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PubMed1983

Plutonium--its behavior in natural water systems and assimilation by man.

There are a number of factors which must be considered in establishing whether or not the inadvertent intrusion of a sizable amount of plutonium-bearing material into a natural water system may have a significant impact on the health of those individuals who use that system as a drinking water resource. These factors include the chemical form(s) and solubility of plutonium in natural waters, its behavior in relation to natural processes (geochemical and biological), its fate in water treatment systems, and its uptake by man from drinking water. From the results obtained in our investigations of the behavior in natural water systems, it appears that (1) the chemical forms of plutonium dissolved in natural waters are Pu(IV) and Pu(V), (2) the soluble plutonium in many waters is bound to the organic constituents which probably enhances plutonium solubility, (3) the natural process responsible for the removal of plutonium from water is adsorption onto sediments, and (4) in water treatment systems, soluble plutonium is oxidized to the VI state and this form is not removed. From our investigations of gastrointestinal absorption, it appears that the value for f1, the fraction transferred from the gut to blood, is surely greater than 1 X 10(-3) and may be as high as 2 X 10(-1). Consideration of these and other factors indicates that, in the event of an accident, the concentration of plutonium could, in certain small natural water systems, approach and perhaps even exceed, the MPC for plutonium. However, the impact on the health of the affected population would not be inordinately high.

Humans↗
PubMed2002

The development of the plutonium lung clearance model for exposure estimation of the Mayak production association, nuclear plant workers.

The purpose of this study was to develop a biokinetic model that uses urinary plutonium excretion rate data to estimate the plutonium accumulation in the human respiratory tract after occupational exposure. The model is based on autopsy and urinalysis data, specifically the plutonium distribution between the respiratory tract and the remainder of the body, taken from 543 former workers of a radiochemical facility at the Mayak Production Association (MPA) plant. The metabolism of plutonium was represented with a compartmental model, which considers individual exposure histories and the inherent solubility properties of industrial plutonium aerosols. The transport properties of plutonium-containing aerosols were estimated by experimentally defining their in vitro solubility. The in vitro solubilities were found by dialysis in a Ringer's solution. Analysis of the autopsy data indicated that a considerable fraction of the inhaled plutonium is systemically redistributed rapidly after inhalation. After the initial dynamic period, a three-compartment model describes the retention in the respiratory tract. One compartment describes the nuclide retained in the lungs, the second compartment describes a plutonium lung concentration that exponentially decreases with time, and the third compartment describes the concentration in the pulmonary lymph nodes. The model parameters were estimated by minimizing sum squared of the error between the tissue and bioassay data and the model results. The parameters reflect the inverse relationship between plutonium retention in lungs and the experimentally derived aerosol transportability. The model was validated by comparing the autopsy results with in vivo data for 347 cases. The validation indicates that the model parameters are unbiased. This model is being used to estimate individual levels of nuclide accumulation and to compute radiation doses based upon the urinary excretion rates.

Autopsy↗
PubMed2004

Plutonium targets the p16 gene for inactivation by promoter hypermethylation in human lung adenocarcinoma.

Lung cancer from radon or (239)plutonium exposure has been linked to alpha-particles that damage DNA through large deletions and point mutations. We investigated the involvement of an epigenetic mechanism, gene inactivation by promoter hypermethylation in adenocarcinomas from plutonium-exposed workers at MAYAK, the first Russian nuclear enterprise established to manufacture weapons plutonium. Adenocarcinomas were collected retrospectively from 71 workers and 69 non-worker controls. Lung adenocarcinomas were examined from workers and non-worker controls for methylation of the CDKN2A (p16), O(6)-methylguanine-DNA methyltransferase (MGMT), death associated protein kinase (DAP-K), and Ras effector homolog 1 genes (RASSF1A). The prevalence for methylation of the MGMT or DAP-K genes did not differ between workers and controls, while a higher prevalence for methylation of the RASSF1A gene was seen in tumors from controls. In marked contrast, the prevalence for methylation of p16, a key regulator of the cell cycle, was increased significantly (P = 0.03) in tumors from workers compared with non-worker controls. Stratification of plutonium exposure into tertiles also revealed a striking dose response for methylation of the p16 gene (P = 0.008). Workers in the plutonium plant where exposure to internal radiation was highest had a 3.5 times (C.I. 1.5, 8.5; P = 0.001) greater risk for p16 methylation in their tumors than controls. This increased probability for methylation approximated the 4-fold increase in relative risk for adenocarcinoma in this group of workers exposed to plutonium. In addition, a trend (P = 0.08) was seen for an increase in the number of genes methylated (> or =2 genes) with plutonium dose. Here we demonstrate that exposure to plutonium may elevate the risk for adenocarcinoma through specifically targeting the p16 gene for inactivation by promoter methylation.

Adenocarcinoma↗
PubMed1982

The release of plutonium from macrophages in rats: the effect of changes in iron status.

Female rats were used to study the loss of plutonium from hepatic and splenic macrophages. The plutonium was administered intravenously either as a "soluble" [Pu] ferric hydroxide colloid or as an "insoluble" plutonium dioxide suspension. The "soluble" plutonium was lost much more rapidly from the liver than the "insoluble" plutonium. If the iron status of the rats was altered, shortly after the injection of the [Pu] ferric hydroxide colloid, either by the removal of blood or by the injection of colloidal iron, the rate of plutonium loss from the liver was changed. The plutonium was retained longer in those animals with excess storage iron than in those with depleted circulatory iron. These results are taken to indicate that iron and plutonium share common pathways of metabolism in macrophages.

Animals↗
PubMed1999

Plutonium fecal and urinary excretion functions: derivation from a systemic whole-body retention function.

Liver-bile secretion directly influences the content of plutonium in feces. To assess the reliability of plutonium metabolic models and to improve the accuracy of interpreting plutonium fecal data, we developed a compartmental model that simulates the metabolism of plutonium in humans. With this model, we can describe the transport of plutonium contaminants in the systemic organs and tissues of the body, including fecal and urine excretions, without using elaborate kinetic information. The parameter values of the models, which describe the translocation rates and recycling of plutonium in the body, can be derived from a multi-term exponential systemic function for whole-body retention. The analytical derivations and algorithms for solving translocation parameter values are established for the model and illustrated by applying them to the biokinetics and bioassay of plutonium. This study describes how to (1) design a physiological model for incorporating liver biliary secretion and for obtaining a fecal-excretion function, (2) develop an analytical solution for identifying the translocation-parameter values incorporating the recycling of plutonium in the body, and (3) derive a set of urinary and fecal excretion-functions from a published systemic whole-body retention function, generally acknowledged to be accurate, as a real and practical example.

Algorithms↗
PubMed2006

Modifying effects of health status, physiological, and dosimetric factors on extrapulmonary organ distribution and excretion of inhaled plutonium in workers at the Mayak Production Association.

This paper summarizes the systemic organ distribution of plutonium in workers exposed by chronic inhalation at the Mayak Production Association (MPA). Using results of radiochemical measurements in soft tissue and bone samples collected at autopsy of 853 autopsy cases, this paper provides data on the effects of various chronic diseases and malignant tumors as well as exposure time, age, sex, and body burden on systemic retention of plutonium in 22 extrapulmonary organs and on the urinary excretion rate of the nuclide. Some aspects of this work have been reported already. The results of present autopsy studies showed that liver pathology accompanied by strong fatty dystrophy of hepatocytes results in a significant relative decrease in the fraction of systemic plutonium in the liver and contravariant increase in the skeletal fraction. The average fractions of systemic plutonium in the liver and the skeleton of those MPA workers were 15% and 75%, respectively, in comparison with 47% and 45% in healthy individuals. Some of the plutonium also redistributed from the liver via blood to other systemic soft tissues. Plutonium not redistributed was excreted with urine. The results of multivariate regression analysis indicated some time-related and sex-related changes not connected with pathology for the liver and the skeleton retention fractions and excretion rate of plutonium. The current ICRP biokinetic models do not account for the influence of different pathological processes in the body on plutonium distribution in systemic organs and urinary excretion. This could have significant consequences for dosimetry calculations and risk estimations.

Administration, Inhalation↗
PubMed2004

Plutonium in the arctic marine environment--a short review.

Anthropogenic plutonium has been introduced into the environment over the past 50 years as the result of the detonation of nuclear weapons and operational releases from the nuclear industry. In the Arctic environment, the main source of plutonium is from atmospheric weapons testing, which has resulted in a relatively uniform, underlying global distribution of plutonium. Previous studies of plutonium in the Kara Sea have shown that, at certain sites, other releases have given rise to enhanced local concentrations. Since different plutonium sources are characterised by distinctive plutonium-isotope ratios, evidence of a localised influence can be supported by clear perturbations in the plutonium-isotope ratio fingerprints as compared to the known ratio in global fallout. In Kara Sea sites, such perturbations have been observed as a result of underwater weapons tests at Chernaya Bay, dumped radioactive waste in Novaya Zemlya, and terrestrial runoff from the Ob and Yenisey Rivers. Measurement of the plutonium-isotope ratios offers both a means of identifying the origin of radionuclide contamination and the influence of the various nuclear installations on inputs to the Arctic, as well as a potential method for following the movement of water and sediment loads in the rivers.

Arctic Regions↗
PubMed2004

Plutonium microdistribution in the lungs of Mayak workers.

The degree of nonuniform distribution of plutonium in the human lung has not been determined; thus current dosimetric models do not account for nonuniform irradiation. A better scientific basis is needed for assessing the risk of developing radiation-induced disease from inhaled alpha-particle-emitting radionuclides. We measured the distribution of plutonium activity in the lung by autoradiography and related the activity to specific compartments of the lung. The study materials were lung specimens from deceased workers employed by the Mayak Production Association. The approach to analyzing these lung samples used contemporary stereological sampling and analysis techniques together with quantitative alpha-particle autoradiography. For the first time, plutonium distribution has been quantified in the human lung. The distribution of long-term retained plutonium is nonuniform, and a significant portion of plutonium was retained in pulmonary scars. In addition, a large fraction of plutonium was present in the parenchyma, where it was retained much longer than was estimated previously. The sequestration of plutonium particles in scars would greatly reduce the radiation exposure of the critical target cells and tissues for lung cancer. Thus the prolonged retention of plutonium in lung scars may not increase the dose or risk for lung cancer.

Adult↗
PubMed1998

Chromosome aberrations in radiation workers with internal deposits of plutonium.

Chromosome analysis of G-banded peripheral blood lymphocytes was performed on two groups of plutonium workers with 20-50% and >50% maximum permissible body burdens (MPBB) of plutonium from the British Nuclear Fuels plc (BNFL) facility at Sellafield, UK, 10 years after an earlier study had reported increases in both symmetrical and asymmetrical aberrations. For each plutonium exposure group there was a significant difference in frequencies of symmetrical aberrations between plutonium workers, workers with similar histories of exposure to mainly external gamma radiation but with little or no intakes of plutonium, and controls with negligible exposure (<50 mSv). In contrast, no significant differences for asymmetrical aberrations were found, and since these are short-lived, this suggests that recent exposure of mature lymphocytes was minimal. Frequencies of symmetrical aberrations had increased significantly since the earlier sampling time. Additional external radiation exposure was negligible in the plutonium worker groups over this period. These results are consistent with the hypothesis that hemopoietic precursor cells are being irradiated by internally deposited plutonium with subsequent selection resulting in only cells with symmetrical aberrations reaching the peripheral lymphocyte pool. After removal of aberrations involving only chromosomes 7 and/or 14, which are thought to arise in vivo during immunological development, the breakpoints involved in the aberrations were distributed randomly among the chromosomes according to length in all three groups of workers. Within the chromosomes the distribution between terminal, interstitial and centromeric regions for the plutonium workers did not conform to that expected, there being an excess in the terminal regions and a deficit in the interstitial regions.

Adult↗
PubMed1997

Variations in the concentration of plutonium, strontium-90 and total alpha-emitters in human teeth collected within the British Isles.

Concentrations of plutonium-239, plutonium-240, strontium-90 and total alpha-emitters have been measured in children's teeth collected throughout Great Britain and Ireland. The concentrations of plutonium and strontium-90 were measured in batched samples, each containing approximately 50 teeth, using low-background radiochemical methods. The concentrations of total alpha-emitters were determined in single teeth using alpha-sensitive plastic track detectors. The results showed that the average concentrations of total alpha-emitters and strontium-90 were approximately one to three orders of magnitude greater than the equivalent concentrations of plutonium-239,240. Regression analyses indicated that the concentrations of plutonium, but not strontium-90 or total alpha-emitters, decreased with increasing distance from the Sellafield nuclear fuel reprocessing plant-suggesting that this plant is a source of plutonium contamination in the wider population of the British Isles. Nevertheless, the measured absolute concentrations of plutonium (mean = 5 +/- 4 mBq kg-1 ash wt.) were so low that they are considered to present an insignificant radiological hazard.

Adolescent↗
PubMed2000

Oxidation-state distribution of plutonium in surface and subsurface waters at Thule, northwest Greenland.

The speciation of plutonium in Arctic waters sampled on the northwest Greenland shelf in August 1997 is discussed in this paper. Specifically, we report the results of analyses carried out on seawater sampled (a) close to the Thule air base where, in 1968, a US military aircraft carrying four nuclear weapons crashed on sea ice, releasing kilogram quantities of plutonium to the snow pack and underlying seabed sediments, and (b) at a reference station (Upernavik) located approximately 400 km to the south. The data show that most of the plutonium in the dissolved phase at Thule is in the form of Pu(V, VI) (mean: 68+/-6%; n = 6), with little if any distinction apparent between surface and bottom waters. Further, the oxidation state distribution at stations close to the accident site is similar to that measured at Upernavik, remote from this site. It is also similar to the distribution observed in shelf waters at mid-latitudes, suggesting that the underlying processes controlling plutonium speciation are insensitive to temperature over the range 0-25 degrees C. Measurements using tangential-flow ultrafiltration indicate that virtually all of the plutonium (including the fraction in a reduced chemical form) is present as fully dissolved species. Most of this plutonium would seem to be of weapons fallout origin, as the mean 238Pu/239,240Pu activity ratio in the water column (dissolved phase) at Thule (0.06+/-0.02; n = 10) is similar to the global fallout ratio at this latitude (approximately 0.04). Thus, there is little evidence of weapons-grade plutonium in the water column at Thule at the present time.

Aircraft↗
PubMed1977

The distribution of plutonium-214 in rodents.

Plutonium-214 citrate solution at pH 6-5 was injected intravenously or intra-peritoneally into hamsters and rats at a dose of 50 MBq kg-1 (1-35 mCi kg-1). The animals were killed 1 day or 1 week later, and tissues were removed for autoradiography and radiochemical analysis. Plutonium-241 was distributed in rats in the same way as plutonium-239, and is a suitable isotope for high-resolution tissue-section autoradiography. Plutonium deposits in cells consisted of a nuclear and a cytoplasmic component. In the hamster kidney cells, the amount associated with the nucleus was about 55 per cent of the total cellular plutonium at 24 hours after injection. Six days later, it was only about 30 per cent. Plutonium deposits were also characterized in hepatocytes, in the interstitial cells of the testes, in the cells of ovarian follicles, in chondrocytes and in bone cells, including osteoblasts and osteocytes. In bone there appeared to be both an extracellular and intracellular deposit. No evidence was found of substantial incorporation of plutonium into the mineral phase of bone.

Adrenal Glands↗
PubMed1990

Sister chromatid exchanges and chromosome aberration frequencies in plutonium workers.

Peripheral blood lymphocytes from controls and from a small population of plutonium workers with internal plutonium depositions, cumulative chronic external irradiation, and occupational exposure to single or multiple chemicals, were analysed for the frequency of sister chromatid exchanges (SCE) and chromosome aberrations. SCE are sensitive to some chemical mutagens, while chromosome aberrations are induced by moderate to high doses of ionizing radiation, and therefore these different cytogenetic end-points are complementary. We analysed the frequency data from workers grouped by internal systemic burdens of plutonium (less than 148, 148-740 and greater than 740 Bq) and to those exposed to five chemicals in the workplace: perchloroethylene, beryllium, carbon tetrachloride, benzene, and trichloroethylene. A significant increase in chromosome aberrations compared with the control frequency was observed only in cells of workers with greater than 740 Bq of internalized plutonium. Based on prior studies, the lack of a dose-response indicator from internal plutonium was not unexpected because of the small sample and the low frequency of aberrations induced at the lower plutonium burdens. There were no significant increases in the SCE mean frequencies when analysed by estimated internal plutonium or from exposure to any of the chemicals.

Adult↗
PubMed2005

Chromosome intra- and inter-changes determined by G-banding in radiation workers with in vivo exposure to plutonium.

Suggestions that exposure to intakes of alpha-emitting radionuclides such as plutonium could result in a specific profile of chromosome damage distinguishable from that of low LET irradiation have led to the re-analysis of the different types of chromosome aberrations in peripheral blood lymphocytes determined by G-banding in a group of 20 plutonium workers from the British Nuclear Fuels plc facility at Sellafield, UK. Comparisons were made with a group of workers with negligible plutonium intakes but similar external gamma doses and with an unexposed control group. Examination of simple translocation frequencies in the three groups indicated a significant difference (P = 0.033), with the higher frequency in the plutonium workers indicating that exposure from plutonium was contributing to the aberration yield. Slightly raised frequencies of both intra-chromosomal and complex aberrations were observed in the plutonium workers in comparison with the comparable external exposure group and the control group but the difference did not reach significance at the P = 0.05 level and there was no variation in the relative frequencies of the different aberration types between the three groups. There was, therefore, no firm indication from this study that either intra-chromosomal or complex aberrations could be used as a specific marker of high LET exposure in workers with historical intakes of plutonium.

Body Burden↗
PubMed1983

Plutonium concentration in human tissues: comparison to thorium.

The concentration of 238Pu, and 239,240Pu, and of 228Th, 230Th, and 232Th were measured in 10 sets of human tissues from Washington, DC, and 12 sets from Grand Junction, CO. The tissues were collected at autopsy by qualified pathologists from normal healthy persons most of whom died suddenly. The subjects had acquired plutonium from fallout of global nuclear testing and burnup of a space nuclear generator utilizing 238Pu. The median concentration of 239,240Pu was 0.08 pCi/kg in lung, 0.46 pCi/kg in tracheobronchial lymph nodes, 0.60 pCi/kg in liver, 0.02 pCi/kg in kidney and 0.17 pCi/kg in bone in Washington, DC subjects. Similarly, the concentration of 239,240Pu in Grand Junction subjects was found to be 0.17 pCi/kg in lung, 0.68 pCi/kg in lymph nodes, 0.55 pCi/kg in liver, 0.03 pCi/kg in kidney, 0.22 pCi/kg in bone and 0.08 pCi/kg in spleen. The median concentration in four gonads was 0.02 pCi/kg; the concentration in one thyroid was 0.01 pCi/kg. 238Pu was below the limit of detection in most organs except the liver where it ranged from 0.02 to 0.17 pCi/kg with a median concentration of 0.06 pCi/kg. The organ distribution pattern shows that most of the plutonium was accumulated in bone and liver with 54-60% in bone and 34-43% in liver. Only 3-6% was found in lung including lymph nodes; kidney, spleen, thyroid and gonads together contained around 1%. The analytical results show three major differences between plutonium and thorium concentrations and organ distributions: (1) for plutonium the liver is a major locus for storage (approximately 40% of that found in the total body), whereas little thorium is accumulated in the liver (around 4%); (2) the relative amounts of 230Th and 232Th are much higher in lung and lymph nodes (10-28%) than currently for plutonium (3-6%); (3) the ratio of throium concentrations in lymph nodes to lung is significantly higher than the ratio of plutonium concentration in lymph nodes to lung showing thereby that fallout plutonium is more soluble than natural thorium.

Body Burden↗
PubMed1983

Dose-response relationships for bone cancers from plutonium in dogs and people.

The risk of bone cancers developing from internally deposited plutonium must be estimated from studies in laboratory animals because no plutonium-induced cancers have been observed in people. Studies of the effects of 226Ra and 239Pu injected into beagle dogs at the University of Utah and 238PuO2 inhaled by beagle dogs at the Inhalation Toxicology Research Institute provide a key link to understanding the longterm effects of inhaled alpha-emitting radionuclides in people. Injected radium and plutonium are rapidly deposited in bone whereas plutonium deposited in lung by inhalation is translocated to bone more slowly, depending on its chemical form. The development of bone cancers is a late occurring effect seen after either injection of plutonium or radium or inhalation of plutonium. The incidence of bone cancers from alpha radiation to the skeletons of dogs was compared to bone cancer incidences in radium dial painters to estimate bone cancer risk from inhaled plutonium in people. A risk factor of 1200 bone cancers/10(6) rad to skeleton (average dose) was estimated.

Age Factors↗
PubMed2005

Plutonium contamination in soils and sediments at Mayak PA, Russia.

The Mayak Production Association (Mayak PA) was established in the late 1940's to produce plutonium for the Soviet Nuclear Weapons Programme. In total, seven reactors and two reprocessing plants have been in operation. Today, the area comprises both military and civilian reactors as well as reprocessing and metallurgical plants. Authorized and accidental releases of radioactive waste have caused severe contamination to the surrounding areas. In the present study, [alpha]-spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS) have been used to determine plutonium activities and isotope ratios in soil and sediment samples collected from reservoirs of the Techa River at the Mayak area and downstream Techa River. The objective of the study was to determine the total inventory of plutonium in the reservoirs and to identify the different sources contributing to the plutonium contamination. Results based on [alpha]-spectrometry and ICP-MS measurements show the presence of different sources and confirmed recent reports of civilian reprocessing at Mayak. Determination of activity levels and isotope ratios in soil and sediment samples from the Techa River support the hypothesis that most of the plutonium, like other radionuclides in the Techa River, originated from the very early waste discharges to the Techa River between 1949 and 1951. Analysis of reservoir sediment samples suggest that about 75% of the plutonium isotopes could have been released to Reservoir 10 during the early weapons production operation of the plant, and that the majority of plutonium in Reservoir 10 originates from discharges from power production or reprocessing. Enhanced 240Pu/239Pu atom ratios in river sediment upper layers (0-2 cm) between 50 and 250 km downstream from the plant indicate a contribution from other, non-fallout sources.

Environmental Monitoring↗
PubMed1992

Transfer of plutonium to rat embryos in vivo and in vitro.

The 239Pu distribution in the 12.5-day-old rat conceptus was compared between in vivo and in vitro experimental systems to establish a possible mechanism of cross-placental transfer of this radionuclide. In the in vivo study, plutonium citrate solution was injected intravenously to pregnant Wistar rats. In the in vitro study, either plutonium citrate or plutonium hydroxide colloid was administered, as a solution of Eagle MEM and FCS containing 239Pu at the concentration used in the maternal serum in the in vivo experiments, to rat conceptuses maintained by the whole-embryo culture method. The concentration of 239Pu in the yolk sac (239Pu activity per gram wet weight) were much higher than in the embryo in both the in vivo and in vitro experiments, suggesting that the yolk sac may be an effective barrier against the transfer of plutonium to the embryos. The ratios of the 239Pu concentration in the yolk sac to that in the embryo were relatively constant with time after administration in the in vitro system; 18-27 for plutonium citrate and 67-84 for plutonium hydroxide. In the in vivo experiment, these ratios changed with time after injection; 15 at 5 min and 62 and 60 min after injection. This suggests that in the in vivo system, the chemical form of 239Pu changed with time after injection, probably to a macromolecular form such as the hydroxide colloid or plutonium-protein complex although 239Pu was injected to the maternal blood as citrate.

Animals↗