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PubMed2004

Plutonium-related work and cause-specific mortality at the United States Department of Energy Hanford Site.

BACKGROUND: Health effects of working with plutonium remain unclear. Plutonium workers at the United States Department of Energy (US-DOE) Hanford Site in Washington State, USA were evaluated for increased risks of cancer and non-cancer mortality. METHODS: Periods of employment in jobs with routine or non-routine potential for plutonium exposure were identified for 26,389 workers hired between 1944 and 1978. Life table regression was used to examine associations of length of employment in plutonium jobs with confirmed plutonium deposition and with cause specific mortality through 1994. RESULTS: Incidence of confirmed internal plutonium deposition in all plutonium workers was 15.4 times greater than in other Hanford jobs. Plutonium workers had low death rates compared to other workers, particularly for cancer causes. Mortality for several causes was positively associated with length of employment in routine plutonium jobs, especially for employment at older ages. At ages 50 and above, death rates for non-external causes of death, all cancers, cancers of tissues where plutonium deposits, and lung cancer, increased 2.0 +/- 1.1%, 2.6 +/- 2.0%, 4.9 +/- 3.3%, and 7.1 +/- 3.4% (+/-SE) per year of employment in routine plutonium jobs, respectively. CONCLUSIONS: Workers employed in jobs with routine potential for plutonium exposure have low mortality rates compared to other Hanford workers even with adjustment for demographic, socioeconomic, and employment factors. This may be due, in part, to medical screening. Associations between duration of employment in jobs with routine potential for plutonium exposure and mortality may indicate occupational exposure effects.

Adult↗
PubMed1984

Plutonium-induced wounds in beagles.

Beagle dogs were given subcutaneous implants of plutonium in their forepaws to mimic hand wounds received by workers accidentally contaminated with plutonium. Ten dogs received 9.46 +/- 0.43 mu Ci of plutonium oxide, and eight dogs received 1.25 +/- 0.60 mu Ci of plutonium nitrate. Surviving dogs were sacrificed at 8 and 5 yr, respectively, after exposure, and radionanalyses were performed on the injection site, regional lymph nodes, liver, spleen and bone. Histopathologic and autoradiographic examinations were performed on injection sites, regional lymph nodes, livers, spleens, kidneys and grossly observed lesions. The injected paws sequestered 21 and 16%, respectively, of the injected activity from plutonium oxide and plutonium nitrate in hypocellular scar tissue. The highest concentrations of translocated radionuclides were found in the regional lymph nodes. Histopathologic and autoradiographic examinations of regional lymph nodes showed that the alpha activity was largely sequestered by scar tissue that replaced lymphoid parenchyma in the plutonium-oxide-injected dogs. In the plutonium-nitrate-injected dogs, activity was widely distributed in relatively intact regional lymph nodes. The liver had the next highest concentration for both radionuclides; activity was present as alpha stars. The spleen had the next highest concentration for plutonium-oxide-injected dogs, although concentrations in the spleen were lower than the skeleton in the plutonium-nitrate-injected dogs. Osteosarcomas and hepatomas were present in one dog injected with plutonium oxide. There does not appear to be any unique risk for dogs related to the subcutaneous route of exposure to plutonium.

Animals↗
PubMed2002

Extrapulmonary organ distribution of plutonium in healthy workers exposed by chronic inhalation at the Mayak production association.

The systemic distribution of plutonium was determined for "healthy" workers who chronically inhaled plutonium at the radiochemical plants of the Mayak Production Association. The data were obtained by radiochemical analysis of soft tissues and bones samples collected upon autopsy of 120 workers who died from acute coronary diseases and accidents. The soft tissue samples were wet-ashed using nitric acid and hydrogen peroxide. Bone samples were ashed in a muffle furnace at 500 degrees C. Plutonium was extracted on anionite and coprecipitated with bismuth phosphate. The precipitation was blended with ZnS powder, and the alpha-activity was measured by ZnS solid scintillation counting in a low-background alpha radiometer. Twenty-five years after the beginning of inhalation exposures, the average percentage of plutonium in the skeleton and liver was 50% and 42% of systemic burden, respectively. A multivariate regression was used to quantify the effects of exposure time, "transportability" of the various compounds, plutonium body content, and age on systemic plutonium distribution. The early retention of plutonium in the liver is assumed to be greater than that in the skeleton. The initial distribution of plutonium between the liver and the skeleton, immediately after entering the circulatory system, was 50:38%, respectively. With time, the fraction of plutonium found in the liver decreased, while the fraction in the skeleton increased at a rate of 0.5% y(-1) of systemic deposition. Exposure time had a greater effect on the relative retention of plutonium in the main organs when compared to age. The statistical estimates that characterized the relative plutonium distribution were less stable for the liver than for the skeleton, likely due to the slower turnover of skeletal tissues and the retention of plutonium in bone.

Administration, Inhalation↗
PubMed1978

Experimental studies of the translocation of plutonium from simulated wound sites in the rat.

Wound contamination with plutonium was simulated in rats by injection into either muscle or subcutaneous tissue. The distribution after the injection of plutonium nitrate indicated that: (i) clearance from the contaminated tissue was due mainly to the movement of soluble complexes of plutonium, principally to the skeleton and liver, but also involved slower movement of polymerized, particulate plutonium to lymph nodes; (ii) clearance of soluble plutonium, and hence the overall state of clearance, was dependent on the tissue fluid flow through the contiminated tissue and the mass of plutonium deposited; (iii) lymphatic clearance of particulate plutonium resulted in the release of some particles into the circulation and subsequent uptake by the liver. Intramuscular deposition of small plutonium dioxide particles (approximately 1 nm in diameter) resulted in a greater rate of clearance of plutonium than deposition of the nitrate. Although the solubility of these particles was evident from the level of skeletal uptake of plutonium, a high level of excretion indicated that some plutonium was filtered into the urine in an undissolved form.

Animals↗
PubMed1990

Effect of mass, oxidation state and duration of chronic ingestion on plutonium absorption in fed rats.

The effects of time, mass and oxidation state on plutonium gastrointestinal absorption and tooth adsorption were studied during and after chronic ingestion of plutonium-238 (IV) or (VI) (1.55-15.60 kBq/ml) in 6.5 mM bicarbonate medium by fed rats via drinking water for 8 days to 3 months. Animals were killed during the ingestion to follow the kinetics of whole-body storage and clearance of plutonium. At 1.55 kBq/ml the amount of plutonium retained in the skeleton increased continuously during the 85 days of ingestion and reached a plateau thereafter. This plutonium retention was therefore dependent on the total mass administered but not proportional to this mass, as the fraction of administered plutonium retained decreased during the first 22 days of ingestion and then stabilized. This is reflected by the gastrointestinal transfer (f1), which had risen to (3.80 +/- 0.82) x 10(-5) on Day 3 of ingestion and then decreased to a stabilized value of (1.07 +/- 0.06) x 10(-5) from Day 30 to the end of the ingestion period. In the liver, the amount of plutonium retained reached a plateau, which lasted from Day 30 to the end of ingestion. The kidneys and spleen were also found to be retention sites. By Day 3 of ingestion, for a mass ingested of 5 x 10(-7) g/kg of body mass, the maximum mean value of f1 we found was smaller than the 10(-4) recommended by ICRP Report 30. The oxidation state had no effect on f1. Large plutonium deposition was observed on the teeth. For both oxidation states (IV) and (VI), about 0.10% of the administered dose was deposited on the teeth after 3 days of ingestion, whatever the plutonium concentration administered. However, whereas the amount of plutonium (IV) deposited did not change throughout the ingestion period, tooth deposition of plutonium (VI) decreased.

Absorption↗
PubMed1975

A method for investigating the metabolism of the transportable fraction of plutonium aerosols.

The metabolism of the transportable fraction of both 'soluble' and 'insoluble' forms of plutonium following their deposition in the respiratory system of the rat by either inhalation or pulmonary intubation has been investigated. The results have shown that the transportable fraction varied considerably with the chemical form of the plutonium. Thus at one week after the pulmonary intubation of a solution of plutonium citrate, the extrapulmonary tissue deposit was 69% of the initial pulmonary deposit whilst in the case of a suspension of plutonium dioxide the corresponding value was only 0.075%. However, the metalbolism of plutonium following its entry into the systemic circulation was largely independent of the original chemical form deposited in the lung. The liver accumulated only about 16% of the activity deposited in tissues from the blood, implying that plutonium was circulating in the blood predominantly in a momomeric form. The cumulative excretion of plutonium in the urine over the first week after pulmonary deposition as either the dioxide, citrate or nitrate was equivalent to about 4.5% of the extrapulmonary tissue deposit and the results suggest that this value could be used as a basis for calculating the activity deposited in tissue from the blood in man. This study also demonstrated that mixed aerosols of plutonium dioxide and sodium oxide are more transportable in the lung than aerosols of plutonium dioxide alone. A maximum transportability was reached at a Pu : Na atomic ratio of about 1:20, when the transportable fraction of plutonium was forty-five times that from a plutonium dioxide aerosol alone.

Aerosols↗
PubMed2003

Evaluation of a conceptual model for the subsurface transport of plutonium involving surface mediated reduction of PuV to PuIV.

A conceptual model is proposed to explain the transport behavior of plutonium in laboratory columns packed with a sandy coastal soil from the U.S. Department of Energy (DOE)'s Savannah River Site. The column transport experiments involved the introduction of a finite step input of plutonium, predominately in the +5 oxidation state, into the columns followed by elution with a low-carbonate solution of 0.02 M NaClO4 at pH 3, 5, and 8. Total plutonium concentrations were measured in the effluent as a function of time. These elution profiles suggest at least two distinct physical/chemical forms of plutonium, each with a different mobility. To explain the observed behavior, the following conceptual model was evaluated: [1] equilibrium partitioning of plutonium (V) and plutonium (IV) between the aqueous and sorbed phases as defined by pH-dependent, oxidation-state specific distribution coefficients and [2] kinetic reduction of plutonium (V) to plutonium (IV) in the sorbed phase. The conceptual model was applied to the column experiments through a one-dimensional advective/dispersive mathematical model, and predictions of the mathematical model were compared with the experimental data. Overall, the model was successful in predicting some of the major features observed in the experiments. It also yielded quantitative estimates of the rate constant for surface mediated reduction of plutonium (V) to plutonium (IV) that were of the same order (10(-4) to 10(-5) s(-1)) as those calculated from batch data both for this soil and for goethite.

Chemical Phenomena↗
PubMed1999

Plutonium contamination in soils in open space and residential areas near Rocky Flats, Colorado.

Spatial analysis of the 240Pu:239Pu isotopic ratio of 42 soil samples collected around Rocky Flats Plant near Golden, Colorado, was conducted to assess the effect of Rocky Flats Plant activity on the soil environment. Two probability maps that quantified the uncertainty of the spatial distribution of plutonium isotopic ratios were constructed using the sequential Gaussian simulation technique (sGs). Assuming a plutonium isotopic ratio range of 0.152+/-0.003 to 0.169+/-0.009 is characteristic to global fallout in Colorado, and a mean value of 0.155 is representative for the Rocky Flats Plant area, the main findings of the current work were (1) the areas northwest and southwest of Rocky Flats Plant exhibited a plutonium ratio > or = 0.155, thus were minimally impacted by the plant activity; (2) the study area east of Rocky Flats Plant (approximately 120 km2) exhibited a plutonium isotopic ratio < or = 0.155, which is a definitive indicator of Rocky Flats Plant-derived plutonium; and (3) inventory calculations across the study area exhibited large standard error of estimates. These errors were originated from the high variability in plutonium activity over a small sampling scale and the uncertainty in the global fallout isotopic ratio. Using the mean simulated estimates of plutonium isotopic ratio, coupled with plutonium activity measured at 11 soil pits and additional plutonium information published elsewhere, the plutonium loading on the open space and residential areas amounted to 111.2 GBq, with a standard error of estimate of 50.8 GBq.

Algorithms↗
PubMed1978

Factors affecting the mobility of plutonium-238 dioxide in the rat.

A major factor influencing the movement of plutonium-238 from the lungs to blood after the intubation of oxide suspensions is the presense of 0.001 micrometer diameter particles. In a polydisperse suspension of particles this fraction increases with time, due it is thought, to fragmentation of larger particles induced by alpha decay. The rate of this process could account for the greater transportability in vivo of plutonium-238 relative to plutonium-239 when the oxides are inhaled. In blood, 0.001 micrometer diameter plutonium-238 oxide particles undergo a rapid reaction to form a low molecular weight species before plutonium is complexed with transferrin and citrate ions. The filtration of this species through the kidneys may explain the observed enhanced urinary excretion of plutonium relative to administered plutonium citrate. The mechanism of urinary excretion and relationship between cumulative urinary excretion and body content for plutonium-238 is similar to that previously observed for plutonium-239, even though different methods of preparation of the oxides were used.

Animals↗
PubMed2003

The effect of state of health on organ distribution and excretion of systemic plutonium in the Mayak workers.

The extrapulmonary distribution of plutonium in 20 organs (excluding the respiratory tract) was studied in workers who chronically inhaled plutonium at the radiochemical plants of the Mayak Production Association (Ozyorsk, Russia). The data were obtained by radiochemical analysis of soft tissue and bones samples collected at autopsy of 591 workers. The systemic plutonium distribution was determined in healthy individuals as well as in those with health impairment, specifically for those with liver diseases. Twenty-five years after the beginning of inhalation, systemic fractions in the liver and skeleton of individuals who were healthy at the time of death approximate the ratio 45%:45% proposed in the International Commission on Radiological Protection (ICRP) Publication 30. Pathological processes in the liver, accompanied by fatty dystrophy of hepatocytes, increased plutonium clearance from the liver. There was a considerable shift of the plutonium from the liver to the skeleton in individuals who died from liver disease. The average fractions of systemic plutonium in the liver and skeleton of those individuals were 14% and 78% respectively, which did not correspond to ICRP models, indicating a significant effect of disease conditions. Plutonium that was not redistributed was excreted. The urinary excretion rate of plutonium also correlated with state of health. The observed excretion as a fraction of systemic content was 1.64 x 10(-5) d(-1) for individuals in good health and 2.34 x 10(-5) d(-1) for individuals with various chronic diseases. The current models do not account for the influence of different pathological processes in the body on plutonium distribution and retention in systemic organs. This could have significant consequences for dosimetry calculations and risk estimations.

Body Burden↗