Polonium - an element in the news

During 1898, Marie Curie was attempting to identify the cause of radioactivity in pitchblende (a common uranium ore). During her investigations she discovered an element associated with bismuth. 

Marie named this new substance, her first discovery of an element, polonium after her native country of Poland. Some sources say that polonium was the first element named to highlight a political controversy as at the time, Poland was not recognised as an independent country and Marie hoped that by naming the new element after her home country, this would draw attention to its plight. 

This radioactive silvery-grey element is very rare in nature and is typically associated with uranium ores that contain on average 100 micrograms (millionths of a gram) of polonium per metric tonne. 25 isotopes of polonium exist, with polonium 210 being the most readily available. 

Initially it could only be separated by extraction from the wastes of uranium, radium and vanadium refining operations. But the discovery in 1934, that the parent element of polonium (210Bi) could be manufactured by bombarding natural bismuth (209Bi) with neutrons, allowed it to be created in milligram quantities. 

As polonium is found throughout the environment albeit in minute quantities, our bodies all contain trace amounts (190-2,900 mBq/kg in a variety of human tissues), though these minute levels pose no threat to human health. Reports do show that tests on the bones of smokers reveal up to twice as much polonium as non smokers.

Polonium is highly toxic and all its isotopes are radioactive - in fact the energy released by its decay is so large, that a capsule containing about 0.5 grams can reach a temperature above 500 kelvin (227 degrees Celsius). 

The ability to produce heat in such small quantities has led it to be used as a possible source of heat for equipment in space. Polonium does have a variety of more mundane earth bound uses as well, for example, in the elimination of static electricity during the manufacture of paper and sheet plastics, and to remove dust from photographic film as well as a source of alpha particles in nuclear physics. 

It is only dangerous if inhaled, eaten, or absorbed as the alpha particles it produces cannot pass through the epidermis. Therefore, it poses the greatest risk to humans during the manufacture of polonium for these activities, as all use polonium that is safely sealed and controlled, minimising risk to the user.

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