Mint-flavored vapes and the trouble with pulegone

By Dr. Liji Thomas, MDSep 18 2019

Even while the recent outbreak of acute serious lung disease in vapers is challenging the skill and technology of the medical field, a new report published in the journal JAMA Internal Medicine on September 16, 2019, says that a natural plant oil called pulegone, which is used to impart a minty flavor to e-cigarettes, could quite possibly be carcinogenic at the levels found in these devices.

In a study of several menthol cigarettes, smokeless tobacco varieties and e-cigarette mint/menthol flavorings, the researchers found high levels of pulegone in the last two categories, above the level accepted by the FDA as potentially causing cancer. This could result in mint-flavored e-cigarette users being exposed to pulegone levels up to a thousand times higher than ever seen before, either in food or in menthol cigarettes.

Image Credit: FOTOGRIN / Shutterstock

Pulegone is used in perfumes and in aromatherapy, besides vaping, because of its deep minty flavor. The tobacco industry has long since reduced the levels of pulegone in menthol cigarettes under consumer pressure after its potential dangers came to light. It has already been banned by the FDA as a food additive following animal tests which showed it might cause cancer. However, researchers are still divided as to its actual risk, because the study on which the FDA’s ban was based showed a risk of cancer only with very high levels of exposure. In fact, the researchers concluded that the risk of cancer in humans was unlikely and that pulegone was not a cause for public health concern.

The FDA ban on pulegone in food was largely the result of consumer group pressure. Other research on pulegone toxicity (or safety) is scanty. However, if it is not fit to be in food, it certainly shouldn’t be considered suitable for inhalation, particularly since the delicate cells of the lung alveoli and bronchioles are far more vulnerable to toxic chemicals than the gut cells. Yet there is no FDA regulation on its use in flavorings for smokeless tobacco or e-cigarettes.

Unregulated vaping chemicals

The real issue raised by the current study is the presence of many chemicals like pulegone in smokeless tobacco or e-cigarettes, which have not been tested for their safety following inhalation before being used as flavorings. The unregulated use of many such chemicals in e-cigarettes is a growing concern among researchers.

“The FDA regulatory regimen for food is much more strict than what is required for e-cigarettes,” comments researcher Sven-Eric Jordt. As a result, the margin of exposure (MOE) for the tobacco and e-cigarettes examined in the current study was well below the recommended level of 10,000, ranging from about 300 to 6,000 for pulegone-containing e-cigarette flavoring liquids and 550-1,600 for smokeless tobacco. The recommended MOE for food carcinogens is that level of the chemical that is 10,000 times below the highest dose that fails to induce cancer in animal studies, thus providing a large safety margin. In this context, the pulegone exposure levels in e-cigarette mint flavorings and smokeless tobaccos are so high as to leave horrifyingly narrow safety margins.

Playing with deadly chemicals

The loose regulation and lack of toxicity data makes it difficult to tell what caused the recent outbreak of disease related to vaping, though it seems to be associated with the inhalation of toxic vapors of volatile oils. Essentially, we don’t know a thing about what pulegone, and a lot of other volatile chemicals, do to lung cells when they are vaporized and inhaled. In addition, e-cigarettes themselves have been around for only ten years or so – far too short a time to assess their health risks in adults, let alone the adolescent users who are taking to it like bees to honey.

In this situation, it seems to be a given that the FDA should do something to mitigate the health risk until the safety of these chemicals in inhaled form has been proved. This is especially when millions of younger users are being drawn to e-cigarettes because of their sweet and fruity flavors. Not to mention that many non-smokers of regular cigarettes are taking to smoking after trying out the ‘safer’ vaping version – and many smokers trying to quit through vaping have instead simply added the latter to their repertoire.

The question on many lips is, how long will this go on before the authorities open their eyes to the very real dangers of vaping?

Jordt says, “Our findings suggest that the FDA should implement measures to mitigate pulegone-related health risks before suggesting mint- and menthol-flavored e-cigarettes and smokeless tobacco products as alternatives for people who use combustible tobacco products.”