A group of toxic chemicals in tobacco smoke causes damage to the genetic material of human cells within minutes after lighting up the first cigarette.
The harmful substances called polycyclic aromatic hydrocarbons (PAHs) cause DNA damage and quickly raise the short-term risk for cancer, according to a study published in Chemical Research in Toxicology.
During their small study, the researchers labeled some PAH molecules which are normally present in tobacco to track them in the body of 12 smokers.
They found that PAHs quickly change to a toxic substance which damages DNA just within 15 and 30 minutes, causing mutations that can cause cancer.
According to researchers, the effect is so rapid that it is equivalent to injecting the toxic chemical directly into the bloodstream.
"These results are significant because PAH diol epoxides react readily with DNA, induce mutations, and are considered to be ultimate carcinogens of multiple PAH in cigarette smoke," the study said.
"The results reported here should serve as a stark warning to those who are considering starting to smoke cigarettes," said lead researcher Stephen S. Hecht, from the University of Minnesota.
Lung cancer kills about 3,000 people globally each day and 90 percent of the toll is related to tobacco smoking.
Although the study has revealed the rapid onset of harmful effects of smoking, experts suggest that the benefits of quitting the habit also begin quickly as well.