Litvinenko Inquiry: What is Polonium 210?

The radioactive poison, Polonium 210, used to murder spy Alexander Litvinenko, is a lethal but hugely expensive substance to manufacture

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Former Russian security agent Alexander Litvinenko pictured before his death at University College Hospital in central London
Alexander Litvinenko pictured before his death at University College Hospital in central London Credit: Photo: PA

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.

His case is the only recorded example of deliberate polonium poisoning anywhere in the world.

It was discovered by Marie Curie and her husband Pierre, who won the Nobel Prize, at the end of the 19th century, and was named after her home country of Poland and radium.

Irene Curie, the chemists' daughter, is believed to have died from cancer caused when a phial of polonium exploded in her laboratory, although that took 15 years.

A 3D graphic showing polonium contamination of the table and chair
Images at the public inquiry show the traces of polonium 210 in the hotel where Mr Litvinenko was poisoned

Polonium is one of the six metalloids on the periodic table, which also include the more familiar poisons arsenic and antimony.

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.

A 3D graphic showing polonium contamination in the teapot. From green (low) to purple (high)
The tea pot that contained the Polonium-laced green tea, which Mr Litvinenko unwittingly drank

But despite its dangers, the radiation from polonium does not pass through other materials easily. Even paper could block it.

It is only lethal when it comes into immediate contact with tissue.

It is extremely rare in nature, but can be found in the same ore as uranium. However, to produce it even in these tiny quantities is likely to require processes found only in nuclear reactors.

The polonium used to kill Mr Litvinenko would have cost “tens of millions of dollars” if bought on the open commercial market.