Menthol-Flavored E-Cigarette Liquids Generate More Harmful Vapor Particles Leading to Decreased Lung Function
In a study recently published in the journal Respiratory Research, University of Pittsburgh researchers found that mint-flavored e-cigarette liquids generate more toxic vapor particles, leading to reduced lung functionality in users.
This conclusion was reached by using a custom-made robotic system that simulates human respiration and vaping habits. The investigation demonstrated that commercially available e-cigarette liquids with menthol commercially, produced an increased number of harmful microparticles in comparison to liquids without menthol.
The research was further corroborated by a subsequent examination of patient records from a group of e-cigarette users. Regardless of age, gender, race, history of smoking (pack-years), and use of nicotine or cannabis-infused vaping products, it was observed that those using menthol-based e-cigarettes exhibited shallower breaths and diminished lung function compared to their non-menthol counterparts.
Youth Appeal and Regulatory Challenges
“Many people, especially youth, erroneously assume that vaping is safe, but even nicotine-free vaping mixtures contain many compounds that can potentially damage the lungs,” said senior author Kambez H. Benam, D.Phil., associate professor in the Division of Pulmonary, Allergy, and Critical Care Medicine at the University of Pittsburgh School of Medicine. “Just because something is safe to consume as food does not mean that it’s safe to inhale.”
University of Pittsburgh scientists developed a vaping robot that mimics human breathing and can predict lung toxicity related to e-cigarettes. Credit: Nate Langer, UPMC and Pitt Health Sciences
To turn young people away from vaping and curb preventable deaths, the U.S. Food and Drug Administration continues to put pressure on cigarette manufacturers to eliminate menthol in combustible tobacco products, such as regular cigarettes and cigars. But the market for vaping products worldwide continues to expand, and mint and menthol flavors remain highly popular among the 2.5 million youth who reported smoking e-cigarettes in 2022.
Because traditional toxicity testing, which involves animals or living cells grown on a flat surface, can take weeks or months to produce high-quality and clinically relevant data, regulatory bodies are struggling to keep up and test products’ safety in a timely manner.
Traditional approaches have other limitations as well. Mice and rats, animals primarily used to test aerosolized products’ safety and biological impact, have very different anatomy of their nasal passages compared to humans, which prevents them from taking an active breath through the mouth akin to taking a cigarette puff. And cell systems used for toxicity testing are either directly exposed to e-liquid on contact or are blasted with continuous aerosols that don’t account for human breathing patterns.
To improve preclinical testing of how mixing vaping liquids and adding flavorings impact vapor composition and its health effects, researchers developed a biologically inspired “vaping robot.” By precisely mimicking the temperature, humidity, puff volume, and duration, this machine can simulate the pattern of healthy and diseased breathing and reliably predict lung toxicity related to e-cigarettes.
The system can measure the size and number of generated aerosolized particles and how those parameters vary depending on liquid composition. The aerosols’ effects can then be tested on engineered “lung-on-chip” devices and quickly yield high-quality data that can be used to infer potential toxicity.
A Hidden Risk Similar to Vitamin E Acetate
In their previous research, Benam and his team found that vitamin E acetate, a common additive in cannabinoid-containing e-cigarette liquids, generates more toxic small particles that can travel deep inside the lung and wedge themselves into the narrowest airways and lining of the walls of the trachea and bronchus.
While future large-scale clinical studies are needed, the new study suggests that menthol additives could be just as dangerous as vitamin E acetate, which was strongly linked to lung injury in users of e-cigarettes and vapes.
“The main message that we want to put out there is for people, especially young adults, who haven’t smoked before,” said Benam. “Switching to e-cigarettes may be a better, safer alternative for someone who is trying to quit smoking regular tobacco products. But it’s important to have full knowledge of e-cigarettes’ risks and benefits before trying them.”
Reference: “Electronic cigarette menthol flavoring is associated with increased inhaled micro and sub-micron particles and worse lung function in combustion cigarette smokers” by Divay Chandra, Rachel F. Bogdanoff, Russell P. Bowler and Kambez H. Benam, 11 April 2023, Respiratory Research.
DOI: 10.1186/s12931-023-02410-9
Other authors of the study are Divay Chandra, Ph.D., and Rachel Bogdanoff, Ph.D., both of Pitt; and Russell Bowler, Ph.D., of National Jewish Health, Denver.
The study was funded by the Division of Pulmonary, Allergy, and Critical Care Medicine at the University of Pittsburgh, the U.S. National Institutes of Health, and the U.S. Department of Defense Congressionally Directed Medical Research Programs Discovery Award.
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