Are Flavorings in E-cigarettes Toxic?

“Flavorings toxic” is also an old rumor about e-cigarettes; compared to nicotine and heavy metals, it is more confusing. People usually claim that: although more than 8,000 kinds of known artificial flavors in the e-juice are up to food-grade standards, but that only means that they are only non-toxic when placed in food, atomized inhalation toxicity is not safe. These exaggerated claims about flavor atomization’s toxicity have been rampant in the past few years. The typical claim is that butanedione in e-cigarette flavor will lead to popcorn lungs.

What’s the truth?

In 2015, a study from Harvard University conducted research on e-liquids. The results showed that 75 percent of the flavored liquids they tested contained a chemical called butanedione (diacetyl), an artificial flavor with a buttery taste, which was thought to have caused eight popcorn factory workers to develop the rare lung disease “Bronchiolitis obliterans” back in 2000.

“Popcorn lung” is an irreversible obstructive lung disease caused by inflammation or fibrosis that narrows and obstructs the fine bronchi. The condition has many causes, including viral infections, transplant rejection, and exposure to toxic chemicals, including chlorine, ammonia, and ozone. The eight workers mentioned above are typical cases affected by a toxic environment. Due to their long-term exposure to high concentrations of butanedione gas, they developed this disease.

In response, Professor Konstantinos Farsalinos of the University of Patras, Greece, found 159 samples of vape juice, 74.2% of which contained butanedione. Under laboratory conditions, he measured in detail the amount of butanedione inhaled by a vapor in a day and found that the average was only 56 micrograms per day, far below the safety standards of the National Institute for Occupational Safety and Health (NIOSH) and was 100 times lower than the exposure from cigarettes.

Interestingly, although the butanedione content of cigarettes is much higher than e-cigarettes, no cases of popcorn lung have been found in smokers.

In addition to the famous “popcorn lung theory,” because the composition of flavors is so complex, many media have created other claims, such as the cytotoxicity of flavors exceeds that of cigarettes, and the substances in flavors can significantly damage lung and heart function. And a report on e-cigarettes released by the UK Department of Public Health in 2018 made a crack at each of these claims.

According to the report, many media claimed that cinnamon-flavored e-liquid has potent cytotoxicity and tobacco-flavored vape liquid has high levels of nitrosamines. Still, the toxic substances in this e-liquid are several orders of magnitude lower than those in cigarettes (orders of magnitude).

The report points out that many experiments to prove the cytotoxicity of flavors used not atomized vape liquid but directly exposed cells to toxic molecules in flavors; such experiments do not have practical significance because the proportion of flavors in e-juice accounted for only 10-15%, the concentration of toxic substances are different, their cytotoxicity will be a world of difference. However, the report found that even so, its toxicity is far lower than that of cigarettes.

Although the medical community does not provide the clear evidence of the size of the artificial flavoring toxicity in the electronic cigarette, out of scientific caution, some reports will point out that because of the complexity of the artificial flavoring composition, there is still a particular potential risk after the inhalation, of course, all this requires more experiments to explore the impact of its inhalation on the human body.