Bottles of e-liquids at a California vape shop. Photo : Justin Sullivan ( Getty Images )

The growing appeal of e-cigarettes, particularly among teens, has often been attributed to the assortment of sweet and fruity flavored vaping fluids—flavors that traditional tobacco cigarettes have long been barred from including. But in addition to making vaping more appealing, these flavoring chemicals may be harmful to health in their own right, according to a new study.


The researchers, led by Sven-Eric Jordt, an anesthesiologist, pharmacologist, and cancer biologist at Duke University, were inspired by earlier studies that showed vaping can leave behind carcinogenic or otherwise damaging chemicals like formaldehyde in your lungs and airways. Vaping manufacturers and advocates have argued these experiments were flawed because they relied on heating up the e-liquid to unrealistic temperatures and causing chemical reactions that wouldn’t be seen while vaping normally. So Jordt and his team tested the chemical makeup of flavored e-liquids before and after they were aerosolized by a first generation e-cigarette.

The flavor additives in e-liquids tend to be chemicals known as aldehydes, such as cinnamaldehyde, which adds a burst of cinnamon. While aldehydes are considered safe to ingest or touch, some research has shown they can irritate our body’s cells when inhaled through vaping. But in vaping fluid, these chemicals are also mixed with an alcohol solvent. And when Jordt’s team looked at flavored e-liquids, they found that this mix created other chemicals known as acetals, long before anyone sparked up the e-cigarette.


“E-cigarette vendors often state that e-cigarettes are inherently more safe since they contain only a few ingredients, flavors, nicotine, and a solvent, compared to traditional cigarettes that produce smoke with 1,000s of chemicals in it,” Jordt told Gizmodo via email. “We found that the e-liquids vaporized by e-cigarettes are in fact chemically unstable and that, after the mixing of components, the flavor chemicals are changed into new chemicals (the acetals) with unknown toxic effects.”



Subsequent experiments of theirs showed that these acetals could linger in the aerosolized vapor that users would breathe in. And in a petri dish at least, the acetals affected human cells even more than the aldehydes did.

“We found that these chemicals activate irritant receptors that trigger cough and inflammation in the airways,” Jordt explained. “This happened in cherry-, vanilla-, and cinnamon-flavored liquids, so we expect this to be a common phenomenon in most flavored e-liquids.”

The team’s findings were published in Nicotine & Tobacco Research.

Like many other studies involving vaping—which has only been popular for less than a decade—it’s difficult to say how these exposures would affect actual users over a long time. And Jordt is careful to call for longer-term research. But more evidence is starting to accumulate that vaping, even if it is ultimately safer than tobacco smoking, isn’t as free of risk as advocates often claim. Other research has thrown into question the notion that vaping will help traditional tobacco smokers ease themselves off the habit, another common talking point.


The Food and Drug Administration has recently taken a much harsher stance towards e-cigarette products, particularly flavored e-liquids. The agency has gone as far as floating the possibility of outright banning flavoring chemicals. That’s an approach Jordt and his team support completely.

“The new e-cigarette devices are much more addictive than old models, making it harder to quit, so users will be exposed to flavor chemicals and their modifications for much longer,” he noted. “Immediate regulation of flavors that target youth—especially the berry and candy flavors—should be FDA’s primary goal, and banning flavors that are clearly toxic (cinnamon flavors, for example).”


Jordt and his team hope to study the effects of these chemicals more closely in animal models, provided they can get more funding and resource support.

“Eventually, long-term studies investigating lung health in users will provide clarity. However, the e-cigarette market is undergoing rapid changes and users often switch from one product to another, making controlled studies very difficult to do,” he said.


[Nicotine & Tobacco Research]