Newswise — Adolescents who smoke e-cigarettes are exposed to significant levels of potentially cancer-causing chemicals also found in tobacco cigarettes, even when the e-cigarettes do not contain nicotine, according to a study by UC San Francisco researchers.

"Teenagers need to be warned that the vapor produced by e-cigarettes is not harmless water vapor, but actually contains some of the same toxic chemicals found in smoke from traditional cigarettes," said lead author Mark L. Rubinstein, MD, a professor of pediatrics at UCSF. "Teenagers should be inhaling air, not products with toxins in them."

For the study, published March 5, 2018 in Pediatrics, researchers analyzed urine from a group of adolescents with an average age of 16.4 years. Sixty-seven used e-cigarettes only and 17 used both e-cigarettes and traditional tobacco cigarettes. They were compared with a control group of 20 non-smoking teens.

Levels of toxic organic compounds were up to three times higher on average in the e-cigarette users compared with the controls. In teenagers who used both e-cigarettes and tobacco cigarettes, levels of toxic compounds were up to three times higher than in e-cigarette users only.

"E-cigarettes are marketed to adults who are trying to reduce or quit smoking as a safer alternative to cigarettes,” said Rubinstein. “While they may be beneficial to adults as a form of harm reduction, kids should not be using them at all."