Stephen S. Hecht of the Masonic Cancer Center at the University of Minnesota and colleagues say evidence indicates harmful substances in tobacco smoke -- polycyclic aromatic hydrocarbons -- play a role in causing lung cancer but the study is the first to detail how PAHs in cigarette smoke cause DNA damage.
The scientists added a labeled PAH -- phenanthrene -- to cigarettes and tracked it in 12 volunteers who smoked the cigarettes. They found phenanthrene quickly forms a toxic substance in the blood known to trash DNA, causing mutations that can cause cancer.
The study, published in Chemical Research in Toxicology, found human smokers developed maximum levels of the substance in a time frame that surprised researchers -- 15-30 minutes after volunteers smoked.
Hecht and colleagues say the effect occurs so quickly it is equivalent to injecting the substance directly into the bloodstream.
"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," Hecht says in a statement."The results reported here should serve as a stark warning to those who are considering starting to smoke cigarettes."