[ RadSafe ] Lethal Amount of Po-210

McLaughlin, David A. mclaughlinda at ornl.gov
Fri Dec 1 11:01:06 CST 2006

The toxicity of Po-210 is discussed within the 1972 peer-reviewed
article "Metabolism and Biological Effects of Polonium-210" by B.B.
Moroz and Yu. D. Parfenov of the Institute of Biophysics of the USSR
Ministry of Health (See Atomic Energy Review, Volume 10, pp. 175 - 232).


>From page 192:  "TOXIC DOSES OF 210-Po......According to data provided
by a number of Soviet authors, when doses of 0.05 - 0.18 uCi per gram of
body weight are injected subcutaneously in dogs, the animals develop
acute radiation sickness and die from ten days to four weeks after
receiving the injection.  Doses of 0.02 to 0.03 uCi/g bring on subacute
radiation sickness and are also absolutely lethal in dogs.  Even a
polonium dose of 0.0025 uCi/g produces chronic radiation damage in dogs
and kills all of them between 6 and 12 months after administration."


By my calculation, applying an effective half-time of 37 days (based on
the ICRP recommended 50 day biological half-life) and assuming that 100%
of the 5.4 MeV alpha energy is absorbed locally, the tissue
concentration range of 0.05 - 0.18 uCi per gram corresponds to an
integrated absorbed dose ranging between 3.2 and 11.5 Gy (320 - 1150
Rad) over 30 days.  This dose is likely not uniform throughout the body;
however, the authors note in their conclusions (page 225) that the
"relatively even distribution of 210-Po through the body results in
irradiation of practically all organs and tissues, although the isotope
accumulates preponderantly in the reticulo-endothelial system."


The referenced paper also provides a clinical description of the
progression of polonium-induced sickness.  From page 199: "THE CLINICAL
PICTURE ... During the first few days after administration of the
radioactive material in doses calculated to produce acute or sub-acute
radiation sickness the animals show no outward differences from normal
animals.  The latent period usually lasts 5-7 days, being slightly
shorter only when very large doses of polonium are administered.
Subsequently the animals become lethargic; loss of appetite and loss of
body weight is observed.  All these effects are progressive; diarrhea
with mucous or an admixture of blood and vomiting are frequently
observed and the animals have a strong thirst.  They develop
photophobia, conjunctivitis and rhinitis with bloody discharges.
Petechial haemorrhages are observed on the skin, the mucous membrane of
the mouth and the ocular conjunctiva.  Spontaneous bleeding from the
rectum and urinary tract occurs.  The dogs cease caring for themselves.
Their blood pressure drops and their rate of breathing slows down.  When
polonium has been given sub-cutaneously, oedema and hyperaemia are
observed at the injection site, followed by infiltration and usually,
when the sickness in sub-acute, necrosis; and ulcer develops with
undermined, feebly granulated edges.  In the final period of radiation
sickness the dogs lie motionless, do not respond to stimuli and refuse
food; their weight drops to 30-40% of the original weight and death


I've not seen a clinical description of Mr. Litvinenko's symptoms.
However, news reports indicated that he began feeling ill shortly
following his suspected poisoning (at a sushi restaurant?).  The onset
differs from the latency period reported for dogs - but perhaps humans
are more aware of their general wellbeing than dogs.   The development
of photophobia, conjunctivitis, and rhinitis would be particularly
noteworthy given the animal data.


David McLaughlin, CHP

Knoxville, TN  





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