Atoms, Nature, and Man: Man-made Radioactivity in the Environment

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

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.

FISH. Fisheries biologist with a large jackfish caught off Engebi Island, Eniwetok Atoll.

COCONUT CRAB. Measuring the radioactivity of the shell of a coconut crab caught on Bikini Island.

GEESE. Banding wild geese to study environmental effects of radionuclides on wildlife and possible entry of radionuclides into the human food chain.

PLANKTON. An ingenious plankton trap is placed in a river as part of a long-range study of radionuclide uptake by aquatic organisms.

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 nonradioactive 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.

Engebi Island, Eniwetok Atoll, home of a colony of rats living in radioactive surroundings.

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?

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”.

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.

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.

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