USTUR whole body case 0262: 33-y follow-up of PuO2 in a skin wound and associated axillary node

This whole body donation case (USTUR Registrant) involved two suspected PuO2 inhalation intakes, each indicated by a measurable Pu alpha activity in a single urine sample, followed about 1 1/2 y later by a puncture wound to the thumb while working in a Pu glovebox. The study is concerned with modelling simultaneously the biokinetics of deposition and retention in the respiratory tract and at the wound site; and the biokinetics of Pu subsequently transferred to other body organs, until the donor's death. Urine samples taken after the wound incident had readily measurable Pu alpha activity over the next 14 y, before dropping below the minimum detectable excretion rate (<0.4 mBq d-1). The Registrant died about 33 y after the wound intake, at the age of 71, from hepatocellular carcinoma with extensive metastases. At autopsy, all major soft tissue organs were harvested for analysis of their 238Pu, 239+240Pu and 241Am content. The amount of 239+240Pu retained at the wound site was 68±7 Bq (1 SD), measured by low-energy planar Ge spectrometry. A further 56.0±1.2 Bq was retained in an associated axillary lymph node, measured by radiochemistry. Simultaneous mathematical analysis (modelling) of all in vivo urinary excretion data, together with the measured lung, thoracic lymph node, wound, axillary lymph node and systemic tissue contents at death, yielded estimated intake amounts of 757 and 1504 Bq, respectively, for the first and second inhalation incidents, and 204 Bq for the total wound intake. The inhaled Pu material was highly insoluble, with an estimated long-term absorption rate from the lungs of 2 x 10-5 d-1. The Pu material deposited at the wound site was mixed: ∼14% was rapidly absorbed, ∼49% was absorbed at the rate of about 6 x 10-5 d-1, and the remainder (∼37%) was absorbed extremely slowly (at the rate of about 5 x 10-6 d-1). Thus, it was estimated that only ∼40% of the Pu initially deposited in the wound had been absorbed systemically over the 33-y period until the donor's death. The biokinetic modelling also indicated that, in this individual case, some of the parameter values (rate constants) incorporated in the ICRP Publication 67 Pu model were up to a factor of 2 different from ICRP's recommended values (for reference man). (authors)