Polonium 210 and Cigarettes

Robbie over at The Times points to a wonderful attempt to climb upon the bandwagon of the Alexander Litvinenko polonium 210 poisoning. The full piece is here in the New York Times.

How much polonium is in tobacco? In 1968, the American Tobacco Company began a secret research effort to find out. Using precision analytic techniques, the researchers found that smokers inhale an average of about .04 picocuries of polonium 210 per cigarette. The company also found, no doubt to its dismay, that the filters being considered to help trap the isotope were not terribly effective. (Disclosure: I’ve served as a witness in litigation against the tobacco industry.)

A fraction of a trillionth of a curie (a unit of radiation named for polonium’s discoverers, Marie and Pierre Curie) may not sound like much, but remember that we’re talking about a powerful radionuclide disgorging alpha particles — the most dangerous kind when it comes to lung cancer — at a much higher rate even than the plutonium used in the bomb dropped on Nagasaki. Polonium 210 has a half life of about 138 days, making it thousands of times more radioactive than the nuclear fuels used in early atomic bombs.

We should also recall that people smoke a lot of cigarettes — about 5.7 trillion worldwide every year, enough to make a continuous chain from the earth to the sun and back, with enough left over for a few side-trips to Mars. If .04 picocuries of polonium are inhaled with every cigarette, about a quarter of a curie of one of the world’s most radioactive poisons is inhaled along with the tar, nicotine and cyanide of all the world’s cigarettes smoked each year. Pack-and-a-half smokers are dosed to the tune of about 300 chest X-rays.

That last line has me slightly scratching my head. I don't deal with radioactive metals (rather the rare earths more generally) so I'm not about to enter the swamp of trying to convert 438 picocuries (30 cigarettes by 365 days by 0.4 picocurie per fag) into rem or sieverts to try and compare directly with chest x-rays but are we absolutely certain that he's got his numbers right there? the same as 300 chest x-rays a year?

Or, if we look at typical exposures, a chest x-ray is 0.00002 Sievert. Multiply that by 300 and we get 0.006 Sievert don't we? That's three times the regular amount we simply get from background radiation. Or 1/666 of the 50% fatal dose.

Or for the truly interested, less than the 0.008 sieverts received as background radiation by those who live in Cornwall.

So, yes, there is polonium 210 in your cigarettes. And no doubt it is dangerous (for some value of danger) for it to be there. But what we want to know is how dangerous? The answer to which would appear to be:

Smoking: Less Dangerous Than Living in Cornwall.

Update: Russell Seitz makes the same point. Alas and alack, as he so often does, more scientifically than I do.