Thorium

Thorium is a chemical element (atomic number 90). Although it is radioactive, the alpha-particles it emits cannot penetrate the skin and cannot cause radiation sickness from external exposure. However, it can lead to an increased incidence of cancer if ingested in a purified form. It has a limited number of commercial uses and exposure is usually occupational. It is ubiquitous in the environment and humans naturally ingest a small but safe dose of it on a daily basis.
Thorium at Wikipedia
Category:Chemistry
Category:Toxins