Pulegone, an oily compound previously banned as a food additive by the FDA due to possible carcinogenic properties, has been found in high levels in a number of mint- and menthol-flavored e-cigarette liquids. While the fundamental toxicity of pulegone is still debated by scientists, the new research raises concerns over the lack of human exposure studies, particularly in regards to exposure via inhalation.
The chemical is a naturally occurring compound found in several plants. It is perhaps most identifiable for its minty odor, and often found in aromatherapy essential oils or perfumes. Last year the FDA essentially banned pulegone as a food additive after animal toxicology studies suggested the chemical is potentially carcinogenic.
The new study examined a number of popular mint- or menthol-flavored e-cigarette liquids, finding they all contained high levels of pulegone. The researchers estimate these pulegone levels to result in exposure to humans at rates higher than previously identified as concerning for food additives or menthol cigarettes.
“The tobacco industry has long known about the dangers of pulegone and has continuously tried to minimize its levels in menthol cigarette flavorings, so the levels are much lower in menthol cigarettes than in electronic cigarettes,” says Sven-Eric Jordt, lead author on the new research. “Our analysis suggests that users of mint- and menthol-flavored e-cigarettes and smokeless tobacco are exposed to pulegone levels higher than the FDA considers acceptable for intake in food, and higher than in smokers of combustible menthol cigarettes.”
The research certainly shines a light on the unregulated nature of e-cigarette liquid flavors, a concern currently in focus following a number of vaping-related hospitalizations in the United States. However, there are a number of limitations to the current study that should temper the anxiety of any regular e-cigarette user.
The study referenced by the FDA in relation to its banning of pulegone as a food additive was actually inconclusive regarding the chemical’s carcinogenic properties for humans. Only in very high levels of exposure did the compound result in cancer in rats, and the research ultimately concluded pulegone “does not pose a public health concern” and, "is unlikely to induce urinary bladder cancer and liver neoplasms in humans."
A 2016 review of the toxicity of pulegone from the European Medicines Agency suggested the data is unclear in regards to human health concerns. While that review focused on dermal exposure, it did point out a distinct lack of research in regards to the effects of pulegone in humans.
All of this is not to say there is nothing to worry about. The ongoing outbreak of vaping-related illness has certainly revealed how little research has been conducted regarding the effect of vaporized oils on the lungs, so it is entirely unknown what effect, or even level of absorption, pulegone has when inhaled as e-cigarette vapor.
Nevertheless, Jordt and Duke University research partner Sairam V. Jabba suggest that if the FDA deems the chemical dangerous as a food additive, then it is reasonable to be concerned about its addition in e-cigarette liquids, particularly when the lungs are more sensitive to chemicals than the digestive tract.
“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,” says Jordt.
The new research has been published in the journal JAMA Internal Medicine.
Source: Duke Health