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US-PALESTINIANS-ARAFAT-SWISS-POLONIUM:Factbox: Polonium: lethal, invisible poison
(Reuters) - A Swiss institute said on Thursday that it agreed to a request from the Palestinian Authority to help exhume the body of its former leader Yasser Arafat and determine whether he was poisoned, but time is running out.
Here is a look at polonium-210 amid suspicions that the radioactive substance may have been used.
* Polonium is a radioactive element that is present in the environment at extremely low concentrations. Polonium-210 is the most common and stable isotope, or variant. Polonium-210 is a metallic solid that can be dissolved in dilute acids.
* The alpha - or radioactive decay - particles that it emits travel only a few centimeters in air, and can be stopped by a sheet of paper or by the dead layer of outer skin on the body. Most traces of it on a person can be eliminated through washing or showering. This means polonium is not a radiation hazard unless it is inhaled, ingested, injected or enters a wound.
* It can be produced by the chemical processing of uranium ores or minerals but, due to its scarcity, it is usually produced artificially in a nuclear reactor, by bombarding bismuth with neutrons. Only about 100 grams a year of polonium-210 are manufactured worldwide in this way.
John Croft, a British radiation expert who worked on the 2006 case of the murdered Russian dissident Alexander Litvinenko, said a dose large enough to kill would most likely have to come from a government with either civilian or military nuclear capabilities.
* The minimum lethal amount of ingested polonium is 6.8 trillionths of a gram. Higher doses will kill more quickly. Once inside someone's body, polonium-210 is not easily detectable from outside, although an individual's urine or feces would show traces of alpha radiation. The intense alpha radiation within tissues would destroy living cells, leading to a rapid decline in health and eventual death from multiple organ failure.
SOURCES: Reuters/ UK's Health Protection Agency/ Argonne National Laboratory at the University of Chicago/Health Physics Society/www.IAEA.org/http://www.nucleonica.net/polonium210.aspx/www.purewatergazette.net/http://periodic.lanl.gov/84.shtml/http://www.chem.info/News
(Reporting by Kate Kelland and David Cutler, London Editorial Reference Unit;)