College kids everywhere take note: the myth that your post-class standby is safe just went up in smoke.

While it may come as a surprise to some, smoking hookah, a water-based tobacco pipe, is no safer than smoking a cigarette. As the CDC points out, an hour-long hookah session produces about 100 to 200 times more smoke-filled air by volume than a single cigarette.

Researchers from the University of California at San Francisco (UCSF) have confirmed in a crossover study of 13 smokers who use both cigarettes and hookahs that a water pipe isn’t necessarily safer than a cigarette. Contrary to popular belief (and the dreams of lounging college students), a water pipe doesn’t remove all the harmful substances from smoke. While hookah smokers don’t consume as much nicotine, they have an increased exposure to carbon monoxide (CO) and the carcinogen benzene.

“The most surprising thing was the finding of an usually high benzene exposure [from smoking hookah] that had not previously been reported,” said study author Neal Benowitz, M.D., professor of medicine at UCSF, in an interview with Healthline.

The increase in benzene exposure from the cocktail of tobacco and additives smoked through a water pipe is particularly worrisome. Exposure to high levels of benzene increases a person’s risk of developing leukemia.

And while a decrease in nicotine consumption is technically a benefit of hookah, the chemical is not altogether missing, meaning that it’s possible to sustain a nicotine addiction by smoking a water pipe.

Though the International Agency for Research on Cancer (IARC) estimates that 100 million people worldwide smoke tobacco from water pipes, outside of Arab-American communities, a water pipe, of which a hookah is just one variety, might sound a bit strange. Water, smoke, and smoldering charcoal?

A water pipe is actually a relatively simple contraption. A bowl of wet tobacco, often mixed with some sort of flavoring, sits atop a chamber of water with connecting hoses and mouthpieces. Burning coals are placed on top of the tobacco bowl, aerosolizing the tobacco components, which are then sucked through the hose, passing across water that cools the smoke and removes some harsh irritants.

A common misconception is that a water pipe is safe because the water acts as a filter, but it’s a bit more complicated than that, says Benowitz. While hookah tobacco typically contains only five to 10 percent crude tobacco mixed with other substances like honey, fermented sugar, and molasses, researchers from the University of Jordan report that water pipe smokers are exposed to CO levels twice that of cigarette smokers. This could potentially strain the heart and lungs of someone with existing cardiovascular disease or risk factors like high blood pressure.

“People believe that a water pipe is filtering out carcinogens and toxins, but that’s a misconception,” Benowitz said. In fact, because inhalation happens so fast, the toxins simply move through the water and remain relatively intact. “What you’re smoking is different than what you’re smoking in a cigarette, and while you’re smoking tobacco and dried fruit, you’re also smoking a charcoal briquette,” Benowitz said.

While most people in the U.S. only occasionally smoke hookah, this study demonstrates that regular hookah smoking, or hookah smoking combined with cigarette smoking, isn’t any better for your health than regular cigarette consumption. “It’s not a benign substitute,” Benowitz said.

While this study was small, involving just 13 people, the participants came from a range of ethnic backgrounds and were representative of a young, diverse population. With an average age of 24 and an average body mass index of 26, participants were relatively young and in good health. On average, participants smoked 10 cigarettes per day and engaged in three water pipe sessions per week, ranging from 45 minutes to one hour in length.

A water pipe may give the impression of purifying smoke before inhalation, but that’s simply a pipe dream perpetuated by tobacco manufacturers.

Sure, hookah smoke contains different carcinogens than cigarette smoke, but trading one set of chemicals and additives for the other isn’t advisable, especially for children and teens.