Faqs 2006 Polonium-210 Factsheets & faqs

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FAQs 2006 - Polonium-210

 

 

 

 

 

 

 

 

 

 

Factsheets & FAQs 

Polonium-210 

Basic Facts 

Polonium-210 (Po-210) is a radioactive element that occurs naturally and is present in the 

environment at extremely low concentrations.  

Polonium was discovered by Marie Sklodowska-Curie and Pierre Curie in 1898 and was 

named after Marie's native land of Poland (Latin: Polonia). This element was the first one 

discovered by them while they were investigating the cause of pitchblende radioactivity. 

It is a fairly volatile (50% is vaporized in air in 45 hours at 55°C) silvery-grey soft metal. 

Po-210 has a half-life of 138 days. This is the time it takes for the activity to decrease by half 

due to a process of radioactive decay. Po-210 decays to stable lead-206 by emitting alpha 

particles, accompanied by very low intensity gamma rays. The majority of the time Po-210 

decays by emission of alpha particles only, not by emission of an alpha particle and a gamma 

ray. Only about one in a 100,000 decays results in the emission of a gamma ray. Alpha 

spectroscopy is the best method of measuring this isotope. 

Origin 

Being produced during the decay of naturally occurring uranium-238, polonium-210 is widely 

distributed in small amounts in the earth's crust. Although it can be produced by the chemical 

processing of uranium ores or minerals, uranium ores contain less than 0.1 mg Po-210 per ton. 

Because Po-210 is produced from the decay of radon-222 gas, it can be found in the 

atmosphere from which it is deposited on the earth's surface. Although direct root uptake by 

plants is generally small, Po-210 can be deposited on broad-leaved vegetables. Deposition 

from the atmosphere on tobacco leaves results in elevated concentrations of Po-210 in tobacco 

smoke. There are tiny amounts of Po-210 in our bodies. 

Po-210 can be manufactured artificially by irradiating stable bismuth-209 with thermal 

neutrons resulting in the formation of radioactive Bi-210, which decays (half-life 5 days) into 

Po-210. Polonium may now be made in milligram amounts in this procedure which uses high 

neutron fluxes found in nuclear reactors. Only about 100 grams are produced each year, 

making polonium exceedingly rare. 

Uses 

Po-210 is used in neutron sources (where it is mixed or alloyed with beryllium). It is also used 

in devices that eliminate static electricity in machinery where it can be caused by processes 

such as paper rolling, manufacturing sheet plastics, and spinning synthetic fibres. Brushes 

containing Po-210 are used to remove accumulated dust from photographic films and camera 

lenses. Static eliminators typically contain from one to tens of GBq of radioactivity. 

Po-210 emits so many alpha particles each second that the energy released from one gram is 

140 watts, and a capsule containing about half a gram will spontaneously reach a temperature 

of 500°C. As a result it has been used as a lightweight heat source to power thermoelectric 

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cells in satellites. A Po-210 heat source was also used in each of the Lunokhod rovers 

deployed on the surface of the Moon, to keep their internal components warm during the lunar 

nights. However, because of its short half-life Po-210 cannot provide power for long-term 

space missions and has been phased out of use in this application. Polonium is not subject to 

IAEA safeguards. 

Toxicity 

Po-210 is highly radioactive and chemically toxic element. Direct damage occurs from energy 

absorption into tissues from alpha particles. As an alpha-emitter Po-210 represents a radiation 

hazard only if taken into the body. It's important to note that alpha particles do not travel very 

far - no more than a few centimetres in air. They are stopped by a sheet of paper or by the 

dead layer of outer skin on our bodies. Therefore, external exposure from Po-210 is not a 

concern and Po-210 does not represent a risk to human health as long as Po-210 remains 

outside the body. Most traces of it on a person can be eliminated through careful hand-

washing and showering. 

Po-210 can enter the body through eating and drinking of contaminated food, breathing 

contaminated air or through a wound. The biological half-time (the time for the level of Po-

210 in the body to fall by half) is approximately 50 days. If taken into the body, Po-210 is 

subsequently excreted, mostly through faeces but some is excreted through urine and other 

pathways. People who come into contact with a person contaminated by Po-210 will not be at 

risk unless they ingest or inhale bodily fluids of the contaminated person.  

Responsible/Contact: Office of Public Information and Communication 

(From 2006)