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.

Image Credit... Luba Lukova

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.

Is it therefore really correct to say, as Britain’s Health Protection Agency did this week, that the risk of having been exposed to this substance remains low? That statement might be true for whatever particular supplies were used to poison Mr. Litvinenko, but consider also this: London’s smokers (and those Londoners exposed to secondhand smoke), taken as a group, probably inhale more polonium 210 on any given day than the former spy ingested with his sushi.

No one knows how many people may be dying from the polonium part of tobacco. There are hundreds of toxic chemicals in cigarette smoke, and it’s hard to sort out how much one contributes compared to another — and interactive effects can be diabolical.

In a sense, it doesn’t really matter. Taking one toxin out usually means increasing another — one reason “lights” don’t appear to be much safer. What few experts will dispute is the magnitude of the hazard: the World Health Organization estimates that 10 million people will be dying annually from cigarettes by the year 2020 — a third of these in China. Cigarettes, which claimed about 100 million lives in the 20th century, could claim close to a billion in the present century.