[ RadSafe ] Fwd: Polonium-210

Cindy Bloom radbloom at comcast.net
Tue Nov 28 09:31:18 CST 2006

>I should first say that I am a health physicist and an internal 
>dosimetrist, but my knowledge of biology and toxicology is related 
>primarily to internal dosimetry (and family and friend's medical 
>crises).  I do have a fair amount of experience in operational health 
>physics and estimating internal doses and find that the alleged polonium 
>poisoning case engages my curiousity.
>The following are some thoughts and questions about polonium.  I don't 
>seem to be able to find any specific information regarding the ingestion 
>toxicity of polonium, but it seems like a number of "poisons" require 
>acute ingestion doses on the order of milligram quantities to produce 
>their short-term toxic chemical (versus radiological) effects.  That would 
>be a whole lot of radioactive polonium:  a milligram of Po-210 would be 
>almost 4.5 curies.
>Polonium-210 (138.38-day half-life) is available in a variety of forms, 
>and as some have pointed out is readily available in static eliminator 
>brushes (I've typically seen quantities of 150 microcuries to 10 
>millicuries, but I'm sure they are available in larger activities), and I 
>suppose it might be easy enough for an experienced chemist to recover this 
>metal and create a chemical form that was readily transportable and easy 
>enough to add to food.  (It would also be possible to collect polonium 
>from the radon in the air, although perhaps not very practical if the 
>radon levels were not elevated.  If you had a facility that had an average 
>Rn concentration of 4 picocuries/liter, and an equilibrium factor of 0.4, 
>about 1.25 billion liters of air would be needed to collect a millicurie 
>of Po-210 (assuming 100% collection efficiency).  A concentrated source of 
>radium might allow for more practical collection, and some have noted 
>there are other means of creating/collecting/obtaining Po-210, but these 
>methods might require special access to equipment/materials.
>Using ICRP 60+ models, the dose from a 1 millicurie Po-210 ingestion 
>intake on November 1 (this would be an intake of about 0.22 micrograms of 
>Po, if I've done my math correctly) would result in the organ doses 
>equivalent and doses as of November 8, 16 (day of hospitalization?) and 23 
>(day of death) shown at the end of this note.  As Jim Barnes pointed out, 
>it probably doesn't make sense to look at dose equivalent, rather the dose 
>in rad should be considered to determine deterministic effects, so the 
>organ doses were calculated by dividing the doses equivalent by the alpha 
>weighting factor of 20.
>Based on the above, it seems like the ingested dose would have had to be 
>at least in the range of 3 to 10 millicuries to result in the effects 
>reported.  This is still in the range of micrograms of Po-210 intake.
>I also wonder what Po tastes like.  Would polonium chloride taste like a 
>salt?  Would Po be easy to add to food or drink.  It seems like the dose 
>added to the food might need to be much larger to ensure that the intake 
>was sufficiently large.
>Po-210 is primarily an alpha emitter, but 1e-5 of the time it emits a 0.8 
>MeV photon.  Using the old 6CEn equation indicates that for a millicurie, 
>the photon exposure rate at a foot would be 0.048 microentgen per 
>hour.  This doesn't seem like much but the 0.8 MeV photon emission rate 
>would be 22,200 per minute, and that seems like a detectable quantity (if 
>someone were really looking).  (A curie (223 milligrams) of Po-210 would 
>produce an exposure rate of about 48 microroentgen per hour, which is 
>about 4 times a typical background level.)
>ICRP 23 notes that we all have Po-210 in us, primarily from foods, but 
>cigarettes are a significant source for some.  Blood levels reportedly 
>range from 1 to 54 pCi/kg (reference man has a blood volume of 5200 ml, 
>and assuming a density of 1 g/ml, reference man's blood would contain 5.2 
>to 280 pCi of Po-210).  At 149 days, dogs exposed to Po-210 aerosols had 
>about half the retained Po-210 in their hair follicles (I can't tell if 
>this was 149 days after exposure or after 149 days of chronic exposure - 
>I'm guessing the former).  Also ICRP 23 notes that trace amounts of Po-210 
>are normally found in hair and sweat.
>(Just an aside pico = 1E-12, micro = 1E-6, milli = 1E-3)
>Below are calculated doses per millicurie ingested (assumed to occur on 
>November 1).  Sorry for not using SI units, but so many values were 
>readily available in curie-based units.  Also, I seem to be unable to 
>align the columns in my table.  They look alligned here, but they shift 
>when I send.
>Ingestion equivalent dose per millicurie
>equivalent dose (rem)   11/8/2006       11/16/2006      11/23/2006      50-y
>Kidneys         1.08E+03        2.25E+03        3.14E+03        9.43E+03
>Spleen          9.33E+02        1.94E+03        2.70E+03        8.12E+03
>Liver                   5.61E+02        1.17E+03        1.62E+03 
>Red Bone Marrow 2.26E+02        4.68E+02        6.51E+02        1.95E+03
>Lower Large 
>Intestine   2.06E+02        2.32E+02        2.53E+02        3.95E+02
>Surface            1.38E+02        2.83E+02        3.94E+02        1.18E+03
>Upper Large 
>Intestine   8.78E+01        1.14E+02        1.33E+02        2.71E+02
>Small Intestine 3.63E+01        6.16E+01        8.08E+01        2.16E+02
>Stomach         3.07E+01        5.59E+01        7.51E+01        2.11E+02
>All other 
>organs        2.62E+01        5.14E+01        7.06E+01        2.06E+02
>Ingestion dose per millicurie for the period defined by an acute intake on 
>11/1/2006 and a period ending on the dates listed below.
>dose (rad)              11/8/2006       11/16/2006      11/23/2006      50-y
>Kidneys         5.42E+01        1.13E+02        1.57E+02        4.72E+02
>Spleen          4.66E+01        9.70E+01        1.35E+02        4.06E+02
>Liver                   2.80E+01        5.83E+01        8.12E+01 
>Red Bone Marrow 1.13E+01        2.34E+01        3.26E+01        9.75E+01
>Lower Large 
>Intestine   1.03E+01        1.16E+01        1.26E+01        1.98E+01
>Surface            6.88E+00        1.42E+01        1.97E+01        5.90E+01
>Upper Large 
>Intestine   4.39E+00        5.68E+00        6.65E+00        1.36E+01
>Small Intestine 1.82E+00        3.08E+00        4.04E+00        1.08E+01
>Stomach         1.54E+00        2.80E+00        3.76E+00        1.06E+01
>All other 
>organs        1.31E+00        2.57E+00        3.53E+00        1.03E+01

More information about the RadSafe mailing list