And it doesn’t take much. A new study shows why all smoke – even secondhand – is dangerous.

We’ve known for a long time that smoking tobacco is extremely unhealthy. Any level of exposure, from a pack-a-day habit to secondhand inhalation, carries a long-term risk of cancer, heart disease, emphysema and more. But this study, published recently in the American Journal of Respiratory and Critical Care Medicine, shows how smoke damages us on the genetic level.

The researchers took urine samples and samples of epithelial tissue – the cells which line your airway – from a group of 121 people. Based on the the nicotine content of the urine samples, they divided the volunteers up into three smaller groups – non-smokers, low-exposure smokers and regular smokers. They then examined the epithelial cells of the groups and reached a stark conclusion.

Think of your epithelial cells like a canary at the mouth of a coal mine, say the researchers. If we examine them, we can see warning signs of deeper, potentially deadly conditions. It turned out that smoke exposure was causing genes in the lung tissue to switch on and off as a result of stress. The regular smokers showed the strongest genetic changes, but changes were also evident in the low-level smoker group – people that only smoke occasionally, or maybe just spent time in a smoky place. So in the words of the study’s lead author Dr. Ronald Crystal, “No level of smoking, or exposure to secondhand smoke, is safe.”

Who cares about your genes? ZocDoc cares about your genes! Check out the government’s website or speak to a doctor about quitting smoking. Need to speak with a lung specialist? We can help you there, too.