Alpha particles are what killed a spy that the Soviet KGB injected with polonium-210-84. The alpha particle emitting isotope must be ingested or injected to slay by 500 rems of radiation or more. The KGB also has killed a spy by ricin injection, so less polonium-210 is needed to kill a spy than ricin, previously the third most toxic poison.

The medical effect of polonium-210 injection is AIDS where radioactivity destroys the body's white blood cells, followed by digestive system failure should the victim avoid infection.