No abstract

ABSTRACT

The efficacy of bronchopulmonary lavage and chelation therapy for removing Pu from beagle dogs after inhalation of 239Pu aerosols having different solubilities has been investigated. The four aerosols used were nebulized from a solution of 239PuC1, and heat treated at temperatures of 325, 600, 900 and 1150°C. Groups of six beagle dogs were exposed to each of the aerosols. Subsequently, three dogs in each group were treated by lavage and intravenous injections of diethylenetriaminepentaacetic acid (DTPA). The remaining three dogs in each group served as untreated controls. At 56 days after exposure, all dogs were sacrificed and necropsied. In the untreated dogs, tissue distribution, as a percentage of the initial lung burden (ILB), was 7% in liver and 9% in skeleton for the 325" aerosol group, 1% in liver and 2% in skeleton for the 600" group and less than 0.6% in these tissues for the 900 and 1150°C groups. In the treated dogs, tissue content of 239Pu was 1.0% or less of the ILB for these organs, regardless of aerosol temperature. Urinary excretion of 239Pu was greater in the treated dogs than in the untreated dogs that inhaled the 325" (4% of the ILB) and the 600" (1% of the ILB) aerosols. In the 900 and 1150" aerosol groups, urinary excretion of 23yPu was similar (0.7%) for both treated and untreated dogs. Ten bronchopulmonary lavage procedures removed a mean of 44% of the ILB of 239Pu from the lungs. The aerosol temperature and resulting differences in solubility of the particles did not influence the efficacy of the lavage procedure. As a result of the treatment procedures, alpha absorbed dose to lung was reduced by 50% at 56 days after exposure.2 3 Y

The whole body of an individual injected with Thorotrast 36 y prior to her death was analyzed for 232Th, 228Ra, 228Th, and 230Th. Measurement of these isotopes in all tissues of the body will provide data necessary to caculate the radiation dose to individual tissues and to evaluate the risk potential associated with deposition of thorium and progeny in humans. The tissues were ashed, dissolved in acid, and the thorium isolated by ion exchange and electrodeposition. The 228Ra was determined by measuring the 0.991-MeV gamma rays associated with decay of the 228Ac daughter. It was estimated that almost all of the 232Th from the original injection was retained in the body, mostly in the tissues of the reticuloendothelial system. A total of 28 kBq (0.76 microCi) of 232Th was measured in the soft tissues and bones. The body also contained 13 kBq 228Ra, 12 kBq 228Th, and 3.9 kBq 230Th. A Thorotrastoma contained about 3.5% of the total activity. Excluding the Thorotrastoma, approximately 45% of all the activity (232Th, 228Ra, 228Th, and 230Th) was retained in the liver, 13% in the spleen, 2% in muscle, 1% in skin, slightly less than 1% in the respiratory tract, 4% in all other soft tissues, and 33% in the skeleton (bone and bone marrow). Sixty to 80% of the thorium activity in bones containing red marrow was located in the marrow. Bones containing yellow marrow had less than 40% of the thorium activity in the marrow. Highest concentrations were found in the hepatic and other abdominal lymph nodes, spleen, hilar lymph nodes, liver, trachea, and bone. Approximately 60% of the 228Ra formed from the decay of the 232Th had been excreted from the body. The 228Ra and 228Th were in approximate equilibrium throughout the body.

Particulate Ni5As2 has been shown to be highly cytotoxic and carcinogenic. By measuring the solubility of Ni5As2 particles in a variety of aqueous solutions, we have determined that particulate Ni5As2 that might be produced during oil-shale retorting could be mobilized to the environment and made available to the cells of living organisms, including humans. Ni5As2 was five times more soluble in ground water taken from aquifers surrounding a major oil-shale source in Colorado, U.S.A., than in distilled water. It was also two times more soluble in oil-shale product water from an above-ground retort than in distilled water. Thus, it is possible that Ni5As2 could be solubilized and mobilized to the environment by the flooding of abandoned in situ retorts with ground water or by the disposal of oil-shale product water by spraying it on spent shale beds. Particulate Ni5As2 was found to be 12 times more soluble in culture growth medium than in distilled water, and much more soluble in solutions of amino acids, inorganic salts, organic constituents of culture medium, and 15% calf serum. These observations suggest Ni5As2 particles in airborne dust would be dissolved when they came in contact with the biological fluids of the lung and gastrointestinal tract. The availability to cells of the soluble products of Ni5As2 was demonstrated by measuring its effects on cell proliferation. As little as 1 ppm soluble Ni5As2 retarded Chinese hamster (CHO) cell proliferation in culture, and 4 ppm resulted in cell death. Flow cytometry measurements indicated there was a preferential cytotoxic effect on S-phase cells. Despite this, many cells survived to form colonies, causing concern that Ni5As2 might cause genetic damage that could be passed on to future cell generations. This did not appear to be the case, however, for no mutations could be detected at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in cells that survived the cytotoxic effects. This suggests that Ni5As2 carcinogenesis might be caused by epigenetic rather than mutagenic mechanisms.