Thorium

Suspected carcinogen. Taken internally as ThO2, it has proven to be carcinogenic due to its radioactivity. On an acute basis it has caused dermatitis. Flammable in the form of dust when exposed to heat or flame, or by chemical reaction with oxidizers. The powder may ignite spontaneously in air. Potentially hazardous reactions with chlorine, fluorine, bromine, oxygen, phosphorus, silver, sulfur, air, nitryl fluoride, peroxyformic acid.