It may be riskier on the lungs to smoke cigarettes today than it was a few decades ago — at least in the US, says new research that blames changes in cigarette design for fueling a certain type of lung cancer. Up to half of the nation's lung cancer cases may be due to those changes, Dr. David Burns of the University of California, San Diego, told a recent meeting of tobacco researchers. It's not the first time that scientists have concluded the 1960s movement for lower-tar cigarettes brought some unexpected consequences. But this study, while preliminary, is among the most in-depth looks. And intriguingly it found the increase in a kind of lung tumor called adenocarcinoma was higher in the US than in Australia even though both countries switched to so-called milder cigarettes at the same time. “The most likely explanation for it is a change in the cigarette,” Burns said in an interview — and he cited a difference: Cigarettes sold in Australia contain lower levels of nitrosamines, a known carcinogen, than those sold in the US. Smokers once tended to get lung cancer in larger air tubes, particularly a type named “squamous cell carcinoma.” Then doctors noticed a jump in adenocarcinoma, which grows in small air sacs far deeper in the lung. Initial studies blamed introduction of filtered, lower-tar cigarettes. When smokers switched, they began inhaling more deeply to get their nicotine jolt, pushing cancer-causing smoke deeper than before. It's well known that cigarettes differ from country to country, because of different tobacco crops grown locally and smokers' varying tastes. Nitrosamines are a byproduct of tobacco processing and levels vary for several reasons, including differences in curing practices.
