Think You're Safe with Just a Cigarette a Day? Think Again

If you’re under the impression that smoking "casually" won’t do you any harm, new research may have you reevaluating that notion. The study finds that even people who are around second-hand smoke have significant changes to their airway cells at the level of the genes.

No matter how low the level of smoke exposure, there were accompanying changes in the participants’ airway cells at the genetic level. And the same genetic pathways that were affected by active smoking were also affected by low exposure smoking.

Ronald Crystal and his colleagues studied 121 people who were "active smokers," "non-smokers", or "low exposure smokers" (this last group smoked rarely or were simply around second-hand smoke). They analyzed the nicotine and cotinine (a derivative of nicotine) in the participants’ urine, in order to determine their exposure level. They also looked at their genomes to see what kinds of genetic changes were going on in the airway cells themselves.

Crystal and his team from New York-Presbyterian Hospital found that "there is no threshold above the detectable limit for urine nicotine below which the small airway epithelium does not respond to low levels of tobacco smoke." In other words, no matter how low the level of smoke exposure, there were accompanying changes in the participants’ airway cells at the genetic level. And the same genetic pathways that were affected by active smoking were also affected by low exposure smoking.

The authors write that "to [their] knowledge, this is the first documentation that exposure to low levels of tobacco smoke is associated with modifications of human lung cell biology." Still, it’s unclear how the changes in the participants’ airways could predict how and when chronic obstructive pulmonary disease (COPD) might develop.

The study may have some interesting implications for public policy, since, as the researchers point out, many people are exposed to second-hand smoke on a daily basis. Some cities have toyed with the idea of banning smoking in all public places including parks, and studies like this lend support to that stance.

The study was published in the August 6, 2010 issue of American Journal of Respiratory and Critical Care Medicine.