Metabolism and Dosimetry of Inhaled 106RuO4 in Fischer-344 Rats

Abstract

Ruthenium-106 is a fission product radionuclide present in nuclear fuel cycles and has potential for release as ruthenium tetroxide. Ruthenium tetroxide is a vapor, diffuses rapidly in air and through porous barriers and is rapidly reduced to the dioxide form when in contact with organic compounds. The current ICRP model for inhaled particles does not predict respiratory tract deposition and clearance for inhaled vapors. This study provides data needed to assess radiation doses to humans exposed to IMRu tetroxide. Rats were given a nose-only exposure to IMRuO4 vapor to determine the subsequent distribution and retention. Initial whole-body activity ranged from 4.1 to 15 pCi of IMRu. Fifty-four per cent was in the upper respiratory tract, less than 1% was in the pulmonary region, the remaining 45% was external contamination. Clearance of l ' Ru from the body was predominately through the gastrointestinal tract to feces. A simulation model was developed to describe retention and translocation of inhaled IMRu04 and to provide estimates of radiation doses to internal organs. Current ICRP recommendations consider lung and gastrointestinal tract as critical organs for inhaled particles of radioactive ruthenium. This study indicated that the nasopharynx should be considered a critical region for vapor forms of radioactive ruthenium in human inhalation exposures.

A new RuO4 solvent solution for pure ruthenium film depositions

“…It was reported that 99% of the 106 Ru initially deposited in the rats was cleared from the body by 15 days after exposure. In the same article, one can also learn that 85% of the initial whole-body activity was cleared with a biological half-life of 0.6 days [3] and that soluble forms of Ru were cleared rapidly from the body following inhalation [4]. Finally, a recent presentation reported a LC 50 (oral, rat) value higher than 250 mg/kg for an aqueous solution of 0.5% and added that sub-dermal injection tests showed no observable toxic effects [5].…”

Uncertainties in Cancer Risk Coefficients for Environmental Exposure to Radionuclides. An Uncertainty Analysis for Risk Coefficients Reported in Federal Guidance Report No. 13

“…Low variant: This is a model developed by Runkle et al (1980) as a fit to measurements of 106 Ru in systemic tissues and excreta of rats exposed to 106 RuO 4 by inhalation or ingestion ( Figure B-2). Radioactive progeny are assigned the biokinetics of the parent.…”

Metabolism and Dosimetry of 106Ru Inhaled As 106RuO4 by Beagle Dogs

“…One report recently described the results from a study in which rats were exposed by inhalation to ' "RuO., (Ru80). This report presents results from a complementary study in Beagle dogs.…”