HANFORD DOWNWINDERS INFORMATION SITE
Potential Health Problems from <br>
Exposure to Selected Radionuclides:
Plutonium, Strontium, Cerium and Ruthenium

HERE YOU'LL FIND...

History of Hanford's Hot Particles

Possible Health Problems

Plutonium

Strontium

Cerium

Ruthenium

Downwinder Perspective

Unresolved Issues Concerning Hot Particles

Summary

For more than 40 years, the U. S. government produced plutonium for nuclear weapons at the Hanford Site in south central Washington State. In 1986, responding to citizen pressure, the U.S. Department of Energy made public hundreds of previously restricted documents. Since then, much attention has focused on the very large releases of iodine-131 as a possible cause of thyroid disease. However, Hanford also released other forms of radiation into the air and the Columbia River.

This report examines the releases of four radionuclides to the air and the potential health effects which might result from people being exposed to these materials. The four radionuclides are: plutonium, strontium, cerium and ruthenium. Other radionuclides were released to the Columbia River. A separate HHIN publication addresses the possible health effects of these radionuclides.

According to the Technical Steering Panel of the Hanford Environmental Dose Reconstruction Project, the largest contributors to dose from the air pathway were first, iodine-131, then cerium-144, plutonium-239, ruthenium-103, ruthenium-106, and strontium-90. Dose is the amount of radiation absorbed by a person's body. There were many other radioactive materials released into the air, as well, but these contributed less to dose, according to the Technical Steering Panel.

The Hanford Environmental Dose Reconstruction (HEDR) Project was established to estimate what radiation dose people living near Hanford some time between 1944 and 1992 might have received from releases of radioactive materials. The Technical Steering Paned, which directed the study, completed its role in 1995. The federal Centers for Disease Control and Prevention (CDC) is now working with the HEDR Task Completion Working Group to continue public participation and to assure completion of the remaining HEDR activities. When using information from this and other studies, readers should keep in mind that research results depend on a number of factors, such as the information available, and the methods and type of analysis used.

What are the possible health problems from exposure to plutonium, strontium, cerium and ruthenium? Most of the information on health effects from these materials has come from studies of plutonium workers and research involving animals. None of these studies contains information that relates to the specific situation of those people who lived downwind from Hanford. While comparisons to the Hanford situation are uncertain, the information in this report may help identify potential health problems which may have been caused or could be caused by exposure to these radionuclides.

Radiation health scientists generally believe that any dose of radiation, however small, carries with it an increased risk of some adverse health effect, such as cancer. This does not mean that everyone who receives an exposure will suffer an effect. It means the risk of a radiation-induced health problem is increased. Even if a particular effect does occur in an individual, it is not possible to determine, with current scientific methods, that it was caused by radiation exposure.

History of Hanford's Hot Particles

Unlike iodine-131 - which was released as a gas - plutonium, strontium, cerium and ruthenium became attached to particles of rust or dust and were then released. There were two time periods in Hanford's operation when there were major releases of radioactive particles:

  • From late 1944 through at least 1951, there were large releases of particles containing plutonium, strontium and cerium.

    From 1952 to 1954, there were large releases of particles containing ruthenium.

    Plutonium, Cerium and Strontium

    Starting in 1944, Hanford produced plutonium for use in nuclear weapons. Uranium fuel was partially transformed into plutonium inside the nuclear reactors along the Columbia River. The irradiation of uranium not only created plutonium but also created numerous other radioactive elements, including the radionuclides of cerium, strontium and ruthenium, which are the subject of this report. After irradiation, the uranium fuel (now containing plutonium and the other radionuclides) was transported several miles to the separations plants at the center of the Hanford Site. It was here that the fuel was dissolved in nitric acid. After numerous chemical steps, the plutonium was separated from the fuel and purified for use in nuclear weapons.

    The process of separating the plutonium released pollution to the air and the ground. This report focuses on the potential health effects from exposure to those radionuclides that were released to the air on particles. These particles are called "hot" because they were radioactive.

    Plutonium, cerium and strontium were released to the air from the original plutonium separations plants from late 1944 through at least 1951. In the fall of 1947, monitoring equipment revealed radioactive particles on the ground surrounding the stacks of the plutonium plants. The ventilation system in the radioactive processing area was the source of the problem. The interior of the plants' ventilation system had started to rust in places. Plutonium and the other radioactive materials attached to the rust. Later, parts of the contaminated rust broke off and went up and out the stacks. The sections inside the plants in which the operators worked had a separate ventilation system that was not affected by the particle problem.

    The particles contained plutonium, cerium and strontium. Other radioactive materials were also present in at least some samples of the particles but in lower concentrations. Most of the particle was rust or other non-radioactive material.

    In January 1948, Hanford replaced the ventilation system. The number of relatively large particles decreased, but smaller particles continued to escape. Hanford scientists believed that the smaller particles had been released from the start of plutonium separations in December 1944. In March 1948, Hanford documents reported the release of as many as 100 million particles per month.

    Because of their size and weight, many of the particles landed on the ground within the Hanford Site boundaries. However, Hanford technicians detected some particles as far away as Mullan Pass (now known as Lookout Pass) in Idaho; and Spokane and Mt. Rainier in Washington. The concentrations of the particles at these locations were "comparable" to those in Richland (Richland is located about 25 miles southeast of the separations plants).1

    Hanford officials were concerned about possible health effects on workers from hot particles. They considered lung cancer (from the inhalation of particles) to be the most serious health threat.

    Hanford radiation protection officials imposed several work restrictions and ordered that some workers be given filter masks. However, most workers, including construction workers and security guards, were not issued filter masks. Hanford officials considered the plutonium particle problem so serious in October 1948 that they stopped separating plutonium for at least three days.2

    It is uncertain how long the problem with the plutonium particles continued. According to a U.S. Senate report, the last reference to the problem was at a meeting in 1951. Herbert M. Parker, Hanford's chief health physicist, said at the meeting: "The particle problem still remains, in my opinion, a very serious health problem."3

    Ruthenium

    After World War II, a new type of chemical process was developed to recover plutonium for use in nuclear weapons. An unintended effect of this process was that flakes of material, including ruthenium, accumulated on the inside lining of the stack at Hanford's Redox plant. "Redox" stood for "reduction-oxidation" and described the kind of chemistry used to separate the plutonium. As in the case of plutonium particles, the ruthenium built up within the process ventilation system, which was separate from the building ventilation system.

    The Redox plant began operations in 1952. Shortly afterward, technicians discovered the ruthenium particle problem. Material containing ruthenium had deposited on the inside of the stack. As the material built up on the stack lining, some of it broke off in the form of flakes and was carried up and out the stack. Radiation surveys found very large flakes, some several inches across, on the ground around the base of the stack.

    The largest reported release was in January 1954 when about 200 curies of ruthenium were released. Hanford radiation technicians tracked the particles as far as Spokane, Washington, about 150 miles to the northeast. In April 1954, airborne radiation equipment tracked the particles as far as northeastern Montana.

    Inhaling ruthenium particles posed a health danger. In addition, the ruthenium particles posed a hazard if any of the large particles had fallen onto a person's exposed skin.

    Hanford Assessment Not Yet Completed

    Since the release of the first 19,000 pages of Hanford historical documents in 1986, much has been learned. However, it is not enough to form a complete assessment of the impact of the Hanford releases. This is especially true in the matter of Hanford's particle problems. For example, the HEDR Project has not yet estimated doses from the hot particle releases.

    Possible Health Problems of Plutonium, Strontium, Cerium and Ruthenium

    Keep the following points in mind when reading the sections on the possible health problems of the selected radionuclides:

  • Researchers have done a few studies involving human exposure to plutonium, as well as several animal studies. For cerium, ruthenium and strontium, the only data available are from animal studies.

  • Comparing the health effects on animals and on people exposed to radiation from Hanford is problematic for three main reasons:

    1. The life span of human beings is much longer than that of the animals used in studies.

    2. It is uncertain if humans are affected in the same way as animals.

    3. Most of the animal studies involved exposure to very high levels of radiation (equivalent to a human exposure of thousands of rem). Hanford exposed people to generally lower levels of radiation but over a long time.

    This report provides information about each of the four radionuclides. The same categories of information are presented for each:
    • the possible health effects
    • a general description of the radionuclide
    • the estimated amount released from Hanford from 1944 to 1972

    The dose estimates are cumulative for 1944-1992, whole body in rem EDE (effective dose equivalent). The release estimates are cumulative for 1944-1972. These numbers are taken from the Hanford Environmental Dose Reconstruction draft reports released in April 1994. Both the release and dose estimates for the four radionuclides are not complete because: (1) the Hanford Environmental Dose Reconstruction Project has not yet reconstructed the amount of the four radionuclides released on particles; (2) the computer model used in the study did not simulate the behavior of particles; and (3) the Dose Reconstruction Project has not yet estimated doses from the hot particle releases. This work is now underway. The federal Centers for Disease Control and Prevention (CDC) is now working with the HEDR Task Completion Working Group to continue public participation and to assure completion of the remaining HEDR activities.

    its chemical form as released from Hanford's weapons plants

    The chemical form of the radionuclide is very important in assessing how the body might handle the material. The chemical form may significantly affect the dose a person receives from incorporating the material into the body. One aspect of the chemical form is whether it is soluble or insoluble. The Hanford Environmental Dose Reconstruction Project assumed that plutonium and cerium were released in soluble forms.

    the range of representative doses

    The dose estimates are cumulative for 1944-1992, whole body in rem EDE (effective dose equivalent).

    a summary of health studies

    Plutonium

    Possible Health Effects: Bone, liver and lung cancer; leukemia; chromosome aberrations

    Description: The isotope of plutonium for which the Dose Reconstruction Project is calculating dose estimates is plutonium-239.

    Estimated Amount Released from Hanford: 1.78 curies

    Chemical Form of Release: Assumed to be soluble4

    Range of Representative Dose Estimates: 0.03 mrem EDE to 3.6 mrem EDE

    Summary of Scientific Studies

    PLUTONIUM:

    Cancer

    Studies of plutonium workers and many animal studies have focused on exposure to insoluble forms of plutonium. The Hanford Environmental Dose Reconstruction Project assumed that the plutonium released to the air was in a soluble form. The potential health problems of soluble and insoluble plutonium are described below.

    When plutonium is inhaled in an insoluble form, most of it that is retained in the body remains in the respiratory tract. In this kind of exposure, cancers of the lung are possible. Plutonium workers are usually exposed to the insoluble forms of plutonium. Studies of these workers have not found an increased risk for lung cancer that is related specifically to plutonium exposure.5 In animal studies, nearly all animals that were exposed to high doses of insoluble plutonium died either of extensive lung damage or lung cancer.

    Most insoluble plutonium particles that are inhaled are removed from the body within a few days. Some particles are removed via the lymph nodes. Some of these particles may remain in the lymph nodes for years. In animal studies, high exposure caused the lymph nodes to stop functioning properly. Dr. H. Metivier with the Experimental Toxicology Laboratory in Montrouge, France, has suggested that plutonium could weaken the immune system in humans and lead to the development of cancers outside of the lymph nodes.6

    In 1987, a study of Rocky Flats workers by Dr. Gregg S. Wilkinson (then at the Los Alamos National Laboratory) and others concluded that workers who had plutonium inside their bodies had an increased risk of lymphopoietic neoplasms (tumors affecting a kind of white blood cells).7 A report by the Committee on the Biological Effects of Ionizing Radiations of the National Research Council (BEIR IV) was skeptical about this finding because the Rocky Flats study did not show any increases in lung, bone or liver cancers.8

    Plutonium in a soluble form acts differently in the body than the insoluble form. Instead of remaining in the lungs and the lymph nodes, as the insoluble form does, soluble plutonium enters the blood relatively quickly and deposits on bone surfaces and in the liver. About 40 percent of the plutonium that enters the blood goes to bone surfaces, 40 percent to the liver and the remaining 20 percent to muscle.9 If a person is exposed to soluble plutonium, cancers of the bone and liver are possible, with the likelihood dependent on the dose.

    Some scientists stress the need for additional studies on humans because of the long time lapse between exposure and when cancers are diagnosed. This period is called the latency period. For plutonium, the latency period is estimated to be more than 30 years, but may vary depending on the dose received.10

    PLUTONIUM:

    Leukemia

    There are conflicting opinions in two studies regarding plutonium exposure and the risk of leukemia. Leukemia is a cancer of the blood and begins in the blood cells formed within the bone. Metivier stated at a symposium presented by the French Society of Biophysics and Nuclear Medicine in 1982 that there is a possibility of leukemia if the bone marrow is exposed to plutonium. 11 However, the 1988 BEIR IV report stated there is no evidence that plutonium can cause leukemia.12 In humans, relatively little plutonium is found in the bone marrow, and the dose to this tissue is quite small compared to the dose to the bone surfaces. The risk of leukemia from exposure to plutonium is likely to be far less than the risk of bone cancer.

    PLUTONIUM:

    Chromosome Aberrations

    E. Janet Tawn and her colleagues in the Medical Department at British Nuclear Fuels, Sellafield, England, did a study of the chromosomes of 54 plutonium workers who were exposed to plutonium mainly by inhalation. Each plutonium worker had a higher number of chromosome aberrations compared with workers not exposed to plutonium. The scientists concluded that the exposure to plutonium increased the number of aberrations.13

    Strontium

    Possible Health Effects: Leukemia, bone cancer, weakened immune system

    Description: The isotope of strontium for which the Dose Reconstruction Project is calculating dose estimates is strontium-90. In the body, strontium is chemically similar to calcium. Therefore, the body is likely to use strontium in the same way it would use calcium.

    Estimated Amount Released from Hanford: 64.3 curies

    Chemical Form of Release: unknown

    Range of Representative Dose Estimates: 0.0007 mrem EDE to 0.07 mrem EDE

    Summary of Scientific Studies

    STRONTIUM

    Leukemia

    Strontium may cause leukemia. 14 More than 90 percent of the strontium that remains in the body is in the bones.15

    According to M. Thomasset, MD, Director of Research at the National Center of Scientific Research, National Institute for Health and Medical Research, Le Vesinet, France, "continuous low doses" of strontium cause relatively more cases of leukemia than high, one-time doses.16

    STRONTIUM

    Cancer

    Because strontium deposits in the bones, bone cancer is also a possible health effect. Animal studies have shown that high doses of strontium produce a relatively large number of bone cancers. At lower levels of exposure, there are very few cases or none. A Utah study conducted on beagles did not find bone cancers at low doses.17

    STRONTIUM

    Immune System

    Thomasset reported that continuous low doses of strontium weakened the immune system for up to one year after the exposure.18

    Cerium

    Possible Health Effects: Leukemia; and bone, liver, and nasal cavity cancers

    Description: The isotope of cerium for which the Dose Reconstruction Project is calculating dose estimates is cerium-144.

    Estimated Amount Released from Hanford: 3,770 curies

    Chemical Form of Release: Assumed to be soluble19

    Range of Representative Dose Estimates: 0.05 mrem EDE to 5.4 mrem EDE

    Summary of Scientific Studies

    CERIUM

    Cancer

    All of the information on cerium's health effects comes from animal studies. Cerium concentrates in the bone marrow. Because of this, the risk of leukemia is the predominant potential health problem.

    When insoluble cerium is inhaled, it remains in the lung. When soluble forms are inhaled, cerium moves into the bones and liver. Bone and liver cancers, as well as liver damage, are possible. The National Council on Radiation Protection has stated that cancers of the nasal cavity are also possible.20

    Ruthenium

    Possible Health Effects: Cancer, skin burns

    Description: There are two isotopes of ruthenium for which the Dose Reconstruction Project is calculating dose estimates: ruthenium-103 and ruthenium-106.

    Estimated Amount Released from Hanford:
    ruthenium-103: 1,160 curies
    ruthenium-106: 388 curies

    Chemical Form of Release: unknown

    Range of Representative Dose Estimates: 0.009 mrem EDE to 0.89 mrem EDE

    Summary of Scientific Studies

    RUTHENIUM

    Cancer

    Very little information is available on the potential for ruthenium to induce cancers. One study that considered the possible health effects from ruthenium did not distinguish between ruthenium-103 and ruthenium-106. In animals exposed to ruthenium, cancers did develop. However, a report on the study by R. Masse, a veterinarian and Chief of the Experimental Toxicology Laboratory in Montrouge, France, did not specify where in the body the cancers developed.21

    RUTHENIUM

    Skin Burns

    Ruthenium particles released from Hanford posed a hazard if any of the particles had fallen onto a person's exposed skin. This could have caused skin burns.

    downwinder perspective

    Many callers to the Hanford Health Information Lines have questions and concerns about the release of plutonium and other radioactive materials from Hanford. Some downwinders have health problems and believe that they are, or might be, related to Hanford. The following personal perspective is offered to help readers understand these experiences and concerns.

    "My father worked at Hanford as an ironworker/rigger, heavy equipment operator and supervisor from 1947 until his death from lung cancer in 1985. He was 60 years old when he died. Thirty-four of his years at Hanford were spent in the 200 Areas (where the plutonium was processed and separated). He and his crew buried contaminated dry waste such as lab equipment or, in some cases, even trucks and cranes in the ground. He helped to construct the tank farms and was involved in the transfer of liquid wastes to the underground tanks.

    "Dad was aware of the problems with the stacks and release of plutonium particles onto the ground and he worried because his crew was there.

    "Years later, in 1974, dad discovered that the Hanford doctors had for four years withheld evidence that he had scarring in his lungs. During his annual medical checkup, a new doctor mentioned that the scarring in his lungs was getting worse. He asked the doctor, 'What scarring?' Being concerned about getting proper medical care, dad went to Seattle for another exam. After a thorough work-up at the Virginia Mason Clinic, he was diagnosed with 'silicosis, caused by particles in the lungs.' His condition continued to deteriorate, eventually becoming lung cancer.

    "I can't help but wonder, what were those particles? Were they 'hot' particles released from the stacks at Hanford decades earlier? Were they just sand? And why did the Hanford doctors, year after year for four years, withhold my dad's medical condition from him?"

    This perspective was contributed by a woman whose father worked at Hanford. She was born in 1948 in Richland and lived there until 1966. She recalls that much of her family's milk and vegetables came from her uncle's farm in Kennewick. Name withheld by request.

    Unresolved Issues Concerning Hanford's Hot Particles

    During the preparation of this report, the technical reviewers raised several important points that should be included.

    Karl Z. Morgan, Ph.D., expressed great skepticism with the estimate for the amount of plutonium released from Hanford. The current estimate from the Hanford Environmental Dose Reconstruction Project is 1.78 curies of plutonium released to the air. Based upon his experience at the Oak Ridge (Tennessee) nuclear weapons facility and his knowledge of Hanford processes, Morgan believes that the current estimate is "a gross underestimate." Morgan is regarded by many as the father of health physics and was chief of radiation protection at Oak Ridge. He was chairman of the Internal Dose Committees of both the International Commission on Radiological Protection (ICRP) and the National Committee for Radiation Protection (NCRP) from 1949 to 1971. These committees set the maximum permissible radiation exposure limits on the international and national level, respectively.

    Professor Ronald L. Kathren felt it was important to state that, given the current low radiation dose estimates from the selected radionuclides, it is "extremely unlikely" that there will be any measurable health problems among those exposed to Hanford's radiation releases. "Measurable health problem" means an effect that could be determined by an epidemiological study as being related to exposure from Hanford's radiation. Kathren is the director of the United States Transuranium and Uranium Registries and a professor at Washington State University.

    Tim Connor stated that the assumption by the Hanford Environmental Dose Reconstruction Project that all of the plutonium released by Hanford to the air was in a soluble form is tenuous at best. Connor is concerned that even if the plutonium separated at Hanford was initially dissolved by nitric acid, further steps in the separation process would have resulted in transforming at least some of the soluble plutonium to an insoluble form. Thus, a considerable fraction of plutonium escaping to the atmosphere may have been in an insoluble form. Connor is a researcher with the Energy Research Foundation in South Carolina and was a staff member of the Hanford Education Action League (HEAL) for several years.

    Summary

    While comparisons to specific individuals are often uncertain, the information in this report may help identify potential health problems from exposure to Hanford's releases of plutonium, cerium, strontium and ruthenium. An important point to recall is that the estimates of the amounts released and the doses received are not yet complete.

    The Technical Steering Panel completed its role in 1995. The federal Centers for Disease Control and Prevention (CDC) is now working with the HEDR Task Completion Working Group to continue public participation and to assure completion of the remaining HEDR activities.

    References for the History of Hanford's Hot Particles

    Stohr, Joe. Memo to the Technical Steering Panel and the Centers for Disease Control: "Preliminary Review of Documents Describing Hanford Particulate Releases, 1944-1954." December 26, 1990.

    Thomas, Jim. Hanford Education Action League (HEAL) Memo to the Technical Steering Panel: "Request for Independent Calculations on the Active Particle Problem." April 20, 1992.

    Till, John, Ph.D., and Charles Miller, Ph.D. Memo to the Technical Steering Panel: "Active Particle Problem at Hanford." Undated.

    U.S. Senate, Majority Staff of the Committee on Governmental Affairs. "Early Health Problems of the U.S. Nuclear Weapons Industry and Their Implications for Today." December 1989.

    NOTES

    1 - HW-11348. "Action Taken with Respect to Apparent Enhanced Active Particle Hazard." H.M. Parker. October 25, 1948; p.2.

    2 - HW-11348, p.2.

    3 - "Early Health Problems of the U.S. Nuclear Weapons Industry and Their Implications for Today." Report of the Majority Staff of the Committee on Governmental Affairs, U.S. Senate, December 1989; p. 9 - Referring to meeting notes from the Advisory Committee for Biology and Medicine, Jan. 12, 1951.

    4 - Telephone conversation with Bruce Napier, June 13, 1994. Napier is a scientist with Battelle Pacific Northwest Laboratory and worked extensively on the Hanford Environmental Dose Reconstruction Project.

    5 - There have been human plutonium studies by several groups of researchers. Three of these are: George L. Voelz, Occupational Medicine Group, Los Alamos National Laboratory, et al. who studied 26 Manhattan Project workers at Los Alamos with 37-year follow-up after exposure (Voelz 1985); J. F. Acquavella et al. who also considered Los Alamos workers (Acquavella 1983); and Gregg S. Wilkinson et al. who studied Rocky Flats workers (Wilkinson 1987)

    6 - H. Metivier in Radionuclide Metabolism and Toxicity; Galle, P. and R. Masse (eds.); Paris: Masson, 1982; p. 184. The book is a compilation of papers presented at a 1982 symposium that was organized by the French Society of Biophysics and Nuclear Medicine and the University of Paris.

    7 - Gregg Wilkinson, Ph.D. "Mortality Among Plutonium and Other Radiation Workers at a Plutonium Weapons Facility." American Journal of Epidemiology. 1987; p. 231-250.

    8 - Committee on the Biological Effects of Ionizing Radiations (BEIR IV); Health Risks of Radon and Other Internally Deposited Alpha-Emitters; Washington, DC: National Academy Press, 1988; p. 328.

    9 - Telephone conversation with Prof. Ronald Kathren, U.S. Uranium and Transuranium Registries, July 22, 1994..

    10 - George L. Voelz, MD. "Health Considerations for Workers Exposed to Plutonium." Occupational Medicine: State of the Art Reviews. Oct-Dec 1991; p. 694.

    11 - H. Metivier in Galle and Masse, p. 193.

    12 - BEIR IV, p. 325.

    13 - Tawn, E.J. et al. "Chromosome Studies in Plutonium Workers." International Journal on Radiation Biology and Related Studies in Physics, Chemistry and Medicine, May 1985; p. 599-610.

    14 - M.C. Thorne and J. Vennart; "The Toxicity of Sr-90, Ra-226 and Pu-239." Nature; October 14, 1976; p. 555-8. Thorne is with the Radiobiology Unit in Hardwell, England.

    15 - M. Thomasset. "Strontium: Metabolism and Toxicity of Strontium" in Galle and Masse, p. 104.

    16 - M. Thomasset in Galle and Masse, p. 111.

    17 - National Committee on Radiation Protection (NCRP) No. 110; Some Aspects of Strontium Radiobiology; 1991; p. 32.

    18 - M. Thomasset. "Strontium: Metabolism and Toxicity of Strontium" in Galle and Masse, p. 110.

    19 - Telephone conversation with Bruce Napier, June 13, 1994.

    20 - National Committee on Radiation Protection (NCRP) No. 60; Physical, Chemical, and Biological Properties of Radiocerium Relevant to Radiation Protection Guidelines; 1978; p. 55.

    21 - R. Masse, "Ruthenium and Activated Metals" in Galle and Masse, p. 131-142.

    References for Selected Radionuclides

    Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Plutonium, TP-90-21. December 1990.

    Galle, P. and R. Masse, eds. Radionuclide, Metabolism and Toxicity. Paris: Masson, 1982.

    NCRP Report No. 60. Physical, Chemical, and Biological Properties of Radiocerium Relevant to Radiation Protection Guidelines. Washington, DC: National Council on Radiation Protection and Measurements, 1978.

    NCRP Report No. 110. Some Aspects of Strontium Radiobiology. Bethesda, MD: National Council on Radiation Protection and Measurements, 1991.

    TOP OF PAGE

    NEXT PAGE

    SITE INDEX

    Click Here to Search This Site

    Hosted by www.Geocities.ws

    1