The study, which is published in the journal Tobacco Control, states that aldehydes, the chemicals released by smoking flavor chemicals, can cause mucosal irritation. The chemicals used to flavor e-cigarettes have been determined as safe for consumption by the FDA, but the new study suggests that the high chemical levels inhaled are more dangerous than when consumed.
"Chronic inhalation of these ingredients has not really been studied much at all," study author James F. Pankow, a professor of chemistry and civil & environmental engineering at Portland State University, told Time. Pankow said that an e-cigarette consumption rate of about 5 ml per day put smokers at twice the occupational limit for exposure.
"The point is that when e-cigarettes manufacturers talk about these things as being food grade or food-like, they are sort of suggesting that use of flavors is equivalent to using them in foods," Pankow told Time. "Never mind the fact that these things have not really been tested for safety, but in food FDA requires labeling ingredients. If they are going to say these are food-like, then why don't they list the ingredients? It's also not food-like product because you are inhaling it not ingesting."
The study concluded: "The concentrations of some flavour chemicals in e-cigarette fluids are sufficiently high for inhalation exposure by vaping to be of toxicological concern. Regulatory limits should be contemplated for levels of some of the more worrisome chemicals as well as for total flavour chemical levels. Ingredient labeling should also be required."