A Rare Material and a Surprising Weapon
If substantial amounts of polonium 210 were used to poison Alexander V. Litvinenko, whoever did it presumably had access to a high-level nuclear laboratory and put himself at some risk carrying out the assassination, experts said yesterday.
Polonium 210 is highly radioactive and very toxic. By weight, it is about 250 million times as toxic as cyanide, so a particle smaller than a dust mote could be fatal. It would also, presumably, be too small to taste.
There is no antidote, and handling it in a laboratory requires special equipment. But to be fatal it must be swallowed, breathed in or injected; the alpha particles it produces cannot penetrate the skin. So it could theoretically be carried safely in a glass vial or paper envelope and sprinkled into food or drink by a killer willing to take the chance that he did not accidentally breathe it in or swallow it.
“This is wild,” said Dr. F. Lee Cantrell, a toxicologist and director of the San Diego division of the California Poison Control System. “To my knowledge, it’s never been employed as a poison before. And it’s such an obscure thing. It’s not easy to get. That’s going to be something like the K.G.B. would have in some secret facility or something.”
In a quick search of medical journals, he could find only one article describing the deliberate use of a radioactive poison to kill. It was from 1994, he said, published in Russian.
Polonium is extremely rare in nature. Named by its discoverer, Marie Curie, after her native Poland, it occurs in trace amounts in uranium ore and has been found in minute quantities in plants like tobacco, as well as in humans who had eaten caribou that ate lichens growing near a uranium mine.
But making the “significant quantities” described in Mr. Litvinenko’s body by the British Health Protection Agency would require a nuclear reactor that could bombard the metallic element bismuth with neutrons.
“To most chemists, this is astonishing,” said Dr. Andrea Sella, a lecturer in inorganic chemistry at London’s University College. “This is not available commercially. It is present in food, but only in the kind of trace quantities that can be detected by ultrasensitive analytical techniques. It is one of the rarest elements on the earth’s crust and also one of the most exotic.”
He added: “This is not the kind of weapon that any kind of amateur could construct. It would require real resources to do it.”
Robert C. Whitcomb Jr., a health physicist for the Centers for Disease Control and Prevention, said polonium had industrial uses and could be produced in commercial or institutional reactors.
“It would take sophistication,” he said.
Polonium 210 does its damage by emitting alpha particles, which have enough energy to tear apart the genetic machinery of cells, killing them outright or causing them to mutate into tumor-producing forms. It gives off 5,000 times more alpha particles than does the same amount of radium.
Alpha-emitters are not picked up by normal radiation-detection devices, a British expert said, so it would be relatively easy to take the substance across a border.
The particles disperse through the body and first destroy fast-growing cells, like those in bone marrow, blood, hair and the digestive tract. That would be consistent with Mr. Litvinenko’s symptoms, which included hair loss, inability to make blood cells and gastrointestinal distress.
It is also a better match than the symptoms caused by thallium, a heavy metal that was first suspected when Mr. Litvinenko fell ill after eating at a sushi bar on Nov. 1. Polonium is so radioactive that it gives off heat, and tiny amounts have been implanted in satellites to make heat and electricity. It was also used in the Soviet Union’s Lunokhod moon rovers.
British authorities said they would monitor and take urine samples from anyone who had been in close contact with Mr. Litvinenko, including hospital staff members who cared for him.
But they said there was little likelihood of danger from exposure to the polonium. Some of it would have passed out through Mr. Litvinenko’s digestion, and the rest would presumably be lodged in his tissues.
“Normal hygiene and cleanliness practices in hospitals should have reduced the likelihood of any significant intake” by hospital staff members, said Dr. Pat Troop, chief executive of the Health Protection Agency.
Burial should be safe, Dr. Cantrell said, because the ground would contain the alpha particles; but cremation might theoretically be dangerous because it could disperse the polonium back into the air.
Stephen Grey contributed reporting from London.