Polonium is back in the news as Palestinian leader Yasser Arafat's wife says Swiss forensic tests show he was poisoned to death by it in 2004. Here are five things to know about the radioactive substance sometimes called the "Perfect Poison."
What Is Polonium?
Polonium is a metal found in uranium ore whose isotope polonium-210 is highly radioactive, emitting tiny positively charged alpha particles. So long as polonium is kept out of the human body, it poses little danger because the alpha particles travel no more than a few centimeters and cannot pass through skin. But if polonium is ingested, even in the tiniest quantity, it will so badly damage internal organs that they shut down and death is certain.
A speck of polonium the size of the dot at the end of this sentence contains about 3,400 times the lethal dose for humans. It was discovered by French scientist Marie Curie at the end of the 19th century and named after her native country, Poland (Polonia in Latin).
Why Is It Called The Perfect Poison?
Oleg Gordievsky, a former officer with Russia's KGB who was a double agent for Britain during the Cold War, says polonium is an ideal assassination weapon because it is absolutely lethal: "Polonium is a perfect poison. It kills absolutely, without hesitation. And if you use it, you use it with 100 percent certainty."
But polonium is not just an immensely powerful poison. Its presence in the body is also very hard for doctors to identify unless they are looking specifically for it.
Part of the difficulty in detecting polonium poisoning is that its outward symptoms resemble poisoning with much less powerful substances. Among the earliest symptoms are hair loss, which is also a standard symptom of poisoning by thallium, an element in rat poison.
This ability of polonium to conceal its presence by appearing to be another, simpler, poison enables it to fool investigators into looking for other culprits than the real assassin.
There is one more reason to consider polonium the perfect poison: it is easy to conceal and transport across borders.
Unlike most common radiation sources, polonium-210 does not set off standard radiation detectors because it emits only alpha particles that do not penetrate even a sheet of paper.
It can be carried in crystalized or powdered form or diluted in a bottle of liquid. Identifying it in any of these forms with current methods is both time-consuming and requires an experienced analyst.
Has It Been Used Before?
Yes. The most famous case is the assassination of Aleksandr Litvinenko, a former Russian security officer who received political asylum in Britain after becoming a highly vocal critic of Russian President Vladimir Putin. He died of polonium poisoning in November 2006.
British prosecutors say he drank polonium-laced tea while meeting in a hotel room with several Russians three weeks before his death. The tiny amount of polonium needed to kill him would have given no taste or color to his drink to alert him of its presence.
"It was very easy for [the assassins], because they went to the little kitchen in [the hotel room], put the poison into the teapot, poured the hot water [on the tea] and gave it to him," Gordievsky says. "He drank and continued to work, meeting people and talking and it was only late in the evening he started to feel unwell. In three days, it was clear that he was a goner."
Litvinenko died after three weeks of agony in a London hospital and the poison wasn't identified as polonium until shortly after his death. Later, British prosecutors named ex-KGB agent Andrei Lugovoi, one of the Russians Litvinenko had met for tea, as their chief suspect. However, Lugovoi had by then returned to Russia and Moscow refused to hand him back for trial. Russian authorities dismissed all charges of Moscow's involvement in the Litvinenko attack as "silly."
Is Polonium Imperfect Because It Leaves A Trail?
Polonium has one significant drawback. If investigators are alert enough to detect it has been used, they can follow the radioactive trail it leaves on everything it has come into contact with before the killing to find and identify a suspect.
This is what happened in the Litvinenko case. Investigators found traces of polonium in the hotel room where the tea was served and followed the trail backward, matching it with Lugovoi's movements.
For this reason, those using polonium count heavily on their murder weapon not being found.
But there is one thing more that assassins using polonium must be careful about. And that is to not to be killed themselves by it.
"The people like the KGB officers who killed in London were instructed how to keep [the polonium]. It was packed very securely in a bottle and it was opened only in the small kitchen of the hotel room and then poured into the kettle," Gordievsky says.
"And they themselves never touched it. But still, the main assassin was held [in a Moscow hospital because he was] unwell the first two weeks after the operation. So there are signs this is really a very risky element."
Today, Lugovoi remains active and in apparently good health. He was elected in 2007 to the Russian parliament on an ultranationalist ticket and is a successful businessman.
How And Where Is Polonium Produced?
Polonium-210 is present in very small amounts in the soil and in the atmosphere but it does not naturally occur in lethal concentrations. However, it can be manufactured in a nuclear reactor by bombarding the isotope bismuth-209 with neutrons. Worldwide, only about 100 grams are produced each year, almost all in Russia.
That means it requires enormous skill and resources to produce polonium and not too many people have access to it.
John Croft, a retired British radiation expert who worked on the Litvinenko case, has said a dose large enough to kill someone would likely have to come from a government with either civilian or military nuclear capabilities.
That category includes Russia and Arafat's foe, Israel. But it also includes dozens of other nations, including the United States.