Doctors earlier said that Scaramella, who is being treated in hospital in London, had tested positive for polonium-210, the rare radioactive substance that has been linked to Litvinenko's death on November 23.
Doctors say Scaramella, who met with Litvinenko in London on November 1, was exposed to a much lower level of the isotope.
In a statement published by Italian media, Scaramella said he believed that both he and Litvinenko may have been targeted because of information that Litvinenko had shared with him.
Scaramella did not accuse anyone of the poisoning or specify what kind of information Litvinenko had sent him.
Scaramella added that investigators do not suspect him of killing Litvinenko and that London police regard him as a victim.
- Polonium, also called "radium F," was discovered by Marie Curie and her husband, Pierre Curie, in 1898 and was later named after Marie's homeland of Poland (Latin: Polonia).
- It is an alpha emitter, meaning that although it is highly radioactive, it cannot penetrate human skin or a sheet of paper. Washing eliminates traces.
- Contact with a carrier's sweat or urine could lead to exposure. But polonium-210 must be ingested or inhaled to cause damage.
- Polonium-210 has a relatively short half-life of 138 days.
- Polonium-210 occurs naturally in the environment (it is found in such things as dirt and tobacco) and in people at low concentrations. But acquiring a lethal amount would require individuals with expertise and connections.
- Polonium-210 emits 5,000 times more alpha particles than radium, and an amount the size of the period at the end of this sentence would contain about 3,400 times the lethal dose. A dose like the one that killed former Russian spy Aleksandr Litvinenko would probably have been manufactured at a nuclear facility.
- Russia exports 8 grams of polonium-210 monthly, all of it to the United States. Exports to Britain ended about five years ago.