Toxicity Of Plutonium Research Articles

Review of the sources and behaviors of plutonium isotopes in the atmosphere and ocean

Plutonium, as well as fission products such as 137Cs, had been released into the earth environment in 1945 after the first atmospheric nuclear explosion of plutonium bomb in the desert of New Mexico (USA, July 16) and later over Nagasaki (August 9), followed then by many other explosions. Thus, plutonium cycling in the atmosphere and ocean has become a major public concern as a result of the radiological and chemical toxicity of plutonium. However, plutonium isotopes and 137Cs are important transient tracers of biogeochemical and physical processes in the environment, respectively. In this review, we show that both physical and chemical approaches are needed to comprehensively understand the behaviors of plutonium in the atmosphere and ocean. In the atmosphere, plutonium and 137Cs attach with aerosols; thus, plutonium moves according to physical and chemical processes in connection with aerosols; however, since plutonium is a chemically reactive element, its behavior in an aqueous environment is more complicated, because biogeochemical regulatory factors, in addition to geophysical regulatory factors, must be considered. Meanwhile, 137Cs is chemically inert in aqueous environments. Therefore, the biogeochemical characteristics of plutonium can be elucidated through a comparison with those of 137Cs, which show conservative properties and moves according to physical processes. Finally, we suggest that monitoring of both plutonium and 137Cs can help elucidate geophysical and biogeochemical changes from climate changes.

The environmental safety and health implications of plutonium

The physical and chemical properties of plutonium are related to its environmental transfer and uptake by man. Once incorporated, plutonium is avidly retained in the lungs, liver and skeleton, the relevant amounts being determined by its solubility in body fluids. A knowledge of the toxicity of plutonium is largely dependent upon animal studies where exposure to relatively large amounts, compared with those associated with known human exposure, can cause tumours in those tissues where it is retained. With one exception, epidemiological studies have not been able to demonstrate adverse health effects in humans. Precautions taken in the processing of plutonium have ensured that average intakes by workers have been consistently low. When it has been released to the environment, it has been of little ecological importance and has caused only small doses to man with no observable adverse effects. The long half-life of plutonium causes anxiety about its storage and disposal, but plutonium is not unique. It is often forgotten that very much larger amounts of permanently toxic elements such as arsenic, cadmium and lead are stored and disposed of with much less concern. Plutonium is a valuable resource and for that reason should not be treated as a waste for disposal into the environment.

Environmental plutonium in humans

Although the current world inventory of plutonium is overwhelmingly man-made, it is important to recognize that 244Pu was a primeval radioelement and that 239Pu is formed continuously by spontaneous fission of 238U; the atom ratio U:Pu being about 10 11:1. It has been calculated that the human body has always carried a base load of, perhaps 10 3–10 5 atoms (< 0.2 amol) of natural plutonium. Since 1945, the release of 239Pu into the environment from atmospheric nuclear weapons testing has added to this base load a civilization-related load which, at ≈ 300 fmol, is at least 5 order of magnitude greater. Within the human body plutonium is deposited mainly in the liver and skeleton where it appears to be retained tenaciously with half-times of many years. Based on 1970–1980 levels, environmental plutonium may give rise to α-particle radiation doses of ≈3–7 μSv/a in human bone and ≈10–20 μSv/a in liver, doses which from our present understanding of the radio-and chemical toxicity of plutonium are far too small to cause any recognizable health effects.

Plutonium in vivo and drugs to remove it from man

Plutonium-239, an important component of the nuclear fuel cycle, can enter the human body by ingestion, inhalation or by absorption through the skin or a wound. If sufficient quantities are deposited in the body the emitted alpha-particle radiation may induce serious toxic effects, including bone and other tumours. Gastrointestinal absorption is influenced by age, physiological and dietary factors, but in adults it appears unlikely to exceed 0.1% of the ingested amount. Absorption through the intact skin is probably less than 0.01%. However, depending on its chemical form, the absorption of inhaled material from the lungs may range from <5 to 100%. Following entry into the systematic circulation, plutonium deposits to more than 80% in the skeleton plus liver of all the species studied. Skeletal retention of plutonium is prolonged with half-times equal to, or longer, than the normal life span of the species; for man a half-time of 100 years is assumed. In liver both the uptake and the retention show marked species variations. Some species, e.g. dog and chinese hamster, show very prolonged, if not infinite, retention while in others, e.g. rat, tupaia, macaque and baboon, more than 90% of the liver plutonium is lost with half times ranging from a few days to a few months. Into which category man falls is uncertain. Complex formation with biological ligands plays an important role in plutonium metabolism. In blood, plutonium occurs as the complex with the ion-transport protein transferrin and this complex may also play a role in cellular uptake. Within the cells of liver and other tissues plutonium is largely deposited in lysosomal structures and within these structures the metal may be associated with ferritin [1]. Human exposure to plutonium comes principally from the metal which has been released into the atmosphere by nuclear weapon testing. Autopsy data suggest that for the general public the total body content of plutonium lies between about 15 and 50 picograms (35 to 110 milliBequerels). Exposure to higher levels of plutonium may occur amongst workers in the nuclear industries. During the past forty years several hundred workers have acquired body burdens of plutonium ranging from some tens of nanograms to about 4 mg and the health of these people is being carefully monitored. To date no late effects which can confidently be ascribed to plutonium toxicity have been observed [2]. During the past thirty years various treatment regimes designed to reduce the risk of late effects arising from internally deposited plutonium have been proposed; these are all based on the assumption that accelaration of the normally very slow excretion of the metal will lead to a proportionate reduction in the risk of late effects. This hypothesis is not yet fully proven. Many substances have been tested for their ability to remove plutonium but only the polyaminopolycarboxylic acids, especially diethylenetriaminepentaacetic acid (DTPA), have proven to be really effective. DTPA, as the Na 3Ca- or the less toxic Na 3Zn salts, has been used widely and successfully in man and this substance is the current agent of choice for the treatment of plutonium contamination in man. Toxicity presents little problem and the possibility of serious depletion of essential trace metals seems to be small, especially when the Zn salt of DTPA is used. The efficacy of DTPA treatment decreases with increasing time after exposure to plutonium and it has only limited ability to remove inhaled insoluble plutonium from the lungs. Removal of fixed bone deposits is also difficult [3]. Normally DTPA is administered by intravenous injection or infusion, but recently inhalation of an aerosol [4] or oral administration [5] have been shown to be effective in animal studies. The search for more effective agents than DTPA continues. Much interest was shown in a lipophilic derivative of DTPA — Puchel — which, unlike the ionized DTPA species, was able to enter cells. However, despite promising early results, this substance proved to be no more effective than DTPA and to be rather more toxic [6]. Recently new types of linear polycatechoylamino ligands (LICAM's) have been developed which are designed specifically to complex plutonium. Initial studies suggest that these may represent an interesting new approach to plutonium removal, but that their true therapeutic advantage over DTPA for human treatment remains to be assessed [7].

A Predictive Model of Early Mortality Following Acute Inhalation of PuO 2 Aerosols

Since data on the pulmonary toxicity of plutonium in people are not available, estimates must be based upon available experimental animal data. For this purpose, inhalation studies with beagle dogs exposed to aerosols of /sup 238/PuO/sub 2/ and /sup 239/PuO/sub 2/ were analyzed and a simple model has been proposed to describe apparent dose-response relationships. It was found that for each aerosol and radionuclide form, the cumulative absorbed lung dose that leads to death from lung damage up to 1000 days could be assumed to have a log-normal distribution of values that was independent of time to death. The data was satisfactorily fit to a model in which the time of death postexposure is given by: t = (K/D), with the time to death, the cumulative dose to lung tissue (the killing dose), and anti D the average dose rate to lung tissue from time of exposure to death. The ratios of median K values, normalized to the value for /sup 90/Sr--Y FAP, indicate a relative biological effectiveness (RBE) of 14 for /sup 239/PuO/sub 2/ particles and 5 for /sup 238/PuO/sub 2/ particles. This demonstrates an effect of particle specific activity on relative biological effectiveness for early mortality, since anmore » increase in specific activity of particles leads to a lower apparent RBE.« less

Hazards from plutonium toxicity.

AbstractBy use of standard models and theories, the number of cancer fatalities caused by dispersal of plutonium is estimated. This process includes development of estimates of Pu toxicity for inhalation and ingestion, calculation of meteorological dispersal using the Gaussian plume model, estimates

The distrust of nuclear power.

Society seems content to strike a more moderate or uncertain balance with other technologies than with nuclear power. This attitude is traced to the social history of nuclear power, the genuine uncertainty and complexity of safety issues, underestimation of the regulatory task, and the rancorous nature of the debate. Nuclear power is not just another problem of technology, of environment, or of health. It is unique in our time. To be more demanding of nuclear safety may be to apply a double standard, but not necessarily an irrational one. Our best course appears to be to keep the nuclear option open, work toward the rapid resolution of problems such as waste disposal, but postpone recycling and the breeder reactor. Time is needed to resolve immediate problems such as transport and disposal of nuclear wastes; to come to terms with trans-scientific issues such as plutonium toxicity, sabotage, and weapons proliferation; and to evaluate long-term energy alternatives.

Toxicity of plutonium and some other actinides

A biochemist takes stock of the present state of knowledge of the health effects of radioactive nuclear fission products; he concludes that the dangers of a plutonium economy may be greater than we...

Hazards of plutonium with special reference to the skeleton.

In the past attempts have been made to deduce plutonium toxicity in man from studies based on animal experimentation. An alternative method is to use the comparative dosimetry of plutonium and radium in man, with results broadly in agreement with maximum permissible levels set by the International Commission of Radiological Protection.

Plutonium--health implications for man. Animal data on plutonium toxicity.

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Book reviewThe Toxicity of Plutonium, pp. 38, 1975. Medical Research Council (London, Her Majesty's Stationery Office), 45p.

Growing concern about energy supplies and the need to reduce dependence on oil for electricity production has quickened public debate about the possible radiation hazards which might result from a greatly expanded nuclear power programme. The appearance of an authoritative and impartial statement on one aspect of the problem—the toxicity of plutonium-239—is to be welcomed.

Plutonium particles: some like them hot

The Medical Research Council's 1975 report The Toxicity of Plutonium (Nature, 253, 385) concludes that “there is no evidence that irradiation by ‘hot particles’ in the lung is markedly more hazardous than the same activity uniformly distributed or that the currently recommended standards for inhalation of plutonium are seriously in error.” Report R29 (1974) of the National Radiological Protection Board (NRPB) states that “there is no biological evidence available at present which suggests that ‘hot spots’ carry a higher risk of cancer induction.” But in the March 20, 1975 New Scientist, Dr A. R. Tamplin warns: “The plutonium exposure standards … must and will eventually be made more restrictive by a factor approaching 1,000.” Behind this disagreement is a major controversy over the risk of lung cancer from inhaled insoluble particles of intensely radioactive alpha emitters such as plutonium. In that controversy—unresolved by any direct data—lies a source of uncertainty about the future of nuclear power. A report by Amory B. Lovins and Walter C. Patterson of Friends of the Earth.

Deposition patterns and toxicity of plutonium and americium in liver.

Deposition patterns and toxicity of plutonium and americium in liver.

Toxicity of Plutonium in Mice

Plutonium citrate given intravenously to mice reduced life expectancy, decreased hemoglobin and leucocyte concentration in the peripheral blood, increased the incidence of liver degeneration, and induced osteogenic sarcomas. In none of these respects were the lowest dosage groups, 0.04 and 0.08 µc/kg, different from the control group.

Preliminary observations on metabolism and toxicity of plutonium in miniature swine.

The toxicity of Pu was investigated in miniature swine. Results are summarized from studies of blood concentra, tion, organ burden, and excretion patterns following various routes of Pu administration, the toxicity of Pu as compared to some other bone-seeking nuclides, and the penetration and removal of Pu from skin when injected or applied topically. (C.H.)

On the role of radiothorium (Th228) in radium poisoning.

The work that we shall report is part of a long-term study of the chronic toxicity of plutonium deposited in the skeleton. Toxicity in man is the objective of our investigation but, since man cannot be used as an experimental subject, ourwork has been done with the dog (beagle), whose skeletal system approximates the human for our purposes. The strategy is to compare the effects of plutonium (Pu239) with radium (Ra226). There is now available a considerable body of knowledge on chronic radium poisoning in man. By combining the dog data on radium and plutonium with the human radium data we should be able to extrapolate to human plutonium poisoning. A complicating factor has recently become prominent in considering the human data. What has been called “radium poisoning” has frequently involved poisoning by mesothorium (Ra228) and/or radiothorium (Th228) also. These radioactive materials are the only two long-lived daughters of the thorium series. Like radium, they are deposited chiefly in bone. We now know ...

Comparison of hematologic effects of internally deposited radium and plutonium in dogs.

The expansion of the atomic energy program and the widespread use of heavy radioactive elements in all areas of research have increased the need for data concerning the permissible total body burden of these elements. Current permissible body burdens are based upon data gathered from several sources. For heavy elements, the information on radium toxicity in man obtained from the luminous dial workers, and from individuals exposed to radium therapeutically or accidentally, serves as a base line (1–4). Permissible total body burdens of other heavy radioactive elements, particularly plutonium, have been arrived at by comparing their toxicity with that of radium in mice or rats and then extrapolating to man on the basis of the radium cases. The toxicity of plutonium has also been studied in a relatively small number of dogs. Thus, the permissible body burden of plutonium has been placed at 0.04 μc, while that for radium is 0.1 μc. Some doubt has arisen as to the reliability of the latter figure, since it has been found that some batches of luminous paints contained significant amounts of mesothorium and radiothorium. A study is being made of the comparative effects of plutonium, radium, radiothorium, and mesothorium in adult beagle dogs. By using a species with a relatively long life span and a skeletal growth pattern generally similar to that of man, we hope to contribute more reliable animal data for extrapolation to human beings. The dose levels of the heavy radioelements which we are employing may produce immediate effects such as the acute radiation syndrome and hematologic changes. Be-nign and malignant bone disease, blood dyscrasias, and hepatic and renal disease are among the recognized delayed effects. This report includes the hematologic alterations which are seen during the first year following injection of plutonium and radium. Results on dogs injected with radiothorium and mesothorium will be reported later. Methods Young adult male and female dogs were selected from a healthy pure-bred beagle colony maintained under optimal conditions. At the time of injection the males have an average weight of 10 kg. and the females of 8 kg. Skeletal maturity is verified by means of roentgenographic examination. We employ five dose levels of each radio-element, estimated on a retained basis as follows: 2.5, 0.81, 0.27, 0.086, and 0.014 μc/kg. The injected doses are based on a 90 per cent retention of plutonium and 25 per cent retention of radium. The injected and retained amounts are given in Table I. The lowest dose level (0.014 μc/kg.) is considered to be equivalent to the current human total permissible body burden of radium, and the other doses are developed from it. The scale of five doses was designed to be sufficiently broad to give an accurate answer on a safe total body burden of radium and plutonium for the dog.