A Russian spy was recently killed with a lethal dose of radiation from a substance that’s being called “Polonium 210”. Most people don’t know what the heck that is. I’m a chemist, so I know what it is. I’ve never seen the stuff, but the information on polonium should be at least addressed so people know what it is and what kind of risk is associated with it.
Polonium is in group 6A, or 16, on the periodic table of elements. It is in the same group as oxygen and sulfur, two elements necessary for life. However, polonium is a metalloid and its reactivity is different than that of the non-metals oxygen and sulfur. In this case, it’s best treated as a heavy metal.
Polonium is also two atomic numbers greater than lead, which bears some special significance. Elements above lead tend to be alpha-emitters, that is, they release alpha particles, a type of radiation. Alpha particles are helium atoms that have no electrons. Because of their mass, they often do not penetrate the skin and are only really dangerous in localized areas inside the body. Alpha emitters will often give off beta particles (the much-smaller electron) as well as gamma radiation (high-energy light). Alpha emitters are great for radiation therapy, and are used in various applications such as fighting cancer (check out Bi-212 & 213). The important part in selecting such isotopes is to use low-gamma emission sources, as gamma penetrates many layers of tissue and is damaging to organs (gamma is the primary concern from nuclear fallout).
Polonium has numerous isotopes. An isotope is a version of that atom which keeps the electrons (83 in this case) and protons (83 again) constant but varies the neutrons, which affects its mass and stability. In this case, the nucleus mass is 210 AMU, and it turns out that Po-210 is not the most stable of the isotopes of polonium. It has a half-life (how long it takes for half of a sample of polonium to turn into something else) of 138 days. Po-209 is the most stable isotope, having a half-life of 102 years. Po-208 has a half-life of nearly 3 years, and Po-206 lasts for 8.8 days. According to the CRC Handbook of Chemistry and Physics:
Polonium is a very rare natural element. Uranium ores contain only about 100 ug of the element per ton. Its abundance is only about 0.2% of that of radium. In 1934, it was found that when natural bismuth (209Bi) was bombarded by neutrons, 210Bi, the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors. Polonium-210 is a low-melting, fairly, volatile metal, 50% of which is vaporized in air in 45 hours at 55 deg C. It is an alpha emitter with a half-life of 138.39 days. A milligram emits as many alpha particles as 5 g of radium. The energy released by its decay is so large (140 W/g) that a capsule containing about half a gram reaches a temperature above 500 deg C. The capsule also presents a contact gamma-ray dose rate of 0.012 Gy/h.
Polonium-210 breaks down to Lead-206 after alpha particle emission, which is non-radioactive but toxic, as anyone can tell you.
As an assassin’s weapon, Po-210 is an odd choice. It would not kill quickly, although it would kill. To an uneducated source, it would look like lead poisoning.
What kind of risks does it pose to anyone nearby the poisoned spy? Minimal, at best. As was said earlier, Po-210 is an alpha emitter, so if it got stuck on your clothes, you wouldn’t even notice it as the alpha particles wouldn’t penetrate your epidermis, or even your clothing. Ingested or inhaled, it is more dangerous, as the alpha and gamma radiation are not stopped by your skin. It is also a heavy “metalloid“, so your body has difficulty processing it just as it would lead.
The good news is that it is short lived. A 0.1 gram dose will be a 0.05 gram dose in 4 months, and after a year it is less than a quarter of what it was. It is also a heavy metal, so the odds of it travelling far as a aerosol are slight.
So there you go. You are up to date on polonium 210 and the risks that it poses. If you were in the same restaurant as the poisoned Russian spy, don’t fret. You’re probably OK. Get double-checked by a doctor, just to be on the safe side, as I’m a chemist and not a medical professional.