Nicotine, Pankow explains, occurs naturally in tobacco plants as either an acid or a base. The acidic form is more stable, and therefore more concentrated. The basic form, known as "free-base" nicotine, is volatile, especially when smoked. As a result, it is absorbed quickly and efficiently into the lungs when a person smokes, where it quickly reaches the brain. Acidic nicotine, conversely, clings to the particles of smoke as they settle into the lungs, and is slowly absorbed before it is transported to the brain.
The difference, Pankow says, is analogous to the difference between powder and crack cocaine, the latter of which is smoked in a similar free-base form and is considered to be the most addictive form of the drug.
Tobacco companies have learned how to maximize the amount of free-base nicotine in commercial cigarettes by carefully blending different tobacco varieties and by directly converting the existing acidic nicotine into the free-base form. The result, researchers think, is a more addictive, and thus more deadly, cigarette.
"In the 1990s, the courts demanded the release of tobacco company documents, which are now available. There's much about converting more nicotine into the freebase form to get more nicotine into the smoke and so that the nicotine in the smoke becomes more available," says Pankow.
Pankow and his team recently compared the levels of free-base nicotine found in the most common brands of American cigarettes (see "Percent Free Base Nicotine.." in the bibliography). They found that some -- including the famously popular Marlboro -- contain 10 to 20 times higher percentages of free-base nicotine than other brands. But the brand with the most free-base nicotine? The "Natural American Spirit" cigarette, marketed here as "100% Chemical Additive-Free Tobacco." American Spirit cigarettes contain 36 percent free-base nicotine, compared with 9.6 percent in a Marlboro, 2.7 percent in a Camel, and 6.2 percent in a Winston.
Nicotine for health nuts?
In response, a whole new crop of products has emerged from the tarpool. American Spirit is one of them. As for the rest, take your pick:
Bidis are the groovy hand-rolled cigarettes from India, popular with teens because they are manufactured in a variety of flavors, like strawberry or root beer. But buyer beware: A study released published last December in the journal Nicotine and Tobacco Research found that after smoking bidis, study participants' blood nicotine levels were higher than when they smoked conventional brands.
"Welcome to the world of nicotine-free smoking!" is the plug for Quest Cigarettes, a cigarette that is available in three nicotine levels, "low," "extralow," and "nicotine-free," intended for smokers who want to cut back or eliminate cigarettes entirely. Unlike nicotine-replacement strategies, Quest cigarettes give smokers a chance to hang onto the habit while kicking the addiction. But many studies have shown that when smokers switch to cigarettes with less nicotine, they simply (and probably unconsciously) take deeper, longer drags to get the familiar buzz.
Philip Morris is testing a high-tech cigarette called the Accord. The $40 kit includes a battery charger, a puff-activated lighter that holds the cigarette, and a carton of special cigarettes. When a smoker sucks on the little box (which could pass for a kazoo), a microchip ignites the cigarette. The process gives the smoker one drag and releases no ashes or smoke. Accord appears to reduce the risk of secondhand smoke, but a study published late last year reported that Accord smokers took bigger and longer puffs than with conventional cigarettes. The researchers concluded that the Accord is unlikely to reduce the smoker's risk.
R.J. Reynolds' Eclipse cigarette heats tobacco rather than burning it. When users light the cigarette-like tube, heated glycerin and tobacco vaporize the nicotine. The process produces less tar, but more carbon monoxide (see "Long-term effects of the Eclipse cigarette..." in the bibliography).
So far, tobacco companies have succeeded in stalling legislation that would require them to disclose -- or even test for -- the amount of free-base nicotine or other additives in their products. "They have always argued these are trade secrets... but we're not talking about making software. This is a product that kills," says Pankow. In the meantime, he says, smokers should be wary of claims that link alternative cigarettes to better health.
Who's in a puff over passive smoking?
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©2003, University of Wisconsin, Board of Regents.