The radioactive poison, Polonium 210, used to murder spy Alexander Litvinenko, is a lethal but hugely expensive substance to manufacture
Polonium-210 is a highly radioactive and extremely toxic material, but to be used as a lethal poison it requires direct contact with a body’s inner tissues.
A microgram of polonium 210 – the size of a speck of dust – would be sufficient to be a lethal dose.
It is a slow and silent killer that attacks the blood cells followed by the liver, kidneys, spleen, bone marrow, gastrointestinal tract and the central nervous system.
Alexander Litvinenko signed his death sentence when he unwittingly drank the substance that had been deposited in a cup of green tea. But he took three weeks to die.
But polonium 210 is a far more lethal substance.
It is an alpha-emitter, rather than the better-known radioactive elements that emit gamma-ray, and decays over a period of months rather than years.
Alpha radiation is absorbed by human tissue so would have been impossible to detect using a Geiger counter outside of a body. But it does show up in urine.
Read more at Litvinenko Inquiry: What is Polonium 210?