E-cigarettes sold as “clear” emerged in Massachusetts after the 2020 flavored tobacco ban, marketed as unflavored products. But chemical testing showed they contained synthetic additives, and a new study links their use to measurable cardiovascular effects.
The study enrolled 207 healthy young adults aged 18 to 45 years. Of these, 23 reported using “clear” e-cigarettes, 111 used non-“clear” flavored e-cigarettes, and 73 were nonusers. Participants underwent a structured 10-minute use session with their own e-cigarette device, while nonusers mimicked the protocol using a straw. Blood pressure and heart rate rose in all groups, but the rise was significantly greater among “clear” users, even after adjusting for age, sex, and combustible cigarette use. Compared with JUUL products, which did not contain synthetic cooling agents, “clear” devices continued to show stronger cardiovascular effects.
Chemical analysis of 19 “clear” disposable products purchased online confirmed synthetic cooling agents WS-23 and WS-3 in all samples, menthol in 18, and additional flavorants in 12. Nicotine concentrations ranged from 28 to 53 mg/g. “Clear” products had not been reported before the flavor ban, but afterward 21% of participants said they used them.
"The presence of synthetic cooling agents along with traditional flavorants in “clear” e‐cigarette products available in the Massachusetts marketplace undermines the efficacy of the flavor ban," said Erika T. Minetti, MS, of Boston University, and colleagues.
Limitations included the small number of “clear” users, variation in device design, and the fact that chemical analysis was performed only on “clear” products and JUUL samples — meaning some flavored products may also have contained synthetic coolants.
Researchers emphasized that while causality cannot be proven, the association between “clear” e-cigarettes and stronger cardiovascular responses warrants further investigation.
The study was funded by the National Institutes of Health, the U.S. Food and Drug Administration Center for Tobacco Products, and the American Heart Association. No relevant conflicts of interest were reported.