Polonium FAQs

by CKR

During my travels this weekend, at least three people asked me about Alexander Litvinenko’s poisoning and polonium-210. I’ve been discussing it here, but I thought it might be helpful to summarize the information via some of the questions I’ve been asked. I’ll link to some useful sites and try to correct some misinformation.

Why is polonium-210 so poisonous?
Polonium is highly radioactive. It emits only alpha particles, which are the nuclei of helium atoms, two neutrons and two protons. Both the mass of the alpha particles and their propensity to pull electrons from other matter do a lot of damage to cells. However, that mass keeps the range of the alpha particles low, so they can’t get through human skin or a sheet of paper.

Once polonium-210 gets into the body, it kills nearby cells and causes acute radiation syndrome. It must get into the circulatory system in order to cause symptoms like hair loss.

Litvinenko must have ingested the polonium-210. Food or drink was immediately suspected, but snorting cocaine has also been suggested, and an injection is even possible. If the route was other than food or drink, it’s possible that he ingested the polonium-210 some time before he became ill, because it would take time for his body to absorb it and get it to the various organs. The timing also depends on the amount of polonium-210 he ingested. The autopsy should have given information on this, but the British authorities are keeping that information confidential.

Where might the poisoner have gotten the polonium-210 from?
Polonium-210 is naturally found in very small quantities in uranium ores. Marie and Pierre Curie first isolated it that way, and it is named for Marie’s home country, Poland. It has a half-life of 138 days, which means that after 138 days, half of the polonium has decayed. There is a report that 10 kilograms of polonium-210 was stolen from Russia in 1993. That could not have been the source of the polonium that poisoned Litvinenko; it has all decayed by now, except for maybe a dozen atoms or so.

Polonium is produced by irradiation of bismuth in a reactor or accelerator, most commonly a reactor. Bismuth is commonly available, and the process is not difficult if you’ve got a reactor or accelerator. However, separating the polonium-210 is extremely hazardous. Polonium-210 creeps out of containers and can contaminate an entire room fairly quickly. It is believed that the energetic alpha decay breaks it up into small particles, which can be carried by air drafts and keep bouncing around as they decay.

Any country with a nuclear reactor or accelerator could produce polonium-210. It has been used, with beryllium, to produce the initiating neutrons for nuclear weapons. More advanced nuclear weapons use other means for producing neutrons because of the short half-life and the difficulty of handling both polonium and beryllium.

You can buy extremely small quantities of polonium-210 on the internet. They are fixed in a matrix and cannot be used for poison without extensive chemical procedures.

What is this half-life business?
Radioactive elements decay statistically. If you could isolate a single atom of polonium-210, you could say that there’s a 50% probability it will decay within 138 days. But in everyday life, we never see a single atom. Even a tiny speck contains millions and more atoms. The half-life is the amount of time it takes for half the element present to decay. The shorter the half-life, the more intense the radiation because the more atoms are decaying at any time. A rule of thumb is that a quantity of a radioactive element is pretty much gone by the end of 10 half-lives.

How much does it take to kill a person?
Wikipedia takes the naïve approach to calculating a lethal dose. They begin by taking the LD50 (dose at which 50% of those affected die) for radiation, and then figuring how much polonium-210 it would take to produce that dose.

The problem with Wikipedia’s calculation is that not all the polonium is absorbed by the body. If Litvinenko snorted the polonium with cocaine, it had to get into his bloodstream from his lungs and then to the various organs. If he swallowed it with his tea, much of it would have gone through his digestive tract without being absorbed. A serious poisoner would have used many times the dose calculated by Wikipedia, and they would have used a soluble form that could move easily through body tissues. Producing that soluble form would have required more handling and chemical manipulation of the polonium-210.

How does it get spread around to so many places?
There are two probable routes: one from the polonium-210 carried around by the poisoner and one from Litvinenko after he ingested it. As I noted above, polonium-210 is extremely hard to contain. It could creep around screw threads and wipe off the container. Once it was applied to the food, drink, or other ingestible, traces would remain wherever that combination had been: in a cup, on a plate, on utensils, and table surfaces. It would be present in Litvinenko’s body secretions.

Situations in which someone becomes contaminated show graphically how we all leave traces of ourselves everywhere. They also show why washing our hands is a good way to prevent disease. Sneezes, coughs, rubbing eyes and nose, we all do this all the time. And we leave cells and germs, polonium if it’s in our bodies, everywhere we touch or breathe.

Those traces of polonium-210 are not dangerous to anyone unless they ingest them. A good shower will keep most people safe.

More significant than a health threat is that the traces of polonium-210 being found may provide a map of the movement of the polonium-210 and those carrying it. The British authorities aren’t emphasizing this aspect of the investigation because of their legal requirements, but I suspect that they’re using the health threat partly to motivate people to come in and add to the evidence.

Can polonium-210 be traced?
If there are additional radioisotopes in the mix, they may point to a particular reactor or a particular method of purification. However, a number of steps are involved in polonium-210 production, and they may mask the ability to trace by removing impurities.

Gordon Prather speculates about the source of the polonium-210, and in doing so, gets an important fact wrong. He says

Polonium-210 is a NPT proscribed nuclear material.

There is no such thing as an NPT proscribed nuclear material. Here is the text of the Nuclear Nonproliferation Treaty. You can see that no materials are mentioned. However, because the major use of polonium-210 is in neutron initiators for nuclear weapons, Iran’s research on it was one of the IAEA’s concerns about Iran’s nuclear program.

More Links: More Q&A on polonium from the Royal Society of Chemistry. Via Arms Control Wonk.

Thanks to parvati_roma, Sweejak, JLK, and Kevin for links and ideas, and to Sarah, John, and Dena for asking good questions.

Comments

[George Chandler]

Cheryl, it may be interesting to point out that Polonium 210 is found in the lungs of smokers and the livers of laplanders who eat reindeer. Po 210 is a decay product of Uranium 238 and Radon 226, its second immediate predecessor being Lead 210, with a half-life of 22 years. Apparently the Radon decaying in the atmosphere deposits lead 210 on the leaves of tobacco (and any other plant) from where it becomes a constituent of the smoke. Once in the lungs it produces Po 210 which decays shortly emitting those fierce alpha particles. Some think it's a major source of lung cancer in smokers. It shows up in the livers of laplanders because the Reindeer eat lichens that collect the stuff from the atmosphere. It appears on other vegetables too but it's not as much a problem in your digestive tract as it is in your lungs.

[CKR]

Thanks, George.

I was trying to stick with the basics that my friends had questions about.

The two facts you cite have fascinated me for some time. I didn't include them partly because they seemed slightly off-topic, and I thought I had seen a possible refutation of the polonium/lung-cancer connection in my surfing the web. So I wanted to do more searching before I said anything about it.

With a little more surfing, here are two articles from reputable sources that indicate that polonium-210 can indeed cause lung cancer.

Lung cancer: is the increasing incidence due to radioactive polonium in cigarettes?

Lung cancer induced in hamsters by low doses of alpha radiation from polonium-210

Neither of them is new; the first is from 1986 and the second, from 1975.

If you google polonium reindeer, you'll find a number of reputable articles on reindeer's dietary habits and the consequences for humans who eat them. Again, most of them not particularly recent.

Neither is a likely source for the levels of polonium now being detected in Britain and Germany.

[liudmila]

I have some questions :

Why Mr. Berenzeksky who is so rich, cut his financial support for Mr. Litvinenko ? Litvinenko saved his life. How hard it is for a billioner to spend 20.000 pounds/year on his friend?
To me it seems that the only person who benefits tremendously from such a high profile murder is Berenzeksky.

Another thing is , they found traces of Polonium on a sofa in Berenzeksky's office, the place where Lugovoi was sitting during his 1st Nov visit. What was Lugovoi doing in Berenzeksky's office? Wating to receive the payment for a job well done?