Smoking a pack (or two) of cigarettes each day is obviously not good for your lungs. But for those who enjoy an occasional smoke, an obvious question is, “How many cigarettes can I smoke before I start to do some damage?”
The sobering answer: Zero.
That’s the conclusion of a new study from researchers at Weill Cornell Medical College and Cornell University in New York.
The researchers recruited 121 healthy volunteers to pee into a cup and submit to a bronchoscopy, a procedure that included removing cells from the lining of the part of the airway that would first come into contact with inhaled smoke.
Smoking status was determined based on levels of nicotine and cotinine (a chemical produced in the body as nicotine is metabolized) found in their urine. The 40 people with undetectable levels of nicotine and cotinine were classified as nonsmokers; those with low levels were considered occasional smokers or people exposed to secondhand smoke; and those with high levels were considered regular smokers.
By comparing the lung biopsies from regular smokers to those from nonsmokers, the researchers identified 372 genes whose expression was triggered by tobacco smoke. Then they checked to see what those genes were doing in the occasional smokers. It turned out that 128 of those genes (34%) had been activated -- presumably by cigarettes -- including 41 (11%) that were “significantly modified,” according to the study.