Just one puff of a cigarette could damage a smoker’s DNA, the first step to cancer and heart disease, researchers said on Friday.

It obviously takes more than that to cause disease, but the team at the University of Pittsburgh were surprised at how little smoke it took to do the initial damage.

William Saunders and colleagues studied the effects of cigarette smoke on human fibroblasts, common cells found in the connective tissue that holds much of the body together.

They exposed batches of growing cells to liquefied cigarette smoke and saw the chromosomes that carry the DNA were pulled apart from both ends.

“Double-stranded breaks are considered the most mutagenic type of DNA damage because the broken ends can fuse to other chromosomes in the cell,” Saunders said in a statement prepared ahead of a weekend meeting of the Environmental Mutagen Society in Pittsburgh.

This happened with very small amounts of smoke, Saunders said.

Cigarette smoking is known to cause lung cancer and is also linked to bladder, larynx and esophageal cancers, as well as heart disease.

“Unfortunately, no amount of scientific evidence arguing against smoking will get everyone to stop or not begin to smoke in the first place. So, perhaps one long-term goal should be to develop cigarettes that somehow prevent what we’ve seen happen to the cells in our lab,” Saunders said.