Thorium Dioxide

**Semantic type:** Hazardous or Poisonous Substance|Indicator, Reagent, or Diagnostic Aid|Inorganic Chemical

**Definition:** A radioactive crystalline solid compound used in a broad range of industrial applications. Thorium dioxide was utilized as a radiographic contrast agent; however, it is no longer considered safe for use in human patients because it was found to be a carcinogen that can cause cholangiocarcinoma.

**Synonyms:** - THORIUM DIOXIDE - Thoria - Thorium Anhydride - Thorium Oxide - Thorium(IV) Oxide - Thorotrast - Thortrast - Umbrathor