Often, casual smokers think that smoking a few cigarettes a week is no big deal. But, in the world of smoking, good news is hard to come by.

According to a new study, having an infrequent smoke or being exposed to secondhand smoke may be doing more harm than people may think. Researchers found that being exposed to even low levels of cigarette smoke may put people at risk for future lung disease, such as lung cancer and chronic obstructive pulmonary disease (COPD). Their work is published in the “American Journal of Respiratory and Critical Care Medicine”.

Long-term studies have long shown that secondhand smoke is dangerous, but there have never been conclusive biological tests demonstrating what it does to the body’s genes — until now.

Even at the lowest rates of cigarette exposure, there are direct effects on the functioning of genes within cells lining the lungs. Genes, commonly activated in the cells of heavy smokers, are also turned on or off in those with very low-level exposure.

While the genetic effect is much lower than in those who are regular smokers, it doesn’t mean that there are no health consequences. Certain genes within the cells lining the airways are very sensitive to tobacco smoke, as it turns out. Changes in the function of these genes are the first evidence of disease in the lungs. It’s where the damage originally takes place, paving the road for cancer.

The study tested 121 people from three different categories: “nonsmokers,” “active smokers” and “low exposure smokers.” Researchers tested urine levels of nicotine and cotinine — markers of cigarette smoking within the body.

The research team then scanned each person to find which genes were either activated or deactivated in cells lining the airways. They found that there was no level of nicotine or cotinine that did not also correlate with genetic abnormalities.

That means that no level of smoking or exposure to secondhand smoke, is safe. The researchers suggest that this is even more evidence to support smoking bans in public places, where non-smokers and employees of businesses that allow smoking are put at risk for future lung disease.

To those social smokers out there, it’s a little impetus to just plain quit.

Tags: Health News, lung cancer, Lungs