J. Eagle & K. M. Wong
Biomedical and Environmental Research Division, Lawrence Livermore Laboratory, University of California, Livermore, California 94550
Reported plutonium levels in fish from both Kwajalein and
In an assessment of the possible plutonium dose to man
from food and other environmental pathways, Wilson ef al.
compiled, in the form of lognormal median concentrations,all
the plutonium survey data collected at Enewetak Atoll during
1972 and 1973 (ref. 1). The concentration values for all the fish
muscle samples taken are reproduced here in Table 1, together
with similar lognormal mean concentrations compiled from
the same survey! data for fish bone and gut from Enewetak
Atoll and muscle, bone, and gut concentrations, also from the
same survey data!, for fish collected off three islands of Kwajalein Atoll (W. R. Robison, private communication). Wilson
et al® found no significant differences in mean plutonium
concentrations among four fish groups, which included,
among others, planktonic and detritus feeders, grazing herbivores, bottom-feeding carnivores, and pelagic carnivores.
Accordingly, they based their predictions of exposures to
Enewetak lagoons, suggest that Kwajalein Lagoon contains
significantly more plutonium in its environment than would
be expected from worldwide fallout levels alone, although
guantities of plutonium greater than fallout concentrations
have not been detected in the lagoon water. If there is no
reason to reject the published fish data, then individuals on
Kwajalein Atoll who supplement their diet with foods from
the local marine environment may have plutonium body
burdens similar to the low levels predicted for individuals
on similar diets at Enewetak Atoll.
KWAJALEIN ATOLL (9°N 167°40’E) is located in the western
(Ralik) chain of the Marshall Islands. In the sameisland chain
and some 300 miles to the north-west ts Enewetak Atoll (11°20’N
162°20’E), one of the United States nuclear testing sites during
plutonium from ingestion of marine foods on the mean concentration of plutonium in the muscles of all the fish taken
from the lagoon of Enewetak Atoll. Significantly, however, the
239.240) in the lagoon water ranged from | to 96 pCi m~* at
the fish samplingsites?.
the 1940s and 1950s. It has been reported! that no immediate
Radionuclide concentration
independent of environment?
1
debris from the nuclear tests at Enewetak and Bikini (another
Pacific test site) was deposited at Kwajalein. Measurements
during 1972 and 1973 between 5 and 15°N, over a wide range
of longitudes, indicated concentrations of between 0.22 and
0.44 pCi m~3 for 7*9-74°Pu in Pacific surface water?'?, The mean
239.240Pu concentration in the surface waters of Kwajalein and
other Pacific atoll lagoons located in this latitude band, therefore, would be expected to be similar to the surface oceanic
level (0.34 +-0.11 pCim~%).
This is not true of Enewetak Lagoon. In late 1972, the
average measured concentration of 7%*?4°Py in the lagoon
surface water? was 39 pCi m~3, approximately 100 times the level
predicted from worldwidefallout. Clearly, some components of
the atoll contaminated by fallout debris during the tests are
contributing substantial amounts of 7°*?4Pu to the lagoon
water masses, The difference in ?°°-?4°Pu concentrations between the two lagoons is a direct reflection of the activity levels
in the environments of the two atolls. It also follows that if
plutonium uptake in living organisms is expressed in terms of a
concentration factor (the concentration of plutonium in the
tissue of the marine organism divided by its concentration on an
equivalent weight basis in the surrounding water), invertebrates, fish, or other marine organismscan be useful as indicator
species of the level of environmental contamination.
Schell and Watters? have given *°9:2#°Pu concentrations in
various organs of selected marine organisms collected at
Enewetak and Kwajalein atolls. They concluded, however, that
the plutonium and americium concentrations in the convict
surgeon fish from Enewetak Atoll, for example, are not significantly higher than those measured at the control station,
Kwajalein Atoll. The mantle and muscle tissues of a clam
(Tridacna sp.) collected in the south-eastern region of Enewetak
Atoll were, moreover, found to contain only one-sixth as much
plutonium as those of a Tridacna sp. collected at Kwajalein
Atoll*. On the other hand, the viscera and kidney of the same
Enewetak Atoll clam had higher concentrations than those of
the Kwajalein Atoll specimen.
The data of Schell and Watters‘, together with those of Table 1,
show that average levels of *°°-?4°Pu in fish bone, muscle, and
gut from Enewetak Atoll are similar to, or even lower than,
those of the fish indigenous to the control station, Kwajalein
Lagoon. There are several possible important conclusions that
can be derived from these data. Thefirst is that fish collected for
consumption by man will contain, on average, essentially the
same concentrations of plutonium radionuclides regardless of
the source or level of plutonium in the local environment.
Obviously, such a conclusion would greatly affect future plans
for releasing low-level transuranics to the marine environment.
Furthermore, it would force us to concede that the concept of a
plutonium concentration factor for fish is meaningless. Also,it
conflicts with a large body of plutonium concentration data
for Atlantic fish species that derive their plutonium body
burdens from worldwide fallout levels in the Atlantic Ocean.
For example, for a number of Atlantic species, including
bottom feeders, water-column feeders, and large predators®*®,
a lognormal! median ofall available bone concentration data is
only 1 x 10~* pCi g-! (wet or dry), 900 times less than that for
the bones of the Kwajalein fish (Table 1). A similar large discrepancy remains when the concentrations in the muscle of the
Atlantic and Kwajalein fish are all normalised to an equivalent
weight basis (wet or dry).
Plutonium levels in the Atlantic waters (where someof the fish
were caught) range only between 0.2 and 1.1 pCi m~?, according to Bowen ef al/.*. Calculating a concentration factor from
the data for Atlantic fish and water and using a value of 0.4
pCi m~’ as the assumed mean plutonium level from
lpgel
the Kwajalein Lagoon, provides values of Ot
cent
10~4 pCi g~ for the bone offish for thisyty
Mose valuce
are orders of magnitude lower than ie(Bho.The median