Some interesting news has surfaced theorizing that Yasser Arafat may have been poisoned. Examination of his clothing, toothbrush, bedding and favorite kaffiyeh revealed high levels of polonium-210. What the heck is that? Well, I'm going to try and tell you. It just so happens that not only am I a forensic pathologist, but I am an 'armchair' radiation biologist! During my training conducted experiments for NASA trying to determine the effects of cosmic radiation on the brain and I was forced to learn as much as I could about the magical world of radiation.
So, what is polonium-210 and why use it as a poison?
So, what is polonium-210 and why use it as a poison?
Before we can dive into the details of how murder by radiation poison occurs, it is important to understand a few principals of
radiation biology. First, what is radiation? There are many different
forms of radiation. What I am going to be talking about is commonly
referred to as ‘ionizing radiation’. Ionizing radiation happens when a
particle moves though a particular medium with enough energy to knock an
electron off an atom within that medium. The loss of an electron leaves
the atom with a positive charge. This positively charged atom is called
an ion, thus, the term ‘ionizing radiation’. If someone is exposed to
high levels or ionizing radiation they will become ill due to the
ionization of their tissues and cells.
The more energy a
radioactive particle has, the more damage it can do. The energy of
radiation is expressed as electron volts (eV). As the particle passes
through tissue it’s energy is transferred in the form of ionization.
This process is called ‘Linear Energy Transfer’ or LET.
The most important factor
to consider in regards to adverse biological effects is not the energy
of the radiation, but the amount of radiation that is absorbed by the
body. The absorbed dose of radiation is the amount of energy available
to cause tissue damage. The more radiation you absorb, the more
ionizations occur. The more ionization, the more tissue is damaged. The
SI unit for the dose of absorbed ionizing radiation is the Gray (Gy).
The Gy is defined as the absorption of one joule of ionizing radiation
per one kilogram of matter. Older literature will refer to the Rad.
Don’t use that word, it’s not cool anymore. But if you see it, know that
100 rad equals 1 Gy.
The Gy doesn’t take into
account the biological effectiveness of different types of radiation. To
understand how different forms of radiation affect the body everything
is compared to a standard x-ray. Here all forms of radiation are
compared to the level of x-ray radiation that would be required to cause
the same amount of damage. The results of these studies give a
correction factor by which the various forms of radiation are
multiplied. After multiplying by the correction factor, the levels of
radiation are expressed in Sieverts (Sv).
To give an example, just so
you can see how all of these terms relate to one another let’s pretend
that a high LET particle has a lot of energy, say 200 eV. Someone
exposed to this high-LET particle absorbs maybe 2 Gy of this radiation.
The damage caused by this process will be the equivalent of 2000 x-rays.
We get our correction and multiply the amount absorbed (the Gy) by it
and give the answer in Sv. So, in our pretend, inaccurate, made up
example, the result would be 2000 x 2 Gy = 4000Sv. It’s certainly more
complicated than that, but you get the picture and understand the terms.
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!
