Jeez - you couldn't write a suspense novel any weirder than this. A former (?) Russian spy Alexander Litvinenko was apparently poisoned with polonium-210. And now its showing up on British planes.
The case of the poisoned former KGB agent took a bizarre twist when British Airways said that traces of radiation had been detected Wednesday on jets that flew between London and Moscow, establishing a possible Russian link and indicating that more than 30,000 people may have been exposed to radiation.
The airline said tests found "very low traces" of radioactivity on one of three Boeing 767s that flew between London and Moscow days before Alexander Litvinenko fell ill from the radioactive poison that doctors say killed him. [More]
And everything you need to know about polonium.
The important detail is the part about being an alpha-emitter. Alpha particles are very large and consequently bump into other nuclei easily, so a sheet of paper can stop them. However, if an alpha-emitter is lodged in your lung or other internal organs, it will definitely be close enough to sensitive tissue to cause damage. This is also the problem with plutonium as well. But it needs to be inside you - not around you.
Polonium-210 is an alpha emitter that has a half-life of 138.376 days. A milligram of 210Po emits as many alpha particles as 5 grams of radium. A great deal of energy is released by its decay with half a gram quickly reaching a temperature above 750 K. A few curies (1 curie equals 37 gigabecquerels) of 210Po emit a blue glow which is caused by excitation of surrounding air. A single gram of 210Po generates 140 watts of power. Because it emits many alpha particles, which are stopped within a very short distance in dense media and release their energy, 210Po has been used as a lightweight heat source to power thermoelectric cells in artificial satellites. A 210Po 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. Some anti-static brushes contain up to 500 microcuries of 210Po as a source of charged particles for neutralizing static electricity in materials like photographic film. The majority of the time 210Po decays only by emission of an alpha particle, not by emission of an alpha particle and a gamma ray. About one in a 100000 decays results in the emission of a gamma ray, this low gamma ray production rate makes it more difficult to find and identify this isotope. Rather than gamma ray spectroscopy, alpha spectroscopy will be the best method of measuring this isotope.
So don't worry about dying from radiation planted by Russian spymasters. Worry about them controlling the market for natural gas.
I'm just here to help.