Polonium-210, Part II.

[This is Part II of our explanation of some of the science behind the Polonium-210 poisoning case of Alexander Litvinenko. Part I. is here.]

In Part I. we sketched the physical background to understand radioisotopes like Polonium-210, the agent in the Litvinenko poisoning, but have yet to explain its connection to the biology. That's today's order of business.

Remember that the chemistry is located in the orbital electrons of each atom. Sharing electrons or pairing charges is how atoms bond with each other -- literally and figuratively. So if you mess up the electron structure you can mess up the chemistry. In particular, if you knock an electron out of its orbit (called ionizing the atom) lots of things can happen to the chemistry. If you do this to a whole lot of atoms and they are ones that are biologically important (like DNA) then you can get some untoward biological effects -- like turning a cell malignant or killing it. Sometimes this happens indirectly, when an abundant molecule like water has some atoms ionized or split off into highly reactive forms called free radicals and they then do some chemical mischief of their own. To make a long story (too) short, if a radioactive particle or gamma ray has enough energy to disturb the electron structure, it can do damage. This kind of radiation is called ionizing radiation, for obvious reasons. We are subjected to natural background radiation all the time and we have numerous ways to repair the damage that causes. It's when the damage accrues faster than it can be repaired that we start to have problems.

In the first post we discussed three kinds of radioactive emissions, beta particles (electrons ejected from an unstable nucleus), gamma rays (electromagnetic radiation of varying energies) and alpha particles. Polonium-210, the poison that apparently killed Litvinenko is a weak gamma emitter and a champion alpha emitter. But first let's talk about beta radiation because it sets the context for the other two.

Beta particles (being energetic electrons) are pretty light and have a single negative charge force field around them. As they scoot through your tissues they strike glancing blows at odd intervals to your body's atoms. Meaning no disrespect to any of you, you are mostly empty space as far as beta particle is concerned. Atomic nuclei are little pinpoints separated by vast distances, so a very energetic beta will knock off electrons (ionize atoms) at irregular intervals along a long path before the collisions eventually slow it down to a slow aimless drift with no remaining force. Some of the knocked off electrons will themselves have enough velocity to cause ionizations nearby, too, so beta particles can do some damage before they are stopped by repeated collisions. Here's an analogy. Think of a huge field with a big parking lot in the middle of it. The cars are not closely packed together. They are your body's chemical molecules. A beta particle is like a fast motor scooter shooting through the lot, carooming off one or another car. It can cause some damage to a bunch of cars and maybe even push one car into another (I'm stretching here; maybe not a scooter, say the beta particle is a Morris Mini). The beta particle, being small and fast, can get a little ways into the lot from the edge but eventually it is stopped by the repeated collisions.

Gamma rays are electromagnetic radiation and they interact with atoms completely differently. Since they aren't particles but oscillating fields, they interact probabilistically with matter and most of them pass straight through without interacting at all. If x-rays didn't do that we could expose the film on the other side of the x-ray machine from you. X-rays are more likely to interact with dense matter containing calcium than with air, hence your bones and fluid leaves shadows. Returning to gamma rays, when they interact with an atom, which is infrequently and not often while passing through your body, they can also knock an electron off which then can do damage of its own, like a beta particle. But the gamma rays of Polonium-210 are pretty weak and interact weakly not doing much damage. Imagine a car thief wandering through the parking lot looking for a particular make and model. If he finds what he is looking for, somewhere in the lot, he hot wires it, jumps in and drives off. Unfortunately since he is surrounded by other cars, he does damage that way. That damage is not confined to the edges of the lot, however, but can be anywhere, even deep within the lot, wherever the chance encounter with the right car occurred. So gamma radiation can damage any part of your body, and if there is massive amounts of it it can kill you.

Now the alpha particle. It is 7400 times as heavy as a beta particle and has twice the electric charge. It is an ionizing behemoth. Last post I compared the alpha particle to the beta particle as a cannonball versus a bee-bee. As long as I doing the parking lot, it's a Mac truck versus a scooter or Mini. In the distance it travels, however, it does an immense amount of very dense damage, far too much for any biological repair mechanism to keep up with. It is a nuclear wrecking ball. An alpha particle interacts with so many other things because of its size and its forcefield it only travels a few centimeters in air before slowing down completely and in water -- i.e., in you, since you are mainly water -- it only travels 5 or 10 microns. That's hardly the width of a single cell and if external to your body it never gets past the dead layer of skin cells on your surface. It's as if the parking lot was surrounded by the hulks of old car bodies. The Mac truck would crash into them and be stopped. What this means is that no matter how big a hunk of Polonium-210 you have, you can put it in your front pants pocket and it won't hurt you. So what's the big deal?

An alpha particle isn't a danger to you outside your body (unlike a gamma source), but if it gets into your body, look out. And Polonium-210 emits 5000 times as many energetic alphas as Radium, on a mass basis. It is extremely dangerous. A lethal dose is estimated to be only 12 micrograms (12 millionths of a gram; a gram is 1/30th of an ounce). An estimate in Wikipedia gives 3370 lethal doses in a cube of Polonium-210 the size of the period at the end of this sentence.

It's radioactive half-life is 138 days, i.e., it takes that long for half of the Polonium to decay. Meanwhile, however, your body is eliminating it in your feces and urine. It dissolves readily in acid solutions and presumably can be distributed throughout the body, including to radiosensitive tissues like the gastrointestinal tract and bone marrow. The biological half life is 30 to 50 days, more than long enough for this stuff to kill you. The UK authorities are trying to stay upbeat:

The Health Protection Agency is providing expert advice on the public health issues surrounding the death of Mr Alexander Litvinenko. Following the results of further assessments we are updating our advice.

Some small quantities of radioactive material have been found in a small number of areas at the Itsu sushi restaurant at 167 Piccadilly, London , and in some areas of the Millennium Hotel, Grosvenor Square , London , and at Mr Litvinenko's home in Muswell Hill.

We are therefore asking anyone who was in the Itsu restaurant, or who was in The Pine Bar or the restaurant of the Millennium Hotel on 1 November to contact NHS Direct on 0845 4647 where they will be given advice on what to do.

The substance found is Polonium-210. The Chief Medical Officer, Professor Sir Liam Donaldson, is issuing advice to GPs and hospitals on the risks and clinical implications of exposure to Polonium-210.

We want to reassure the public that the risk of having been exposed to this substance remains low. It can only represent a radiation hazard if it is taken into the body ? by breathing it in, by taking it into the mouth, or if it gets into a wound. It is not a radiological hazard as long as it remains outside the body. Most traces of it can be eliminated through handwashing, or washing machine and dishwasher cycles.

The Agency is also investigating the clinical areas of the two hospitals where Mr Litvinenko was treated.

The police investigation continues. We will provide further public information as appropriate.(Update Statement on Public Health Issues)

This is not just an assassination. It is a potential public health disaster. Polonium-210 volatilizes (evaporates) relatively easily, so if there is a source out there it could spell trouble.


More like this

It's bigger news in the UK than elsewhere but it's still big news. Apparently Russian dissident and former KGB agent Alexander Litvinenko was fatally poisoned with Polonium 210. Time for some science. Polonium 210 is a radioisotope, meaning it is an isotope of the element Polonium that is…
We mostly like being right, but we sometimes wish we weren't. A few days ago we concluded a post) on some scientific background about Polonium-210 by saying this assassination could also become a public health problem. That now seems to be the case, as a trail of radiation is being found in the…
Polonium-210 is a radioisotope that's gotten lots and lots of press in the last few weeks because of its purported role in the death of Alexander Litvinenko. Polonium is an alpha emitter - that is, in the process of decay, it gives off energetic helium nuclei. They're massive, so they are stopped…
Having spent several posts on the science behind Polonium-210 (here, here, here), we thought we'd bring you a follow up on the case to date. The murder weapon seems to be a pot of tea. How very English: British officials say police have cracked the murder-by-poison case of former spy Alexander…

What this means is that no matter how big a hunk of Polonium-210 you have, you can put it in your front pants pocket and it won't hurt you. So what's the big deal?

Except for the fact that it gives off so much heat it would burn a hole in your pocket faster than casino winnings.

By epistemology (not verified) on 28 Nov 2006 #permalink

epistemology: LOL. Great Balls of Fire! You are quite right. I was pretty focused on the alphas and neglected the great heat genearated by polonium decay. Thanks for the correction.

epistemology: which brings up a good point. How did this stuff get transported and then passed off to Mr. Litvinenko without igniting everything around it?

I would assume if it was placed into a drink the liquid would boil? Or is the quantity to boil sufficiently larger than a lethal dose.

rickr: No, we're talking microgram or at most milligram amounts here. That wouldn't generate enough heat.

The news on this today was that they have found traces of a radioactive substance on a British Airways jet that frequented the London-Moscow route. It sounds like someone used the front door, rather than the back door, for this one.

Any theories as to how this stuff could have been transported on a common carrier? Can someone walk through airport screening with such a substance?

mpb: That's for 0.1 µCuries. The Annual Limits on Intake (ALI) via ingestion in the occcupational environment are 3 µCi (thirty times that) and via inhalation 0.6 µCi. So this amount is not close to but not that far form the occupational limits. There are cheaper and easier ways to kill someone than using this stuff and buying it over the net like this. You can buy guns over the net for less and kill a lot more people. So I'm not particularly worried about these quantities being sold in this fashion.

Pixie: I may post about the plane issue, which is a bit puzzling.

Sorry, I should have added the punchline.


United Nuclear was set up by researcher Bob Lazar, who claims to have been involved in reverse engineering alien spacecraft which crash landed at Area 51.

And yes, we know the amount in the United Nuclear sample probably wouldn't kill anyone, but that's not really the point of the above is it?

Could you do a follow up post on the politics of Polonium?

Since the use of it is mostly a political message, in my opinion.

Why choose it as a weapon? Where would it come from? How could it have been transported? How would it be traced?

It was apparently done pretty sloppily if traces were found in all the places (hotel, restaurant, airplanes) that it is said to have been.

Pixie, you and Revere hit the airplane on the nose. A veritable flurry of activity is being investigated of people that are known agents, in country under diplomatic immunity. The old story goes of course is that someone could smuggle a nuke in pieces into a commercial aircraft and take it to the embassy because those parts are under diplomatic seal. Aeroflot probably brought it in unwittingly, the likelyhood that it was a British plane are very low. The carriers are responsible for proving to the recieving nation that their security procedures are acceptable to ensure that no aircraft will enter their airspace with a hazard or hazardous people aboard. Sounds like they got both. There are radiation detectors on board the BA's, NWA's, Lufties so I wouldnt worry too terribly much on that part. The fact that the stuff got in country without being detected is bothersome.

By M. Randolph Kruger (not verified) on 29 Nov 2006 #permalink

Randy: Radiation detectors would not have picked up an alpha emitter. Alphas only travel a tiny distance. I don't think this would be hard to transport without detection.

neil: I think you have it right. This is a lousy weapon. It was meant to be an example, not just assassinate someone. That would be easy to do with a gun or a hit and run. This was meant to be noticed. I am not sure about the airplane stories. They only say radioactivity was detected. That could be from a lot of things and special detectors would be needed for an alpha only source. I think we might find out later that it isn't polonium on the planes, but I don't know. I thought about posting more but we don't know much at the moment.

Yet another victim is the Italian, Mario Scaramella who has tested positive for radioactive poison poloniem 21. He has a significant quantity of the poison in his urine. So he would also have been exceting it in the toilet at the sushi bar.

Heavy handed, old style KGB to my way of thinking. Not at all subtle, anymore than the poisoning of the Ukranian politician. They didn't pull that one off thanks to the Swiss. The trail is there, and so many red herrings have been thrown in for good measure that it is the most intriguing mystery of 2006. I wonder how much of the investigation will be made public. It must be a psychological weapon as well as precautionary for any dissident. You are hungry, but what food is safe to eat. You are thirsty, but what can you safely drink? I was once advised to travel with the pack in Russia, as a group has more leverage in a sticky situation. The man had a support group of fellow Russians and he wasn't safe.

"It is a potential public health disaster."

don't see it. The amount that you would get off L via sweat would be measurable, but insignificant on a health basis. Sure he would excrete vast amounts in urine or feces, but that goes down the toilet.

If he was poisoned via food/drink, then the residue in the utensil would be hazardous, but most dishes get washed, so it would be drastically reduced.

I see measurable amounts of radiation, but very little reason to believe that there is any significant risk to public health. It is an alpha emitter.


per: The anthrax episode in the US showed it doesn't have to be a real threat to be a public health disaster. The resources now being devoted to it in the UK are likely stressing the system considerably to the point where a lot of routine things aren't being done that should be. In the US we spent weeks responding to "white powder calls" and nothing got done. That's what I meant.

okay, fair point. In faith, the HPA have gone overboard in saying how little risk there is to the general public, but it is true some people are worried.

Our local papers, N.J., are full of the murder. Down to explainations of how the Polonium 210 works. Todays editorial page featured a cartoon of a xmas eggnog being mixed by Putin, and one man suggesting to the other, "I wouldn't drink the eggnog." I don't think its frightening the general public,except for travelers who might worry a bit. How many have been to the sushi bar on Nov.1? Litivenko feared the new Russian law which allows extermination of enemies of the state in foreign countries. I don't know if it is in place at this time. It is a assassination which may never be resolved. Ian Fleming could have done a spin on this one.I've been getting most of my information from overseas papers, so it is of international import. Everything that the Russian goverenment does will be under microscopic review. I still think it is a psychological and heavy -handed intimidation of dissidents,which could well backfire on those responsible., though it is probable that no one will ever be prosecuted.

Just read an article from the Sunday Express by James Murray.... http://express.lineone.net/news_detail.html?sku=814 Another twist. A next door neighbor ,Akhmed Zakayev,claims Litvinenko converted to Islam before he died. Scotland Yard detectives are now trying to discover if he had any secret links with Islamic extremist terror groups. Their biggest fear is that the former Soviet spy who died of polonium-21 posioning in a London hospital, may have been helping
Al Queda terrorists or other extremist groups bet hold of radioctive material to be used in a devastating "dirty" atom bomb. This story become more and more bizarre. Counterterrorism officers will now be scrutinising any possible Muslim links.