The poisoning death of Alexander Litvinenko in November caused by the radioactive isotope polonium-210 sparked a sharp interest in the exotic material, but the onetime Russian spy was not the first to swallow the lethal element.
At the height of World War II, in an isolated medical ward at the University of Rochester in New York, Dr. Robert M. Fink gave water laced with polonium-210 to a terminal cancer patient and injected four others with the isotope. None of the five apparently died from the minute doses, though one succumbed to his cancer six days later.
The ethically dubious experiment, prompted by concern for the safety of workers in the Manhattan Project to develop the atomic bomb, yielded the first solid information about the isotope's health effects on humans.
It also underscores the mystery and intrigue that have marked the history of the element since it was discovered by Marie and Pierre Curie a century ago. The isotope has left a distinctive trail of deaths, most of them a consequence of ignorance.
For The Record
Los Angeles Times Saturday January 06, 2007 Home Edition Main News Part A Page 2 National Desk 2 inches; 72 words Type of Material: Correction
Polonium-210: An article Monday in Section A about the radioactive isotope that killed Russian ex-spy Alexander Litvinenko said that traces of polonium-210 had been found in the U.S. and Europe; no traces have been found in the U.S. The article called polonium-210 the most stable of the element's isotopes; two isotopes are more stable. The article said polonium-210 completely decays into lead after about three years; about 99.9% decays in that time.
Although scientists suspected polonium-210 was dangerous, they failed to appreciate how easily it could spread -- escaping laboratory confinement like a genie from a bottle and spreading its lethal radiation on faint currents of air.
Engineers have struggled to find a use for the isotope, incorporating it for a time in spark plugs, nuclear warhead triggers and spacecraft power supplies. It plays a small role today as an antistatic agent for printing presses.
Assassins may have finally hit on its most effective use.
"The scientific community is intrigued" by Litvinenko's slaying, said radiation biologist David A. Dooley, who studied exposure levels in workers who produced polonium for the Manhattan Project. "It's pretty clever they came up with this."
In many ways, polonium-210 is an ideal poison for espionage -- deadly, and undetectable until it's too late.
A dose of the white powder smaller than a grain of salt could have been dropped into Litvinenko's drink at the Millennium Hotel's Pine Bar in London without altering the taste, according to chemist John Emsley of Cambridge University.
Within minutes of ingestion, the energetic particles shooting off the polonium-210 molecules began killing the cells lining Litvinenko's gastrointestinal tract. As the cells sloughed off, they caused nausea, severe internal bleeding and enormous pain.
"It was as if his internal organs received a severe sunburn and peeled," said Peter Zimmerman, a physicist at King's College London.
Pound for pound, polonium-210 is at least a million times more toxic than hydrogen cyanide, the poison used to execute prisoners in gas chambers, according to medical toxicology books. Radiation safety experts calculate that a single gram of polonium could kill 50 million people and sicken another 50 million.
But it is extremely hard to get. About 100 grams -- or 3 1/2 ounces -- are produced each year, primarily by Russia.
It is also elusive. Whereas most radioactive elements emit gamma rays, which register on radiation detectors, polonium-210 instead emits alpha particles.
"There was no way that forensic scientists could detect it" until it had done its damage, Emsley said.
Unlike other radioactive elements, polonium-210 is relatively safe to transport. Highly lethal gamma rays pass through most substances, but alpha particles -- each composed of two protons and two neutrons -- can be blocked by a sheet of paper or the thin layer of dead cells on the surface of the skin.
To kill, polonium must be inhaled or ingested so that it is in direct contact with healthy tissue.
"I could put it in a tiny Ziploc bag, and I would be fine," said Dooley, president and chief executive of MJW Corp., a consulting firm in Amherst, N.Y., that specializes in radiological and health physics services.
But that doesn't mean it's easy to handle. Polonium-210 is a determined escape artist.
The energy produced as it naturally disintegrates is so great that "small chunks, perhaps a few hundred atoms in size, are blasted out of the surface and then drift around the room," Zimmerman said.
"It would tend to creep around the lab," Dooley said. "If you had polonium in an open jar and you left it overnight, the next thing you knew, it would be all over the lab. It would jump on a dust particle and end up on lab benches and floors and things."
Since identifying polonium-210 as the poison that killed Litvinenko, investigators have found traces of it in hotel rooms, airplanes, embassy rooms and other sites in the U.S. and Europe visited by Andrei Lugovoy, a former KGB bodyguard who is considered a potential suspect in the case. Lugovoy has said he is being set up by persons unknown.