(CNN) - Remember the pungent chemical used in biology class that preserved the animal you dissected? According to a new study, that chemical is found in e-cigarettes. And researchers say more formaldehyde is found in e-cigs than in traditional cigarettes. The study published in the New England Journal of Medicine is preliminary. But it does add to growing fears of the popular vaporizers. Researchers say with that kind of exposure, long-term e-cig users could be up to 15 times more at risk for cancer than long-term cigarette smokers. E-cigarettes advocates say not so fast. Proponents say actual users would never smoke as much or as often as what researchers tested.