Program of the 2001 Annual Meeting, Fallout from Atmospheric Nuclear Tests—Impact on Science and Society
April 4-5, 2001
Introduction
Harold L. Beck, Session Chairman
Historical Overview of Nuclear Weapons Testing and Fallout from Atmospheric Tests
Harold L. Beck
Over 500 weapons tests with a total yield of about 440 MT and a total fission yield of about 190 MT were conducted in the atmosphere by the United States, Soviet Union, United Kingdom, France, and China between 1945 and 1980. Although data for specific high yield tests are still classified, the fission and fusion yields of the various tests and test series have been estimated and these will be discussed. The quantities of specific fission and activation products released into the atmosphere, including long-lived activation products such as H-3 and C-14 produced primarily by high yield thermonuclear tests, are estimated. The various national and international monitoring programs established to trace the fallout through the atmosphere and biosphere will be described. These programs included continuous monitoring of ground-level air, exposure rates and deposition as well as periodic sampling of food, bone, water, soil, and stratospheric air. Estimates have been made of the geographic and temporal variations in the fallout deposition of specific radionuclides based on both measurements and model calculations. These deposition estimates provide a basis for reconstructing population exposure and dose. Local, intermediate and global fallout deposition density levels downwind from test sites will be discussed as will the potential for local anomalies having resulted from rainout of debris from the atmosphere. Fallout at various distances downwind from test sites also was found to depend on the height of burst, the yield, and the half life and volatility of the particular fission or activation products. The impact of weapons fallout on our ambient radiation environment will persist for thousands of years and remain an important factor in the assessment of past and future releases of radioactivity into the biosphere.
Impact on Science Burton G. Bennett & Andre Bouville, Session Co-chairmen
Radiation Measurement Science
Radioactive Fallout Assessment Needs and the Development of Field-Based Measurement Methods
Kevin M. Miller, U.S. Department of Energy
The advent of the atomic age during the 20th century brought about significant advances in ionizing radiation and radioactivity detection methods. These methods were needed to support work in such areas as nuclear weapons production, nuclear power development, medical radioisotope and x-ray use, basic scientific research, and assorted industrial applications. While advances in detection methods were generally interrelated among these various areas, it is clear that the need to assess the impact of weapon tests fallout was a prime impetus in the development of instrument systems to rapidly measure radiation and radioactivity levels directly in the environment. Noteworthy advances took place in aerosol sampling to provide radionuclide concentrations in air, ground-based and aerial surveys to determine external dose rates, and in situ spectrometry to quantify specific gamma-emitting nuclides in soil. The methods and equipment that were developed in these areas are still used today for such important applications involving as routine environmental measurements at nuclear installations, evaluations of accidents involving radioactive materials, surveys to support decontamination and decommissioning of facilities, and global monitoring for nuclear nonproliferation. This paper provides an overview of some of the developments in fallout assessment methods and the evolution of the associated instrumentation to the systems that are currently used for environmental measurements.
Laboratory Analyses: Environmental and Biological Measurements
Naomi H. Harley, New York University School of Medicine
Detection of radioactive fallout away from the Nevada test site first occurred in Rochester, New York in February 1951. This commenced the first large-scale, global environmental monitoring network in history. Ten collectors to monitor total fallout were set up in the United States in the Spring of 1951 and beginning in 1954 this number escalated to 46 United States stations, 68 stations in North America and overseas, with an additional 64 maintained in cooperation with the United Nations. Duplicate, one foot square gummed film samples were mailed daily from these 178 locations to the Atomic Energy Commission, Health and Safety Laboratory for over 10 y. The fallout activity was measured by beta counting using automated counters. With the injection of megaton weapons fallout into the stratosphere in 1954, and subsequent long atmospheric residence times, it became difficult to calculate decay rates and individual nuclide concentrations. Pot collectors were deployed along with, and then finally replaced, the adhesive film so that nuclides could be measured directly using radiochemical separation.
Concerns over the health impact of fallout ushered in large programs in the United States, the United Kingdom, and other countries to measure the radionuclides of dosimetric interest. Programs were set up to determine dietary intake and human and animal tissue distribution of 90Sr and 137Cs. Some of the first measurements of natural background dietary radium and body potassium were a response to identify analog elements. The impact of the environmental measurements made for fallout went far beyond any dosimetric consequences. For example, present day information on bone tissue turnover rates are derived mainly from radiochemical analysis of 90Sr measurements in human bone, and historical fallout deposition measurements were used in the NCI study to calculate the United States county-by-county thyroid dose from 131I.
The spin off from the enormous expenditure in effort to make these measurements and to determine the health consequences of global fallout, laid a rich basic and applied scientific foundation in many disciplines.
Atmospheric Science
Meteorological Benefits from Atmospheric Nuclear Tests
Lester Machta, National Oceanic and Atmospheric Administration
The injection of detectable particles and gases into the atmosphere by nuclear tests permitted the meteorologist to better understand air trajectories, dispersion, and transfer of these substances to the ground. Measurements on and near the ground, by aircraft and balloon, while obtained for operational and safety needs, were used by many scientists to better understand and verify atmospheric processes.
The injection of major air pollutants by the nuclear tests and associated substantial funding also invigorated the field of atmospheric chemistry. The industrial expansion after World War II put a variety of pollutants into the air. The advances in meteorology and air chemistry derived from the study of atmospheric nuclear test debris were helpful in meeting new demands to understand the fate of the pollution.
In addition, improved instrumentation and sampling platforms were used to study cosmogenic and radon-thoron radionuclides. The transmission of sound waves from the massive explosions were useful for high-altitude temperature and wind studies.
Since the atmospheric tests were conducted for operational needs rather than as a tool for the scientist, not all of their characteristics were ideal. The choice of timing and location of the tests, uncertainties in their strength and in the distribution of radioactivity with height, plus the incomplete availability of all measurements limited their benefits for the atmospheric scientist.
Worldwide Dispersion and Deposition of Radionuclides Produced in Atmospheric Tests
Burton G. Bennett, U.S. Department of Energy
Radionuclides produced in atmospheric tests were widely dispersed in the global environment. From the many measurements of the concentrations in air and the deposition amounts, much was learned of atmospheric circulation and environmental processes. The fallout radionuclides served as tracer materials in observations of dispersion and deposition dynamics. The amounts of fallout radionuclides released were determined by the fission and fusion yields of the weapons. The total yield of each test, the latitude, and the detonation height above the ground determined the initial partitioning of radionuclide debris between the troposphere and stratosphere. The radionuclides then encountered the seasonally dependent air circulation patterns and were incorporated into the particle settling and deposition processes.
Based on reported fission and total yields of tests and extensive measurements of the dispersed debris, it has been possible to devise an empirical model of the movement and residence times of particles in the various atmospheric regions. This model, applied to the individual weapons tests, allows extensive calculation of air concentrations and deposition amounts for the entire range of radionuclides produced throughout the testing period. Especially for the shorter-lived fission radionuclides, for which measurement results at the time of the tests are less extensive, a more complete picture of levels and isotope ratios can be obtained, forming the basis for accurate dose estimations. The contributions to worldwide fallout can be inferred from individual tests, from tests at specific sites or by specific countries.
Progress was also made in understanding the global hydrological and carbon cycles from the tritium and 14C measurements. A review of the global measurements and modeling results is presented in this paper. In the future, if injections of materials into the atmosphere occur, their anticipated motions and fates can be accurately predicted from the knowledge gained from the fallout experience.
Oceanographic Science
A Millennium Perspective on the Contribution of Bomb Fallout Radionuclides to Ocean Science
Hugh D. Livingston, International Atomic Energy Agency
Five decades ago, radionuclides began to enter the ocean from the fallout from atmospheric nuclear weapons tests. The start of the 21st century is an appropriate vantage point in time to reflect on the fate of this unique suite of man-made radionuclides—of which more than two-thirds arrived at the surface of the oceans of the planet. During these five decades much has been learned of the behavior and fate of these radionuclides and, through their use as unique tracers, of how they have contributed to the growth of basic knowledge of complex oceanic physical and biogeochemical processes. Some of the highlights of the ways in which fallout radionuclides have given new insights into these processes are reviewed in the historical context of technological and basic ocean science developments over this period. The review addresses major processes involved, such as physical dispersion and mixing, particle association and transport of reactive nuclides, biological interactions, and mixing and burial within ocean sediments. These processes occur over a range of scales ranging from local to global. Finally, an account is given of the present spatial distribution within the oceans of the various components of the fallout radionuclide suite.
Ecological Science/Environmental Transfer
Movement of Radionuclides in Terrestrial Ecosystems by Physical Processes
Lynn R. Anspaugh, University of Utah
The rate of movement of radionuclides through terrestrial ecosystems is dependent upon both physical and biological processes. The former are radionuclide dependent, whereas the latter are highly dependent upon the element and its chemical form. Some of the more important physical processes are (1) the interception of airborne and rain-borne radionuclides by vegetation, (2) the loss of radionuclides from vegetation surfaces, (3) the resuspension of radionuclides from the ground surface and redeposition on vegetation, and (4) the weathering of radionuclides from the soil surface into deeper layers of soil. The first three processes are important determinants for the rate of ingestion of radionuclides through the contamination of foods, and the fourth process determines the long-term rate of external gamma exposure. The purpose of this paper is to summarize and synthesize information on these subjects with emphasis on the first, third, and fourth processes. The knowledge base on these processes has been significantly enhanced in recent times by the availability of data from the Russian Federation and new measurements made following the accident at Chernobyl.
Food Chain Pathways
F. Ward Whicker, Colorado State University
This presentation will provide selected illustrations of how measurements of global fallout from atmospheric nuclear testing have contributed to basic knowledge on biogeochemical cycles of many elements and enhanced understanding of food chain pathways. The necessity to monitor the radionuclide content of environmental media and foodstuffs during and after the nuclear testing era led to clever sampling designs and experiments, which in many cases, have led to new and sometimes rather unexpected insights about basic ecological, physiological and chemical processes which control the movements of materials and energy in the biosphere. Examples of knowledge gained through fallout-related studies include such topics as plant nutrition, feeding habits and intake rates of animals, trophic relationships, bioenergetics, migration patterns, agricultural processes, physiological rate parameters in animals and humans, and the ability to construct credible transport models for use in dose/risk assessments. It will be concluded that despite the regrettable aspects of historical atmospheric nuclear testing programs, a wide variety of useful contributions to our understanding of biogeochemical, ecological, agricultural and physiological processes resulted from studies on the radioactive fallout generated by them.
Twenty-Fifth Lauriston S. Taylor Lecture on Radiation Protection and Measurements
Introduction of the Lecturer, Marvin C. Ziskin
Assuring the Safety of Medical Diagnostic Ultrasound, Wesley L. Nyborg
Impact on Society
Charles W. Miller, Session Chairman
Human Exposures and Effects Estimates of Doses from Global Fallout
Andre Bouville, National Cancer Institute
The testing of nuclear weapons in the atmosphere was the most significant source of exposure of the world population to man-made environmental sources of radiation. The practice continued from 1945 to 1980. Nuclear weapons tests were conducted at various locations on and above the earth’s surface, including mountings on towers, placement on barges on the ocean surface, suspensions from balloons, drops from airplanes and high-altitude launchings by rockets. Depending on the location of the explosion and its yield, the radioactive debris produced by the nuclear explosion entered the local, regional, and global environments to various degrees. The purpose of this paper is to summarize the available information on external and internal doses resulting from global fallout. Most of the data are extracted from the UNSCEAR reports, in which the radiation exposures from fallout are extensively reviewed at regular intervals. In addition, specific information on the doses from fallout received by the American people are based on the preliminary results of a study requested by the U.S. Congress and conducted by the Centers for Disease Control and Prevention and the National Cancer Institute.
A Summary of Doses Received Locally from Fallout Originating at Nuclear Weapons Testing Sites Worldwide
Steven L. Simon, National Cancer Institute
Nuclear weapons testing was conducted at numerous sites worldwide and resulted in exposures to local populations as a consequence of fallout of radioactive debris. These sites included the northern hemisphere locations of Nevada, USA; several island locations in the mid-Pacific (primarily Bikini and Enewetak in the Marshall Islands, Johnston Island, and Christmas Island); in the former USSR at Semipalatinsk, Kazakstan and at Novaya Zemlya; Lob Nor in China; central Algeria, and in the southern hemisphere in French Polynesia. There were large differences in the numbers of tests conducted at each location and in the total explosive yields. Those factors, as well as differences in lifestyle and environment at each site, led to large differences in the doses received by local populations, though the amount of information available for a few of these sites is minimal compared to the Nevada Test Site. These disparities in available information add difficulty to determining the relative health impacts on local populations. It is the goal of this report to summarize the available information on external and internal doses received by the public living in the regions near each of the mentioned nuclear test sites as a consequence of fallout deposition.
Health Effects from Fallout
Ethel S. Gilbert, National Cancer Institute
Cancer is the main health effect that might be expected as a result of radiation exposures from atmospheric nuclear test fallout. Studies of persons exposed at relatively low doses and dose rates, including those exposed to fallout, have not definitively demonstrated increased risks, and are inadequate for developing reliable risk estimates. For this reason, risk estimates must be based primarily on data from epidemiological studies of Japanese atomic-bomb survivors and of medically exposed populations. Uncertainties in estimated doses and uncertainties in risk estimation models mean that fallout-related risks cannot be estimated precisely. Because estimated doses from fallout for most individuals are several orders of magnitude smaller than doses that drive current risk estimates, the need to extrapolate from high to low doses and dose rates is a particularly important source of uncertainty. In addition, some dose from fallout, especially that to the thyroid, comes from internal exposure to radionuclides such as 131I, whereas atomic-bomb survivors and medically exposed persons were exposed primarily to external gamma and x rays. Both the dose rate and uniformity of the dose within the organ may be different for these types of exposures, and the manner that this affects risks is not known with certainty. Currently available estimates of doses to the American public from atmospheric nuclear tests indicate that doses to the thyroid are much larger than doses to other tissues. Based on a model developed from a pooled analyses of data from seven studies, it has been estimated that between 11,300 and 212,000 thyroid cases would be expected to occur as a result of exposure to 131I from the Nevada test site. Risks from doses to tissues other than the thyroid could also be estimated when dose estimates become available. Several studies may eventually improve our understanding of risk from exposure to 131I. These include studies of children exposed to 131I as a result of the Chernobyl accident, and of children exposed to atmospheric fallout in Utah, the Marshall Islands, Semipalatinsk in Kazakstan, and near the Mayak nuclear plant in Russia.
Public Perception and Perspective A Perspective on Public Concerns about Exposure to Fallout from the Production and Testing of Nuclear Weapons
F. Owen Hoffman, SENES Oak Ridge, Inc.
Exposures of the American public occurred nationwide from the testing of nuclear weapons in the United States, the Pacific, and the former Soviet Union. After decades of diminished interest by the public on the subject of fallout, the release of the National Cancer Institute’s 1997 report on nationwide exposure to 131I released from the Nevada Test Site has led to renewed concerns. Public concerns are focused on individual and family health problems, the right to credible sources of information, and the need for medical care and assistance. There is concern about:
- the lack of complete information on the exposures and health risks from all biologically significant radionuclides,
- the lack of independent oversight that includes public participation, and
- reliance on results averaged over very large segments of the population without a focus on individuals or population subgroups likely to be at highest risk.
These concerns have developed largely from the legacy of government secrecy regarding the development and testing of nuclear weapons, public distrust of government sources of information about radiation exposures and health risks, and the injustice of past exposures imposed without informed consent. Members of the public participating in the oversight of dose reconstruction projects managed by the Centers for Disease Control and Prevention are requesting information on the total impact from all relevant sources of exposure at each site, including exposure to local releases and to NTS and global fallout. Information is being requested on individual doses and risks, with estimates of uncertainty, including estimates of the absorbed organ dose (as opposed to the effective dose), the excess lifetime risk of the incidence of neoplastic and non-neoplastic disease (as opposed to the risk of a cancer fatality), and the chance that a person’s diagnosed disease was caused by past exposure (i.e., the probability of causation). In this presentation, the implications of combined exposures to multiple sources of fallout and local releases will be discussed, along with the types of targeted public health initiatives that might be warranted for individuals at highest risk.
The Program Committee
Harold L. Beck, Chair
Lynn R. Anspaugh
Burton G. Bennett
Andre Bouville
Ethel S. Gilbert
Naomi H. Harley
Lester Machta
Charles W. Miller
F. Ward Whicker
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