So, what is polonium-210 and why use it as a poison?
Polonium-210 was discovered in 1898 by Marie and Pierre Curie while working on their 'baby' uranium. Marie decided to name the element after her country of origin, Poland. Polonium can be found naturally in the Earth's crust, but in very low concentrations because it has a short half-life. It is most commonly found in nuclear reactors as a by product or energy production. Polonium has been used in industry to measure the thickness of very thin things and as an insulator in space probes as a way to eliminate static electricity. This means that access to polonium is very restricted and only a few people on Earth have access to it.
Polonium is an alpha particle, meaning it decays by releasing two protons and two neutrons. It's a heavy particle with high energy. However, because of its large mass, it is pretty weak in that it can't penetrate skin. You could carry it around in a vial or paper envelope and no radiation would be detected. Which is why it would be an excellent poison: it's safe to carry around and it can go undetected! BUT if ingested, it can be lethal. If you ingested a grain of salt-sized portion of polonium-210 it would be lethal. This is because of its high relative biological effectiveness. Once ingested it can injure all the vital organs, including bone marrow. After some time the individual would experience the signs and symptoms of radiation poisoning. Keep in mind that these symptoms can vary from person to person and be dose-dependent. Sometimes the symptoms would be vague with no distinguishing feature screaming out 'radiation poisoning!'. Could Arafat's mysterious wasting illness be the result of radiation poisoning? Hummmm....
The odd thing about using polonium as a poison is its scarcity. Only a few nations have access to it and if detected sometimes scientists can get enough information to establish a 'chemical fingerprint' allowing them to trace it back to the county of origin. In the case of former KGB agent Alexander Litvinenko, the origin of the polonium-210 poison was traced to the USSR. Thus, if discovered, there is a chance you might get caught!
Was Arafat poisoned with polonium-210? Preliminary news reports are concerning. Why would he have it on his clothes and personal affects? After 8 years, a high proportion of the polonium-210 would have decayed but would still be higher than any background levels, and that appears to be the case. Would an autopsy help? YES! After exhuming his body scientists could get a much more accurate reading of how much radiation is emitting from the corpse. They could also study his tissues and bone marrow looking for signs of radiation injury. Time will tell. It will be interesting to watch how this plays out. If in fact Arafat was poisoned, will we ever learn the origin of the poloium-210? Imagine that political hot potato!