A new study has found that e-cigarettes labeled as “clear” may cause a greater increase in blood pressure and heart rate than other flavored e-cigarettes or no use at all.
The research was led by scientists from Yale University and Boston University’s Chobanian & Avedisian School of Medicine, and published in the Journal of the American Heart Association.
E-cigarettes with appealing flavors have become popular with young people. To reduce their use, some states like Massachusetts have banned the sale of flavored tobacco products. However, companies may be finding ways around the rules by using vague terms like “clear” that aren’t clearly defined in regulations.
“Clear” e-cigarettes may look unflavored, but researchers discovered that they contain synthetic cooling agents, menthol, and other flavoring chemicals. These ingredients are similar to those used in products marketed as “ice” flavors.
The synthetic compounds, known as WS-3 and WS-23, make the e-cigarette vapor feel cool without giving off a strong mint smell. That makes them harder to detect under flavor bans.
To understand how “clear” e-cigarettes affect the body, researchers studied 207 people aged 18 to 45 in Boston between 2019 and 2023.
The group included 23 people who used “clear” e-cigarettes, 111 who used other flavored e-cigarettes, and 73 nonusers. Participants avoided food, caffeine, and tobacco before the study and took one puff every 30 seconds over 10 minutes in a controlled setting.
The study showed that “clear” e-cigarette users experienced a greater rise in blood pressure and heart rate after vaping compared to the other groups. These effects were measured 10 minutes after the vaping session.
Even when the researchers adjusted for factors like age, sex, and smoking history, the increase in blood pressure remained more noticeable in the “clear” group.
To understand why this happened, scientists bought 19 “clear” disposable e-cigarettes online and analyzed their ingredients using advanced lab equipment at Yale. All 19 products contained WS-23 and/or WS-3, with menthol also present in most samples. Other flavoring chemicals included substances often found in candies, mints, and perfumes.
Nicotine levels in “clear” e-cigarettes ranged from 28 to 53 mg/g. One product was nicotine-free as labeled, but some had large differences between labeled and measured nicotine content. For comparison, JUUL menthol pods had similar nicotine levels but didn’t contain synthetic cooling agents.
The study concludes that the use of synthetic cooling agents in “clear” e-cigarettes may make them feel smooth while still delivering strong doses of nicotine and chemicals. These agents might be helping companies get around laws meant to ban flavored products.
Because of their greater impact on heart and blood pressure and their ability to avoid flavor bans, the researchers say it’s important to monitor products labeled as “clear” and include synthetic coolants in future regulations. Doing so could better protect young people from health risks and make current flavor bans more effective.
The study is published in the Journal of the American Heart Association.
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