A report published in Chemical Research in Toxicology shows that smoking damages the body in minutes, not years.
Chemicals which cause cancer form rapidly after smoking, according to the research, which was funded by the US National Cancer Institute.
The results have been described as a stark warning to people considering smoking, said scientists involved in the small-scale study.
The research is “chilling” and a warning that it is never too early to quit, said anti-smoking charity Ash.
Though it is well known that the long term impact of smoking goes from heart disease to a range of cancers, this study suggests the damage begins just moments after the first cigarette is smoked.
The researchers looked at the level of chemicals linked with cancer, polycyclic aromatic hydrocarbons (PAH), in 12 patients after smoking.
A PAH added to the subject’s cigarettes, was then modified by the body and turned into another chemical which damages DNA and has been linked with cancer.
This process only took from 15 to 30 minutes to take place, according to the research.
Professor Stephen Hecht, from the University of Minnesota, said: “This study is unique, it is the first to investigate human metabolism of a PAH specifically delivered by inhalation in cigarette smoke, without interference by other sources of exposure such as air pollution or the diet.
The results reported here should serve as a stark warning to those who are considering starting to smoke cigarettes.”
Martin Dockrell, director of policy and research at Ash (Action on Smoking and Health), said: “Almost everybody knows that smoking can cause lung cancer.
“The chilling thing about this research is that it shows just how early the very first stages of that process begin – not in 30 years but within 30 minutes of a single cigarette for every subject in the study.
He added : “The process starts early but it is never too late to quit and the sooner you quit the sooner you start to reduce the harm.”