Since Alexander Litvinenko's death there's been a lot of talk about polonium-210, the radioactive material that killed him. This brought to light another issue seldom discussed in the media -- that tobacco contains high levels of the stuff, due to chemical fertilizers. In 1990 Surgeon General C. Everett Koop went on record stating that radiation from tobacco was responsible for approximately 90 percent of tobacco-related cancers. So I ask you, Cecil: what's the straight dope on this? Does smoking organically grown tobacco instead of commercially grown tobacco lower the chance of lung cancer?
DM, via e-mail
Nothing in the world, DM, is so powerful as an idea that tells people exactly what they want to hear, and by this standard the notion that fertilizer-borne polonium might be the truly lethal ingredient in cigarettes is a blue-ribbon champ. Smokers are thrilled to learn it’s not the tobacco itself that’s murdering them, while hemp advocates see an argument for weed’s relative safety. Anticorporate types get another tale of ghoulish multinationals swigging the peons’ blood; conspiracy freaks get another instance where They keep us from discovering What’s Really Going On. The only problem: beyond a few key nuggets of truth, the story doesn’t hold up.
The radioactive metal polonium occurs in nature as a result of the decay of uranium; radon is another stage in the same process. Polonium-210, the isotope in question, isn’t too harmful when outside your body because it emits only alpha radiation, which is easily blocked by skin. But once inside it packs a serious radioactive punch. Thankfully, it’s usually found in extremely low concentrations, but as I discussed in a recent column on poisons, doses measured in the millionths of a gram can still kill you, while long-term low-grade exposure causes cancer.
Nugget of truth number 1 is that yes, there’s polonium-210 in tobacco (as well as radioactive lead-210). It’s mainly absorbed from the soil, though some amount of polonium-bearing dust adheres to tobacco’s unusually sticky leaves. Nugget 2 is that yes, using phosphate fertilizers increases the polonium content of tobacco, as mineral phosphate can contain significant amounts of uranium, and thus more of its decay products. None of this has been hushed up, or at least not well – researchers were reporting polonium-210 in cigarette smoke back in the early 60s, and the studies are easy to find online. Decades of small-animal testing shows a connection between inhaled polonium and lung tumors, although the relation between dose and response isn’t always tidy.
But tobacco’s hardly the only place one encounters polonium. Other plants absorb it too, meaning it’s in the food we eat, possibly as much as 20 cigarettes’ worth in a day’s intake; at any given time our bodies contain about 23,000 cigarettes’ worth of polonium, largely in the liver, kidneys, spleen, and bone marrow. Granted, if you smoke as well as eat, your cancer risk likely goes up, but what part of that concept isn’t widely understood?
It’s true that polonium-210 seems to be more carcinogenic when inhaled than when ingested, possibly because it concentrates at forks in the bronchial tubing, creating “hot spots” of radioactivity. Sounds grim, but remember, we’re talking about cigarette smoke here – it’s an all-star team of things that are very bad for you. The National Cancer Institute has identified 20 smoke components that “convincingly cause lung tumors,” among which polonium doesn’t rank high. And a 1999 Washington Post Magazine article on a Philip Morris scientist turned whistle-blower names nitrogen compounds called nitrosamines as the big cancer culprits.
Generally the cancer risk due to polonium-210 inhalation is believed to be quite small. Doctors writing to the New England Journal of Medicine in 1982 compared the radiation exposure from smoking a pack and a half daily to getting 300 chest x-rays in a year, but (a) that’s really not so much radiation and (b) they still couldn’t assess the resulting cancer threat.
The alleged claim by C. Everett Koop that radioactivity causes 90 percent of tobacco-related cancer has so far resisted the tracking skills of my research team (it’s all over the Web, typically attributed to a Koop appearance “on national television”), but if he said it, it’s way off from what everyone else says – including surgeon generals’ reports from before, during, and after his tenure. The U.S. National Council on Radiation Protection and Management estimates that if you’ve smoked for 50 years, polonium-210 accounts for 1 percent of your overall lung cancer risk. According to data from Argonne National Laboratories, the chances of polonium causing fatal cancer in a two-pack-a-day smoker after 25 years may be less than one in 1,000; by contrast, World Health Organization figures suggest that cigarettes kill about half of all smokers, with half of those deaths coming in middle age. So sure, maybe you can improve your odds a bit by going organic, but basically a smoker demanding a polonium-free cigarette is like a suicide insisting on using a polonium-free bullet.
Send questions to Cecil via firstname.lastname@example.org.