Smoking tobacco delivers cancer-causing carcinogens just as quickly as injecting the substance directly into the bloodstream, study results published recently in Chemical Research in Toxicology suggest.

The study, conducted by Stephen S. Hecht, PhD, and colleagues at the Masonic Cancer Center and the department of pharmacology at the University of Minnesota, both in Minneapolis, is the first to examine the mechanisms by which polycyclic aromatic hydrocarbons (PAH) — a harmful substance in tobacco smoke — cause DNA damage.

“PAH require metabolic activation to exert their carcinogenic effects […],” the researchers wrote. “However, no previously published studies have examined this critical pathway in humans specifically exposed to PAH by inhalation of cigarette smoke.”

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The researchers enrolled 12 volunteers, who smoked at least 10 cigarettes daily in the previous year, were in good health and were mentally stable, to smoke cigarettes spiked with [D10] phenanthrene, a noncarcinogenic substance representative of PAH.

Smokers were monitored with a topography apparatus to ensure that they inhaled approximately 10 µg [D10]Phe per cigarette. Blood samples were taken at baseline, and at regular intervals for 24 hours beginning 15 minutes after volunteers finished smoking.

The researchers then analyzed plasma to determine the presence of [D10]PheT — a diol epoxide that results when phenanthrene has been metabolized. They found that plasma samples contained maximal [D10]PheT levels at the earliest time points examined, just 15 to 30 minutes after volunteers finished smoking.

“These results demonstrate the formation of a PAH diol epoxide occurs rapidly in smokers,” the researchers wrote. “Because PAH diol epoxides are mutagenic and carcinogenic, the results clearly demonstrate immediate negative health consequences of smoking, which should serve as a major warning to anyone contemplating initiating tobacco use.”

In a separate study examining the relationship between routine hand gestures and tobacco use, researchers gained valuable insight into behavioral aspects of nicotine addiction.

“Our findings support prior studies that show smokers who exit a movie that had images of smoking are more likely to crave a cigarette, compared with ones who watched a movie without them,” Todd F. Heatherton, PhD, of Dartmouth College in Hanover, N.H., and colleagues, wrote in the Journal of Neuroscience.

Heatherton and colleagues used functional magnetic resonance imaging to measure brain activity among 17 right-handed smokers and 17 non-smokers while they watched the first 30 minutes of the movie “Matchstick Men.” The movie was chosen for it’s prominent smoking scenes, but lack of alcohol use, violence and sexual content. Participants were unaware of the study’s goals.

The researchers found that, compared with nonsmokers, smokers had robust neural activity in response to smoking cues in several areas of the brain involved in simulating contralateral hand-based gestures, and brain regions thought to be involved in drug-seeking behavior and tobacco craving.

“These results demonstrate that smokers spontaneously represent the action of smoking when viewing others smoke, the consequence of which may make it more difficult to abstain from smoking,” the researchers wrote.

Although the researchers acknowledged that additional studies are needed to determine whether brain activity stimulated by movie smoking can predict relapse for a smoker trying to quit, the CDC has been warning for years that exposure to on-screen smoking makes adolescents more likely to take up the habit. Even though tobacco use in films has decreased, about half of popular movies in 2009 still contained tobacco imagery, according to a 2010 agency report.