Sitting before a mound of books, coffee cups and empty cigarette packs at the Purple Onion Cafe, Liz Chapman knows she should quit smoking.

“I have come to the conclusion that while in school, it’s not an option,” the public relations junior said. “It’s just my vice. And I like cigarettes with red wine.”

Chapman is one of the nearly 40 percent of people age 18 to 24 who smoke at least once in a while, according to a survey released yesterday by the Minnesota Department of Health, the Minnesota Partnership for Action Against Tobacco and other groups.

In addition, a University study published Wednesday in the Journal of the National Cancer Institute suggests smokers who cut back on the number of cigarettes they smoke might not reduce their intake of cancer-causing toxins or carcinogens.

For example, smokers who reduced their cigarette consumption 90 percent saw a 46 percent carcinogen drop, according to the study.

Stephen Hecht, a professor at the University’s Cancer Center, said the study suggests that when smokers smoke fewer cigarettes, they tend to smoke them differently.

The theory is that they inhale longer and more deeply, he said.

This method results in a carcinogen level that does not drop at the same rate as the number of cigarettes smoked.

Hecht said some people experienced greater drops in their carcinogen levels than others and that the next step will be to understand why these levels differ.

As she completed her French homework, Chapman said she understood why smokers would inhale differently when they were smoking less.

When she is not working, Chapman said, she smokes about one cigarette per hour. But during her break at her job, after four hours without one, she said, she inhales more deeply.

Patrick Gudjonsson, a self-described “senior-plus, plus” studying cultural studies and German literature, agreed with Chapman.

Going without a smoke definitely makes somebody smoke harder and faster, he said.

“I sometimes smoke two in the time it takes somebody to smoke one,” he added.

The University study involved 151 smokers who reduced the number of cigarettes they smoked per day every two weeks.

Researchers tested participants’ urine for byproducts of NNK, a carcinogen considered a major cause of lung cancer.

Hecht said the University study points out that quitting is the only sure way for smokers to reduce their risks of lung cancer.