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A Toxicological Profile for Plutonium

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  • A Toxicological Profile for Plutonium

    U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
    Public Health Service
    Agency for Toxic Substances and Disease Registry
    November 2010


    Below are highlights I found of interest. To see entire paper: http://www.atsdr.cdc.gov/ToxProfiles/tp143.pdf
    http://www.atsdr.cdc.gov/ToxProfiles...id=648&tid=119

    Plutonium-238 and plutonium-239 give off alpha particles (sometimes referred to as alpha radiation) and transform into uranium-234 and uranium-235, respectively. The half-life is the time it takes for half of the atoms of a radionuclide to undergo radioactive decay and change it into a different isotope. The half-life of plutonium-238 is 87.7 years. The half-life of plutonium-239 is 24,100 years. The half-life of plutonium-240 is 6,560 years...

    Plutonium released during atmospheric testing of nuclear weapons, which ended in 1980, is the source of most of the plutonium in the environment worldwide. The plutonium released during these tests was deposited on land and water. The small amount that remains in the atmosphere continues to be deposited as it slowly settles out...

    Plutonium can be transported in the atmosphere usually when it is attached to particles in the air. It can be deposited on land or water by settling or by rain. Plutonium can stick to particles in soil, sediment, and water. Plutonium isotopes will undergo radioactive decay in the environment...

    Plutonium leaves your body very slowly in the urine and feces. If plutonium
    were to enter your lungs today, much of the plutonium would still be in your
    body 30–50 years later..

    Plutonium released to the atmosphere reaches the earth's surface through wet and dry deposition to the soil and surface water. Once in these media, soluble plutonium can sorb to soil and sediment particles or bioaccumulate in terrestrial and aquatic food chains...

    Internally deposited plutonium, however, possesses the potential to produce significant health effects via transfer of energy from alpha particles to nearby cellular molecules. Once plutonium is internalized, the distribution, retention, and excretion kinetics, paired with the plutonium decay and energy deposition parameters, determine how the radiation dose increases over time...

    For example, for a person who inhales a given activity of 239Pu (measured in becquerel [Bq] or curies [Ci]), a certain portion is retained and the body will absorb all of the alpha and beta energy emitted and some of the gamma energy in a pattern reflecting the temporal and spatial (tissue) distribution of the 239Pu (which might be a function of age), the isotope decay rate, the production and decay rates of the progeny radionuclides, and radiation energy absorption factors. Each tissue, therefore, receives a tissue-specific radiation dose. The effective dose reflects the integration of dose over the time interval of interest and a tissue weighting factor scheme based on the relative sensitivities of the tissues and organs...

    These data are discussed in terms of three exposure periods: acute (14 days or less), intermediate (15–364 days), and chronic (365 days or more)...

    …these studies provide evidence for an association between cancer mortality (bone, liver, lung) and exposure to plutonium.
    Information on the general pattern of distribution of absorbed plutonium in humans is available from direct measurements of plutonium in human autopsy tissues. Such measurements generally reflect the long-term distribution pattern, in some cases being heavily influenced by discrete exposure events that occurred years before death...

    The highest concentrations of absorbed plutonium are usually found in liver, bone, and spleen (Filipy and Ford 1997; Filipy et al. 1994; McInroy et al. 1991; Yamamoto et al. 2008a). However, concentrations of plutonium in the respiratory tract and associated lymph nodes can exceed that of other tissues when exposures occur from inhalation (McInroy et al. 1991; Singh and Wrenn 1983)…

    Absorbed maternal plutonium can be transferred to the placenta and fetus (Lund and Tkatchev 1996; Prosser et al. 1994; Russell et al. 2003)…

    Occupational accidents have resulted in dermal exposures and/or penetration of plutonium into skin wounds and subsequent systemic absorption of plutonium (McInroy et al. 1989; Woodhouse and Shaw 1998)…

    Following inhalation exposure to PuO2, plutonium is excreted in feces and urine (DOE 1991c; Khokhryakov et al. 2004; Kurihara et al. 2002; Voelz et al. 1979)…

    ICRP (1996a) classifies insoluble plutonium oxides as Type S and recommends assigning all other plutonium aerosols to Type M in the absence of specific information supporting an alternative classification…
    • For Type M, about 70% of the deposit in AI reaches the blood eventually. There is rapid absorption of about 10% of the deposit in BB and bb, and 5% of material deposited in ET2. Thus, there is rapid absorption of approximately 2.5% of the deposit in ET for nose breathing, and 5% for mouth breathing.
    • For Type S, 0.1% is absorbed within 10 minutes and 99.9% is absorbed within 7,000 days, so there is little absorption from ET, BB, or bb, and about 10% of the deposit in AI reaches the blood eventually…

    Initial deposition of plutonium is assumed to occur from blood directly to bone surfaces, where it can be transferred to bone marrow or to bone volume. Elimination of plutonium in bone surface and bone volume is assumed to occur through bone marrow to blood…

    Toxicity of plutonium derives from the biological effects of radiation emitted during the radiological decay of plutonium isotopes. The isotopes 238Pu and 239Pu decay by emitting a high-energy alpha particle. A very small amount of the energy in the form of gamma rays is also released during the decay of plutonium isotopes. However, gamma radiation from 238Pu and 239Pu decay is of such small magnitude and energy that the dominant mechanisms of toxicity are associated with alpha radiation. Molecular damage results from the direct ionization of atoms that are encountered by alpha (and gamma) radiation and by interactions of resulting free radicals (e.g., H•, OH•) with nearby macromolecules (e.g., lipids, nucleic acids, proteins). Tissue damage results when the molecular damage is sufficiently extensive and/or repair of the damage is not sufficiently rapid…

    Alpha radiation emitted by plutonium isotopes cannot penetrate the outer layers of the skin. However, once plutonium is internalized, the extremely short-range alpha radiation produces a very localized radiation dose. As a result, toxicity of plutonium coincides with the distribution of plutonium in the body…

    Children may be more or less susceptible than adults to health effects, and the relationship may change with developmental age (Guzelian et al. 1992; NRC 1993). Vulnerability often depends on developmental stage…

    Absorption has been shown to be 10–1,000 times greater in neonates compared to adults, depending on animal species and chemical form of plutonium (Sullivan 1980a, 1980b; Sullivan and Gorham 1983; Sullivan et al. 1985)…

    The toxicokinetics of plutonium appear to be influenced by exposure to cigarette smoke…
    At 49 days postexposure, animals exposed to plutonium and cigarette smoke retained approximately 20% more plutonium than those animals exposed to plutonium alone…

    Exposure to inhaled 239PuO2 followed by intratracheal instillation of benzo(a)pyrene resulted in a higher incidence of lung tumors and a decrease in median survival time compared to animals exposed to 239PuO2 alone (Métivier et al. 1984)..

    A decrease in median survival time was observed in rats injected intravenously with 239Pu, immediately followed by exposure to x-rays (Ballou et al. 1962), as compared to those animals exposed to plutonium alone…

    Exposure of rats to 239PuO2 and asbestos by intraperitoneal injection resulted in a higher incidence of abdominal tumors compared to animals exposed to 239PuO2 alone (AEC 1973b)...

    An increased incidence of metaplasia was observed in rats experiencing a single inhalation exposure to 239PuO2 followed by administration of 1 or 10 mg vitamin C/mL of drinking water for 1 year postexposure, compared to rats exposed to plutonium only (Sanders and Mahaffey 1983). However, the incidence of squamous cell carcinomas in animals exposed to plutonium and vitamin C decreased with increasing dose of vitamin C. The authors stated that vitamin C may interfere with the progression of squamous cell metaplasia to squamous cell carcinoma…

    Pretreatment of rats with subcutaneous injection of cadmium or copper followed by intravenous injection of 238Pu or 239Pu resulted in changes in the distribution patterns of plutonium, but not in total retention of either isotope…

    They found that smaller and more uniformly distributed particles have the same or greater potential to produce neoplasms than less uniformly distributed particles.

    Animal studies have shown the effects of chelation therapy on the removal of previously incorporated actinide elements, such as plutonium. Single intravenous injection of polymeric 239Pu (plus 237Pu as a tracer) into young adult beagle dogs, followed by weekly exposure to diethylenetriamine-pentaacetate (DTPA) as calcium salt (Ca-DTPA) or daily exposure of DTPA as zinc salt (Zn-DTPA), resulted in 14.6 or 10.4% 237Pu excretion, respectively, vs. 7.1% plutonium excretion at 24 hours postexposure in those animals exposed to plutonium alone (Lloyd et al. 1978c). After 28 days, cumulative excretion (corrected for radioactive decay) reached 38.2% for Ca-DTPA, 49.4% for Zn-DTPA, and 12.1% for those animals treated with plutonium alone. The study indicated that daily exposure of beagle dogs to Zn-DTPA is more effective in increasing the excretion of incorporated plutonium than weekly exposure to Ca-DTPA. As speculated by the authors, the enhanced plutonium excretion may have occurred as a result of calcium replacement in Ca-DTPA or zinc replacement in Zn-DTPA by plutonium at the cellular level…

    Treatments using chelators are well accepted. REAC/TS has tested and possesses the investigational new drug license for the use of calcium and zinc diethylaminetriaminepentaacetic acid (Ca-DTPA and ZN-DTPA) in the United States. These substances were tested on adults and their safety and effectiveness was established for the adult population. This was extrapolated to the pediatric population based on comparability of pathophysiologic mechanisms (REAC/TS 2010a, 2010b). Pulmonary lavage is a unique treatment for reducing the lung burden from inhaled insoluble plutonium compounds. It has been used only occasionally and is useful only in cases involving relatively high lung burdens of insoluble plutonium compounds…

    Topical applications of DTPA solution have been used to remove plutonium from skin and wounds after accidental dermal exposure (Khokhryakov et al. 2003)…

    DTPA has been used as a chelating agent to accelerate the urinary excretion of plutonium in humans who were accidentally exposed to plutonium…

    Recent recommendations suggest using the Ca-DTPA complex for initial treatment and the Zn-DTPA complex for subsequent administrations (Ménétrier et al. 2005), although Zn-DTPA has not been universally authorized for use. Prolonged use of Ca-DTPA results in the depletion of essential metals (particularly zinc), whereas gram quantities of Zn-DTPA can be administered indefinitely without such depletion. With the exception of the liver, DTPA appears to form complexes primarily with plutonium in soft tissues other than the liver, which exchanges more rapidly with plutonium in plasma than in bone. Therefore, DTPA may be less effective in reducing bone plutonium levels (Durbin 1973)…

    Encapsulation of DTPA in conventional and stealth liposomes resulted in increased accumulation of DTPA in liver, bone, and spleen of rats administered a single intravenous dose of 238Pu (as the citrate) and, presumably, increased decorporation of plutonium from these tissues and increased urinary excretion (Phan et al. 2004, 2006b)…

    Oral or intravenous administration of octadentate spermine-based siderophore analogues, 3,4,3-LIHOPO and 4,4,4-LIHOPO, appears to be much more effective than DTPA for decorporation of internalized plutonium in laboratory animals (Durbin et al. 2003; Ramounet-Le Gall et al. 2003). Orally-administered amphipathic triethylenetetraminepentaacetic acids (TT) appear to be useful in removal of plutonium and other actinide elements from the body, particularly when longer-term decorporation is indicated (Miller et al. 2006)…

    Contaminated cooling water containing plutonium from nuclear production facilities may have been discharged into oceans or rivers. If release occurs from waste containers, buried radioactive wastes may migrate or seep into groundwater (NEA/OECD 1981)…

    In January, 1968, while attempting to make an emergency landing, a U.S. military aircraft with four nuclear weapons on board crashed in Thule, Greenland. The impact resulted in detonation of the high explosives in all four nuclear weapons aboard. The oxidized plutonium was dispersed by both the explosion and the fire involving the fuel in the jet (Harley 1980). Amounts of plutonium released to the air in this accident have been estimated at 24 Ci (8.9x1011 Bq) of insoluble plutonium (NEA/OECD 1981). The maximum concentration of plutonium in ocean sediments was found 1 km from the point of impact. The sediment-bound plutonium was found to migrate both downward in the sediment column and horizontally from the point of impact. The concentrations decreased with distance from the point of impact...

    The plutonium in the ocean sediments at Bikini Atoll, for example, was found to be resuspended and released to the bottom waters (DOE 1980b). In a freshwater waste pond at the Hanford reactor, plutonium was found to be bound to the sediments and was not available for uptake by plants or animals in the pond (DOE 1980f). The difference between the observations in the two ecosystems may be due to the dynamic nature of the ocean water near Bikini Atoll versus the relatively static nature of a waste water pond…

    Several of the major nuclear facilities in the United States use plutonium and some of these have released plutonium to the environment. These releases have taken place at remote sites and generally have not been measurable outside the plant property…

    The larger the particles, the faster fallout will occur. The particle size expected to be released from either of the above mentioned sources ranges from 0.3 to 1.1 μm. At the highest altitudes, aerosols in the atmosphere descend by gravity; at lower levels, they are transported with the general air movement (UNSCEAR 2000a). In the lower stratosphere, the mean residence time of
    aerosols range from 3–12 and 8–24 months in the polar and equatorial regions, respectively. Removal half-times from the upper atmosphere to the next lower region range from 6 to 9 months and removal half-times from the high atmosphere were found to be 24 months (UNSCEAR 2000a)…

    The highest concentrations of plutonium are likely to be found in the fine silt-clay particle size range. Particles of this size tend to be transported the farthest distance by wind and water (WHO 1983)…

    Once plutonium enters the soluble phase, it then becomes available for uptake by plants. The plutonium(IV) oxidation state is found in plants due to the ability of the environment to hydrolyze it (DOE 1987c; Garland et al. 1981). Cataldo et al. (1987) postulate that reduction of the higher oxidation states, such as plutonium(VI), occurs prior to absorption/transport across the root membrane…

    Sorption onto marine clays was found to be largely irreversible (Higgo and Rees 1986). Higgo and Rees (1986) also found that the initial sorption of plutonium onto clays was effective in removing most of the plutonium species that would be able to sorb onto the clay…
    Plutonium can become adsorbed onto colloids, small (micrometer) particles that are often found in groundwater. Adsorption to colloidal particles can enhance the mobility of plutonium in groundwater (DOE 1999a)…

    In studies on orange trees, Pinder et al. (1987) found that 238Pu was deposited on the leaf or soil surface, remained there, and that no measurable quantities were transferred to the fruits…
    Peeling of potatoes and beets removed 99% of the residual plutonium (DOE 1980d)…

    Plutonium uptake by grazing herbivores was predominantly located within the animal's pelt and gastrointestinal tract (DOE 1980i)…

    Plutonium was found to bioaccumulate in aquatic organisms, primarily at the lower end of the food chain…Plutonium is concentrated in the bones of fish rather than in muscle tissues…
    Swift (1992) reported that whole-body concentration factors for juvenile lobsters did not exceed 250 over an exposure period of 49 days in seawater containing 237Pu. 237Pu was found to accumulate mostly in the gills and exoskeleton...

    For plutonium injected into the atmosphere from a weapon detonation, the residence half-time of particulate debris in the troposphere of approximately 30 days (Bennett 1979; Nero 1979)…

    The lower oxidation states (III and IV) are more stable under acid conditions; the higher oxidation states (VI and VII) are more stable under alkaline conditions…

    In waters with low suspended solids, plutonium is generally found in oxidized forms, dissolved in the water. In waters with high suspended solids, plutonium is generally reduced and sorbed onto either suspended solids or sediments (DOE 1987a, 1987h; Higgo and Rees 1986)…

    The presence of fulvic acid (a naturally occurring organic acid) facilitates the reduction of plutonium(IV) to plutonium(III), especially below pH 3.1. The reduction of the higher oxidation states appears to be even less dependent on pH, especially below pH 6 (IAEA 1976d)…

    These complexes may then be absorbed by roots and move within plants; however, the relative uptake by plants is low…

    Yamada and Zheng (2008) reported 239,240Pu surface water concentrations in samples taken in the vicinity of the nuclear fuel reprocessing plant at Rokkasho, Japan of 7.6 and 7.8 mBq/m3 (0.20 and 0.21 pCi/m3) on sampling dates September, 1991 and June 1993, respectively. 239,240Pu concentrations in surface water collected at sites along the Japan Sea coast sampled in June, 2003 were 4.9 and 5.9 mBq/m3 (0.13 and
    0.16 pCi/m3) at Sado Island and at Ajigasawa, respectively. Yamada et al. (2007) reported 239,240Pu concentrations of 13.4, 20.7, 37.2, 26.8, 39.6, 20.6, and 19.2 mBq/m3 (0.362, 0.559, 1.01, 0.724, 1.07, 0.557, and 0.519 pCi/m3) at depths of 0, 150, 250, 600, 900, 1,200, and 1,490 m, respectively, in samples from Sagami Bay, Japan, western Northwest Pacific Ocean collected on March 23, 1992…

    The average annual dose equivalent from all background radiation to an individual residing in the United States is estimated to be 360 mrem (3.6 mSv) (NCRP 1987)..

    Daily ingestion of 239,240Pu in food in Japan between 1978 and 1980 due to atmospheric fallout was estimated to be 4.5x10-3 pCi/day (1.7x10-4 Bq/day) (Hisamatsu et al. 1987)…

    The EPA has not derived reference concentrations (RfCs) or reference doses (RfDs) for plutonium (IRIS 2009), but has derived a maximum contaminant level (MCL) of 15 pCi/L for total alpha-emitters (including plutonium), less uranium and radon (EPA 2003)…

  • #2
    Re: A Toxicological Profile for Plutonium

    Interesting article. Thanks.

    .
    "The next major advancement in the health of American people will be determined by what the individual is willing to do for himself"-- John Knowles, Former President of the Rockefeller Foundation

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