Actinides concentrations in human tissues

Validation of ICRP metabolic models for the transuranics in a Japanese population

Distributions of (239,240)Pu and 241Am in the tissues of Japanese were determined and then compared to those estimated using recent ICRP metabolic models. Intakes by inhalation and ingestion were calculated and used as input to the ICRP-30 model or a combination of the ICRP-66 lung model and the ICRP-67 metabolic model. The (239,240)Pu distribution in the lung, liver, skeleton, kidney, and muscle using the combination ICRP-66 and 67 models agreed well with the measured data. However, the measured plutonium concentration in the spleen was higher than predicted and than found in the kidney or muscle and indicates that the spleen should be treated as a separate organ in the ICRP model. The fractional uptake via ingestion of (239,240)Pu was estimated to be 11% with 5 x 10(-4) as the f1 value. The combination of ICRP-66 and 67 models were adequate descriptors of the organ burdens of 241Am measured in Akita and Niigata district populations. The 241Am ingrowth from 241Pu taken into in the human body contributes 90% of the measured burden.

Plutonium in Colorado residents: results of autopsy bone samples collected during 1975-1979

Concentrations of (239,240)Pu and the 240Pu/239Pu atom ratios were measured in rib samples from 55 non-occupationally exposed Colorado residents. Samples were collected at autopsy during 1975-1979 under an earlier study intended to compare plutonium levels in liver and lung of people who lived at various proximities to the Rocky Flats Environmental Technology Site (RFETS) near Denver. Overall, median (239,240)Pu concentrations from rib samples were 100, 80, and 57 microBq g(-1) ash weight for area locations A, B, and C, respectively. Area A encompassed subjects who lived within 25 km of RFETS, area B was between 25 and 50 km from RFETS, and area C included all of Colorado outside 50 km from the site and east of the continental divide. The corresponding median plutonium skeletal burdens estimated for these area locations were 146, 93, and 71 mBq, respectively. A statistically significant difference was noted only between plutonium concentrations in male rib samples and their skeletal burdens from area A compared to area C. However, based on a regression analysis of all study subjects, distance from RFETS was not statistically correlated to plutonium rib concentrations or skeletal burdens in this sample. Overall, median 240Pu/239Pu atom ratios were 0.20, 0.18, and 0.17 for areas A, B, and C, respectively. Although higher (239,240)Pu concentrations and skeletal burdens were indicated in area A males than area C males, we cannot conclude that RFETS releases may have caused this difference. The decreasing trends in the 240Pu/239Pu ratios with distance from RFETS are contrary with such a conclusion and strongly indicate that the material was primarily global fallout rather than weapons-grade plutonium that was processed at RFETS. Furthermore, there are other plausible explanations for the differences observed between area A and C residents. These include a decreasing trend in global fallout from the Rocky Mountain foothills eastward, smoking history differences, sample selection criteria, and possibly other unidentified factors. Nevertheless, estimated levels of total plutonium in this sample of Colorado residents were low and within the range of reported literature values for general, world-wide populations.

Human radiation experiments: what price informed consent?

In 1992 a system of public access was established to more than three million pages of files in government depositories related to radiation experiments on US citizens, including children, pregnant women, and convicts, studying the effects of radioactive isotopes and testicular irradiation. The background to some of these studies is described; many were considered by Ethics Committees and the results published in the open literature after peer review.