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I saw a YouTube video by a guy demonstrating Geiger Counter use and one of his radioactive test sources was a disk with Polonium. He casually mentioned that this was the poison used to kill that Russian defector (Alexander Litvinenko). I am referring to "antiproton" (see http://www.youtube.com/watch?v=EMGF-nnNdL8 for example).

How dangerous are isotopic sources like that? The NRC summary of the isotope says "If swallowed or inhaled, this form can be fatal in very small amounts." They go on to say "The chance of someone acquiring a lethal dose of polonium-210 is very small. Both the form and amount of radiation in exempt sources mean they would pose no health problem if ingested. It would take tens of thousands of these sources to make a fatal dose."

This would seem to imply that the source the YouTube guy had was so dilute that it is harmless, even if ingested. Is that correct?

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  • $\begingroup$ Or in a form which it couldn't be absorbed, such as plated on an insoluable stainless steel disk. If it stays on the disk you can swallow it and have it come out the other end! $\endgroup$
    – Martin Beckett
    Commented Jan 27, 2016 at 23:26
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    $\begingroup$ The NRC does put in some effort into their regulations on radioactive sources. And, as @MartinBeckett points out, if you don't damage the source it is designed to be as safe as it is labeled. Once it is damage, well, all bets are off (and it is not fun to deal with damaged sources - too much paperwork). $\endgroup$
    – Jon Custer
    Commented Jan 27, 2016 at 23:35
  • $\begingroup$ I would agree with Jon Custer... it's much more likely that your local health and safety person will go postal and do some damage to you or the tires of your car over the endless amount of paperwork that has to be filled out if you lose one of these than that the radiation of such a small source will do much to you. Having said that, there are some enormously dangerous industrial sources out there and nobody wants to mess with those. If you were to "lose" one of those, you could probably expect to get a visit from the FBI these days... at home. $\endgroup$
    – CuriousOne
    Commented Jan 27, 2016 at 23:46

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Let's suppose you have swallowed one of the Po-210 sources from this student kit. Its activity is 3700 Bq (0.1 μCi). Based on the Table 6 in the meta-study [1], it is probably safe to ingest up to 0.02 MBq/kg of the Po-210.

This means, that for 80 kg person, it is probably safe to ingest 1.6 MBq of the Po-210, so you "need" to eat approx. 400 of these sources. This is a rather conservative estimate since the Po-210 in these sources is not "free" but firmly attached to some matrix which makes its digestion much less efficient.

[1] Scott, B. R. (2007). Health Risk Evaluations for Ingestion Exposure of Humans to Polonium-210. Dose-Response, 94–122. http://doi.org/10.2203/dose-response.06-013.Scott

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Here is what wiki has to say about Polonium radiological toxicity:

By mass, polonium-210 is around 250,000 times more toxic than hydrogen cyanide (the LD50 for 210Po is less than 1 microgram for an average adult (see below) compared with about 250 milligrams for hydrogen cyanide[66]). The main hazard is its intense radioactivity (as an alpha emitter), which makes it very difficult to handle safely. Even in microgram amounts, handling 210Po is extremely dangerous, requiring specialized equipment (a negative pressure alpha glove box equipped with high performance filters), adequate monitoring, and strict handling procedures to avoid any contamination. ...

The median lethal dose (LD50) for acute radiation exposure is generally about 4.5 Sv.[71] The committed effective dose equivalent 210Po is 0.51 µSv/Bq if ingested, and 2.5 µSv/Bq if inhaled.[72] So a fatal 4.5 Sv dose can be caused by ingesting 8.8 MBq (240 µCi), about 50 nanograms (ng), or inhaling 1.8 MBq (49 µCi), about 10 ng. One gram of 210Po could thus in theory poison 20 million people of whom 10 million would die. The actual toxicity of 210Po is lower than these estimates, because radiation exposure that is spread out over several weeks (the biological half-life of polonium in humans is 30 to 50 days[73]) is somewhat less damaging than an instantaneous dose. It has been estimated that a median lethal dose of 210Po is 15 megabecquerels (0.41 mCi), or 0.089 micrograms, still an extremely small amount.

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    $\begingroup$ In order to build my Po-210/C-13 calibration source I ordered 1.5 mCi of the stuff which came as a salt dissolved in 8 ml of hydrochloric acid. I did dry runs with inert materials in full kit until I had done it perfectly three times running (took 10 tries because I'm all thumbs) before cracking the ampule. $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Jan 29, 2016 at 21:59

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