Just half an hour after smoking a cigarette, genetic damage has been done, according to a new study.

Researchers found that our bodies can metabolize harmful substances in cigarettes, called polycyclic aromatic hydrocarbons (PAHs), in just 15 minutes. The resulting molecules can cause DNA damage and even cancer, said study researcher Stephen S. Hecht, of the University of Minnesota.

This DNA damage can become cancer-causing gene mutations. And "once [gene mutations are] there, they're there for good," Hecht told MyHealthNewsDaily.

The study shows just how quickly cigarettes can impact the DNA in a person's body, he said.

The study was published Jan. 15 in the journal Chemical Research in Toxicology.

From inhalation to DNA damage

Scientists gave participants cigarettes specially made to contain noncancerous PAHs called phenanthrenes. They then tracked how fast the chemicals would metabolize in the bodies of 12 smokers.

They found that the phenanthrenes were completely metabolized in as little as 15 minutes, sometimes taking 30 minutes. This same amount of time would have been expected had the chemicals been injected directly into the bloodstream, the researchers said.

However, each person in the study had a different amount of metabolized PAH molecules in their blood after smoking the cigarette. That means there are differences in the ways metabolize down PAH, researchers said.

When PAHs are metabolized, the resulting molecules are markers of how quickly genetic damage could be occurring in lung cells, said David Orren, associate professor of toxicology at the University of Kentucky, who was not involved in the study.

"It's not a direct measure of genetic damage, but an indication that there can be genetic damage in the DNA in the lung even faster" than the first 15 minutes of smoking , Orren told MyHealthNewsDaily.

Why some smokers get cancer but others don't

Researchers have long measured the metabolism of cigarette compounds in smoking studies. But in previous studies, the participants were either all smokers with constantly high levels of byproducts in their blood, or nonsmokers with constantly low levels of the byproducts in their blood, the researchers said. It was also impossible to differentiate the metabolism of toxins from the environment or food in the body from those of cigarettes.

"There was no way to say when the [metabolism of the compounds] occurred," Orren said.

But in the new study, because researchers created special cigarettes with phenanthrene, they could use it as a marker.

Differences in the way our bodies metabolize PAHs could also help to explain why some smokers develop cancer , while others don't, Orren said.

With more research, phenanthrenes could be used to determine cancer risk in smokers, Hecht said.

"Our goal is to use a phenanthrene as a probe to see which smokers have the greatest chance of getting cancer when they smoke" by looking at the levels of broken-down phenanthrene in their bodies, Hecht said. "We would try to convince those people in particular not to smoke ."

More research is needed, however, to determine just how much of the metabolized PAHs are needed to actually cause cancer , Hecht said.

Pass it on: Our bodies can metabolize harmful substances in cigarettes in just 15 minutes and dump the resulting molecules of those substances in our bloodstream. The molecules can cause DNA damage and even cancer.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @AmandaLChan.