What We Now Know
Chapter 11: What We Now KnowWhile the other intentional releases addressed in the Committee's charter were part of the effort to develop the U.S. nuclear arsenal, the Green Run was conducted to develop intelligence techniques to understand the threat posed by the Soviet Union. In 1947 General Dwight D. Eisenhower assigned the Air Force the mission of long-range detection of Soviet nuclear tests. Based on observations from Operation Fitzwilliam, the intelligence component of the 1948 Sandstone nuclear test series, the Air Force determined aerial sampling of radioactive debris to be the best method of detecting atomic releases. An interim aerial sampling network was in place in early September 1949 that detected radioactive debris from the first Soviet nuclear test.
Around the same time, Jack Healy of Hanford's Health Instrument (HI) Divisions noticed anomalous radioactivity readings from an air filter on nearby Rattlesnake Mountain. The HI Divisions were responsible for radiological safety, and Healy had set up this filter to test how radioactive contamination varied with altitude. The rapid decay of his radioactive samples led Healy to conclude that they had come from a recent nuclear test. Soon after news of Healy's observation reached Washington, D.C., Air Force specialists arrived and took Healy's samples and data for analysis. It is not clear whether Healy's observation came in time to support President Harry Truman's announcement on September 23 that the Soviet Union had exploded its first atomic bomb, but it did confirm that radioactivity from a nuclear test could be detected on the other side of the globe.
Now that the Soviet Union knew how to make atomic weapons, the United States needed to know how many weapons and how much of the critical raw material plutonium the Soviets possessed. Like nuclear testing, plutonium production released radioactive gases that sensitive instruments could detect, though not at such great distances. To identify Soviet production facilities and estimate their rate of plutonium production, the Air Force now needed to test ways to monitor these gases.
Hanford: The World's First Plutonium FactoryIn 1942 General Leslie Groves selected the Hanford site overlooking the Columbia River in southeast Washington state for the Manhattan Project's plutonium factory. The river would provide a large, reliable supply of fresh water for cooling the plutonium-production reactors, and Hanford's relative isolation from major population centers would make it easier to construct and operate the facility without attracting unwanted attention. The nearby towns of Richland, Kennewick, and Pasco soon became boom towns whose economies depended on Hanford.
At Hanford, neutrons converted uranium 238 in the production reactor's nuclear fuel into plutonium 239. Chemical separation plants then separated this plutonium from the fission products and residual uranium in the irradiated fuel elements. The first separation plants, the T and P plants, used acid to dissolve these fuel elements, but this was superseded by the more efficient Redox and Purex processes in the 1950s.
In late 1948 and early 1949, Air Force and Oak Ridge personnel conducted a series of twenty air-sampling flights at Oak Ridge and three at Hanford. The results were disappointing: instruments detected airborne releases of radioactive material at ranges of up to fifteen miles in the hills and valleys near Oak Ridge, but no farther than two miles from Hanford, because of measures taken to reduce radioactive emissions there. At an October 25, 1949, meeting at Hanford, representatives of the Air Force, the Atomic Energy Commission, and General Electric (the postwar contractor for the Hanford site) agreed to a plan to release enough radioactive material from Hanford to provide a larger radioactive source for intelligence-related experiments.
This intentional release took place in the early morning of December 3, 1949, but information about it remained classified until 1986. Two periodic reports of the HI Divisions described a plutonium production run using "green" fuel elements. The story of this "Green Run" has emerged piecemeal since then. The most complete account comes in a 1950 report co-authored by Jack Healy (referred to as the Green Run report), which was declassified in stages in response to requests from the public under the Freedom of Information Act and inquiries by the Advisory Committee.
Although cooling times of 90 to 100 days were common by 1949, the fuel elements used in the Green Run were dissolved after being cooled for only 16 days. This short cooling time meant that much more radioactive iodine 131 and xenon 133 were released directly into the atmosphere, rather than decaying while the fuel elements cooled. Furthermore, pollution control devices called scrubbers normally used to remove an estimated 90 percent of the radioiodine from the effluent gas were not operated.
When these "green" fuel elements were processed, roughly 8,000 curies of iodine131 flowed from the tall smokestack at Hanford's T plant. This stack was built in the early years of Hanford's operation when large quantities of radioactive gases were routinely released in the rush to produce plutonium. Although the Green Run represents roughly 1 percent of the total radioiodine release from Hanford during the peak release years 1945-1947, it was almost certainly larger than any other one-day release, even during World War II.
One clear purpose of the Green Run was to test a variety of techniques for monitoring environmental contamination caused by an operating plutonium-production plant. A small army of workers, including many from Hanford's HI Divisions, took readings of radioactivity on vegetation, in animals, and in water and tested techniques for sampling radioactive iodine and xenon in the air. The Air Force operated an airplane carrying a variety of monitoring devices--the same aircraft used in earlier aerial surveys at Oak Ridge and Hanford--and set up a special air sampling station in Spokane, Washington.
Those operating the equipment encountered numerous technical problems, including a lost weather balloon and failed air pumps. The greatest problem, however, was the general contamination of monitoring and laboratory equipment. The contamination created a high background signal that made it difficult to distinguish radioactivity on the equipment from radioactivity in the environment. The main cause of this contamination was the weather at the time, which led to much higher ground contamination near the stack than expected.
The plans for the Green Run included very specific meteorological requirements. These requirements were designed to facilitate monitoring of the radioactive plume by aircraft, but they were similar to the normal operational requirements, which were designed to limit local contamination:
Jack Healy reports that he made the decision to go ahead with the Green Run on the evening of December 2, 1949, even though the weather did not turn out as expected. Some have suggested that the Air Force pressed to go ahead with the release in spite of marginal weather conditions, but Healy recalls no such pressure. The plume from the release stagnated in the local area for several days before a storm front dispersed it toward the north-northeast. As a consequence, local deposition of radioactive contaminants was much higher than anticipated. The Green Run report concludes:
Under the worst possible meteorological conditions for such a test, the airborne instruments detected the radioactive gases at a distance better than 100 miles from the stack. Under favorable conditions, it was estimated that with the same concentrations this distance could have been increased by up to a factor of ten.
Despite the contamination of equipment, the monitoring provided a record of the extensive short-term environmental contamination that resulted from the Green Run. Measurements of radioactivity on vegetation produced readings that, while temporary, were as much as 400 times the then-"permissible permanent concentration" on vegetation thought to cause injury to livestock. The current level at which Washington state officials intervene to prevent possible injury to people through the food supply is not much higher than the then-permissible permanent concentration. Animal thyroid specimens showed contamination levels up to "about 80 times the maximum permissible limit of permanently maintained radioiodine concentration."
In spite of this contamination, the public health effects of the Green Run, discussed later in this chapter, were quite limited. However, in 1949, at the time the Green Run was conducted, the most important environmental pathways for human exposure to radioiodine were unknown. (Understanding developed shortly thereafter that environmental radioiodine enters the human body from eating meat and drinking milk from animals that grazed on contaminated pastures.) Thus, the effects of exposure through these pathways could not have been planned for, and it is fortunate that the risks were not higher.
The Control of Risks to the Public from Plutonium Production at HanfordFrom the first years of Hanford's operation, its health physicists were aware of the problems of contamination of the site by radioactive wastes, and it quickly became clear that radioiodine posed the greatest immediate hazard. Most fission products would remain in the dissolved fuel, but iodine gas would bubble out of the solution, up through Hanford's tall stacks into the atmosphere and down onto the surrounding countryside. Other radioactive wastes could be stored and dealt with later, and other radioactive gases were chemically inert and would quickly dissipate.
Over the years, Hanford health physicists adopted three main approaches to the iodine problem:
During World War II, producing plutonium for bombs was an urgent priority and knowledge of both the environmental hazards from iodine and the ways to prevent it were limited. Over the period 1944-1947, Hanford released nearly 685,000 curies of radioiodine into the atmosphere, about eighty times what was released in the Green Run. After the war, an improving understanding of how iodine could contaminate the food supply, evolving techniques to remove iodine from the plants' emissions, and policy decisions to limit the risks to the nearby population led to a marked reduction in iodine emissions.
When the AEC began operation in 1947, it promptly moved to review safety practices at Hanford and other operating facilities, which had operated largely autonomously until then. The advisory panel established for this purpose concluded that "the degree of risk justified in wartime is no longer appropriate." To address the radioiodine problem at Hanford and related problems, the AEC established a Stack Gas Working Group, which met for the first time in mid-1948 to study air pollution from AEC production facilities. The chair of this group noted that the AEC "desires the removal from gaseous effluents of all [radioactive] material insofar as is humanly and economically feasible" and that because of uncertainties in risk estimates "no limit short of zero should be considered satisfactory for the present." By 1949, daily emissions of radioiodine had fallen by a factor of 1,000 from their wartime highs.
The Green Run clearly did not conform to the practices designed to ensure public safety at Hanford in 1949 or even during the rush to produce plutonium for the first atomic bombs. In his monthly report for December 1949, Herbert Parker, Hanford's manager, concluded that the Green Run had posed a "negligible" risk to personnel, but "[t]he resultant activity came close enough to significant levels, and its distribution differed enough from simple meteorological predictions that the H.I. Divisions would resist a proposed repetition of the tests." This suggests that Parker, at least, considered the risks of such releases potentially excessive even for a one-time event, particularly given the degree of uncertainty.
Parker's recognition of the uncertainties surrounding environmental risks from Hanford's radioiodine emissions was appropriate. At the time, it was not known that drinking milk from cows that graze on contaminated pastures is the main source of exposure, especially for children. Jack Healy recently suggested that if Parker had known of the milk pathway, he would have objected strongly to the Green Run. The question remains as to the consideration that was given by the Green Run's planners to the possibility that they might not fully understand the risks that might be imposed on nearby communities.
Benefits of the Green RunThe Advisory Committee attempted to assess of the national security benefits that were expected and actually resulted from the Green Run. A planning memorandum before the Green Run notes, "the possibility of the detection of stack effluents is of great importance to the intelligence requirements of the country." How important the detection of stack effluents was to the security of the nation in 1949 is not something the Advisory Committee was in a position to judge. We did attempt to ascertain, however, the purpose of the Green Run and the extent to which this purpose was served.
The Green Run report focuses primarily on ground-based monitoring of radioactive contamination in the environment, which provided a test for techniques that could be used on the ground in the Soviet Union. The report also describes efforts to track the radioactive plume by aircraft, but their significance is unclear. Aerial monitoring turned out to be the most effective method for detecting atmospheric nuclear tests, and perhaps it was expected to be equally effective for monitoring Soviet plutonium production. Plutonium production releases relatively little radioactivity into the atmosphere, however--too little to detect outside Soviet air space, and flying inside Soviet air space would have been risky. Alternatively, aerial radiation tracking may have been designed to test techniques for use in monitoring nuclear weapons tests. Finally, the Green Run report compares the pattern of the plume's dispersion with theoretical models, but this appears to be an attempt to estimate the pattern of contamination rather than to test the already well-established theory regarding atmospheric diffusion of gases developed in the 1930s.
It is difficult to ascertain how useful the Green Run actually was. The classified histories of the Air Force's atomic intelligence activities contain no references to the Green Run. These histories jump from events that directly preceded the Green Run--the Oak Ridge and Hanford aerial monitoring tests--to later ones, without any mention of the Green Run. Perhaps most telling, a 1952 AEC report entitled "Technical Methods in Atomic Energy Intelligence" does mention the Green Run in the text, but only in a list of occasions on which a particular type of instrument was used. In describing ways of detecting plutonium-production facilities, the report relies on routine reports of environmental surveys from Hanford's routine operations.
Secrecy and Public RiskThe Advisory Committee accepts that there may be conditions under which national security can justify secrecy in intentional releases like the Green Run, even as we recognize that secrecy can increase the risk to the exposed population.
In discussing this question it is important to explain that when we use the term secret we can be referring to secrecy regarding the very fact that a risk has been posed, secrecy regarding the purpose behind the risk, or secrecy regarding the means (for example, the science of technology) by which the risk was imposed. These distinctions are important because even if we agree that the undertaking of an activity is required for national security reasons, it does not follow that secrecy should govern all aspects of the activity. Thus, as an obvious example, atomic bomb tests were quintessential national security activities; information on the design of the bomb was secret, as was information on many of the specific purposes of the tests; however, in many (but not all) cases the public was given notice that a hazardous activity was being undertaken. Similarly, in the cases of other environmental releases, it may be that national security requires secrecy for some aspects of the release but does not necessarily preclude public disclosure sufficient to give basic notification of the existence of potential risk. The Committee is not equipped to say whether this was so in the case of the Green Run. However, in the case of radiological warfare, as we will discuss later, there was contemporary argument that some public disclosure was not inconsistent with national security.
If a release is conducted publicly, affected communities have an opportunity to comment and perhaps influence the conduct of the release in ways that serve their interests. Downwinders can be warned, giving them the options of staying indoors with their windows closed, wearing protective clothing, altering their eating habits, or evacuating the area. If the release is conducted in secret, foreign adversaries are less likely to be alerted, but downwinders will be deprived of their options. Of course, evacuation may not be warranted, and other precautions may not be needed, or they may be of limited value. But, as we have learned during the course of our work, secrecy, even where initially merited, has its long-term price.
At Hanford, as we have noted, the Green Run represented only a fraction of the risks (including nonradiation as well as radiation hazard) to which local communities may have been exposed in secret. The delayed legacy of these risks, in uncertainty and distrust, as witnesses from the Hanford community told the Committee, is only becoming apparent as the secret history of early Hanford operations has been made public.
During World War II, officials at Du Pont, the contractor for Hanford at that time, proposed a practice evacuation to prepare for a possible emergency. General Groves turned them down, saying that "any practice evacuation of the Hanford Camp would cause a complete breakdown in the security of the project." As noted in the Introduction, at the onset of the Manhattan Project concern for the effects of Hanford operations on the surrounding environment, including the salmon in the Columbia River, led to a secret program of research on the environmental effects of Hanford's operations.
Secrecy remained the rule at Hanford after the war. In 1946, as recalled years later by an early biologist at Hanford who wrote to radiation researcher and historian Newell Stannard, Hanford researchers resorted to deception simply to collect information about possible iodine contamination in livestock, by having employees pretend to be agricultural inspectors while surreptitiously monitoring iodine levels in animal thyroids. The biologist wrote: "Though the Environmental Study Group at Hanford had been sampling air, soil, water, and vegetation in a wide area surrounding the Hanford site for several years previous to 1946, it was agreed that sampling from farm animals for uptake of fission product plant wastes would be a much more sensitive problem. At the time, the revelation of a regional I-131 problem would have had a tremendous public relations impact and furthermore the presence of other radionuclides . . . was of possible National Defense significance."
He explained that he was called at home and told to report to work at the director's office in downtown Richland. There:
I was introduced to two security agents of the Manhattan Engineer District . . . who were to be my escorts and contact men during the day. They proved to be the best straight faced "liars" I had ever known. I was no longer "Karl Herde of DuPont" but through the day would be known and introduced as Dr. George Herd of the Department of Agriculture. I was to simulate an animal husbandry specialist who had the responsibility of testing a new portable instrument based on an unproven theory that by external readings on the surface of the farm, the "health and vigor" of animals could be evaluated. I was advised not to be alarmed if at times during the conversations with farmers that they appeared critical or skeptical. I was to be very reserved and answer questions as briefly and vaguely as seemed acceptable. They agreed to carry a clipboard . . . I was to concentrate on the high readings (thyroids, of course) and furnish those for recording when not being observed.
In 1948, the AEC prepared a public relations pamphlet entitled Handling Radioactive Wastes in the Atomic Energy Program. The Department of Defense objected to the description of Hanford's operations, arguing that any description of the methods used to reduce contamination might be used by the Soviet Union to avoid detection of its plants. The AEC decided at its October 7, 1949, meeting to release the pamphlet, which contained no specific numbers, in order to "dispel and allay possible latent hysteria."
With a major expansion of Hanford's operations under way in 1954, questions arose over whether to publish information about contamination of the Columbia River. Parker warned that it might be necessary to close portions of the river to public fishing, but he and others noted that this could have a substantial public relations impact. At the same time, there was concern that information on river contamination could make it possible to ascertain Hanford's plutonium output. For this combination of public relations and security reasons, Hanford did not release any quantitative information or public warning on contamination of fish in the Columbia River until many years later.
It is difficult to argue with the need for secrecy about the purposes of the Green Run. Making information on U.S. atomic intelligence methods openly available could have led the Soviet Union to develop countermeasures to these methods. The issue remains important today in responding to the potential proliferation of nuclear weapons capabilities around the world.
But the results of the long delay in informing the public about the activities of which the Green Run was only a part are now evident in public anger and distrust toward the government. At the Advisory Committee's public meeting in Spokane on November 21, 1994, Lynne Stembridge, executive director of the Hanford Education Action League, argued that
Information regarding that radiation release was kept secret for almost 40 years. There was no warning. There was no informed consent. Citizens down wind were never advised of measures that could have been taken to safeguard the health of themselves or their children.
Among the most damaging dimensions of the legacy of distrust created by the secrecy that surrounded the routine and intentional releases at Hanford is the government's loss of crediblity as a source of information about risk. Now, when the government is attempting to find out what damage these releases actually did and share that information with the people affected, these people question why they should believe what the government says. Federally funded scientists at the Fred Hutchinson Cancer Research Center in Seattle, Washington, are now studying those exposed as children to all of Hanford's iodine emissions--the many routine emissions as well as the Green Run--to see whether any health effects are detectable. Whatever this study concludes, many residents are convinced that they have already seen the effects. Tom Bailie, who grew up and still lives on a farm near Hanford, spoke to the Advisory Committee's meeting in Spokane in November 1994. He pointed on a large map to what he called a "death mile," where "100 percent of those families that drank the water, drank the milk, ate the food, have one common denominator that binds us together, and that is thyroid problems, handicapped children or cancer." It is doubtful that the results of any study supported with federal funds, no matter how impeccably conducted, would be believable to people like Mr. Bailie. Assuming that the Hutchinson Cancer Research Center study is so conducted, and assuming the study finds that at least some outcomes of concern to the community are not attributable to the Hanford emissions, government secrecy will have deprived Mr. Bailie and people like him of an important source of reassurance and peace of mind.
The Green Run, and the far greater number of environmental releases resulting from Hanford's routine operations, raises challenging questions about the balance between openness and secrecy in settings where citizens may be exposed to environmental hazards. Citizens may reasonably ask whether releases have been determined to be necessary in light of alternatives, whether actions have been taken to minimize risk and provide for any harm that might occur, whether disclosure will be made at the earliest possible date, and whether records will be created and preserved so that citizens can account for any health and safety consequences at the time of disclosure. As we will see, these questions were posed with regard to other environmental releases, and they remain with us today.
Radiological WarfareThe first proposed military application of atomic energy was not nuclear weaponry but radiological warfare (RW)--the use of radioactive materials to cause radiological injury. A May 1941 report by the National Academy of Sciences listed the first option as the "production of violently radioactive materials . . . carried by airplanes to be scattered as bombs over enemy territory." It was not until later that year that a calculation by British physicists demonstrated the feasibility of nuclear weapons, and attention quickly turned to their development.
Military interest in both offensive and defensive aspects of radiological warfare continued throughout World War II. In the spring of 1943, when it was still unclear whether the atomic bomb could be built in time, radiological weapons became a possible fallback. Manhattan Project scientific director J. Robert Oppenheimer discussed with physicist Enrico Fermi the possibility of using fission products, particularly strontium, to poison the German food supply. Oppenheimer later wrote to Fermi that he thought it impractical unless "we can poison food sufficient to kill a half a million men." This proposal for offensive use of radiological weapons appears to have been dropped because of its impracticality. At the same time, military officials developed contingency plans for responding to the possible use of radiological weapons by Germany against invading Allied troops.
The peacetime experience of Operation Crossroads in 1946, particularly the contamination of the Navy flotilla from the underwater nuclear test shot labeled Baker, revived interest in radiological warfare. Some, including Berkeley's Dr. Joseph Hamilton, concluded that radiological poisons could be used as strategic weapons against cities and their food supplies. Once absorbed into the body, radioactive materials would cause slow, progressive injuries. Others proposed that RW could be a more humane form of warfare. Using radioactive material to contaminate the ground would render it temporarily unhabitable, but it would not be necessary to kill or injure people.
Although many discussions of radiological warfare took place in classified military circles, the basic notion of radiological warfare was not secret and was a subject of public speculation. But the government's program in radiological warfare remained largely secret, except in its broadest outlines. The postwar interest in radiological warfare spawned competing programs on radiological warfare both in the AEC and in various parts of the Department of Defense. To meld these into a coherent program, the AEC and DOD established a joint study panel in May 1948, chaired by the chemist W. A. Noyes from the University of Rochester and including civilian experts and DOD and AEC officials.
At its first meeting that month, the Noyes panel recommended work in three areas: (1) biological research on the effects of radiation and radioactive materials, to be carried out mainly at the Army Chemical Corps's Toxicity Laboratory, located at the University of Chicago; (2) studies on the production of radioactive materials for use in radiological warfare, carried out mainly by the AEC; and (3) military studies of possible RW munitions, also carried out mainly by the Chemical Corps.
The latter program was the focus of the Advisory Committee's attention because it involved the intentional release of radioactive materials during several dozen tests of prototype radiological weapons at the Chemical Corps's Dugway Proving Ground in the Utah desert. The offensive radiological warfare program field-testing program coincided with the Korean War years. The Noyes panel issued its final report after its sixth meeting, in November 1950, and was revived briefly in 1952 to assess the status of the RW research program.
The first two field tests were conducted at Oak Ridge. These involved sealed sources of radioactive material that were placed in a field in order to measure the resulting radiation levels. These measurements may have helped predict the effectiveness of radiological weapons. The sources were then returned to the laboratory and left no residual contamination in the environment.
Most of the radiological warfare field tests were carried out by the Chemical Corps at the Dugway Proving Ground, using radioactive tantalum produced at Oak Ridge. From 1949 to 1952, the Chemical Corps conducted sixty-five field tests at Dugway, intentionally releasing onto the ground roughly 13,000 curies of tantalum in the form of dust, small particles, and pellets. These were prototype tests, releasing much smaller quantities of radioactive material than the millions of curies per square mile that an operational radiological weapon would need to render territory temporarily uninhabitable. Furthermore, the field-test programs used tantalum primarily because it could be produced at existing facilities. An operational radiological warfare program required materials that could be produced in greater quantities than tantalum, but this would have meant constructing special production facilities.
In May 1949, the Chemical Corps established a panel of outside experts to provide advice on the safety of its field-testing program. Chaired by Dr. Joseph Hamilton, a strong advocate of the RW research program, the panel was chartered to consider radiological hazards to the civilian population, including hazards to "the water supply, food, crops, animal population, etc." Occupational safety was left to the Chemical Corps.
Under Hamilton's leadership, this panel raised a number of safety concerns but in the end appears to have been satisfied with the safety of the test program. Several months before the first panel meeting, Hamilton himself had objected to the use of the relatively long-lived isotope tantalum 182 (half-life, 117 days) as the radiological warfare agent in these field tests. He proposed using gold 198 instead (half-life, 2.7 days) to eliminate any lingering radiation hazard to the general population.
At its first meeting, on August 2, 1949, the RW test safety panel provisionally accepted the proposed testing program of the Chemical Corps, subject to a radiological safety review of the results of the first two tests. Hamilton's potential opposition clearly was of consequence, and his agreement to proceed was cause for relief.
Other members of the test safety panel, including Karl Morgan, head of health physics at Oak Ridge, raised concerns about the possible hazard posed by radioactive dust at an arid site like Dugway, both on- and off-site. Morgan proposed the use of airborne monitoring equipment developed at Oak Ridge in tests that preceded the Green Run. The use of such aircraft and other monitoring equipment evolved and expanded as the Dugway field tests continued over the next few years. Panel members approved the continuation of the program based in part on the results of these radiological surveys, which showed that contamination of the area was limited in size.
In 1952 the Chemical Corps proposed a significant expansion of the radiological warfare program, with a large test of 100,000 curies planned for 1953 and still larger tests proposed for later. The test safety panel once again raised concerns over the radioactive dust hazard. Hamilton noted that there were several "hot spots"--areas of unusually high radiation--at Dugway and that trucks at one of the target areas were kicking up significant quantities of radioactive dust. A Chemical Corps study in early 1953 concluded that the hazard was relatively slight.
Hamilton favored going ahead with the 1953 tests and was greatly disappointed when they were canceled, and with them the entire radiological warfare test program. The reasons for this cancellation are not entirely clear, but two factors are evident. The next phase of the program would have required the construction of expensive new production facilities, which collided with military budget cuts at the end of the Korean War. Furthermore, by 1953, only the Chemical Corps maintained a strong interest in the radiological warfare program, making it vulnerable to questions about whether it satisfied any unique military need. The radiological warfare program did not end completely, but its focus narrowed to defensive measures, including shielding and decontamination, with atmospheric nuclear tests providing the main opportunity for study.
The radiological warfare test safety panel was an early example of the use of an expert panel to evaluate possible risks of planned government activities. Ideally, such a panel should not be chaired by a proponent of the program in question, although those with such knowledge of, and interest in, the program are of obvious value to a safety effort. Hamilton's evident enthusiasm for radiological warfare research raises questions about his impartiality as head of the panel, but the panel as a whole appears to have dealt with serious public health issues in a responsible manner.
Secrecy in the Radiological Warfare ProgramThe U.S. radiological weapons-testing program appears to have remained formally secret until 1974 and remained largely unknown to the public until the GAO's report in 1993. There was a recurring tension at the time between those who wanted to release information to allay unwarranted public fears about radiation hazards and those who thought that publicity would create unwarranted attention and public apprehension that could interfere with the successful prosecution of the program. If there was a concern that public knowledge of the general outlines of the program would undermine national security, none of the available documents state this argument explicitly, except through their classification markings.
In May 1948, at its first meeting, the Noyes panel recommended that the entire program be classified Secret, Restricted Data; the Chemical Corps's RW program was classified at this level. At its second meeting, in August, the Noyes panel revised this recommendation to conclude that "[t]he existence of an RW Program should be considered as unclassified information." The Noyes panel was responding to the recommendation by the AEC's ACBM "that the Advisory Committee on Biology and Medicine urge that the broad subject of Radiological Warfare be declassified" on the grounds that "the subject appears in nearly every Sunday supplement in a distorted manner" and that "better work could be done from the scientific and medical standpoint" if the program were declassified.
In February 1949, Defense Secretary James Forrestal, responding to requests for greater public disclosure of U.S. nuclear activities, appointed Harvard University President James Conant to chair a confidential ad hoc committee to make recommendations on "the information which should be released to the public concerning the capabilities of, and defense against, the atomic bomb and weapons of biological, chemical, and radiological warfare." This high-level committee's work ended in October 1949 in deadlock, without making any strong recommendations. Its report to President Truman was quickly forgotten and, if anything, provided the basis for continuing the existing pattern of secrecy.
Among the listed rationales provided by the majority of committee members who opposed the release of further information on the capabilities of atomic weapons was the absence of "public demand" for the information. (The positions taken "by certain well-known and probably well meaning pressure groups," they suggested, "do not spring from any general public sentiment in this regard and should, therefore be ignored.") James Hershberg, in his biography of Harvard University President James Conant, who chaired "The Fishing Party" (as the committee was code-named), has observed:
Notably missing from this list is any indication that they were worried that the Soviet Union might derive military benefit from the release of data under consideration. . . . The observation [of the majority] that the "public would seem to be more concerned lest their officials release too much classified information, rather than too little" may have been accurate, but would the attitude have been the same if it were known the government was hiding the information not from Moscow but from its own people because it did not trust them? How else to explain the fear that "even a carefully reasoned statement . . . might have a very disturbing effect on the general public and could be misinterpreted by pressure groups in support of any extreme position they were currently advocating"?
In May 1949, while Conant's panel deliberated and the Chemical Corps was preparing for the initial Dugway field tests, the Defense Department's Research and Development Board (RDB) addressed the question of releasing information on radiological warfare. The RDB's Committee on Atomic Energy recommended against a public release of information. Soon after, a joint meeting of the Military Liaison Committee and the General Advisory Council considered, but rejected a drafted letter to the President, also recommending a press release on the RW program. Later that year, on advice from Joseph Hamilton, the Chemical Corps prepared a release regarding munitions tests at Dugway. The Chemical Corps's proposal for a release was discussed with AEC and DOD officials, who rejected it, saying such a release was "not desirable."
At roughly the same time, Defense Secretary Louis Johnson briefed President Truman on the radiological warfare program. The briefing memorandum prepared for Truman said that the planned tests posed a "negligible risk," but argued that "should the general public learn prematurely of the tests, it is conceivable that an adverse public reaction might result because of the lack of a true understanding of radiological hazards." It also noted that "a group of highly competent and nationally recognized authorities is being assembled to review all radiological aspects of the tests before operations are initiated at the test site."
The reference in the briefing memorandum was to the radiological warfare test safety panel, which was being selected at that time. In August, at the first meeting of this panel, Albert R. Olpin, president of the University of Utah, noted the risk that uranium prospectors might stumble onto the site. Citing Olpin's concern, Joseph Hamilton noted,
While the hazards to health for both man and animals can be considered relatively slight, the adverse effects of having public attention drawn to such a situation would be most deleterious to the program. In particular, Dr. Olpin brought up the interesting point that most of Utah is being very carefully combed by a large number of prospectors armed with geiger counters. Needless to say, it is imperative that such individuals be denied the opportunity to survey any region containing a perceptible amount of radioactivity arising from the various radioactive munitions that are to be employed.
Soon after this meeting, Hamilton also proposed a public release of information, perhaps reasoning that a program that was announced, but played down, would attract less attention than one that was discovered accidentally. Hamilton's proposal was refused. Echoing Hamilton's concerns, the Chemical Corps proposed once more that the tests be made public, again citing the risk of discovery by uranium prospectors. Robert LeBaron, chairman of the DOD's Military Liaison Committee to the AEC, turned down this request, claiming the need for review by the Armed Forces Policy Council.
The official silence about the prospects for radiological warfare prompted some public speculation about the government's activities, including a report appearing in the Bulletin of the Atomic Scientists, a journal created following the war to give a policy voice in print to many of the physicists who had worked on the bomb. The journal had some following in the general public as well as the scientific community. The report mirrored much of the analysis of the Noyes panel and concluded that RW had significant military potential.
In September 1949, the AEC's Declassification Branch recommended that certain general information, civil defense problems, and medical aspects of RW be declassified. Details regarding specific agents and methods of delivery, however, should remain secret. These suggestions appear to have been adopted shortly thereafter, as AEC and DOD reports at the end of 1949 and into the early 1950s discuss some aspects of the RW program in very broad terms. The closest thing to an official announcement of the field-test program appears to have come in a report for the first half of 1951. This report briefly noted that "research and development activities in chemical, biological, and radiological warfare were accelerated," and that "Dugway Proving Ground . . . was reactivated, and major field-test programs in offensive and defensive toxicological warfare were started," but provided no details. The 1994 summary of declassification policy by the Department of Energy notes that offensive radiological warfare was declassified in 1951 by the AEC, although the Defense Department appears to have kept this aspect of the program classified until much later.
The secrecy that surrounded the radiological warfare field-test program raises two related questions. The first question is whether concerns over public reaction are a legitimate basis for security classification. Officials at various levels cited fears of "public anxiety," "undue public apprehension," and even "public hysteria" to justify keeping even the most general information secret.
The documents reviewed by the Advisory Committee do not record the actual decisions at various stages to keep the field-testing program secret; they refer only to such decisions being made by others. It may be that those decisions reflected other reasons for secrecy. Or it may be that public reaction was considered a national security issue. This can be a legitimate argument, when the program in question is considered vital to the nation's security. However, the nation has a vital interest in open public participation in representative government, and making exceptions to the rule of openness requires a high standard of national need.
The second question is the same as the one raised for the Green Run: Can potentially important public health information about secret activities be made available to the public without compromising secrecy about the details and purposes of the activity? As described later in this chapter, this remains a live issue today.
The RaLa Tests: Two Decades of ExperimentationFrom 1944 to 1961, the Los Alamos Scientific Laboratory used lanthanum 140 (also known as radiolanthanum or RaLa) in 244 identified tests of atomic bomb components. These tests were critical to the development of the plutonium bomb, which required a highly symmetrical inward detonation of high explosive--known as implosion--to compress the plutonium fuel and allow a critical chain reaction. The RaLa method (see "What Were the RaLa Tests?") was the only technique available for measuring whether the implosion was symmetrical enough and continued to be used for testing bomb designs until the early 1960s, when technical advances allowed the use of alternative techniques.
What Were the RaLa Tests?Implosion devices use carefully timed detonations of carefully shaped high-explosive charges to generate a spherically symmetrical inward-directed shock wave. This shock wave in turn compresses the nuclear fuel of an atomic bomb--usually plutonium--causing it to "go critical" and undergo a nuclear chain reaction.[a]
In the RaLa tests, the plutonium core was replaced by a surrogate heavy metal with an inner core of lanthanum. Lanthanum 140 has a half-life of forty hours, emitting a high-energy gamma ray in its decay. Some of these gamma rays were absorbed as they passed through the outer components of the implosion device, the degree of absorption depending on how compressed those components were. Radiation measurement devices placed in various directions outside the device would indicate the overall compression and whether that compression was symmetrical or instead varied with direction. The lanthanum sources typically ranged from a few hundred to a few thousand curies, the average being slightly more than 1,000 curies, and were dispersed in the cloud resulting from the detonation.
a . Lillian Hoddenson et al., Critical Assembly: A Techincal History of Los Alamos during the Oppenheimer Years, 1943-1945 (New York: Cambridge University Press, 1993), 268-271.
In 1950 the Air Force flew a B-17 aircraft carrying an atmospheric conductivity apparatus in four radiation-tracking experiments at Los Alamos. These four experiments were identified subsequently by the General Accounting Office and appear in the Advisory Committee's charter. A historical analysis undertaken by the Los Alamos Human Studies Project Team in 1994 identified three of these experiments, in which the environmental release of radiation was incidental to the experiment, as part of the series of 244 intentional releases mentioned above; the presence of the tracking aircraft is all that distinguishes the three in the Advisory Committee's charter from the other 241.
The Los Alamos Scientific Laboratory was established in 1943 as the atomic bomb design center for the Manhattan Project on a mesa overlooking the Rio Grande valley, about forty miles northwest of Santa Fe, New Mexico. The RaLa tests were conducted in Bayo Canyon, roughly three miles east of the town of Los Alamos, which grew up next to the lab. Although radioactive clouds from the RaLa tests occasionally blew back toward the town, the prevailing winds usually blew those clouds over sparsely populated regions to the north and east. Aside from a small construction trailer park and a pumice quarry within three miles, the next nearest population center was the San Ildefonso pueblo, roughly eight miles downwind of the test site in the Rio Grande valley. Several Pueblo Indian and Spanish-speaking communities lie within twelve miles of Los Alamos.
Risks to the PublicConcerns over risks to the public arose at the beginning of the RaLa program. In the early years, Los Alamos planners and health physicists worried that the detonations could cause some contamination in areas outside the test site, such as the construction trailer park and nearby hiking trails.
As the RaLa program continued, several patterns of public safety practices developed. Initially, the principal way to protect people was to keep them out of the immediate test areas, but in later years it became the practice to test only when the weather was favorable, and later still to survey surrounding roads to detect whether contamination had reached hazardous levels.
Perhaps because early atmospheric monitoring had produced only negative results and because surveys in Los Alamos had indicated only minimal levels of contamination, ground contamination was not believed to be a significant problem at first. Environmental surveys after RaLa tests indicated significant contamination at some locations within three miles of the release, but not at greater distances.
This observation, and the opening of a pumice quarry within three miles of Bayo Canyon, led to intensive studies of fallout from the RaLa tests in 1949 and 1950. These studies led Los Alamos to conclude that "any area which is two miles or more from the firing point may be regarded as a non-hazardous area." As a result of these studies, Los Alamos restricted RaLa testing to take place only when the winds were blowing away from the town and laboratory of Los Alamos. Systematic weather forecasting, therefore, began only in 1949, after more than 120 tests had been carried out, and maintaining the capability to forecast wind conditions for these tests remained an important requirement over the years.
The meteorological constraints presumably reduced the radiation exposures in Los Alamos itself; exposures in more distant communities, while probably more frequent, remained lower than Los Alamos. At the Advisory Committee's public meeting in Santa Fe on January 20, 1995, however, Los Alamos activist Tyler Mercier commented that most of the "shots were fired when the wind was blowing to the northeast. At this point in time, that's where most of the population of this region lived. I mean, half of it is Spanish and half of it Native American." Mercier concluded that there "appears to be a callous disregard for the well-being and lives of the Spanish and Native Americans in our community."
The RaLa tests were suspended from July 1950 to March 1952. Routine radiological survey procedures were put into place when testing resumed. Surveyors would drive along roads in three sectors monitoring radiation hazards. Readings were typically below 1 mrad per hour (1 mR/hr), but reached levels of up to 15 mR/hr at nearby locations and up to 3 mR/hr at distances of several miles. Readings in excess of 6 mR/hr required further action, including possible road closure. If the surveyors detected significant levels, they would continue monitoring in the next canyon downwind. On at least one occasion, ground contamination at relatively large distances from Los Alamos led monitors to extend their survey to a nearby town (Espanola), where they detected no radioactivity.
The RaLa tests were understood from the beginning to be hazardous, but they were also critical to the design of nuclear weapons. Los Alamos officials took significant steps to understand and limit those risks. On at least two occasions--in late 1946 and from 1950 to 1952--they suspended testing amid questions about the continuing need and decided to continue testing. When the RaLa tests finally ended in 1961, an alternative means of obtaining needed information had become available.
Risks to WorkersFrom the beginning, the RaLa tests also raised concerns over hazards to workers, particularly the chemists, in spite of elaborate measures adopted to limit these chemists' radiation exposures. Lanthanum 140, with a half-life of forty hours, is itself the decay product of barium 140, which was separated from spent reactor fuel at Oak Ridge or Idaho National Engineering Laboratory in later yearsand transported in heavily shielded containers to Los Alamos. There, chemists would periodically separate out the highly radiaoactive lanthanum for use in the implosion tests.
Soon after testing began on September 21, 1944, the RaLa program posed a puzzle for radiation safety. On October 16, Louis Hempelmann, director of the Health Division at Los Alamos, wrote to Manhattan Project medical director Stafford Warren about blood changes observed in the chemists working on the most recent RaLa test:
[I]t looks now as though I was too excited about the blood changes, but at that time it seemed to me to be such a clear cut case of cause and effect that I thought the measurements of dosage must have been incorrect. Now I feel reasonably certain of the dosage. . . . It was a case where risk was taken knowingly and willingly because it seemed necessary for the project. . . . It is my feeling that it should be the decision of the Director whether or not risks of this type should be taken. . . .
In August 1946 Hempelmann termed the exposures of personnel in the Chemical Group "excessive" and recommended that no more "RaLa shots" be attempted until "replacements are obtained for each member in this team." The tests were suspended temporarily "because of over-exposure of personnel to radiation." Los Alamos was faced with the alternative of increasing its staff (so that individual exposures could be reduced) or shutting work down until safety measures were installed.
RaLa testing resumed in December 1946, after a review to determine whether it was still necessary, but no documents are available to determine whether safety procedures or staffing were changed. What did change was that researchers began a formal study of the relationship between the radiation exposures and blood counts of the Bayo Canyon chemists. The chemists' depressed white blood counts (lymphopenia), presumably the same changes noted two years earlier, posed a puzzle that continued for at least a decade, resulting in three scientific reports. In 1954, Thomas Shipman, who had replaced Hempelmann as Health Division director, wrote to the AEC that
The blood counts were done with extreme care . . . and we are satisfied that the changes in counts are actual and not imaginary. It is our belief, however, that they don't mean anything; if they do mean anything, we don't know what it is.
The cause of these blood effects remains uncertain. The reported doses of roughly 10 rad per year are well below levels expected to produce any detectable blood changes, a fact that was known by 1950. While it is possible the effect could have been due to undetected internal contamination, a more likely explanation may be that the chemists were exposed to chemical compounds that produced the observed blood changes.
It appears that in the latter part of the 1940s some Los Alamos officials worried about the possible consequences of publicly releasing data on health effects, including those related to the chemists. A 1946 internal Los Alamos memo records that Dr. Oppenheimer asked that "all reports on health problems be separately classified and issued at his request." The author of the memo indicated his belief that the purpose was to "safeguard the project against being sued by people claiming to have been damaged." Two years later, Norman Knowlton, a Los Alamos hematologist, reported on the blood changes in ten workers at the lab. A 1948 memo from the AEC's insurance branch argued that releasing this report on blood counts could have "a shattering effect on the morale of the employees if they became aware that there was substantial reason to question the standards of safety under which they are working" and concluded that "the question of making this document public should be given very careful study." The report was not classified, however, although later reports were stamped "Official Use Only."
While the remaining information on the Los Alamos chemists is fragmentary, the experience raises an enduring question: What are the obligations of the government and its contractors to notify and protect employees whose work may expose them to continuing hazards, even when the risk is known to be small or is uncertain? As is discussed in chapter 12, during the same period, issues of worker protection and notification were raised much more starkly in the case of the uranium miners, who were placed at significant risk, a risk they had not "knowingly and willingly" taken.
Informing the PublicAlthough many in Los Alamos--those who worked on bomb design--knew of the RaLa program and its potential hazards, there is no indication of any discussion with other workers or local communities. For example, from the mid- 1940s to the mid-1950s many Pueblo people who may not have been informed worked at the lab as day laborers, domestics, and manufacturers of detonators. The first public mention appears to have come in 1963, when the Los Alamos laboratory newsletter printed an article describing the cleanup of Bayo Canyon. Los Alamos reports that its first concerted efforts to tell the Pueblo people about the RaLa program did not occur until 1994, when Los Alamos began its review of the RaLa program.
Representatives of the pueblos near Los Alamos most likely to be affected by the RaLa tests have complained about past and continuing failures of laboratory officials to communicate with Pueblo workers or communities. Recent efforts at Los Alamos to undo this legacy of secrecy have created a continuing sense of frustration; Pueblo representatives state that information and other relations with the lab are still too tightly controlled to be trusted completely.
It is difficult for any outsider to appreciate fully the unique cultural and religious viewpoint from which the Pueblo Indians perceive the effects of environmental releases. In addition to having several holy sites located near Los Alamos, the Pueblo have a deep respect for the land, which appears to have been violated by many of the activities at Los Alamos. The Pueblo continue to rely to some degree for the basic necessities of food, heat, and shelter on plants, animals, and the earth, and they suspect that they may be at added risk of exposure to radioactivity in the environment.
George Voelz, a Los Alamos physician who was at the lab during some of the RaLa tests, told the Advisory Committee, "As far as I know there was not much communication going on with the people in the area. And that, in retrospect was a mistake." As a result of these failures of communication, Los Alamos now faces a difficult challenge, five decades later, of attempting to establish trust with neighboring communities that have become more suspicious because of what they have learned. Here, as in Hanford, credibility is the casualty of silence and secrecy.
Studies of Environmental Risks and SafetyThe Green Run and the radiological warfare and RaLa programs were by no means the only government-sponsored experiments in which radioactive materials were intentionally released into the environment. Scientists undertook a wide variety of studies designed to understand the risks of environmental exposure to radioactive materials. For example, tests of experimental nuclear reactors at the National Reactor Testing Station in Idaho and the National Reactor Development Station in Nevada were designed to simulate possible accident scenarios under carefully controlled and isolated conditions. Similarly, tests at the Nevada Test Site were designed to understand the possible effects of an accidental (nonnuclear) explosion of a nuclear weapon.
In addition to intentional releases designed to test the safety of nuclear machinery, safety was also a concern in studies designed to understand the fate of radioactive materials in the environment. Many of these studies simply took advantage of releases that occurred accidentally or were incidental to other projects. In 1943, studies of the exposure of salmon in the Columbia River to the radioactive effluent from Hanford's reactors set in motion the growing and largely public science of radioecology. The environmental analogue of radioisotope tracer studies designed to better understand the workings of the human body, these studies were intended both to follow the course of radionuclides released into the environment during nuclear weapons production and testing, and use radionuclides to trace the basic workings of the environment. The deliberate release of very small quantities of radioactive material provided the opportunity for more-controlled environmental study than those studies that simply observed radionuclides already released into the environment. The Advisory Committee did not attempt to survey the entire field of radioecology, but we have reviewed the following examples in some detail.
Project ChariotProject Chariot was a component of Project Plowshare, the brainchild of physicist Edward Teller, who helped develop the first hydrogen bomb. Plowshare arose in the late 1950s in response to public protests against atmospheric nuclear testing and was intended to demonstrate that "clean" nuclear explosives would provide safe, peaceful uses of atomic energy.
In 1958, Teller selected a site in northern Alaska for Project Chariot, the proposed excavation of an Arctic seaport using a series of nuclear explosions. The site chosen was near Cape Thompson, roughly thirty miles from the Inupiat Eskimo village of Point Hope. This proposal, which was the subject of public debate, died in 1962 in the face of popular opposition. However, extensive observations of the Alaskan ecosystem were undertaken between 1958 and 1962 to provide a baseline for comparison with results of the planned nuclear explosions. These observations led to the first awareness of the environmental hazards of cesium 137 from distant (primarily Soviet) atmospheric nuclear tests and led to a series of studies on cesium in the food chain and in humans.
Most of the environmental studies in Project Chariot were purely observational, but one series of studies involved the intentional release of small quantities of radioactive materials--a total of 26 millicuries of iodine 131, strontium 85, cesium 137, and mixed fission products. In several studies, researchers from the U.S. Geological Survey spread radioactive materials on the surface of small plots of land and observed their spread across the surface when sprayed with water to simulate rainfall. In another, researchers placed mixed fission products in a small pit and measured their transport through the subsurface clay, and in yet another, researchers studied the spread of radioactivity in a creek contaminated with radioactive soil from Nevada. After these studies, the contaminated soil was removed and buried in above-ground mounds. Although this was a technical violation of regulatory requirements, an AEC memo expressed general satisfaction with the cleanup, noting that burial in the permafrost would have been too difficult.
After the initial cleanup, the site remained dormant for thirty years until 1992, when a researcher discovered correspondence between the AEC and USGS about the tracer studies. In response to public concerns, the Department of Energy undertook to clean up the mounds' potentially contaminated soil. A survey indicated no externally observable radioactivity, and very little, if any measurable, radioactive material was believed to remain. In 1993, the mounds of soil were removed for disposal at the Nevada Test Site. Caroline Cannon, an Inupiat Indian resident of Point Hope, told the Advisory Committee at its public meeting in Santa Fe,
I have lived in Point Hope all my life and eaten the food from the sea and the land and drank the water of Cape Thompson, along with the others. I have to wonder about my health, what impact the poison on the earth will have all through my lifetime, emotionally, physically, and most of all for my children and my grandchildren.
Although the risk to the population was minimal, residents still wonder whether other experiments might have occurred and remain secret. Here again, government secrecy in the past is undermining government credibility in the present. How much comfort are Ms. Cannon and others like her able to take in reassurances from the government about risks to future generations, a government that they perceive unjustifiably kept them in the dark?
Controlled Radioiodine ReleasesA small number of intentional releases involved the deliberate exposure of human subjects to trace quantities of radioisotopes in the environment. The most systematic of these were five of the roughly thirty Controlled Environmental Radioiodine Tests (CERT), carried out at Idaho National Engineering Laboratory (INEL) between 1963 and 1968. Small quantities of I-131 were released into the atmosphere under carefully monitored meteorological conditions.
In one study, seven volunteers drank milk from cows that grazed on the contaminated pasture. The quantity of iodine was measured carefully in the air, on the grass, in the milk, and later in the volunteers' thyroids, allowing a quantitative reconstruction of the full environmental pathway. The maximum exposure among these volunteers was reported as 0.63 rad to the thyroid, nearly a factor of 50 below the contemporary annual occupational exposure limits. In four other studies, a total of about twenty volunteers stood downwind at the time of the release; their exposures, from inhaling I-131 in the air, were much lower. Apparently, all these volunteers were members of the INEL staff. Measurements of the radioactivity in their thyroids provided a quantitative reconstruction of the inhalation pathway.
Studies similar to the CERT took place at Hanford in 1962, 1963, and possibly in 1965. The 1963 Hanford test involved human volunteers from Hanford's health physics staff, as did studies of iodine uptake from milk.
The subjects in all these studies are referred to as volunteers in the relevant documents. No evidence is available bearing on what these subjects knew or were told about the experiments or the conditions under which they agreed to participate. The subjects were all staff members of the agency (or its contractors) conducting the research. The documents suggest that these staff members included knowledgeable individuals who participated in these experiments in the spirit of self-experimentation.
Reconstructing, Comparing, and Understanding RisksThus far, we have only briefly characterized the risks associated with the intentional releases reviewed in this chapter. Just how risky were those intentional releases and how much of this risk materialized? Although these questions cannot be answered with certainty, the answers can be approximated. Actual and suspected failures to respect public health in the environmental practices of the past have often led to efforts to reconstruct the basic facts and estimate the likely harm from environmental releases of radioactive materials. This process of environmental dose reconstruction has become an essential part of informing the public.
The task of estimating past environmental exposures to radioactive materials is a complex, multistep process. The first step is to collect data from historical records on the amount of material released. The second is to use records on weather, actual measurements of radioactivity in the environment, and computer models to reconstruct where this material went. The third step is to estimate how this distribution of material might result in radiation exposures to humans. Finally, these exposure estimates can be combined with mathematical models of radiation risks to estimate the resulting harm to people who were exposed.
Radioactive materials released into the environment can affect humans in two ways. First, they can be a source of radiation external to the body: beta radiation, which affects the skin, or more penetrating gamma radiation. Second, they can enter the body from contaminated air, food, or water and provide an internal source of radiation. Of these environmental pathways to radiation exposure, the food pathway is by far the most complicated. Radionuclides can enter the food chain at many points, through contaminated air, water, and soil, resulting in contaminated fruits, vegetables, meat, and dairy products.
The hazards from environmental exposures to radionuclides differ in important quantitative ways from those due to medical procedures or participation in biomedical research. The natural dilution of materials in the environment means that individual exposures even from massive releases are often quite small, although the chemical and biological processes involved in exposures through the food chain can lead to effects that counteract this dilution. Finally, many more people may be exposed, with exposures that vary widely from person to person.
Because individual exposures are generally too low to produce any acute effects, the main form of injury possible from environmental radiation exposure is cancer, which may occur many years after the exposure, and the number of cases attributable to such exposures can be expected to be relatively small. Evidence of cancer from exposure to radiation is difficult to separate out from other possible causes of those injuries; for the intentional releases discussed in this chapter, it is essentially impossible. Instead, we must rely on models of risk based on studies of other human radiation exposures.