James F. Mcinroy

Uranium in the tissues of an occupationally exposed individual

Uranium concentrations were radiochemically determined in samples of lung, kidney, liver and bone collected at autopsy from an occupationally exposed individual. Levels of U in these tissues were clearly in excess of those expected from environmental exposure. Deposition followed the pattern: skeleton greater than liver greater than kidney, with ratios of 63:2.8:1. The data suggest there is an important long-term storage depot in the skeleton, but the fraction transferred to this compartment, as proposed by ICRP 30, may be too small. In vivo chest counts obtained over about a 10-y period prior to death indicated about a factor of 2 greater in total U content and 235U enrichment than deposition estimates made at autopsy for the lungs and associated lymph nodes.

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.

Macrodistribution of plutonium and americium in four human skeletons

Three human half-skeletons were radiochemically analysed by the United States Transuranium Registry (USTR) for 239Pu+240Pu and 241Am and another was analysed for 241Am only. The distribution of activity in individual bones or groups of bones has been characterised as a percentage of the total skeletal content and compared with published distributions reported for primates (baboons and monkeys) and human injection cases. Americium and plutonium distributions in the four skeletons were similar; however, there was somewhat less variability in the plutonium data for the individual bones. In humans, the skull, tarsals (as a group), humeri, scapulae and patellae contained the most consistent percentages of the total skeletal activity and can be individually used to estimate total skeletal content. The patella is particularly suitable because of the ease with which this bone can be obtained at autopsy. The greatest variations in the fraction of the total skeletal activity were found in the mandible, sacrum, coccyx and sternum.

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.

Determination of thorium and uranium in total diet samples by inductively coupled plasma mass spectrometry

The Th and U contents in total diet samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). The internal standardization method was adopted to compensate for non-spectral interferences arising from matrix elements in the sample solutions. Concentration levels of the order of pg ml–1 of Th and U in the total diet sample were determined easily and rapidly by using Bi as an internal standard. The mean concentrations and standard deviations of Th and U in the total diet samples were found to be 25 ± 12 and 44 ± 20 ng g–1 of ash, respectively (for n= 62).

U.S. Transuranium Registry report on the 239Pu distribution in a human body.

The distribution of 239Pu in a human whole body is reported. The body contained 246 Bq of 239Pu of which 130 Bq (52.8%) was found in the lungs and associated lymph nodes. Of the remaining 116 Bq (47.2%) that constituted the systemic deposition, 51.2 Bq (44%) were in the skeleton, 48.6 Bq (42%) in the liver, and the remainder (14%) in the rest of the body exclusive of the lungs and associated lymph nodes. An unexpectedly high concentration was observed in the pituitary. The systemic distribution of Pu in this case, when combined with the exposure history, is suggestive of an initial partitioning ratio of 239Pu between skeleton and liver of less than unity, and a tentative initial distribution from the transfer compartment of 25% to the skeleton, 50% to the liver, and 25% to the rest of the body and early excretion is proposed for this case. Older biokinetic models, when used with the available urinalysis data for this case, typically overestimated the deposition when compared with the tissue analysis results, but more recent models provided estimates in close agreement with the autopsy results.

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.

A bone ash standard for90Sr,210Pb,210Po, uranium and the actinides

A bone ash standard for a number of radionuclides is required as a quality control sample in dosimetry studies with bone as the critical organ. The procedures that were used to prepare a candidate bone ash standard are given with some initial encouraging measurements that the candidate sample will meet the requirements of NIST standard reference manual.

Comparison of systemic plutonium deposition estimates from urinalysis and autopsy data in five whole-body donors.

The systemic deposition of (239 + 240)Pu was determined by postmortem radiochemical analysis of the tissues from five whole-body donors to the United States Transuranium Registry (USTR). All were males with intakes typically occurring many years prior to death. The postmortem radiochemical results were compared with estimates of systemic deposition made with 13 different biokinetic models using urinary excretion data obtained during life. In general, estimates made with older biokinetic models were severalfold greater than those obtained from radiochemical analysis of the tissues. For all five cases, agreement within a factor of two with the tissue analysis results was obtained with two of the biokinetic models evaluated: the Langham power function model as modified by Leggett and Eckerman and the two compartment exponential model proposed in ICRP Publication Nos. 19 and 30.

Interlaboratory comparison of actinides in human tissue239Pu and240Pu

An international laboratory intercomparison of actinides in human tissues was organized by the United States Transuranium Registry and the National Institute of Standards and Technology. Five laboratories from the United States, United Kingdom, and Japan participated in the intercomparison. The laboratories were requested to analyze Standard Reference Materials 4351 (Human Lung) and 4352 (Human Liver) for239Pu and240Pu concentration. Approximately equivalent measurement capabilities were generally found among the participants. The results of this intercomparison were statistically comparable to those used for the original certification of the SRMs and were combined for a re-evaluation of the certified values. The combined data sets provide a better characterization of the inhomogeneity of these reference materials and result in a better basis for certification.