Thorium dioxide

Thenardite, see Sodium sulfate Thionyl, see Sulflnyl Thorianite, see Thorium dioxide Topaz, see Aluminum hexafluorosilicate Tridymite, see Silicon dioxide Troilite, see Iron(II) sulflde... 

None of the products or experimental preparations is currently in clinical use or under development. Thorium oxide was not excreted at all furthermore it proved to be toxic because of long-lived a-radiation [4]. Other agents were not pursued because they displayed various types of toxicity or were less well tolerated than the extracellular contrast agents. Except thorium dioxide, none of them resulted in reliable and satisfactory contrast or provided important diagnostic information which could not have been obtained with a similar quality by more recently established imaging methods. In spite of an everlasting... 

Thorium dioxide, 24 761-762 Thorium fluorides, 24 762 Thorium halides, 24 762-763 Thorium hydrides, 24 761 Thorium hydroxide, 24 756 Thorium iodides, 24 763 Thorium isotopes, 24 753-754... 

Thomson-Bertheiot principle phys chem The assumption that the heat released in a chemical reaction is directly related to the chemical affinity, and that, in the absence of the application of external energy, that chemical reaction which releases the greatest heat is favored over others the principle is in general incorrect, but applies in certain special cases. tam san ber te lo, prin-s3-p3l thoria See thorium dioxide. thor e-3 )... 

No compound-related mortality was found in mice exposed to 114-330 mg/m (12.54-36.3 nCi/m = 464-1343 Bq/m ) thorium nitrate intermittently for 18 weeks (Patrick and Cross 1948). No compound-related mortality was found in rats, guinea pigs, rabbits, or dogs exposed intermittently for 1 year to 5 mg thorium/m (0.550 nCi/m = 20 Bq/m as thorium dioxide (Hodge et al. 1960). These NOAEL values are reported in Table 2-1 and plotted in Figure 2-1. 

Gn Pig = guinea pig Hemato = hematological LOAEL = lowest-observed-adverse-effect level Musc/skel = muscular/skeletal NOAEL = no-observed-adverse-effect level RBC = red blood cell Resp = respiratory TF4 = thorium tetraf1uoride ThN03 = thorium nitrate Th02 = thorium dioxide. 

Eleven months after intratracheal and intraperitoneal injection of thorium dioxide in rats, a sharp and persistent fall in blood pressure was found (Syao-Shan 1970). The fall in blood pressure could not be directly attributed to the chemical or radiological effects of thorium. 

Muller et al. 1975). Pavlovskaia et al. (1974a) determined that the excretion of intratracheally-administered thorium-228 (as thorium dioxide or thorium chloride) in the feces occurred in two phases in the rat in the first phase, up to 60% of the thorium-228 contained in the body was eliminated, and in the second phase, the rate of thorium-228 excretion in the feces averaged 0.25% of the body burden daily. 

In contrast to the thorium from Thorotrast (a thorium dioxide and dextran suspension) after intravenous injection, a higher percentage of thorium from more soluble thorium compounds is excreted. Following intravenous injection of thorium-234 citrate in humans, there is a relatively rapid but small (7%) amount of excretion within the first 20 days. A urine/feces ratio of 12 for male subjects and 24 for female subjects was determined. About 93% of the injected thorium-234 was retained at 100 days after injection, with a biological half-time of more than 5 years (Maletskos et al. 1969). 

Immunotoxicity. No studies were located regarding the immunological effects of thorium in humans or animals following any relevant route of exposure (inhalation, oral, dermal). One report, however, showed intraperitoneal and intravenous injection of thorium dioxide in mice resulted in a suppression of the immune response. Studies on the immunotoxic effects of thorium, both histopathological and effects on the immune response, by all relevant routes of exposure in animals may determine the potential immunotoxic effects in humans. 

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