Tools & Technology

Nuclear Option

Poisoners have long made use of the periodic table of elements for their dirty work—think arsenic and mercury—but modern technology offers a new elemental option: a disappearing poison.

By Sam Kean | July 6, 2014
Yasser Arafat

Was Yasser Arafat assassinated with polonium?

UN Photo

Down in the southeastern quadrant of the periodic table lurks what I like to call poisoner’s corridor. Lead, mercury, arsenic, cadmium—they’re the ugliest mug shots in chemistry, staples of Superfund sites and the cause of many a recalled toy. And most people haven’t even heard of the worst poison down there: thallium, an element so lethal that the CIA reportedly considered assassinating Fidel Castro with it by dusting a little thallium powder into his socks. (Beyond killing Castro, the CIA supposedly relished the fact that element 81 would make his beard fall out and thereby humiliate El Comandante.)

Lately, modern technology has introduced a new member to poisoner’s corridor, the nuclear toxin polonium. In 2006 Alexander Litvinenko—a former Russian spy who’d become a harsh critic of Vladimir Putin’s government—grew violently ill after drinking polonium-laced green tea in a sushi restaurant in London. No one had ever been assassinated with polonium before: it’s rare naturally and requires advanced technology to manufacture. But photographs of Litvinenko in his hospital room, especially after his hair had fallen out, made element 84 notorious worldwide: so notorious, in fact, that a few toxicologists have now implicated it in another purported assassination, that of Palestinian politician Yasser Arafat.

In October 2004, during what had been a lengthy house arrest, Arafat fell ill one evening after dinner, vomiting and cramping up. He died in a French hospital a month later, reportedly of a stroke brought on by widespread blood clots. For unknown reasons the hospital skipped the autopsy, and rumors have always circulated that Arafat—aged 75 and in good health until then—was poisoned, either by Palestinian political rivals or (the most common accusation) by Israeli officials.

In 2012 Arafat’s widow let toxicologists test some of his belongings, including his underwear, toothbrush, headscarves, and glasses. They found no trace of conventional poisons but did find evidence of polonium. The underwear, for instance, showed levels of polonium dozens of times higher than background levels.

Why use polonium in an assassination? It’s tasteless and odorless, both handy features. And it’s so rare that few tests exist to detect it. Finally, and surprisingly, it’s safe to transport. That’s because polonium emits only alpha particles, bundles of protons and neutrons that are so bulky that even clothing can stop them cold. Assassins can therefore carry it around with impunity.

However benign outside the body, alpha particles do massive damage if ingested or inhaled—degrading organs, crumbling bones, destroying white blood cells, and scrambling DNA. (In the longer term, polonium also causes cancer, especially lung cancer in smokers, since it’s found in tobacco.) Polonium decays pretty quickly, with a half-life of 138 days. That makes it especially deadly, able to bombard your cells with blitzkrieg intensity. Overall, toxicologists have estimated that polonium is 250,000 times more deadly than even cyanide.

After finding evidence of polonium in Arafat’s clothes, authorities dug up his remains in 2013 and gave tissue samples to three labs. French and Russian teams found no evidence of polonium in Arafat’s body. But a Swiss team that used silver plates to extract polonium atoms from the tissue did find evidence of poisoning (polonium gloms on to silver). You can guess which result got more headlines.

The Swiss results, however, come with big caveats. Polonium’s short half-life means it disappears quickly. Just since 2004, 25 half-lives have passed, leaving behind just 1/30,000,000th or so of any supposed dose of poison—barely above background levels.

As an alternative to looking for polonium itself, toxicologists can look for decay products, like certain isotopes of lead. But the Swiss team’s lead results were equivocal, offering no firm conclusions. Worse, the soil near Arafat’s grave contained radon, which decays into both lead and polonium, making any interpretation of the results complicated.

Certain medical facts weaken the polonium theory, too. Unlike Litvinenko, Arafat never lost his hair—a classic sign of radiation poisoning. Arafat also had elevated white blood cell counts, a sign of infection but not of exposure to radioactivity. Overall, then, the case for Arafat’s poisoning is shaky, with two labs voting nay, one lab voting maybe. And unfortunately, the chance to resolve the controversy will only get worse as any polonium in the remains, if there ever was any, continues to dribble away.

This is a problem unique to new, nuclear poisons. Even extended delays generally don’t hamper testing for conventional elemental poisons. In 1991, for example, U.S. President Zachary Taylor was exhumed 140 years after his death to test for arsenic—none was found—and scientists 140 years hence could do the same. But even 2004 is ancient history with polonium. We’re used to science advancing over time, giving us more and more accurate results to determine the truth. But the nature of radioactive poisons ensures that some cold cases are likely to remain frigid.