M.J. Swint

Partitioning of 238Pu, 239Pu and 241Am in skeleton and liver of U.S. Transuranium Registry autopsy cases.

The content of 238Pu, 239Pu and 241Am in the liver and skeleton was estimated from radiochemical analysis of human liver and bone samples obtained at autopsy from former actinide workers whose occupational histories were suggestive of chronic inhalation exposures, with minor skin contamination and wounds documented in a few individuals. For times estimated to be several years to a few decades post intake, 75.8 +/- 15.3% of the total 241Am in the skeleton and liver was found in the skeleton (25 cases) as compared with 63.4 +/- 24.1% for 238Pu (36 cases) and 53.2 +/- 18.2% for 239Pu (43 cases). These differences are significant at the 95% confidence level. Of these cases, 34 included data on both 238Pu and 239Pu and were divided into high and low activity subgroups. The difference in the fractionation of the two Pu isotopes was apparent only in the low activity subgroup, suggesting that the difference observed between the Pu isotopes may be an artifact of the data. The different partitioning of these three nuclides suggests that the ALIs for 238Pu and 241Am may be high by about 25-50% if only the dose to bone is considered and may be high by 12-13%, based on the weighted committed dose equivalent in target organs or tissues.

Modified biokinetic model for uranium from analysis of acute exposure to UF6.

Urinalysis measurements from 31 workers acutely exposed to uranium hexafluoride (UF6) and its hydrolysis product UO2F2 (during the 1986 Gore, Oklahoma UF6-release accident) were used to develop a modified recycling biokinetic model for soluble U compounds. The model is expressed as a five-compartment exponential equation: yu(t) = 0.086e-2.77t + 0.0048e-0.116t + 0.00069e-0.0267t + 0.00017 e-0.00231t + 2.5 x 10(-6) e-0.000187t, where yu(t) is the fractional daily urinary excretion and t is the time after intake, in days. The excretion constants of the five exponential compartments correspond to residence half-times of 0.25, 6, 26, 300, and 3,700 d in the lungs, kidneys, other soft tissues, and in two bone volume compartments, respectively. The modified recycling model was used to estimate intake amounts, the resulting committed effective dose equivalent, maximum kidney concentrations, and dose equivalent to bone surfaces, kidneys, and lungs.

Actinide distribution in the human skeleton

Radiochemical analysis of two half skeletons donated to the United States Transuranium Registry from individuals with occupationally incurred depositions, one of 241Am and the other of 239Pu, revealed an inverse proportionality between the concentration of actinide in the bone ash and the fraction of ash (or the calcium content of the ash). A similar relationship was observed in a third case suffering from osteoporosis, but the slope was shallower. These results suggest that accurate estimates of the total skeletal content of actinide can be made from radiochemical analysis of only a few bone samples.

Distribution of 239Pu in Occupationally Exposed Workers, Based on Radiochemical Analyses of Three Whole Bodies

only-Three whole bodies donated to the US. Transuranium Registry by deceased nuclear industry workers have been radiochemically analyzed for their Pu content. All had worked in the industry for 30 y or more and had been exposed to Pu, primarily by inhalation. Highest concentrations of Pu were measured in the tracheobronchial lymph nodes, followed by that in the lung and liver. Using muscle concentrations as a standard for nonconcentrating tissues, higher concentrations of Pu were found in the spleen, esophagus, pericardium, aortic arch, gallbladder, pancreas, prostate, and pituitary in one or more of the bodies examined. The ratio of skeleton content:liver content ranged from 1.0 to 3.3. The pulmonary deposition (lung, associated lymph nodes, and trachea) ranged from 20 to 53% of the total whole-body deposition. Although the concentration was low, the striated muscle contained 3 to 5% of the total Pu retained. The differences and similarities among quantities of Pu retained at the time of death by these three individuals were discussed in terms of their exposure and medical histories.

Evaluation of health effects in Sequoyah Fuels Corporation workers from accidental exposure to uranium hexafluoride

Urine bioassay measurements for uranium and medical laboratory results were studied to determine whether there were any health effects from uranium intake among a group of 31 workers exposed to uranium hexafluoride (UF{sub 6}) and hydrolysis products following the accidental rupture of a 14-ton shipping cylinder in early 1986 at the Sequoyah Fuels Corporation uranium conversion facility in Gore, Oklahoma. Physiological indicators studied to detect kidney tissue damage included tests for urinary protein, casts and cells, blood, specific gravity, and urine pH, blood urea nitrogen, and blood creatinine. We concluded after reviewing two years of follow-up medical data that none of the 31 workers sustained any observable health effects from exposure to uranium. The early excretion of uranium in urine showed more rapid systemic uptake of uranium from the lung than is assumed using the International Commission on Radiological Protection (ICRP) Publication 30 and Publication 54 models. The urinary excretion data from these workers were used to develop an improved systemic recycling model for inhaled soluble uranium. We estimated initial intakes, clearance rates, kidney burdens, and resulting radiation doses to lungs, kidneys, and bone surfaces. 38 refs., 10 figs., 7 tabs.

Postmortem tissue contents of 241Am in a person with a massive acute exposure

241Am was determined radiochemically in the tissues of USTUR Case 246, a 76-y-old man who died of cardiovascular disease 11 y after massive percutaneous exposure following a chemical explosion in a glove box. This worker was treated extensively with a chelation drug, DTPA, for over 4 y after exposure. The estimated 241Am deposition at the time of death was 540 kBq, of which 90% was in the skeleton, 5.1% in the liver, and 3.5% in muscle and fat. Among the soft tissues, the highest concentrations were observed in liver (22 Bq g-1), certain cartilaginous structures such as the larynx (15 Bq g-1) and the red marrow (9.7 Bq g-1), as compared with the mean soft tissue concentration of approximately 1 Bq g-1. Concentration in muscle was approximately that of the soft tissue average, while concentrations in the pancreas, a hilar lymph node and fat were less than the average. Concentrations in bone ash were inversely related to the ratio of ash weight to wet weight, a surrogate for bone volume-to-surface ratio. The distribution of activity in this case is reasonably consistent with that observed in another human case, when allowance is made for chelation therapy, and also tends to support more recent models of 241Am metabolism.

Comparison of estimates of systemic Pu from urinary excretion with estimates from post-mortem tissue analysis

Urinalysis data for 17 individuals with known exposure to Pu were supplied to six laboratories, each of which made an estimate of systemic deposition. In general, the evaluation was done with the Langham model or one of its derivatives, and the values obtained by the laboratories for any single case were typically within a factor of two of the mean for all laboratories. The estimates made from urinalysis data typically were several-fold greater than those made from autopsy data. The results indicate that estimates based on urinary excretion overestimate systemic deposition and tend to confirm previous observations that the Langham equation underestimates urinary excretion.