A gram of vaporized polonium can kill more than a million people and thus is the most potent poison known to Man. Having read this article, my crazy dictator immediately assembled the most experienced (and craziest) WMD engineers of his country and tasked them with developing a Polonium-based device able to eradicate whole countries or even kill off Humanity as a whole if required.

You are one of those engineers. Your task is to come up with a method of:

  • quickly boiling and dispersing 1kg (one kilogram) of Polonium-210 and
  • dispersing it over an area as large as possible.

Bonus points will be given for:

  • covert dispersal (of smaller amounts of Polonium)
  • unconvertional delivery methods (Be creative!).
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    $\begingroup$ How is your Bad Person (r) going to get 1 Kg of Po^210? It's almost entirely synthetic, and 1 Kg is apparently ten year's worth of production, and needs access to a reactor core to make! See: chemicool.com/elements/polonium.html $\endgroup$
    – Catalyst
    Commented Mar 5, 2017 at 16:58
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    $\begingroup$ This will be another question. The preparation may or may not take 10 or 20 or 50 years, what matters is the dispersal. $\endgroup$ Commented Mar 5, 2017 at 17:02
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    $\begingroup$ @MedwedianPresident With a half-life of 138 days, every fourth year (10 half-lives) your mad scientist dictator will be left with 1 / 1000 of what they had at the start of those four years. Another 4 years and it is down to 1 in 1 000 000. You cannot stockpile this. Once your production rate becomes equal to the decay rate of your stockpile, then that is it, you are not getting any more after that. The maximum stockpile you can have is twice the production rate per half-life. In other words: if you can produce 1 kg per half-life, you can at the very most have a stockpile of 2 kg. $\endgroup$
    – MichaelK
    Commented Mar 5, 2017 at 21:07
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    $\begingroup$ FBI please go... $\endgroup$ Commented Mar 6, 2017 at 5:51
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    $\begingroup$ Can relativistic effects help you store things with half-lives? E.g. launch into space at significant fraction of C, exploit time dilation. Ok, not a trivial operation, but neither is making polonium in that kind of quantity in the first place. $\endgroup$
    – Sobrique
    Commented Mar 6, 2017 at 9:16

9 Answers 9


You do not. Unless...

This is not realistic.

However... see addendum for some hand-waving.

Ok, so Polonium-210 has a really high LD-50 value, that is all fine and well.

But where are you going to get it?

Your first problem is that Polonium is an extremely rare substance because it can only be created in nuclear reactors.

The next problem that it has a half-life of only 138 days, meaning that even if you have a phenomenally high production rate of 1 kg per 138 days, you can only ever have 2 kg available. The current world production of Polonium is 0.1 kg per annum.

Another big problem you have is that Polonium-210 is an alpha emitter. An alpha emitter must be ingested to do any actual harm. So you must get people to breathe or eat the Polonium.

That turns your task into a problem of logistics. And this is not some fun exotic little scheme you can just hand-wave. A few years ago, someone described the problem of logistics and getting stuff to people like this:

Suppose the cure for AIDS is a glass of water. All we need to do is deliver from our place, a glass of water, to every person with AIDS. How many can we save?

Answer: only about 50%. The rest will have died before you get the water to them.

One more problem — as brought up by WhatRoughBeast — is that Polonium-210 generates lots of heat. A single gram generates heat like two old-school 70W light bulbs, in a volume of a mere tenth of a cubic centimeter. And since you need to keep this material properly shielded and sealed while transporting it to your dispersal sites, you have a problem trying to keep this from setting fire to your transportation device.

Yet another problem you have is that this LD-50 amount only counts for an instant dose. A dose that is stretched out in time immediately raises the amount of Polonium that is needed.

And your final — huge — problem is: people are watching out for it. Radiological watchdogs all around the Earth will instantly pick up on this as soon as it gets out and sound the alarm.

These things put together: that they must — in an impossibly short time span — produce, distribute, disperse and make people ingest this substance, all while not being noticed, means that your evil dictator is faced with an impossible task.

Reading on the same page that you linked to, you have a much better candidate: the botulin toxin.

The Clostridium Botulinum bacterium is everywhere. You can get it from plain soil if you want to. The botulin toxin even has everyday consumer applications, such as being the active ingredient in a Botox treatment.

If your dictator is going to be a prestigious twit that must go for the highest LD-50 value of all, then their plan will fail. Sorry, but it just will.


Suppose we solve the production problem. Let us say that the newly discovered mother lode of element 118 — Unobtainium — conveniently found only in your mad dictator's country, will turn to Polonium-210 when subjected to some really intense hand-having. Your dictator now has an unlimited amount of Po-210 available.

Let us then go for maximum damage with least amount of notice. How to deliver a radioactive substance as close to people as possible, with least amount of notice, and as distributed as possible. How would you do it?

Smoke detectors

Smoke detectors contain Americium-241, a radioactive substance. It is an essential part that makes them work. No-one would notice if that is replaced with a sample Po-210, in the form of nanometer-sized aerosol particles instead. Po-210 also has a really convenient decay chain: it turns to Pb-206, a stable isotope of Lead, meaning there will be no leakage of tell-tale decay products.

Then on a given signal, or at a given time, the little explosive charge present in all the smoke detectors go off at once. In every home, office, warehouse, hospital and other places where Mad Dictator Inc. have delivered their smoke detectors, you have contaminated the place with dust clouds of Polonium-210.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ Commented Mar 10, 2017 at 22:46

Only a very small part of the polonium will be inhaled by the humans.

This polonium quantity is calculated if you find a way to transfer it into the bodies of the people directly. For example, you have to inject some polonium salt into their body, or smuggle it into their tea.

If you disperse the polonium in the air, its only unimaginable small part will be actually inhaled.

Dictators won't kill the whole humanity, they want to rule it. Of course it may mean "some" killing, if they see it needed.

To kill the possible most people with polonium would require to insert it into some water supply. Now the problem is that such water supplies are regularly checked for everything, although their main focus is not radioactivity, but ordinary biochemical poisons.

Of course it is possible first to remove this regular check, or somehow solving it that they won't check for radionuclides.

Boiling and dispersing 1kg of polonium would be only the equivalent of a minor radioactivity accident. Ordinary radioactivity detectors would detect it very soon. People would probably thought that some nuclear accident has happened in a nearby nuclear power plant. Secondary examinations would show, that not the power plant is the source.

The Po is chemically reactive, thus it would be relatively fast bound into the soil. Some nearby city should be evacuated.

Its half life is 138 days, thus at most in 1-2 years it would be safe again to move back.

It is perfectly incapable for large-scale mass murder. If you want to exterminate continents, use cobalt bombs.

To vaporize polonium in the atmosphere most effectively, you could use a water-soluble polonium salt. The best soluble is polonium nitrate. You can scatter it with aircraft disinsection planes. The pilot probably won't survive long without careful safety precautions.

  • $\begingroup$ Nice answer, but you don't answer op's question, so -1. $\endgroup$
    – Nova
    Commented Mar 5, 2017 at 21:30
  • $\begingroup$ @Nova I extended a "good"-looking solution into the answer. $\endgroup$
    – Gray Sheep
    Commented Mar 5, 2017 at 22:09

Polonium boils at 1235K. While that is no where near unattainable, it would be unlikely to actually stay long enough to kill everyone. Your dictator would be better off making a really fine powder and dispersing it in the air. This could be delivered by dropping it out of a plane or a helicopter (or maybe even a weather balloon or blimp, if your dictator would prefer) over a populated area, which would get scattered in the air. A big portion of it will not get ingested by anyone, so don't expect millions of deaths, but enough of it will be ingested that many people will suddenly die of radiation poisoning.

After that, just let the panic set in and the country will fall.

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    $\begingroup$ If you vaporize and disperse polonium, the atomic sized chunks of it will be the finest dust possible. It doesn't have to stay that hot or in gaseous state; at atomic size it can float around on the air as long as it needs to. $\endgroup$
    – kingledion
    Commented Mar 5, 2017 at 19:07

This is an entertaining question, and one with considerable intricacies attached.

First, of course, is the problem of production, which has already been mentioned. The low half-life is a real problem, and packaging and distribution must be accomplished very quickly.

Now, as to distribution. The obvious way to do this is to produce nanoparticles of PoO2 (polonium dioxide) with a mass on the order of 200 nanograms. Inhaled LD50 is estimated at about 89 ng, so 200 ng seems a reasonable figure. In this case the worst-case lethality of 1 kg of mother polonium is about 5 million people. Of course, as mentioned this requires a very small delay between polonium production and application. At a guess, you'd dissolve the Po in some acid, then do a controlled precipitation of PoO2 to produce the required fine powder. (Drying the powder would be no problem, due to self-induced heating.) The powder would need to be mixed with some sort of anti-clumping agent, but that is left as an exercise for the reader.

With a density of about 8.9 g/cm^3, the diameter of such particles would be around 10 um. For nominal dust, the settling rate for such particles is on the order of 30-40 mm/sec, although PoO2 has a greater density and will settle somewhat faster. As a result, the particles will remain airborne for considerable periods if properly dispersed, but are unlikely to drift for long distances in the air.

Making a single polonium bomb is not in the cards, either. A gram of Po210 puts out about 140 watts, so a 1.13 kg slug of PoO2 will produce 140 kW, and fuse in a matter of moments. Plus, of course, the dispersal charge will be destroyed as well in very short order. So delivery would be by way of multiple much smaller bombs, each with some mechanism for cooling the things during transport. Since the settling rate for the particles is not terribly low, fairly powerful dispersing charges seem a good idea, and design of such units would do well to unmask the bombs just before detonation in order to prevent the ejecta from being trapped in surrounding material.

Weather will play a part in producing a successful operation, since rain will tend to wash the active particles out of the atmosphere. And while contamination of drinking water is nearly as bad as inhalation, there are two mitigating factors. The first, of course, is that existing supplies of water can be used until imported water takes up the slack, and the second is that the problem is "temporary", in the sense that in a few years the activity level will have greatly reduced due to the short lifetime of polonium. In other words, you do have to breathe local air, but you don't have to drink local water.

The refugee problem associated with a successful deployment of such a system of devices will be considerable. The problem is that each refugee would need meticulous decontamination (probably including shaving the head) to rid them of any dust which might become airborne and then inhaled by the host community. In broad outline, the refugees would have to be treated as if they are carriers of some really scary disease like Ebola, and the history of such events is not very reassuring.


There are organic molecules that contain a single metal atom, which operates in a synergistic way to the normal protein forms. This talk from SLAC is very interesting on this subject.

Since it has a similar chemical nature as bismuth, which is used in biology, you can swap Po for Bi in the synthesis of some molecule that

  • is easily dispursed, e.g. water soluable; and
  • is readily taken up by the body.

Now the iconic example of a bismuth compound may not be the best for dispursal, but it shows hiw even in this simple small molecule there is a single atom of the metal.



TL;DR: Spike the Gas supply (or, Big Oil really is going to kill everyone)

Gasoline is generally refined, pumped to storage facilities on the outskirts of major cities, and then trucked in to gas stations. Your evil dictator is going to use ninja insertion teams to quietly break into several of these storage facilities and inject Polonium into the tanks - he'll use 1kg per site, because he doesn't believe in overkill. Then his ninjas will disappear.

This gas will be distributed all over the city by industrious truckers and then disbursed by thousands of drivers who will gas up at those stations. It doesn't matter that the Polonium has spent days in toxic environment, because it's not a biological agent. Likewise it doesn't matter that the Polonium has been exposed to high heat and pressure in an internal combustion engine because it's not a chemical agent.

It's a nuclear reaction: the material simply needs to be inside of the target individual for long enough to decay. Cities are full of low level smog - it's an inevitable part of having internal combustion vehicles on the road - and the Polonium is now a constituent of that smog.

People will start dying, and the cause will not be obvious. They will be young and old, rich and poor, people who never interacted - because contaminated vehicle travel all over the city. Much of the Polonium may be filtered out by the vehicles' emission control system. But you don't need very much to make it out to poison people. The unexplained deaths mount, as authorities struggle to trace this poison to it's source.

When the cause is finally discovered, panic is immediate. Every family knows that it could have a contaminated vehicle sitting in their garage. Industry grinds to a halt. Delivery of basic goods - like food - is suspended as as trucks are forced off the road. Starvation and panic set in.

The government halts the delivery of gas, and it opens the strategic oil reserve to public use while they investigate the extent of the contamination.

This, of course, triggers Phase II of the evil dictator's master plan...


Going off of what has been said by others in this thread, you can't really just get a hunk of polonium in one place. Assuming you want quick dispersion through airborne particles, I would design a small spherical hollow shell. You need to keep a thin (~5-10mm layer of polonium in between the layers of the sphere, with an explosive inside. If placed on the roofs of various tall building or in ventilation systems (subway for example), you could easily disperse the particles over a moderate radius. This wouldn't be a country killer by any means, but if you produce enough smaller bombs you can place them quickly and easily throughout a city and enforce a very effective attack.


Like most highly toxic radio actives, you need an high-rise apartment fairly high up. Mount the material on a small asbestos screen on top of the burner of a gas powered stove. Open the windows. Put a fan in. Turn on the stove. Leave town.

  • $\begingroup$ Can you go into more detail? What rates of distribution can you expect? I think this is off by orders of magnitude and the bulk of the Po will be unused. $\endgroup$
    – JDługosz
    Commented Mar 5, 2017 at 22:58
  • $\begingroup$ First, the bulk of Po will be unused. Trying to slice up something to ingest into discrete micrograms is near impossible. You do better to the Joker's plan in Batman-1 to taint consumer products. Second, this is from old area denial studies for Plutonium and Uranium, both highly toxic. The dispersal in the range of 2 km (about a mile), and the area is destroyed. That is, you kill a lot of people and you get your own Pripyat. This is assuming a kg or more of material and a six hour response time. $\endgroup$ Commented Mar 6, 2017 at 6:12

Same as for any (toxic) substance you want to distribute to the entire population: Put it in the water supply.

It worked just fine fluoride. Why not Polonium?


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