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Title: Atoms, Nature, and Man - Man-made Radioactivity in the Environment
Author: Hines, Neal O.
Language: English
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ATOMS, NATURE, and MAN
Man-made Radioactivity in the Environment
by Neal O. Hines
The Understanding the Atom Series
Nuclear energy is playing a vital role in the life of every man, woman,
and child in the United States today. In the years ahead it will affect
increasingly all the peoples of the earth. It is essential that all
Americans gain an understanding of this vital force if they are to
discharge thoughtfully their responsibilities as citizens and if they
are to realize fully the myriad benefits that nuclear energy offers
them.
The United States Atomic Energy Commission provides this booklet to help
you achieve such understanding.
Edward J. Brunenkant, Director
Division of Technical Information
UNITED STATES ATOMIC ENERGY COMMISSION
Dr. Glenn T. Seaborg, Chairman
James T. Ramey
Wilfrid E. Johnson
Dr. Theos J. Thompson
Dr. Clarence E. Larson
CONTENTS
INTRODUCTION 1
SOME PRELIMINARY IDEAS 2
A VIEW IN PERSPECTIVE, 1946-1963 8
THE ATOM IN ENVIRONMENTAL STUDIES 20
ENVIRONMENTS—SINGULAR, YET PARTS OF A WHOLE 29
PROBLEMS AND PROJECTS 41
WHERE ARE WE NOW? 52
SUGGESTED REFERENCES 55
United States Atomic Energy Commission
Division of Technical Information
Library of Congress Catalog Card Number: 66-61322
1966
[Illustration: THE COVER
Scientists aboard a seagoing vessel prepare to study contents of a
plankton net as part of their research into radioactivity in an oceanic
environment.]
[Illustration: THE AUTHOR
NEAL O. HINES is an established writer and experienced academic
administrator with an unusual background in radiobiological surveys of
the Pacific Ocean atomic test sites. He holds degrees from Indiana and
Northwestern Universities. A former journalism teacher at the University
of California and Assistant to the President of the University of
Washington, Mr. Hines also worked for a number of years with the
Laboratory of Radiation Biology of the University of Washington, where
he served from 1961-1963 as administrative assistant and as Executive
Secretary of the Advisory Council on Nuclear Energy and Radiation for
the State of Washington. He was a member of the survey teams visiting
Bikini and Eniwetok in 1949 and 1956 and Christmas Island in 1962. His
“Bikini Report” (_Scientific Monthly_, February 1951) was one of the
earliest descriptions of radiobiological studies in the Pacific. He is
the author of _Proving Ground_ (University of Washington Press, 1962), a
detailed history of radiobiological studies in the Pacific from
1946-1961.]
ATOMS, NATURE, and MAN
Man-made Radioactivity in the Environment
By NEAL O. HINES
INTRODUCTION
Mankind, increasingly crowding the earth, modifies the earthly
environment in uncounted subtle and unpredictable ways, too rarely to
the benefit of either earth or man. In this century it has become
critically important that we comprehend more precisely than ever before
the biological mechanisms and balances of our environment and that we
learn to detect changes and to understand what they imply.
The release of atomic energy added a new dimension to the possibility of
environmental change. In man’s first experiments with atomic energy, he
added small but perceptible amounts of radioactivity to the earth’s
natural total; as the Atomic Age matures, he inevitably will add more.
But, in the course of his experiments, man has come to realize that
environmental and biological studies, which now are necessary because of
the use of atomic energy, may help solve not only the problems atomic
energy creates but also the larger problem of how to manage wisely the
world’s limited natural resources.
This booklet describes the environmental investigations that have been
conducted with the aid of the atom since the first atomic detonation
near Alamogordo, New Mexico, in 1945. The earth’s mysteries, however,
are not easily unlocked, and investigations of our environment with
atomic tools have only begun. The story thus is one of beginnings—but of
beginnings that point the way, it is hoped, to a new understanding of
the world in the atomic future.
SOME PRELIMINARY IDEAS
Biologists are interested in every kind of living thing. When they study
organisms in relation to atomic radiations, they enter the field of
radiobiology, which really is not a science in itself but merely a
branch of the larger interest in biology. Biologists find that atomic
energy has significance both in the study of individual organisms and in
studies of organisms in their natural communities and habitats.
[Illustration: _Skin-diving biologist collecting giant clam from coral
bottom of Bikini Lagoon in the Pacific Ocean._]
Radioactivity introduced into any community may be “taken up” by the
biological system, becoming subject to cycling in food chains or to
accumulation in plant or animal tissues. The presence of radioactivity
permits study of the workings of a system as large as an ocean, perhaps,
or of one no larger than a tree. And in each case it thus may be
possible to observe how the cycles of organic renewal are related to the
larger systems of life on earth.
The Single Environment
The environment in which we live is recognizable as a single complex,
composed of many subenvironments—land, oceans, atmosphere, and the space
beyond our envelope of air. The deer in the forest, the lizard in the
desert burrow, and the peavine in the meadow are different kinds of
organisms living in situations that are seemingly unalike. Each creature
is part of its environment and a contributor to it, but it also is part
of the total biosphere.[1] All creatures are linked to each other,
however remotely, in their dependence on limited environments that
together form the whole of nature.
[Illustration: _Gray shark photographed in another Pacific lagoon._]
We know much about the life of the earth, but there is far more that we
do not know. Understanding of the large cyclical forces has continued to
elude us. We do not even yet grasp the small and seemingly random
biological relations between individual organisms—relations involving
predator and prey, for instance, and those among species and
families—such as exist together in symbiotic[2] harmony and
interdependence. Through centuries of observation we have gained a store
of information. We are left, however, with a still unsatisfied curiosity
about the reach and strength of the tenuous biological cords that bind
together the lives of the deer, the lizard, and the peavine.
The Need to Understand
Life on earth evolved amid constant exposure to ionizing[3] radiation,
from the earth itself and from space, known as background radiation.
Therefore environmental studies must be conducted in relation to, and
with understanding of, background radioactivity.
[Illustration: _This Pacific Ocean coconut crab, member of a family that
usually sticks to tide-covered beaches, depends on coconut trees for its
food._]
Of some 340 kinds of atoms that have been found in nature, about 70 are
radioactive. Three families of radioactive isotopes[4]—the uranium,
thorium, and actinium series—produce a large proportion of the natural
radiation. Other radionuclides[5] occur singly, rather than in families,
and some of them, such as potassium-40 and carbon-14, are major
contributors of natural radioactivity. Traces of natural radioactivity
can be found, in fact, in all substances on earth.
When man began experimenting with atomic fusion and fission, he placed
in his environment—across vast landscapes, in the oceans, and in the
atmosphere—measurable additional amounts of radioactivity. These
additions were composed of the longer-lived members of some 200 kinds of
atomic radiation. Although the additions constituted but a fraction of
the background burden, they represented the first alteration of the
radiological balance that had existed since the early ages of the
planet. Thus it became necessary to determine what the impact of such a
change might be. In the process of inquiry, these ideas emerged:
1. The addition of man-made radioactivity presents the possibility of
delayed or cumulative effects. Long-term studies, geared to the
assessment of biological effects from extremely low radioactivity, are
essential.
2. The addition of radioactivity makes possible broad-gauged studies
to trace the movement and concentration of radionuclides in the
environment. These studies, in turn, can disclose new information on
biological complexes and mechanisms.
[Illustration: _A flying atmospheric physics laboratory studying
concentration of radionuclides over an Atomic Energy Commission
laboratory. Instrument pod under wing samples air to provide a visual
record of radioactivity._]
[Illustration: _Transferring a sample of water taken from the depths of
the Columbia River for radiochemical analysis in a laboratory._]
The quantities of low-level long-lived radioactivity already released
into our environment will provide materials for future studies covering
decades. Further, because radioisotopes are chemically similar to
nonradioactive forms, observation of their biological fate will provide
clues to the transport, concentration, dilution, or elimination of many
other kinds of man-made toxic agents and contaminants of the
environment.
Operating Concepts
[Illustration: _Oceanographers bringing aboard a 50-gallon seawater
sampler from the ocean depths find it a difficult task, even in moderate
seas. This photo was taken aboard the R. V. Crawford in the Atlantic._]
Environmental problems are best approached in the environment itself,
where all the natural variables and unknowns are present. Laboratory
work is essential, but no laboratory can carve from nature or reproduce
artificially all the complexities of the natural environmental
“laboratory”, the ecosystem.[6]
Environmental studies frequently demand the coordinated attentions of
ecologists,[7] chemists, physicists, geologists, oceanographers,
meteorologists, botanists, zoologists, and others, all working together
to approach the environment as a synchronized mechanism.
Finally, environmental studies are conducted with a special
consciousness of the need to withhold judgment as to what is meant by
“effect”, particularly “radiation effect”. Gross, immediate effects may
be determinable. Ultimate effects may be generations in the making,
remote in time and space from their causes. Studies thus are focused on
biological processes and on isolation and identification of the
long-range trends.
A VIEW IN PERSPECTIVE, 1946-1963
Bikini Atoll, in the Marshall Islands, represents, in miniature, a world
that has experienced all the forces, immediate and residual, that can
result from nuclear detonation.
Bikini in 1946 was the scene of the first peacetime tests of atomic
weapons. One of these tests involved the detonation of an atomic device
under water, in the heart of the atoll’s aquatic circulatory system.
Bikini also was used for 5 years, from 1954 through 1958, for the
testing of thermonuclear[8] devices. Its islands and reefs were burned
by atomic heat, and the waters of its lagoon were contaminated by
deposits of radioactive fallout. Thus, for almost a score of years,
Bikini, a small outcropping of coral in the mid-Pacific, was identified
with the earliest experiments in nuclear explosion.
Through the years of testing and later, Bikini also was the site of
repeated biological investigations. Teams of scientists examined Bikini
annually from 1946 to 1950 and from 1954 to 1958. Then in 1964, after an
interlude of 6 years in which Bikini was undisturbed either by weapons
tests or human visitors, scientists went there again to make a
comprehensive ecological resurvey.
The scientists found in the Bikini ecosystem, in low but perceptible
amounts, residual traces of radioactivity deposited by the tests. On
certain islands, craters dug by nuclear explosions still gaped in the
reefs. The test islands still bore nuclear scars, and in some areas of
the lagoon corals and algae had been killed by silt stirred up by the
detonations. But Bikini’s life system clearly was in a process of
healing. Large islands were covered by regrowths of vegetation; on some,
the masses of morning glory, beach magnolia and pandanus were growing so
densely that field parties had extreme difficulty cutting paths through
them. Bikini Atoll, scientists believed, needed only clearing and
cultivation to make it once again suitable for human habitation.
[Illustration: _Autoradiograph of a plankton sample collected from a
Pacific lagoon a week after a 1952 test._]
What, then, may be concluded from the Bikini case? A final answer still
cannot be phrased. It is not a conclusion to say that nature and time
have permitted recovery, reassuring though such knowledge may be. It
becomes important to know the processes of recovery. Meantime, it is
helpful to examine the Bikini case in the context of developments during
the period from the end of World War II to the signing of the Nuclear
Test Ban Treaty of 1963.
The Bikini Tests of 1946
The early period of nuclear testing in the atmosphere was a time that
will not be seen again. It was the beginning of an era of unparalleled
scientific activity and of worldwide emotional and intellectual
adjustment to the knowledge that power of unimaginable magnitude, locked
in the nucleus of the atom since the creation of the world, now could be
released at will.
When World War II was ended, the impulse to test the new power was
irresistible. There was profound curiosity about the revolutionary
nature of the new force. There was a perplexed and fearful realization
that the release of energy would have to be guarded and controlled.
There was the knowledge that nuclear fission produced a miscellany of
radioactive products presenting unexplored possibilities of hazard. The
word “fallout” was coined to describe the deposition on the earth of
radioactive debris from nuclear explosions.
Joint Task Force One
The first peacetime nuclear tests, conducted at Bikini in 1946 in a
military-scientific exercise designated Operation Crossroads, were
designed to assess the effects of nuclear weapons on naval vessels. The
test organization, Joint Task Force One, an adaptation of the wartime
joint task force combat concept, was a massive waterborne force
including 42,000 members of the armed services, civilian scientists,
consultants, and observers.
[Illustration: _The Bikini Lagoon before testing._]
Bikini Atoll was selected for the tests because, among other things, it
was remote from heavily populated areas, it offered a protected
anchorage, and it had the relatively stable and predictable
meteorological and oceanographic conditions considered essential to
operations in which the unknowns loomed so large. Three test detonations
originally were projected; two ultimately were carried out. The first,
Test Able, was an airdrop of an atomic bomb on July 1, 1946, over a test
fleet of 70 ships anchored in Bikini Lagoon. The second, Test Baker, was
the detonation on July 25 of an atomic device suspended in the lagoon 90
feet below a small target vessel.
Scientific Interests
Although Crossroads was a military program, the mobilization of
scientific interests was in many ways of historic proportions. For
months before the explosions, oceanographers studied the waters and the
structure of the mid-Pacific basin and meteorologists the winds and
upper airs. Geologists, zoologists, botanists, and other specialists
examined the atoll in detail. Bikini became, as it remains to this day,
one of the most thoroughly familiar ocean structures in the world.
There was awareness, even then, of the significance of radioactivity as
an element of nuclear effect. The task force made elaborate preparations
to assure the safety of personnel and sent to the atoll thousands of
radiation-detection instruments. Plans were made to observe the effects
of radioactivity on test animals placed on ships of the target fleet.
The Underwater Detonation
The first of the Bikini events, Test Able, the explosion of a bomb
dropped from an aircraft over the target fleet, sank a number of major
vessels, left others sinking or crippled, contaminated many with
radiation, and laid a plume of fallout northward over the rim of the
atoll into the waters of the ocean. It was Test Baker, however, the
underwater explosion, that would make Bikini the subject of
radiobiological investigations for many years.
The Baker test was the first occasion in which nuclear debris was mixed
with water and ocean sludge and returned to the area of detonation. The
explosive device was of what later would be called nominal size, its
force equivalent to 20,000 tons of TNT. The test still is regarded as a
classic demonstration of the phenomena of shallow-water atomic
explosion.
[Illustration: _The Baker Test. A cauliflower-shaped cloud, after
dumping one million tons of water that had been sucked up by the
explosion, rises over the target warships, silhouetted in front of the
spreading base surge._]
At the moment of release, the surface water of the lagoon was first
lifted and then penetrated by a lighted bubble that vanished in seconds
in a hollow column of water of gigantic dimensions—a column 2000 feet in
diameter (its walls 300 feet thick) rising to a height of 6000 feet and
containing 1,000,000 tons of water. At the base of the column, foam was
churned upward for several hundred feet, and, moving out from the base,
as the column sank back into the lagoon, surged a monstrous wave
initially more than 80 feet high.
Radioactivity in the water was intense. The immediate total was
described as equal to “many hundred tons of radium”. Decay and dilution
of radioactive materials quickly reduced the total radioactivity. After
3 days, by which time water contamination had spread over an area of 50
square miles, the dose rate from the water was well within safe limits
for persons remaining for brief periods. Yet it was several more days
before inspection and scientific parties could spend useful time among
the surviving target vessels.
At the bottom of the lagoon, below the point of detonation, Navy divers
months later found that the explosion had scooped out thousands of tons
of mud and coral sediment, creating a shallow basin half a mile wide.
This basin, in the slow settling of returning sludge, became an area
from which long-lived radioactivity entered Bikini’s biological system.
First Assessments
In 3 weeks of final work after Test Baker, the Bikini scientific teams
took from the islands and the lagoon many hundreds of samples of plants,
corals, crabs, fish, plankton, and water. They noted that radioactivity
was present in all samples taken from every part of the atoll, which
indicated an early uptake of radionuclides by the biota[9] and suggested
that there was a continuing circulation of radioactive debris in the
water. They took samples of fish in the open ocean outside the atoll and
made comparative collections at other atolls. The instruments and
techniques for analyzing radioactivity were far from refined, but all
available evidence pointed to the need for more particular efforts to
examine radiobiological results.
The Bikini Resurvey of 1947
A resurvey of Bikini, the first of many, was conducted with heavy
radioenvironmental emphasis in July 1947, a year after the Crossroads
tests. The scientific expedition was supported by 2 vessels and included
70 scientists and several hundred Navy personnel.
[Illustration: _Bikini Beach as it appeared in the years after Operation
Crossroads._]
The resurvey group, entering an oceanic environment that had been
completely undisturbed for nearly a year, established at once that
traces of residual radioactivity still were cycling in Bikini’s
ecosystem. For 6 weeks the scientists probed every realm of the atoll
environment, sampling biota, making inventories of plant and animal
communities, and obtaining core samples from the lagoon floor. When the
data had been assembled and reviewed and the reports filed, months
later, there was consensus that Bikini had produced no evidence that
radioactivity, as a separate and identifiable factor, was having any
immediate effect on the health of the atoll, and probably no cumulative
effect, either.
There were, of course, unknowns. So long as radioactivity remained in
the biological cycles there were possibilities of future developments.
In 1947 no other place on earth offered an opportunity to observe the
natural processes by which radiation contamination is eliminated from an
environment. It therefore seemed prudent to compile a longer record,
consisting of other, purely radiobiological surveys at Bikini.
By 1947 the new U. S. Atomic Energy Commission had taken over from the
wartime Manhattan Engineering District the management of the national
effort in the field of atomic energy. A primary responsibility of the
AEC in that period was to press ahead with nuclear weapons development,
but the agency also had specific obligations and interests in the fields
of biology and medicine. Meantime, the testing of nuclear weapons had
been started at a new proving ground at Eniwetok Atoll, 190 nautical
miles west of Bikini.
[Illustration: _Islands on the rim of Eniwetok Atoll, as they appear
today. The marks of man, such as a landing strip, are visible, but
regrowth of vegetation is apparent. Note extent of the reef on both
sides of islands._]
Studies at Nuclear Test Sites, 1948-1958
The first test series at Eniwetok, Operation Sandstone (1948),
incorporated no formal radiobiological studies, but radiobiologists
visiting Bikini also made surveys at Eniwetok in 1948 and 1949. Then,
for a time, world events intervened. The detonation of an atomic device
by the U.S.S.R. in 1949 was followed in 1950 by the outbreak of the
Korean War, and these events produced a national mood oriented toward
national defense. By 1951, because events in the Pacific had interrupted
tests there, the Atomic Energy Commission had established a continental
test site in Nevada. In that year, too, tests were made at Eniwetok
preliminary to the detonation of the first thermonuclear device.
After 1951 each of the test programs had its radiobiological component.
In the Pacific, radiobiological surveys were associated with Operation
Ivy (1952), Operation Castle (1954), Operation Redwing (1956), and
Operation Hardtack (1958). A small field station, the Eniwetok Marine
Biology Laboratory, was established for use by scientists conducting
biological studies. Bikini was incorporated into the Pacific Proving
Ground in 1953, and new biological surveys were performed there in
connection with the tests of 1954 and later.
[Illustration: _The Eniwetok Marine Biology Laboratory. Monument at
right commemorates the battle for Eniwetok in World War II._]
In these years, 1951 to 1958, the U.S.S.R. was testing nuclear weapons,
as was Great Britain after 1952. Fallout from these contributed to the
total of man-made radioactivity potentially available to the
environments of the world.
Landmarks
The years between the establishment of the Pacific Proving Ground and
the signing of the 1958 nuclear test moratorium were years in which the
quest for environmental information could not keep pace with the rapid
growth of nuclear capability. But the growth in the field of weapons
served to underline the need for information and produced certain
landmark developments in environmental research.
The detonation of the first thermonuclear device projected the problem
of environmental contamination to the stratosphere and, literally, to
every part of the earth. This explosion, Test Mike, largest on earth to
that time, was set off on Elujelab Island, on the north rim of Eniwetok
Atoll, on November 1, 1952. In the reef where Elujelab had been, the
blast left a crater almost a mile in diameter and 200 feet deep. The
towering nuclear cloud rose in 15 minutes to a height of 130,000 feet.
Test Mike marked a point of change. Before, fallout from nuclear
detonation had been principally local, touching the waters and reefs of
an atoll or a desert landscape. After Test Mike, the implications of
fallout obviously were global.
A mishap in connection with a 1954 thermonuclear test at Bikini
contributed in two important ways to the enlargement of environmental
investigations. Fallout from the test, swept off its predicted pattern
by unexpected winds at high altitudes, deposited debris on Rongelap, an
inhabited atoll east of Bikini, and on fishermen aboard a Japanese
vessel operating in the Bikini-Rongelap area. The accident, unfortunate
in its consequences at Rongelap and in Japan, had other results of even
wider impact. From it came the first international approaches to the
problems of ocean contamination and, later, long-term bioenvironmental
studies at Rongelap itself.
[Illustration: _School of surgeonfish off Arji Island, Bikini Atoll,
August 1964. Note coral growth on lagoon bottom._]
Wide-ranging studies of ocean-borne radioactivity were initiated by the
Japanese. The experience of the fishermen produced in Japan a fear of
contamination of fisheries resources as a result of the United States
tests. One result was the organization, in the summer of 1954, of a
government-sponsored ocean survey expedition that cruised from Japan
into and through the Bikini-Eniwetok area to determine what amounts of
radioactivity were being carried, by water and by aquatic organisms,
toward the shores of Japan.
The expedition made significant observations of the role of plankton[10]
in the biological utilization of ocean fallout. A United States
scientific team, following up the Japanese effort, made a similar but
far more extensive cruise through the Western Pacific early in 1955 and
went on to Japan to discuss its findings with the Japanese. During and
after the test series in the Pacific in 1956 and 1958, United States
surveys of the ocean were made routinely. Exchanges of information
between scientists of Japan and the United States continued.
The Rongelap case produced results of another kind. The Rongelap people
were found to have suffered exposure requiring medical attention and
continued observation. Evacuated from their atoll because it was not
safe, members of the community were given care at other atolls until
they could be repatriated in 1957, and received continued medical
supervision thereafter.
The bioenvironmental condition of Rongelap was unique. The fallout had
made the atoll the only place in the world contaminated on a single
occasion by relatively heavy deposition of radioactive debris without
also being disturbed by a nuclear explosion. In 1957-1958, after the
Rongelapese had been returned to a new village constructed on their
atoll, Rongelap was the site of a long and thorough study of the
circulation of radionuclides in the terrestrial-aquatic environment.
Before the 1963 Test Ban Treaty
The first break in the pattern of nuclear testing came in 1958, when the
nuclear powers agreed to a 1-year test moratorium. The world’s political
and emotional climates were changing. For more than 5 years, the United
States, which had announced its Atoms-for-Peace Program in December
1953, had been endeavoring to place emphasis on the use of atomic energy
for constructive purposes. The Atomic Energy Act of 1954, liberalizing
provisions of the 1946 law, contemplated for the first time private
development of nuclear power resources and established authority for
international activities. In 1957 the Atomic Energy Commission initiated
its Plowshare Program for the development of peaceful uses of nuclear
explosives.[11]
[Illustration: _Distribution of fallout radioisotopes on Rongelap Atoll
as determined by a survey in 1961. Note the interrelationships of man,
plants, animals and the environment._]
Amid such changes there was arising, too, a wider apprehension
concerning the possible effects of fallout. The United Nations in 1955
appointed a committee of scientific representatives of 15 nations to
study the effects of radiation on man. In the United States the National
Academy of Sciences published in 1956 the first of its summary reports
on the biological effects of atomic radiation.
Nuclear testing was not ended by the 1958 agreement, yet the
moratorium—which was renewed annually until 1961, when the U.S.S.R.
broke the agreement by initiating a new test series—was significant as
an experiment in nuclear restraint. After the United States conducted a
final test series near Christmas Island in 1962, new discussions of ways
to halt successive rounds of nuclear test programs were held. Finally,
in 1963, the Nuclear Test Ban Treaty was signed by most of the nations
of the world. The treaty was, among other things, a declaration against
worldwide fallout.
THE ATOM IN ENVIRONMENTAL STUDIES
Although his experience with radioactivity has been brief, man probably
already knows more about the effects of radiation than he knows about
the effects of many other contaminants that alter his environment. Even
so, he knows far less than he needs to know to make certain that atomic
energy is wisely managed in the future.
There has been neither time nor opportunity, for example, to gather
radiation-effects data on more than a few hundred of the 1,500,000 kinds
of living organisms inhabiting the earth. Nor is it possible to predict
the extent to which life can adjust itself to environmental changes
resulting from scarcely perceptible alterations of natural radiological
balances. Also undetermined is the relation between environmental
changes and the biological exchanges making up the often mentioned, but
insufficiently understood, “balance of nature”.
The case of carbon-14 is an example of a permanent man-made modification
of the environment. From the early ages of the earth, carbon-14 has been
created in the upper atmosphere by the transmutation of nitrogen in
cosmic-ray reactions. Carbon itself is an almost universal component of
living matter, and the ratio between stable carbon and radioactive
carbon is believed to have been unchanged for thousands of years. It is
this circumstance that permits the use of carbon-14 as a tool for
“dating”, or determining the ages of, fossil remains, prehistoric
artifacts, and geologic formations. But carbon-14 also is produced in
nuclear fusion, and the testing of thermonuclear devices after 1952
produced an estimated increase of 4% in the amount of carbon-14 on
earth. This is enough to disturb the natural equilibrium. Since the
half-life[12] of carbon-14 is some 5800 years, the addition will be a
factor of environmental consideration for scores of human generations.
Nuclear tests, although not the only sources of man-made radioactivity,
have been until now the most significant ones and the only sources
touching large areas of the earth. The total product of nuclear testing
is small in relation to the natural burden of radioactivity, raising the
level of radiation to which all life is subject by a factor of one-tenth
or less. But it is the unknown element, the degree to which fallout
radioactivity may introduce new influences into the environment, that
gives concern.[13]
[Illustration: _One of the last cows of the herd exposed to fallout by
the world’s first atomic detonation in New Mexico in July 1945,
photographed in 1964. The calf is her 15th to be born in 15 years. The
cow, believed about 20 years old, has been under observation by
scientists, who found she suffered little apparent effect, although the
fallout caused some hair to turn gray (see light patches on back). Other
cows in the herd died natural deaths._]
When a nuclear device is detonated, the release of energy is due to the
fission of uranium or plutonium atoms or to the fusion of hydrogen
atoms. At the instant of fission, some 75 radionuclides, or fission
products, are created.
From these primary fission products, about 100 other radionuclides may
be formed, some existing only for microseconds and others for thousands
of years. The radionuclides of significance to biologists are those that
exist long enough—no matter how brief the time—to have an impact on a
biological system.
Factors of biological transport and concentration of long-lived
radionuclides make efforts to assess possible environmental effects
particularly difficult. It has been asserted, for example, that probably
every living cell formed since the early 1950s contains some of the
radionuclides produced by nuclear testing. No one knows the significance
of such a condition, if it indeed exists. It is certain only that some
of the long-lived radionuclides already placed in the environment will
be detectable there for hundreds of years and hence will continue to
provide material for biological studies.
Examining Environments
[Illustration: _Seeds produced by plants grown in soil of a radioactive
waste disposal area pass (in aluminum cups) on moving belt through a
radioactivity detector as part of a study of movement of radioisotopes
in food chains._]
When radioactivity is injected randomly into the atmosphere by a nuclear
detonation, biological disposition begins in many ways, each related to
the character of the explosion and the environment in which it occurs.
Fallout studies thus involve the tracing of mixed fission products in
the biosphere and the collection and analysis of thousands of samples of
plant and animal tissue, and usually of water and soils, at many
successive times. The radiobiologist then attempts to interpret the
accumulated evidence of uptake of radionuclides. Some fallout studies
may require sampling over large areas of the earth. Other investigations
of fallout or of radioisotopes introduced deliberately into controlled
field plots may require years of patient observation in small and
circumscribed areas.
Studies of ocean fallout, for example, have ranged over hundreds of
thousands of square miles of open water. The 1955 United States survey
of the Western Pacific was conducted by a scientific team aboard a Coast
Guard vessel, the _Roger B. Taney_, in a program called Operation Troll.
In 7 weeks the team cruised 17,500 miles, making collections of water
and marine organisms at 86 ocean stations on a route extending from the
Marshall Islands through the Caroline Islands and the Mariana Islands to
the Philippines and finally to Tokyo. The expedition took samples of
plankton at depths down to 200 meters and water from the surface down to
depths of 600, 800, 1000, and 1200 meters.
Environmental studies at nuclear test sites or in controlled ecosystems
involve not only long-term, periodic sampling of plants and animals but
also years of detailed examination of soils, meteorological conditions,
and other factors.
TERRESTRIAL ECOLOGY RESEARCH
[Illustration: _An ecologist inspects cages placed around bagworm
infestations of a red cedar tree that had been injected with radioactive
cesium-134 to determine uptake of radioactivity in the larvae._]
[Illustration: _Checking pine seedlings exposed to ionizing radiation
from a radioactive source (on tripod) in a controlled ecosystem.
Seedlings on left were fully exposed, those in the middle were exposed
on their tops only, and those on the right were exposed on their stems
only._]
[Illustration: _Biologist studying the root distribution of plants by
injecting radionuclides into the soil and measuring plant uptake._]
[Illustration: _A thriving_ Messerschmidia _plant growing on Rongelap
Atoll is studied for growth-rate and root-systems data after the island
was accidentally subjected to radioactive fallout_.]
[Illustration: _Aerial view of a “Gamma Forest”, where growing trees are
exposed to chronic irradiation from a source at the center of the
picture. This environmental biology study shows varying sensitivity of
various trees. Trees in the center were killed by extremely high doses
of radiation for 20 hours a day over a 6-month period._]
[Illustration: _Apparatus containing a strong radiation source being
installed by biologists in a semitropical rain forest for terrestrial
ecology research._]
In programs of such scope and duration, the problems of interpretation
are great. Broadly, environmental studies give consideration to:
1. The amounts and kinds of radioactivity released to the environment.
2. The rates of uptake by the biological system.
3. The amounts and kinds of radioactivity within the system.
4. The rates of metabolic transfer or elimination.
5. The amounts and kinds of radioactivity concentrated in tissue and
acting internally.
6. The time required for biological processes to be completed and for
any biological effects to develop.
Biological Inventories
Familiarity with the biological components of an ecosystem is essential
to meaningful radiobiological assessment.
Inventories of natural components were not made in the early nuclear
test programs because of inadequate realization of the biological
potential. Later, they could be made only after radionuclides already
had been introduced into the environments.
The survey of the mid-Pacific region before Operation Crossroads
represented the earliest effort to examine an environment in detail
before a nuclear detonation, but was designed so that it had only
inferential value for other long-range biological research. The test
surveys were useful, however, in expanding knowledge of specific
environments. In addition, it was standard practice to make comparative
collections of organisms in regions removed from the test sites to
establish base lines, or “controls”, against which to measure
radiobiological developments.
The most extensive inventory of an environment—an inventory designed
specifically in relation to an anticipated nuclear detonation—was that
made between 1959 and 1962, as a preliminary phase of Project Chariot,
in the Cape Thompson area of Northwest Alaska. Chariot was a part of the
AEC Plowshare Program in which it was proposed to excavate a harbor at
the mouth of the Ogotoruk Creek, which empties into the Chukchi Sea.
Although the excavation project actually never was undertaken, the
“predetonation” environmental investigations involved 3 years of
coordinated research into the climatic, marine, coastal, and terrestrial
aspects of the region, and detailed studies of the history and the
radiological and ecological situations of the human population.
[Illustration: _Taking a soil sample for the Project Chariot biological
inventory to determine kinds and relative abundance of invertebrates and
other soil organisms._]
The program was an effort to make a model environmental inventory. Its
significance was both in its assessment of the base for determining the
“biological cost” of the proposed operation and in the thoroughness of
its documentation of the environmental features of a part of the world
that previously had been virtually unexplored. It was a prototype for
future studies.
Measurements and Interpretations
Determination of the amounts and kinds of radioactivity in a biological
sample is a process wholly dependent on instruments, since radiation
usually cannot be detected by the senses.
A biological sample is any material of measurable biological
significance. A sample of tissue or similar organic material usually is
dried or reduced to ash in a muffle furnace before it is examined with a
radiation counting device.
Improved instruments now permit the counting of radioactivity at levels
so low as to have been imperceptible a few years ago. The samples,
placed in lead chambers for maximum shielding from background
radiations, are examined by multichannel analyzers capable of recording
radiation emissions continuously over long periods of time.
Data-processing techniques have been employed in the handling and
interpretation of information from long-range biological sampling and
analysis programs. Analog computers have been used experimentally for
theoretical projections of results.
[Illustration: _Instruments record radiation, weather, sunlight, and
other factors transmitted from remote sensors to this data center
established for a long-range terrestrial ecology study program._]
Scientists at the AEC’s Oak Ridge National Laboratory, for example, have
developed experiments in which an analog computer is programmed to keep
a running balance of the net changes—simultaneous gains and losses—of
radioactivity in the various compartments of a representative ecosystem.
The computer becomes an electronic image of the biosphere, using known
or assumed rates of energy transfer and photosynthesis to predict
probable radiological results of tracer experiments of environmental
contamination.
ENVIRONMENTS—SINGULAR, YET PARTS OF A WHOLE
Each environment presents its own sets of conditions and unknowns. It is
important to appreciate those that are characteristic of water, land,
and atmosphere.
Aquatic Systems
The oceans are the basins into which are poured all the nutrients or
wastes transported from the land by rivers and winds.
The difficulty of determining the fate of radionuclides in aquatic
systems is complicated by chemical and biological differences within the
system and by the variety and scope of the circulatory mechanisms. In
oceans the sheer immensity of the water volume usually makes observation
superficial or fragmentary. Rivers present great differences in flow,
and lakes vary in internal dynamics. Above all, an ocean, a river, or a
lake is an area of constant physical and biological motion and change.
In the ocean the surface waters form a theater of kaleidoscopic, and
frequently violent, action. The presence of man-made radioactivity in
water has made it possible to follow the disposition of nutrients and
wastes in the restless aquatic ecosystem.
Biological Uptake
In a water environment the minerals necessary to life are held in
solution or lie in bottom sediments. They become available to animal
life after being absorbed by plants, both large floating or rooted
plants and tiny floating ones called phytoplankton; because the
phytoplankton are found everywhere in the sea, they play a larger role.
The phytoplankton concentrate minerals and become food for
filter-feeding fish and other creatures, including the smaller
zooplankton,[14] which, in turn, are food for other organisms. Thus the
minerals enter extremely complex food chains. The cycles of nutrition
are completed when fish and plants die and decomposition again makes the
minerals available to the phytoplankton.
ENVIRONMENTAL RESEARCH
[Illustration: _RAIN FOREST. A giant fan pulls air through a
plastic-enclosed portion of a Puerto Rico rain forest to study the
metabolism rate of trees._]
[Illustration: _HARDWOOD FOREST. Technicians preparing to tag Tennessee
trees with a solution containing a radioactive cesium isotope in the
start of a 10-year project. Scientists will study movement of the
radioactivity into insects and their predators._]
[Illustration: _FRESHWATER. Aquatic biologists emptying plankton traps
to study concentrations of radioactivity in microscopic organisms in the
Columbia River downstream from the Hanford atomic plant in Washington
State._]
[Illustration: _MOUNTAINS. Weather station in a deer-forage area of the
Rocky Mountains in Colorado provides environmental data and fallout
samples that are correlated with levels of radionuclides found in the
deer._]
[Illustration: _TUNDRA. This caribou was examined in detail as part of a
study of transfer of fallout nuclides in food chains from plants to
animals to man. Caribou is the principal meat animal of some Alaska
Eskimos._]
[Illustration: _DESERT. Zoologist examines an animal trap as part of a
field ecological study of a Nevada nuclear test site._]
Some radionuclides that are introduced into an aquatic environment enter
the food chains exactly as do the stable minerals essential to life,
because the radionuclides are merely radioactive forms of the nutrients.
Elements such as copper, zinc, and iron are less plentiful in the water
environment than hydrogen, carbon, or oxygen, for example, but are
concentrated by phytoplankton because they are necessary for life. Such
elements are in short supply but in constant demand; thus, when their
radioactive forms are deposited in water, they are immediately taken up
by aquatic plants and begin to move through the food chains. Fission
products such as strontium-90, for which there is little or no metabolic
demand, are taken up by aquatic food chains to only a minor extent.
The precise paths of radioelements through aquatic ecosystems are almost
unknown. In addition to their movement in food chains, radioelements
also may be moved physically from place to place in the tissues of fish
or other creatures. Some radionuclides for which there is no biological
demand may sink into bottom sediments and remain there until they have
lost their radioactivity. Or radioactivity actually may be transported
“uphill”, from water to land, as when birds that feed on fish containing
radioactivity leave their excretions at nesting areas. The routes and
modes of transport seem numberless.
[Illustration: _Movement of radioactive elements in a forest-lake
ecological system. Most nutrient-flow is “downhill”, but birds,
migrating fish, and the evaporation-rainfall cycle may move them
“uphill”._]
The Oceans
The surface waters of the seas, down to depths of 200 meters, are areas
of rapid mixing in which temperature, density, and salinity are almost
uniform. Below the surface water is a zone in which temperature
decreases and density and salinity increase with depth. This zone, known
as the thermocline, may reach a depth of 1000 meters. Because density is
increasing here, vertical motion is reduced, and exchanges between the
surface and the deep waters are impeded. Knowledge of temperature,
density, and salinity is important to understanding what happens to
radionuclides in the ocean. Physical conditions affect the rates of
physical movement of radioactivity in the mixed (surface) layer, the
degree to which radionuclides are held at the thermocline, and the
processes by which radionuclides pass the thermocline and enter the
deep-water cycles and upwellings.
[Illustration: _Men aboard the research vessel_ Shimada _pulling in
plankton nets during sampling operations at sea_.]
The surface currents of the ocean are largely wind driven and their
patterns generally well known. New concepts of the vertical and
horizontal diffusion of substances introduced into the ocean were
developed, however, in studies of ocean-borne fallout during and after
nuclear tests in the Pacific.
The first of these surveys was conducted near Eniwetok and Bikini.
Scientists aboard a Navy vessel sampled water and plankton to depths of
300 meters at some 90 points spread over an area of 78,000 square miles
to determine the disposition of early fallout from the nuclear
detonations. Some weeks later another expedition voyaged from Eniwetok
to Guam and returned, covering an area of 375,000 square miles to follow
(by sampling) the mass of water-borne radioactivity resulting from the
test and to note the intervening effects of diffusion, dilution,
biological uptake, and decay. In 1958 two more surveys were conducted,
the first to ascertain the spread and depth—with samplings below the
thermocline—of a radioactively tagged water mass immediately following
an underwater detonation, and the second to follow the westward drift of
the tagged water mass.
Significantly, it was found that plankton immediately take up large
amounts of radioactivity. Planktonic forms, in fact, proved to be the
most sensitive indicators of the presence of radioactivity in the marine
environment. Further, the daily vertical migrations of plankton—down in
response to sunlight and up at night—seemed a part of the process by
which radionuclides move from the upper waters to the deeps.
The expedition scientists noted that the masses of low-level
radioactivity moved in the ocean significantly slower than the surface
currents, a circumstance attributable in large measure to biological
factors. The distribution of residual radioactivity in the sea a month
after the close of a nuclear testing program could be determined by
counting radioactivity in plankton samples.
It was established that strontium-90 and cesium-137, important in
fallout on land, enter the marine cycles only in minute amounts.
Practically no fission products are found in fish. Since strontium-90 is
not concentrated strongly by marine organisms, the question of what
happens to it in the ocean remains unanswered. Studies have suggested,
however, that strontium moves in solution and thus indicates the
movement of water. If this is true, strontium-90 may be contained in the
deep currents and eventually will be brought again to the surface. Some
observers believe this process has begun.
Rivers, Lakes, and Estuaries
The freshwater environment differs from the marine in the greater
variety of its minerals, among other things. As sites for
radiobiological studies, rivers and lakes present problems of great
complexity, but conditions at river mouths or estuaries are even more
difficult because of the mixing by tidal action of fresh and salt water.
Rivers vary greatly in character and change radically from season to
season because of rainfall and other factors. General understanding of
their biological workings is difficult to formulate. But rivers are the
routes by which minerals and wastes are transported toward the sea, and
estuaries are significant because of the many forms of life that
flourish there.
Studies of radioactivity in rivers and estuaries usually have been made
in relation to the fate of effluents from nuclear plants. Among the
longest and most intensive studies are those near Hanford, Washington.
Observations were started in 1943, when the federal government was
preparing to build plutonium-producing reactors to be cooled by waters
of the Columbia River.
[Illustration: _Fisheries biologists studying hatchery fish reared in
water containing radioactivity from the Hanford plutonium reactors._]
For more than two decades, observations have been made of the physical
dispersion and biological disposition of low-level effluents in the
Columbia. Concentration factors have been established for significant
radionuclides in phytoplankton, algae, insects, and fish, and typical
patterns of dilution and dispersion have been plotted.
Similar programs, in an entirely different freshwater system, have been
conducted over a similar span of years near the Oak Ridge National
Laboratory in Tennessee. One area of interest has been the biological
disposition of trace amounts of strontium-90 released to the Tennessee
River via tributary streams.
Among the few broad estuarial studies yet undertaken is one started in
1961 to plot the dissemination in the lower Columbia River, and in the
Pacific Ocean, of radioisotopes transported by the river from the
Hanford plant. Radiobiologists are studying biological distribution.
Oceanographers are using the trace amounts of effluent radioactivity to
verify the patterns of dispersion of river waters in the ocean.
Land
[Illustration: _Plant ecologists “tagging” experimental forest plots
with radioactive cesium for long-term studies._]
Natural radionuclides find their way into plants’ metabolic processes.
Man-made radionuclides also are so incorporated—even some, such as
uranium or radium, that have no known metabolic role. The man-made
nuclides, whether they reach the earth in fallout or by other means, mix
with the stable nuclides to which they are chemically related,
increasing by small fractions the total amount of each element available
to participate in plant growth cycles. Because artificial radionuclides
behave so typically, they present, on the one hand, a possible long-term
hazard and, on the other, the expectation that their detectability will
reveal much about the biological courses of minerals and nutrients.
The disposition of man-made radioactivity on land is determined in part
by such factors as topography and the presence or absence of water.
Topography may influence the distribution by setting patterns of
drainage and exposure of surface soils to wind and rain. Water may
affect dilution, or it may leach radionuclides out of surface soils and
thus remove them from the level in which plants are rooted. The leaching
may carry radionuclides elsewhere, however, possibly causing mild
contamination of the water table.
[Illustration: _Trench dug on Rongelap Island to expose soil strata and
root systems to determine penetration of radionuclides in coral-sand
“topsoil”._]
Plants take up radionuclides through their roots or through their
foliage. But the role of soils is significant. Some radionuclides are
bound as ions to clays and thus are withheld in large measure from entry
into the plant system. Cesium-137, for example, is held so tightly by
soils that uptake through plant roots is slight, and thus a more
significant mode of entry of cesium-137 into food chains is by direct
deposit on plant leaves. Variables are introduced by the physical
configuration of the plant itself, by seasonal differences in plant
metabolism, and by the effects of rain and snow. In the case of
iodine-131, a short half-life—8 days—virtually precludes the possibility
of extensive uptake through plant roots. But the half-life is not too
short to prevent grazing cattle from ingesting radioiodine deposited in
fallout and thus allow the appearance of radioiodine in milk.
[Illustration: _Survey of pasture grasses to determine whether
radioactive materials are present. If they are, they could be passed
from the grasses to cows and then from the cows’ milk to humans._]
Much attention has been devoted to strontium-90 and to its availability
to man by deposit on plants and soils. Because strontium bears a close
chemical relation to calcium, a unit expressing this relation, the
_strontium unit_ (one picocurie[15] [1 × 10^-12 curie of strontium-90
per gram of calcium]) is used in following strontium-90 through food
chains. Soils, however, present confusing factors. Experiments and
fallout observations show that strontium-90 does not penetrate soils
deeply. In typical instances it remains in the upper inch or two of the
soil surface, where its availability to root systems is as variable as
the conditions of mixing, leaching, and plant growth. Experiments have
shown that plant uptake of strontium from soils can be reduced by
introduction of calcium in available form into the soil.
Radiobiological developments on land result from combinations of
environmental influences. Studies in the Rocky Mountains show that
ecological conditions above the timberline, particularly in areas where
snowbanks accumulate, are efficient in concentrating fallout
radionuclides. Concentrations thus take place in the snow-packed heights
that are the sources of mountain streams flowing to the plains far
below.
Atmosphere
The environment of the earth is a product of “weather”—of the transport
of moisture, of the actions between winds and oceans, of the cycling of
energy through biotic systems. Understanding of biological potentials of
atmospheric factors involves understanding of atmospheric motions
affecting transport and mixing of contaminants and the processes of
deposition of radionuclides from atmosphere to earth.
[Illustration: _Network of towers on the Atomic Energy Commission
reservation near Richland, Washington, used by atmospheric physicists in
measuring quantity, concentration, and dilution of radioactive materials
in the atmosphere._]
At some thousands of feet above the earth’s surface—at 30,000 to 40,000
feet in the middle and polar latitudes and at 50,000 to 60,000 feet in
the tropics—there is a level, the tropopause, at which air temperature,
rather than decreasing, becomes constant or increases with height. Below
this level is the troposphere, the turbulent zone of clouds, rain, and
fog. Above it is the stratosphere, where there is no turbulence and only
a slow mixing of dry and cloudless air. The stratosphere continues to a
height of about 100,000 feet. Investigators have noted the importance of
rain or snow in washing fallout particles from the air in the
troposphere. There is disagreement on the precise modes of distribution
of radioactive materials projected into the stratosphere.
In the detonation of low-yield nuclear devices, fission products are not
projected beyond the troposphere, and fallout is washed down in periods
of days or weeks. Because winds move principally in east-west
directions, tropospheric fallout appears on the earth in bands centered
approximately at the latitude of detonation. But when high-yield
explosions propel contaminants into the stratosphere, the pattern of
subsequent developments is less clear. It once was believed that fallout
from the stratosphere was distributed more or less evenly—though over
long periods of time—over the surface of the earth. The present view is
that fallout debris placed in the stratosphere remains in that
hemisphere in which the explosion occurs. This concept is based on an
atmospheric circulation theory that air enters the stratosphere at the
equator and descends again in temperate and polar latitudes each spring.
The theory presumes a much shorter “residence time” of stratospheric air
and thus a quicker return of fallout particles to the turbulent
troposphere.[16]
The presence of radionuclides in the atmosphere has provided clues to
cyclical movements of biological importance. During the period of
nuclear tests in the Pacific, observers noted spring “pulses”, or
increases, of strontium-90 deposition in the northern hemisphere, a
phenomenon difficult to verify or explain satisfactorily while testing
was proceeding. Later, when testing had been suspended, the spring peaks
reappeared. The observation seemed to support the theory that nuclear
debris injected into the stratosphere was descending years later through
a gap in the tropopause.
Samplings of nuclear debris by balloon have been under way for several
years at altitudes of 100,000 to 150,000 feet, and rocket-borne air
samplers and other systems have been developed for taking atmospheric
samples up to 200,000 feet.
Programs for studying airborne contamination from industrial
activities—operated at the more accessible but equally difficult levels
of the atmosphere—have been sponsored by the Atomic Energy Commission
near the Hanford Plant, Washington, and at the Oak Ridge, Argonne, and
Brookhaven National Laboratories in Tennessee, Illinois, and New York.
The Hanford studies were started before plutonium production was begun
in 1943, and findings on industrial stack-discharge rates established
patterns for meteorological programs at other sites.[17]
PROBLEMS AND PROJECTS
The range and variety of environmental studies now in progress make it
almost impossible to provide any all-encompassing statement of results.
Almost all places associated with nuclear programs have become focal
points of research in environmental biology. Fallout, deposited in
patterns determined by the mechanisms of the atmosphere, has created at
certain points on the earth’s surface—the Arctic, for example—ecological
conditions that require investigation. New information of
bioenvironmental significance has come in bits and fragments. We can,
however, attempt to summarize what has been learned and to show, in
broad terms, how radiobiological experience has extended appreciation of
the earth as a single ecosystem—a system comprised of an infinity of
interactions of water, land, and atmosphere, and of all living things.
The spectrum of environmental investigation—investigations using
man-made radioactivity—incorporates research in which:
1. Fallout radioactivity is assessed as a potential specific hazard to
human populations.
2. Conditions created by fallout are examined for their potential
long-term ecological significance.
3. Radionuclides introduced into the environment by nuclear tests,
reactor operations, or other means are used as trace materials in
basic studies in biological systems.
4. Radioactive forms of minerals and nutrients are deliberately
introduced into biosystems—in measured amounts and under conditions of
control—for studies of metabolic cycles and rates of flow of energy
and nutrition.
It will be useful to look in detail at some typical programs and
results.
ANIMAL RESEARCH
[Illustration: _RAT. A lightly anesthetized, wild trapped rat is weighed
and measured prior to marking it, taking a blood sample, and releasing
it in a controlled ecosystem._]
[Illustration: _FISH. Fisheries biologist with a large jackfish caught
off Engebi Island, Eniwetok Atoll._]
[Illustration: _COCONUT CRAB. Measuring the radioactivity of the shell
of a coconut crab caught on Bikini Island._]
[Illustration: _GEESE. Banding wild geese to study environmental effects
of radionuclides on wildlife and possible entry of radionuclides into
the human food chain._]
[Illustration: _PLANKTON. An ingenious plankton trap is placed in a
river as part of a long-range study of radionuclide uptake by aquatic
organisms._]
[Illustration: _SKATE. A clear-nosed skate being monitored by fisheries
personnel to gather data on accumulation of radionuclides in its blood
and tissues._]
Wasps and Radioactive Mud
At Oak Ridge National Laboratory, Tennessee, it was discovered in 1964
that two kinds of mud-dauber wasps were building their mud nests in
equipment, cabinets, and electronic gear in the vicinity of a field
station on the Oak Ridge reservation.
Some nests, investigation disclosed, were built of radioactive mud. It
seemed obvious that the wasps were obtaining mud from radioactive waste
pits or from the White Oak Lake bed, which is the site of a former
40-acre lake used for 12 years as a detention pool for radioactive
wastes.[18]
The mud daubers were carrying mud as far as 650 feet from the
contaminated sources. Almost 90% of 112 nests built by the yellow-legged
mud-dauber species were radioactive, and the mud was delivering to the
wasp eggs each hour a dose of penetrating radiation equal to that
received by a man from all natural sources over a period of many years.
The development presented no human health problems, but further
observation revealed a fascinating circumstance.
At the same time, another variety of wasp, the pipe-organ mud dauber,
was building nests only of _non_radioactive mud. Of 150 pipe-organ wasp
nests examined, none was radioactive. The nests were found in similar
locations, and it was apparent that the same sources of nest materials
were available to both species.
WASP NEST RESEARCH
_Mud-dauber wasps, building nests of radioactive mud in a waste disposal
area near an Oak Ridge, Tennessee, atomic plant, are the object of
intensive environmental radiation study. A shows radioactivity reading
from a nest. B is an enlarged view of the nest with two tiny dosimeters
in place to measure radiation. In C an ecologist inspects new nests
built in a laboratory flight cage from radioactive mud provided in pans
at the bottom. In D wasps are anesthetized, marked with tiny plastic
disks for future identification, and released._
The question, then, was why wasps of one species were using radioactive
mud while the other species seemingly discriminated against contaminated
mud. The muds appeared to be entirely alike. X-ray-diffraction studies
showed no material differences, nor were there detectable differences in
“feel”, smell, or plasticity. Radioactive isotopes in the mud included
cesium-137, cobalt-60, ruthenium-106, and zinc-65. Oak Ridge scientists
began to try to find out whether the pipe-organ wasps actually were
discriminating against muds containing all or some of these
radioisotopes or against the ionizing radiation from them. If so, how
could the wasps detect it? These investigations were continuing in 1965.
There is no answer yet.
Survival of an Animal Population
The case of Bikini already has been discussed as an example of a
predominantly aquatic environment apparently recovering from association
with nuclear experiment. Eniwetok offers an instance of the toughness of
an animal population exposed both to direct and long-range radiological
impact.
Engebi Island, on Eniwetok’s northeast reef, is the home of a wholly
self-contained colony of Pacific rats living in a network of burrows in
the shallow coral sands. After 1948 Engebi was exposed repeatedly to
atomic detonations, and in 1952 the whole island was swept clean of
growth and overwashed by waves from the thermonuclear explosion of
Operation Ivy. On each of these occasions, exposure of the rat colony to
radiation was intense. In 1952, by later estimates, the animals
aboveground received radiation doses of 2500 to 6000 roentgens per hour,
and those in burrows doses of 112 to 1112 roentgens per hour.[19] The
island environment was so altered by atomic forces and by contaminated
water that radiobiologists believed it impossible that any of the rats
had survived. Because there was no natural route by which the island
could be repopulated, scientists even considered introducing a new rat
colony for study of a population growth in a mildly radioactive
environment.
[Illustration: _Engebi Island, Eniwetok Atoll, home of a colony of rats
living in radioactive surroundings._]
[Illustration: _Close-up shows one burrow in the soil._]
Contrary to all expectations, however, the original colony had not been
eliminated. Biologists visiting Engebi in 1953 and 1954 found the rats
apparently flourishing. New generations of rats were being born and were
subsisting on grasses and other plants in an environment still slightly
radioactive. In 1955 analysis of the bones of rats revealed the presence
of strontium-89 and strontium-90 in amounts approaching what was assumed
to be the maximum amount that would not cause bodily harm. The rats’
muscle tissues contained radioactive cesium-137. But no physical
malformations were found in the rats. All animals appeared in sound
physical condition, despite these body burdens of radioactivity. By 1964
the rat population had so increased that it apparently had reached
equilibrium with available food supplies.
Questions relating to the reestablishment of the colony are intriguing.
Why are new generations of these warm-blooded animals continuing to
thrive after the colony was exposed to devastating nuclear effects? Is
there a different dose-effect relation for these rats than for other
animals? Even if it is assumed, as it must be, that some members of the
colony survived the original nuclear heat and radioactivity because they
were shielded by concrete bunkers or other man-made structures, how is
it that there have been no observable effects among rats existing for
years in an area that continually exposed them to radiation?
[Illustration: _A native rat, captured alive on Engebi Island, being
held by a scientist before having its toenails clipped as a means of
identification. Note the animal’s healthy appearance._]
Fallout and Populations
In Arctic regions lying on opposite sides of the North Pole, fallout has
created conditions that are given continuous scrutiny by scientists of
Scandinavia and the United States.
The two cases, one involving the Lapps of northern Finland and the other
the Eskimos of Alaska, are essentially the same. Hemispheric fallout
introduced quantities of long-lived radionuclides, particularly
cesium-137, into the food chains and consequently into the diets of
native peoples. In each instance there had occurred a slow accumulation
of radionuclides in the lichens and mosses and in other plants that are
the foods of the reindeer and caribou. The meat of these animals forms a
substantial part of the human diets, and as a result the members of the
native communities were found to have, on the average, body burdens of
radioactivity approaching the acceptable limit for human populations.
A preliminary study of the Lapp environment was made in 1958-1959, and a
Lapp dietary study was made in 1960. The results showed close
correlation between the consumption of reindeer meat and the Lapps’ body
burdens of cesium-137. The Scandinavian investigators concluded that the
levels of concentrated cesium approximated the maximum permissible dose
range for large populations. They noted, however, that “the final answer
... has to be given by the geneticists”.
[Illustration: _Placing equipment to measure fallout in precipitation
north of the Arctic Circle in Alaska._]
In Alaska, where studies of the native populations have been proceeding
for several years, adult Eskimos living in the vicinity of Anaktuvuk
Pass[20] were found in 1964 to have average body burdens of cesium-137
more than 20 times as great as the average for adults in the area of the
original 48 states. There was an expectation that even without further
nuclear testing the levels of cesium-137 would continue to rise slowly
in Arctic regions until about 1968.
The Variety of Approaches
Bioenvironmental studies form a background against which all atomic
energy research is conducted. The central objective of the Atomic Energy
Commission’s environmental radiation studies is “to determine the fate
and effect of radionuclides in the environment”. This objective calls
for hundreds of concurrent approaches to the interlocking problems of
the air, the sea, and the land. The AEC alone, through its Division of
Biology and Medicine, is supporting research costing about $75 million a
year, about two-thirds of this amount going to biological and medical
programs at AEC laboratories and the remainder to some 650 individual
contract studies at universities, nonprofit institutions, and commercial
research organizations. Additional programs, large and small, are
supported by foundations or other agencies. Work goes on in other
nations. Many programs are international. Although only a fraction of
this total activity is specifically related to environmental problems,
the concern throughout is with the effect, for good or ill, of
radioactivity on man and his world. It is possible to suggest by example
the lines of inquiry.
[Illustration: _A University of Georgia Research Institute ecologist
studying biological specimens in a controlled environment near the AEC
Savannah River Plant, Aiken, South Carolina._]
The Trinity site in New Mexico, scene of the first atomic detonation in
history, was studied for a number of years after 1945, particularly in
relation to the distribution and effects of residual radioactivity in
the desert environment. In 1963 and 1964 scientists from the University
of Missouri undertook to determine the state of revegetation of the
original atomic bomb crater.
The Nevada Test Site, where nuclear programs have been conducted for a
decade and a half, has invited investigations of revegetation. Project
Sedan, an underground thermonuclear detonation in 1962, established
conditions for one such study. The crater produced by this detonation
was 320 feet deep and 1200 feet in diameter. Vegetation growing within
2500 feet of ground zero was almost completely destroyed, and the
original soil was covered by radioactive throwout. Shrubs as far as 5000
feet away from ground zero were damaged by air blast, and, in the weeks
after the detonation, plants within a two-mile radius were covered by
radioactive sand and silt or by deposits of windblown radioactive dust.
Studies in 1963 by scientists from the University of California at Los
Angeles showed that native plants—Russian thistle and various
annuals—had become well established in the zone around the Sedan crater
where the earth was thrown out. This area had remained barren for less
than a year. Some of the shrubs most severely damaged by the blast, and
exposed to cumulative gamma radiation doses of more than 4000 roentgens,
had produced new growth. Populations of creosote bush, evergreen plants
that in 1962 appeared to have been killed by heavy doses of radiation,
were producing leafy branches in the summer of 1963. These developments
permitted no conclusions, of course, for the possible radiation effects
still needed to be identified. Studies were conducted, for example, of
the effect of deliberately depositing nonradioactive dust on healthy
creosote plants, and comparative studies of other phenomena were made.
Since 1959, ecological studies have been carried forward at the Nevada
site by investigators from Brigham Young University who are interested
in the abundance, seasonal occurrence, and ecological influences
affecting the vertebrate and invertebrate animals in plant communities
of the region. Surveys have been made in areas where nuclear explosions
had obliterated natural ecological relationships and in similar areas
undisturbed by nuclear effects. The investigations are concerned
primarily with desert ecology—with the identification of biotic
communities and of predominant animal species.
Among research programs in marine environments is that initiated in 1963
and 1964 by the University of California’s Institute of Marine Resources
at La Jolla, where studies of marine food chains are conducted by a team
of zoologists, chemists, botanists, and microbiologists. The program
studies the interrelations among organisms at the lower levels of the
food chains and the dynamics of marine phytoplankton cell division,
photosynthesis, and excretion of organic matter as related to
temperature, light intensity, and nutrient conditions. The work is
conceived as a basic study of marine ecology. It is focused, however, on
questions found to be significant in studies of radioactivity in the
sea.
The University of California’s Lawrence Radiation Laboratory has
launched a long-term investigation of the effects of the release of
radionuclides on the biosphere, which encompasses the origins,
transport, and final localization of radionuclides in all types of
organs, tissues, cells, and subcellular constituents. The objective is
“to develop the most complete understanding possible of the potential
hazards to man that arise from the release of nuclear radiation and
radionuclides into the biosphere and to apply this knowledge to the
prevention of damage to living forms...”.
In programs such as these—multiplied by hundreds—the problems are being
attacked.
WHERE ARE WE NOW?
Radiobiological studies that are environmental in scope became, with the
release of atomic energy, a mandate on the twentieth century.
Environmental studies are not new. They have been implicit in thousands
of biological research efforts, large and small, for generations. Atomic
energy, however, is a new factor. Also new is the intensity of the
approach. Not until the explosion of inquiry of this century has man
brought together the necessary resources—the time, the funds, the
instruments, the ingenious technological devices, the ideas, and the
organizational and management skills—to attack problems that are global
in scale.
The atom as a tool of the environmental radiobiologist has, of itself,
solved few problems. Its significance is that it has speeded up—to a
degree still not fully tested—our ability to study ecosystems and their
relations to each other.
The First Twenty Years
_Instruments for environmental research._
[Illustration: _A radiation analyzer for laboratory examination of field
samples._]
[Illustration: _Installing environmental research equipment in the
field._]
The first two decades of the Atomic Age have comprised a period of swift
maturity. Much has been done to gain perspective. Atomic energy as a
potential force for destruction has not been controlled. But there is a
surer knowledge of the hazard inherent in the absence of control and a
rational hope that the new power will be directed toward peaceful
objectives. We know that:
1. The uninhibited release of nuclear products into the environment of
the earth will create problems—fundamentally biological problems—of
long duration and of still-unassessed ultimate effect.
2. Use of atomic weapons in war could have a “biological cost” beyond
calculation.
Yet, in terms of constructive employment of atomic resources, we also
know that:
1. Atomic energy may help solve the very problems that the new age
presents.
2. Careful and controlled development of atomic forces will provide
the reservoirs of energy that will be needed to sustain the world’s
populations of the next century and beyond.
In whatever case, the solutions lie in the direction of environmental
knowledge.
Man, the human animal, will live in the environment he has the
intelligence to understand and to preserve.
[Illustration: “_... All creatures are linked to each other ... in their
dependence on limited environments that together form the whole of
nature ..._” (_Page 3_). (_White-capped noddy tern nesting colony,
Engebi Island, Eniwetok Atoll, photographed in 1965._)]
SUGGESTED REFERENCES
Basic
_Sourcebook on Atomic Energy_, Samuel Glasstone, D. Van Nostrand
Company, Inc., Princeton, New Jersey, 1958, 641 pp., $4.40.
What is Ionizing Radiation?, Robert L. Platzman, _Scientific
American_, 201: 74 (September 1959).
Weapons Testing and Fallout
_The Effects of Nuclear Weapons_, Samuel Glasstone (Ed.), U. S. Atomic
Energy Commission, 1962 (revised edition), 730 pp., $3.00. Available
from Superintendent of Documents, U. S. Government Printing Office,
Washington, D. C. 20402.
_Fallout from Nuclear Weapons Tests_, Hearings Before the Special
Subcommittee on Radiation of the Joint Committee on Atomic Energy,
86th Congress, First Session, Superintendent of Documents, U. S.
Government Printing Office, Washington, D. C. 20402, 1959. Vol. I, 948
pp., $2.75; Vol. II, 1967 pp., $2.75; Vol. III, 2618 pp., $1.75.
“Summary-Analysis of Hearings”, 42 pp., $0.15, is available only from
the Office of the Joint Committee on Atomic Energy, Congress of the
United States, Washington, D. C. 20510.
_Bombs at Bikini_, W. A. Shurcliff, William H. Wise & Co., Inc., New
York, 1947, 212 pp., $3.50. Out of print but available through
libraries.
Biological Effects of Radiation
_Health Implications of Fallout from Nuclear Weapons Testing Through
1961_ (Report No. 3), Federal Radiation Council, Washington, D. C.,
May 1962, 10 pp., free.
_Estimates and Evaluation of Fallout in the United States from Nuclear
Weapons Testing Conducted Through 1962_ (Report No. 4), Federal
Radiation Council, Washington, D. C., May 1963, 41 pp., $0.30.
_Report of the United Nations Scientific Committee on the Effects of
Atomic Radiation_, General Assembly, Seventeenth Session, Supplement
No. 16 (A/5216), United Nations, International Documents Service,
Columbia University Press, New York, 1962, 146 pp., $5.00.
Radioactivity in the Environment
_Environmental Radioactivity_, Merril Eisenbud, McGraw-Hill Book
Company, Inc., New York, 1963, 430 pp., $12.50.
_Proving Ground: An Account of the Radiobiological Studies in the
Pacific_, 1946-1961, Neal O. Hines, University of Washington Press,
Seattle, Washington, 1962, 366 pp., $6.75.
_Radioecology_, Proceedings of the First National Symposium on
Radioecology Held at Colorado State University, Fort Collins,
Colorado, September 10-15, 1961, Vincent Schultz and Alfred W.
Klement, Jr. (Eds.), published jointly by the Reinhold Publishing
Corporation, New York, and the American Institute of Biological
Footnotes
[1]The biosphere is the living world, the sum of all living, interacting
organisms.
[2]Symbiosis is a condition in which two organisms or communities of
organisms live together in close association, either on a basis of
mutual benefit or of benefit to one only, with or without harm to
the other.
[3]Ionizing radiation is radiation that can cause damage to biological
tissues.
[4]Isotopes are variant forms of atoms of the same element.
[5]Nuclides is a term used to describe all the forms of all the atoms.
Radionuclides are radioactive nuclides.
[6]An ecosystem is a natural community, taken as a whole, including all
biological and environmental factors.
[7]Ecologists are scientists concerned with the interrelations of
organisms and their environments.
[8]A thermonuclear device is an explosive, such as a hydrogen bomb,
based on a fusion reaction. In other atomic weapons the energy is
derived from nuclear fission.
[9]The living organisms.
[10]Plankton are the floating, minute plants and animals that live in
the sea (and also in fresh water), including diatoms, algae,
protozoans, and crustaceans.
[11]For more on this program, see _Plowshare_, a companion booklet in
this series.
[12]The half-life of a radioactive element is the time required for half
its atoms to lose their radioactivity.
[13]Atmospheric tests of nuclear weapons through 1962 produced a fission
yield equivalent to 191 million tons of TNT and introduced about
10.01 megacuries of strontium-90, for example, as fallout entering
the environment.
[14]Floating one-celled animals.
[15]A picocurie is one trillionth of a curie; a curie is the basic unit
of intensity of radioactivity, approximately equal to that in 1 gram
of radium.
[16]For more about these studies, see _Fallout from Nuclear Weapons
Tests_, a companion booklet in this series.
[17]Information on this research is found in _Radioactive Wastes_, a
companion booklet in this series.
[18]The lake, drained in 1955, makes an interesting natural basin in
which residual radionuclides are used in studies of mineral cycling.
[19]A roentgen is a unit of exposure to radiation, measuring the
alteration of the atoms (ionization) of the radiated tissues. The
rat dosages compare with recommended limits of exposure to man-made
radiation for average individuals in human populations of an amount
that approximates 0.5 roentgen per year.
[20]The area where highest readings were obtained in the survey. These
studies are described in more detail in _Whole Body Counters_, a
companion booklet in this series.
Transcriber’s Notes
--Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
--In the text versions only, text in italics is delimited by
_underscores_.
--In the text versions only, superscript text is preceded by caret.
--In the ASCII version only, subscripted numbers are preceded by
underscore and delimited by brackets.
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