Thorium oxide (ThO2)

264.04

264.02800

215-225-1

2910|2909

DTXSID0051657

White crystal powder|White cubic crystals|Heavy white powder|Cubic

34.14000

-0.23760

Thorium oxide, [radioactive material, low specific activity] is a white powder. Density 9.7 g / cm3. Not soluble in water. Used in high-temperature ceramics, gas mantles, nuclear fuel, flame spraying, crucibles, non-silicia optical glass, catalysis, filaments in incandescent lamps, cathodes in electron tubes and arc-melting electrodes.

10.0 g/cm³

3390 °C

4400 °C

Index of refraction: 2.20 (liquid) at 20 °C

Partially sol in biological fluids (gastric juice, plasma, etc)

Heavy, infusible|Hardness 6.5 (Mohs)|Amorphous thoria crystallizes upon fusion with sodium carbonate or potassium orthophosphate.|Thoria forms double oxides with the alkaline earths, eg, thorium barium oxide (12230-90-9). Double oxides with the alkali metals are of the type sodium thorium oxide (12058-67-2). It also forms oxides with germanium, titanium, vanadium, niobium, tantalum, and molybdenum.|For more Other Experimental Properties (Complete) data for THORIUM DIOXIDE (6 total), please visit the HSDB record page.

Insoluble in water.

Non-Redox-Active Inorganic Compounds

Radioactive Material

Has only weak oxidizing powers. Redox reactions can however still occur. Not water-reactive. Soluble in sulfuric acid.

UN29107

45-23/24/25-33

53-36/37/39-45

XO6950000

T,R

P201, P202, P260, P261, P264, P270, P271, P280, P281, P301+P310, P302+P352, P304+P340, P308+P313, P311, P312, P314, P321, P322, P330, P361, P363, P403+P233, P405, P501

H301

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.|Disposal of ... wastes /containing uranium/ should follow guidelines set forth by the Nuclear Regulatory Commission & the EPA. /Uranium & cmpd/

National Toxicology Program. Eleventh Report on Carcinogens (2005). The Report on Carcinogens is an informational scientific and public health document that identifies and discusses substances (including agents, mixtures, or exposure circumstances) that may pose a carcinogenic hazard to human health. Thorium Dioxide (1314-20-1) is listed as known to be a human carcinogen. /Ionizing Radiation: Thorium Dioxide/[Available from, as of July 31, 2009: http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s097zird.pdf]

Excerpt from ERG Guide 161 [Radioactive Materials (Low Level Radiation)]: Some of these materials may burn, but most do not ignite readily. Many have cardboard outer packaging; content (physically large or small) can be of many different physical forms. Radioactivity does not change flammability or other properties of materials. (ERG, 2016)

|Danger|H301 (85.43%): Toxic if swallowed [Danger Acute toxicity, oral]|P201, P202, P260, P261, P264, P270, P271, P280, P281, P301+P310, P302+P352, P304+P340, P308+P313, P311, P312, P314, P321, P322, P330, P361, P363, P403+P233, P405, and P501|Aggregated GHS information provided by 247 companies from 4 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Excerpt from ERG Guide 161 [Radioactive Materials (Low Level Radiation)]: As an immediate precautionary measure, isolate spill or leak area for at least 25 meters (75 feet) in all directions. LARGE SPILL: Consider initial downwind evacuation for at least 100 meters (330 feet). FIRE: When a large quantity of this material is involved in a major fire, consider an initial evacuation distance of 300 meters (1000 feet) in all directions. (ERG, 2016)

Excerpt from ERG Guide 161 [Radioactive Materials (Low Level Radiation)]: Do not touch damaged packages or spilled material. Cover liquid spill with sand, earth or other non-combustible absorbent material. Cover powder spill with plastic sheet or tarp to minimize spreading. (ERG, 2016)

Excerpt from ERG Guide 161 [Radioactive Materials (Low Level Radiation)]: Positive pressure self-contained breathing apparatus (SCBA) and structural firefighters' protective clothing will provide adequate protection. (ERG, 2016)

If material involved in fire: Contact the local, state or Department of Energy Radiological Response Team. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible.

Uranium thorium recovery: Working up of uranium-thorium wastes in Kernel casting process: ... evaporating a soln of uranium thorium oxide waste dissolved in a nitric acid hydrofluoric acid mixture up to the appearance of nitrous gases, the residue diluted in the hot condition with water and this soln brought to a pH between 2.5 and 3.5 with ammonia at a temp below 40 °C. The soln recovered by the process can be adjusted to any heavy metal (ie, uranium thorium) concn up to about 300 g/l at a pH of 3 to 3.5, is stable for over 1 month and is miscible with ... polyvinyl alcohol. This soln can be adjusted through further addition of uranium or thorium to the desired uranium ratio for the casting soln. ... According to the process, all wastes can be returned without loss during the production process.

If material not involved in fire: Contact the local, state, or Department of Energy Radiological Response Team. Keep sparks, flames, & other sources of ignition away. Keep material out of water sources & sewers.|Personnel protection: Keep upwind. Avoid breathing fumes from burning material. ... Do not handle broken packages unless wearing appropriate personal protective equipment. Wash away any material which may have contacted the body with copious amounts of water or soap & water.|SRP: Contaminated protective clothing should be segregated in such a manner so that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. Quality assurance to ascertain the completeness of the cleaning procedures should be implemented before the decontaminated protective clothing is returned for reuse by the workers. Contaminated clothing should not be taken home at end of shift, but should remain at employee's place of work for cleaning.

Radionuclides has been designated as a hazardous air pollutant under section 112 of the Clean Air Act. /Radionuclides/

Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 100 curie or 3.7x10+12 becquerel. The toll free number of the NRC is (800) 424-8802; In the Washington D.C. metropolitan area (202) 426-2675. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b). /(226)Thorium/|Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 1 curie or 3.7x10+10 becquerel. The toll free number of the NRC is (800) 424-8802; In the Washington D.C. metropolitan area (202) 426-2675. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b). /(227)Thorium/|Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 0.01 curie or 3.7x10+8 becquerel. The toll free number of the NRC is (800) 424-8802; In the Washington D.C. metropolitan area (202) 426-2675. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b). /(228)Thorium/|Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 0.001 curie or 3.7x10+7 becquerel. The toll free number of the NRC is (800) 424-8802; In the Washington D.C. metropolitan area (202) 426-2675. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b). /(229)Thorium/|For more CERCLA Reportable Quantities (Complete) data for THORIUM DIOXIDE (8 total), please visit the HSDB record page.

LD50 Rat intratracheal > 1140 mg/kg body wt (Death in 24 hr)

Thorium dioxide is a constituent of many minerals, and those of industrial importance incl monazite, thorite, and thorianite.|Monazite may contain 2.5-2.8% thorium oxide mixed with rare earth elements, zirconium, titanium, cadmium, niobium, and uranium. It is almost always found mixed with products of its disintegration ... .|The vein deposits of thorite (ThSiO4), such as occur in the area of Lemhi Pass, Idaho, are the highest grade thorium mineral, containing about 25 to 63 percent thorium oxide (ThO2).

Potential exposure to thorium dioxide may occur through inhalation of dust or gas, intravenous injection, ingestion of liquid thorium dioxide, and skin absorption. ...|Workers in plants where thorium oxide is refined ... .|Occupations at greatest risk of possible exposure were ceramic makers, incandescent lamp makers, magnesium alloy makers, metal refiners, nuclear reactor workers, chemists, and vacuum tube makers. OSHA estimated that 128,500 workers were possibly exposed to the compound during its production and use. A number of patients were exposed to Thorotrast when it was administered for x-ray procedures.

Retention of thorium from inhalation of thorium dioxide dust for 1 yr ... left 98% of the body burden of thorium in the lung and pulmonary lymph nodes, 2% in bone, and less than 0.1% in the rest of the body. The relative immobility of tissue deposited thorium is shown by the finding in the femur, and fractions of the latter amount in the kidney, spleen, and liver 6 to 7 yr after inhalation exposure had been terminated.

Collodial soln of thorium dioxide have been used /in the past/ as X-ray contrast media for exam of the liver and spleen, for arteriography, and occasionally for outlining the cerebral ventricles.

Its elimination is very slow and incomplete. ... As it is radioactive ... this accumulation is dangerous and there is strong evidence that the ensuing prolonged exposure to its radiation is a contributing factor in the development of malignant diseases and blood disorders often 20 to 30 yr after its admin.

Substances that increase the risk of NEOPLASMS in humans or animals. Both genotoxic chemicals, which affect DNA directly, and nongenotoxic chemicals, which induce neoplasms by other mechanism, are included. (See all compounds classified as Carcinogens.)

Retention of thorium from inhalation of thorium dioxide dust for 1 yr ... left 98% of the body burden of thorium in the lung and pulmonary lymph nodes, 2% in bone, and less than 0.1% in the rest of the body. The relative immobility of tissue-deposited thorium is shown by the presence of 97.7% in the pulmonary lymph nodes, 2.1% in the lung, and 0.003% in the femur, and fractions of the latter amount in the kidney, spleen, and liver 6 to 7 yr after inhalation exposure had been terminated.|The fecal to urinary ratio was 1.6 compared with 45 at higher dose levels, and in two patients given iv injections of 12 to 14 g Thorotrast, one excreted 0.37% in the urine on the first day and only a total of 0.7% in the next 16 days, and the other, only 0.1% in 108 days.|Thorium dioxide is taken up by the cells of the reticuloendothelial system ... and none of the thorium dioxide from the reticuloendothelial system is transferred to the skeleton.|The absorption of ... /thorium dioxide/ in rats ... is almost negligible. ... Thorium dioxide remains at the site for a long time, and only small quantities are gradually removed by lymphocytes to the regional lymph nodes.|For more Absorption, Distribution and Excretion (Complete) data for THORIUM DIOXIDE (10 total), please visit the HSDB record page.

Two cytogenetic parameters of radiation exposure, the frequency of micronucleus in erythroblasts, lymphocytes and red cells (Howell-Jolly) as well as chromosome aberrations in bone marrow cells and in lymphocytes were studied in 24 Thorotrast patients and in 32 atomic bomb (A-bomb) survivors who were exposed within 1 km from the Hiroshima (Japan) hypocenter. The incidence of both micronucleus and chromosome aberrations in these two exposed groups were significantly higher than that in non-exposed controls. ... The characteristics of lymphocyte chromosome aberrations differed considerably between Thorotrast patients and A-bomb survivors the incidence of unstable type aberrations and intracellular complexity of chromosome aberrations were much higher in the former group. The incidence of micronucleus in erythroblasts and lymphocytes was also higher in Thorotast patients. Such differences are attributable to the differences in the radiation quality (alpha-ray or gamma-ray + neutron) and in the mode of exposure (persistent or single) of these two groups.

Biological half-life for the long term clearance from the body was at least 14-15 yr, presumably because of the amt deposited in the skeleton.|In a subject who had accidentally inhaled thorium-228 dioxide (alpha emitter, radioactive half-life of 1.9 years), the biological half-life for long-term clearance of thorium-228 from the body was at least 14 years as a result of skeletal deposition

Excerpt from ERG Guide 161 [Radioactive Materials (Low Level Radiation)]: Radiation presents minimal risk to transport workers, emergency response personnel and the public during transportation accidents. Packaging durability increases as potential hazard of radioactive content increases. Very low levels of contained radioactive materials and low radiation levels outside packages result in low risks to people. Damaged packages may release measurable amounts of radioactive material, but the resulting risks are expected to be low. Some radioactive materials cannot be detected by commonly available instruments. Packages do not have RADIOACTIVE I, II, or III labels. Some may have EMPTY labels or may have the word "Radioactive" in the package marking. (ERG, 2016)|Carcinogens

Excerpt from ERG Guide 161 [Radioactive Materials (Low Level Radiation)]: Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves. Call 911 or emergency medical service. Medical problems take priority over radiological concerns. Use first aid treatment according to the nature of the injury. Do not delay care and transport of a seriously injured person. Give artificial respiration if victim is not breathing. Administer oxygen if breathing is difficult. In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. Injured persons contaminated by contact with released material are not a serious hazard to health care personnel, equipment or facilities. (ERG, 2016)

Basic Treatment: Establish a patent airway. Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if needed. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with normal saline during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 ml/kg up to 200 ml of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . Cover skin burns with dry sterile dressings after decontamination ... . /Poison A and B/|Advanced Treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious. has severe pulmonary edema, or is in respiratory arrest. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Monitor cardiac rhythm and treat arrhythmias as necessary ... . Start an IV with D5W /SRP: "To keep open", minimal flow rate/. Use lactated Ringer's if signs of hypovolemia are present. Watch for signs of fluid overload. Consider drug therapy for pulmonary edema ... . For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs Of fluid overload ... . Treat seizures with diazepam (Valium) ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Poison A and B/

Of 1107 patients given thorium dioxide between 1930 and 1952 primarily for the radiological visualization of blood vessels, 699 had died and 408 were alive up to the end of 1963. The long term sequelae were shown, statistically, to incl local granulomas in 81, cirrhosis of the liver in 42, fatal blood disorders in 16, and hemangioendotheliomas occurring in 22 and virtually thorium dioxide specific.|Brief case histories of 6 patients seen between 1967 and 1975, who had received thorium dioxide many yr earlier. Complications incl leukemia, aplastic anemia, tumors, and ... hyposplenism.|Tumors of the hepatic vasculature have been induced by thorium dioxide ... .|... After iv admin of thorium dioxide, most cancers were tumors of the reticuloendothelial system esp involving the liver with an equal distribution of sarcomas and carcinomas. Injection of thorium dioxide into the sinus cavities results in carcinomas. The latent period for tumor development is long (approx 15 yr), and tumorigenesis arises from alpha radiation.|For more Human Toxicity Excerpts (Complete) data for THORIUM DIOXIDE (31 total), please visit the HSDB record page.

Dioxide, Thorium

Suspension containing 20-25% Thorium dioxide, Thorotrast|3-12 mm, sintered; -30, +200 mesh; -150, +325 mesh; -325 mesh, +10 microns, 99.5, 99.9 and 99.99% purity grades.|Technical and purities to 99.8% thorium dioxide; granular particles, crystals|Sterile contrast medium made up of 24-26% stabilized colloidal thorium dioxide in 25% aq dextrin and 0.15% methyl parasept as preservative|Umbrathor /is/ a soln of thorium dioxide.

Thorium oxide (ThO2): ACTIVE|The most important thorium compound ... owing to its high chemical and thermal stability.|The U.S. Department of Energy's inventory at year's end was 535,000 kg.

Health Hazards -> Carcinogens