Polonium Lethal Dose

December 14th, 2006

United Nuclear


With the recent news of Polonium-210 being used as a poison, a good deal of incorrect information has been passed around (primarily by the media) concerning the Polonium isotope and radioactive materials in general. It’s important to get the facts correct. The general public is quite ignorant when it comes to knowledge about radioactive materials and radiation in general.

The amount of Polonium-210, as well as any of the isotopes we sell is an ‘exempt quantity’ amount. These quantities of radioactive material are not hazardous - this is why they are permitted by the Nuclear Regulatory Commission (NRC) to be sold to the general public without any sort of license.

Although we do sell these isotopes, distributors such as United Nuclear Scientific Supplies (and just about any isotope distributor) do not actually stock them.
All isotopes are made to order at an NRC licensed facility in Oak Ridge Tennessee. When the isotope is made, it is shipped directly to the customer from the manufacturer to insure the longest possible half-life.

The exempt quantity amount of Polonium-210, or any of the radioactive isotopes sold is so small that they are essentially invisible to the human eye.
In the case of needle sources, the radioactive material is electroplated on the inside of the eye of a needle.

You would need about 15,000 of our Polonium-210 needle sources at a total cost of about $1 million - to have a toxic amount.

New York Times

NY Times article gives an indication as to how much polonium was needed to kill Alexander Litvinenko:
Polonium 210 is highly radioactive and very toxic. By weight, it is about 250 million times as toxic as cyanide, so a particle smaller than a dust mote could be fatal. It would also, presumably, be too small to taste.


Weight-for-weight, polonium is around 5 million times more toxic than hydrogen cyanide (the oral LD50 for Polonium 210 is about 50 ng compared to about 250 mg for hydrogen cyanide[23]). The main hazard is its intense radioactivity (as an alpha emitter), which makes it very difficult to handle safely - one gram of Po will self-heat to a temperature of around 500°C.

Even in microgram amounts, handling Polonium is extremely dangerous, requiring specialized equipment and strict handling procedures.

Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed (though they do not penetrate the epidermis and hence are not hazardous if the polonium is outside the body).

The lethal dose (LD50) for acute radiation exposure is generally about 4.5 Sv. The committed effective dose equivalent Polonium 210 is 0.51 µSv/Bq if ingested, and 2.5 µSv/Bq if inhaled. Since Polonium 210 has an activity of 166 TBq per gram (1 gram produces 166×1012 decays per second), a fatal 4-Sv dose can be caused by ingesting 8.8 MBq (238 microcurie), about 50 nanograms (ng), or inhaling 1.8 MBq (48 microcurie), about 10 ng.

One gram of Polonium 210 could thus in theory poison 100 million people of whom 50 million would die.

In addition to the acute effects, radiation exposure (both internal and external) carries a long-term risk of death from cancer of 5–10% per Sv. The general population is exposed to small amounts of polonium as a radon daughter in indoor air; the isotopes 214Po and 218Po are thought to cause the majority of the estimated 15,000-22,000 lung cancer deaths in the US every year that have been attributed to indoor radon. Tobacco smoking causes significant additional exposure to Po.

Mario Alemi calculation of the Polonium 210 lethal dose

The Lifetime Cancer Mortality Risk factor[1] for 1pCi (10^-12 curie[2] one milion of milion of curie) of Po 210 is 1.6 10^-9 (see http://www.ead.anl.gov/pub/doc/polonium.pdf)

That means giving 1pCi of Po210 someone has 1.6 10^-9 probability to die for cancer in a lifetime (80y).

To kill someone in one week I have to give him 80*52/(1.6 10^-9) pCi = 2.6 10^12 pCi = 2.6 Ci

One gram of Po has a radioactivity of 4500 Ci, then about 6 mg are lethal (a cube mm).

[1] It gives the probability to get a mortal cancer during the lifetime. In this case it means that absorbing 1 pico courie of radioactivity from Polonium one person out of 600,000,000 (that is 1/(1.6*10^9)) will get cancer.
[2] One curie is the activity of one gram of radium. By definition, now, one curie is 37 billion (3.7 x 10^10) disintegrations per second. That means that a gram of polonium emits 37 bilion alpha particles (2 protons and 2 neutrons all together) per second. A pico curie means 10^-12 or 0.000000000001 courie.

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