Some brands of cigarette are likely to be far more habit-forming than others because of the amount of highly addictive "freebase" nicotine they produce.
Scientists have found wide differences between different cigarette brands in the amount of freebase nicotine, which is quickly absorbed through the lungs and carried in the bloodstream
to the brain.
Just as smoking "crack" causes vapourised cocaine to reach the brain within seconds, freebase nicotine also has an almost instantaneous effect on the central nervous system, making addiction more likely.
The researchers, from the Oregon Health and Science University in Portland, compared 11 cigarette brands available in the US and found that some contained between 10 and 20 times higher levels of freebase nicotine than expected.
Brands were compared with a laboratory "reference" cigarette containing 1 per cent freebase nicotine. The results ranged from 1 per cent or 2 per cent to 36 per cent for a speciality brand called American Spirit. The popular Marlboro brand contained up to 9.6 per cent freebase nicotine. Other well-known brands included Camel (2.7 per cent), Winston (5 to 6.2 per cent) and Gauloises Blondes (5.7 to 7.5 per cent).
Professor James Pankow, who led the study reported in the journal Chemical Research in Toxicology, said: "During smoking, only the freebase form can [evaporate] from a particle into the air in the respiratory tract. Gaseous nicotine is known to deposit super-quickly in the lungs. From there, it's transported rapidly to the brain.
"Since scientists have shown that a drug becomes more addictive when it is delivered to the brain more rapidly, freebase nicotine levels in cigarette smoke are thus at the heart of the controversy regarding the tobacco industry's use of additives such as ammonia and urea."
A 1997 study led by Professor Pankow linked ammonia additives in tobacco with increased freebase nicotine levels in cigarettes. Separate measurements were made of the first three puffs and about eight subsequent puffs. In many cases, the freebase content was higher in the first puffs. Marlboro, for instance, had a freebase nicotine level of 9.6 per cent in the first three puffs and 2.7 per cent in later puffs.
A spokeswoman for the Tobacco Manufacturers' Association in the UK said: "We cannot comment without seeing the full results of this research. Cigarettes manufactured here ... may be quite different from those in America."
- INDEPENDENT
