Teenagers who smoke e-cigarettes are poisoning their bodies with the same chemicals present in traditional tobacco cigarettes, according to research released this week.

E-cigarettes, or vape pens, combine flavored fluid and nicotine to deliver a less harsh form of smoking. Research published this week in the journal Pediatrics finds that teens who only smoke tobacco-based cigarettes such as Marlboro and Camel brands have the highest levels of cancer-causing chemicals present in their bodies.

Those who only vape had higher levels of certain chemicals in their body than traditional smokers and nonsmokers, tied to the “flavoring” used in many vape products. The rising number of young Americans smoking e-cigarettes are at great risk for exposing themselves to these cancerous contaminants despite the products being marketed as healthier.