‘Clear’ e-cigarettes linked to greater acute rises in blood pressure and heart rate

Department of Chemical and Environmental Engineering, Yale University and Boston University Chobanian, Avedisian School of Medicine-led researchers report that e-cigarettes labeled “clear” produced greater acute increases in blood pressure and heart rate than non “clear” flavored products or nonuse, and that “clear” e-liquids contained synthetic cooling agents alongside menthol and other flavorants.

Flavored electronic cigarettes have a specific appeal to youth and young adults. Regulatory policies to restrict access to flavored e-cigarettes are part of a public policy strategy to reduce use among youth.

For example, Massachusetts enacted a statewide sales ban on all flavored tobacco products in June 2020 that prohibits any person, retailer, or manufacturer from selling, distributing, or offering flavored tobacco products or tobacco product flavor enhancers to any consumer in the commonwealth. Massachusetts law defines a characterizing flavor as a distinguishable taste or aroma other than tobacco, including menthol, mint, wintergreen, herb, or spice.

In a possible effort to circumvent the restrictions, the term “clear” has been introduced to e-cigarettes, a word which lacks a regulatory definition. The Centers for Disease Control and Prevention documented sales of disposable products identified as “clear/other cooling” in Massachusetts after the ban.

Clear products include synthetic cooling compounds. Synthetic coolants WS-3 and WS-23 activate the same TRPM8 cooling receptor as menthol yet lack a minty odor, showing up previously as “ice” marketed e-cigarettes which typically included flavoring.

In the study, “Cardiovascular Health Effects and Synthetic Cooling Agents in E-Cigarettes Labeled as ‘Clear’ Marketed in Massachusetts After the Tobacco Product Flavoring Ban,” published in the Journal of the American Heart Association, researchers evaluated acute hemodynamic impact and chemical composition.

Participants aged 18–45 years from the Boston, MA site of the CITU 2.0 study were assessed between April 2019 and May 2023, with “clear” users (N=23), non “clear” flavored users (N=111), and nonusers (N=73). All “clear” e-cigarettes used by CITU 2.0 participants were disposable devices.

Participants fasted from food and caffeine for eight hours and abstained from tobacco and exercise for six hours before visits were completed in the morning. Acute exposure used a structured session of one 3–4-second drag every 30 seconds over 10 minutes as tolerated. Nonusers participated by breathing through a straw.

Blood pressure and heart rate were measured in triplicate at baseline and 10 minutes after exposure using an Omron upper arm device.

Chemical analysis included 19 disposable devices labeled “clear” purchased online in April–May 2023 and analyzed at Yale University using gas chromatograph coupled with mass spectroscopy for characterization and gas chromatography with flame ionization detection for quantification, with JUUL pods purchased as a comparison.

Multivariable models adjusted for age, sex, intensity of combustible cigarette use, and number of puffs, with secondary analysis restricting non “clear” users to JUUL. All “clear” e-liquids contained WS-23 and/or WS-3, with WS-23 detected in 19/19 samples at 14–37 mg/g and WS-3 detected in 7/19 samples at 1.8–25 mg/g.

Menthol was detected in 18/19 “clear” devices at 0.5–9.2 mg/g, with other flavorants present in 12/19 including benzyl alcohol, carvone, γ-decalactone, γ-dodecalactone, ethyl maltol, eucalyptol, isopulegol, menthone, piperitone, isopropyl benzoate, vanillin, and vanillin PG acetal. JUUL “Menthol” contained menthol at 10 mg/g without synthetic coolants in samples tested.

Nicotine ranged from 28–53 mg/g in “clear” devices, with one nicotine-free product consistent with the label, and 48–54 mg/g in JUUL e-liquids. Deviations between label and measured nicotine content ranged from −35% to +5% in “clear” devices and −3% to +8% in JUUL.

Baseline blood pressure and heart rate measures were similar between “clear” and non “clear” flavored users and nonusers. Following exposure, “clear” e-cigarettes resulted in a greater increase in systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate compared with non “clear” flavored e-cigarette use and nonuse.

In multivariable models among e-cigarette users, increases in systolic and diastolic blood pressure and mean arterial pressure remained higher in “clear” users versus non “clear” flavored users, with borderline significance for heart rate, and sensitivity analysis restricting the comparator to JUUL showed similar directions.

Authors conclude that 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, and that the potential for more pronounced effects necessitates further study.

There is a clear public interest in monitoring new products and chemical usages and in considering synthetic coolants in regulation to maximize the impact of flavor bans and protect adolescents and young adults.

© 2025 Science X Network

Department of Chemical and Environmental Engineering, Yale University and Boston University Chobanian, Avedisian School of Medicine-led researchers report that e-cigarettes labeled “clear” produced greater acute increases in blood pressure and heart rate than non “clear” flavored products or nonuse, and that “clear” e-liquids contained synthetic cooling agents alongside menthol and other flavorants.

Flavored electronic cigarettes have a specific appeal to youth and young adults. Regulatory policies to restrict access to flavored e-cigarettes are part of a public policy strategy to reduce use among youth.

For example, Massachusetts enacted a statewide sales ban on all flavored tobacco products in June 2020 that prohibits any person, retailer, or manufacturer from selling, distributing, or offering flavored tobacco products or tobacco product flavor enhancers to any consumer in the commonwealth. Massachusetts law defines a characterizing flavor as a distinguishable taste or aroma other than tobacco, including menthol, mint, wintergreen, herb, or spice.

In a possible effort to circumvent the restrictions, the term “clear” has been introduced to e-cigarettes, a word which lacks a regulatory definition. The Centers for Disease Control and Prevention documented sales of disposable products identified as “clear/other cooling” in Massachusetts after the ban.

Clear products include synthetic cooling compounds. Synthetic coolants WS-3 and WS-23 activate the same TRPM8 cooling receptor as menthol yet lack a minty odor, showing up previously as “ice” marketed e-cigarettes which typically included flavoring.

In the study, “Cardiovascular Health Effects and Synthetic Cooling Agents in E-Cigarettes Labeled as ‘Clear’ Marketed in Massachusetts After the Tobacco Product Flavoring Ban,” published in the Journal of the American Heart Association, researchers evaluated acute hemodynamic impact and chemical composition.

Participants aged 18–45 years from the Boston, MA site of the CITU 2.0 study were assessed between April 2019 and May 2023, with “clear” users (N=23), non “clear” flavored users (N=111), and nonusers (N=73). All “clear” e-cigarettes used by CITU 2.0 participants were disposable devices.

Participants fasted from food and caffeine for eight hours and abstained from tobacco and exercise for six hours before visits were completed in the morning. Acute exposure used a structured session of one 3–4-second drag every 30 seconds over 10 minutes as tolerated. Nonusers participated by breathing through a straw.

Blood pressure and heart rate were measured in triplicate at baseline and 10 minutes after exposure using an Omron upper arm device.

Chemical analysis included 19 disposable devices labeled “clear” purchased online in April–May 2023 and analyzed at Yale University using gas chromatograph coupled with mass spectroscopy for characterization and gas chromatography with flame ionization detection for quantification, with JUUL pods purchased as a comparison.

Multivariable models adjusted for age, sex, intensity of combustible cigarette use, and number of puffs, with secondary analysis restricting non “clear” users to JUUL. All “clear” e-liquids contained WS-23 and/or WS-3, with WS-23 detected in 19/19 samples at 14–37 mg/g and WS-3 detected in 7/19 samples at 1.8–25 mg/g.

Menthol was detected in 18/19 “clear” devices at 0.5–9.2 mg/g, with other flavorants present in 12/19 including benzyl alcohol, carvone, γ-decalactone, γ-dodecalactone, ethyl maltol, eucalyptol, isopulegol, menthone, piperitone, isopropyl benzoate, vanillin, and vanillin PG acetal. JUUL “Menthol” contained menthol at 10 mg/g without synthetic coolants in samples tested.

Nicotine ranged from 28–53 mg/g in “clear” devices, with one nicotine-free product consistent with the label, and 48–54 mg/g in JUUL e-liquids. Deviations between label and measured nicotine content ranged from −35% to +5% in “clear” devices and −3% to +8% in JUUL.

Baseline blood pressure and heart rate measures were similar between “clear” and non “clear” flavored users and nonusers. Following exposure, “clear” e-cigarettes resulted in a greater increase in systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate compared with non “clear” flavored e-cigarette use and nonuse.

In multivariable models among e-cigarette users, increases in systolic and diastolic blood pressure and mean arterial pressure remained higher in “clear” users versus non “clear” flavored users, with borderline significance for heart rate, and sensitivity analysis restricting the comparator to JUUL showed similar directions.

Authors conclude that 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, and that the potential for more pronounced effects necessitates further study.

There is a clear public interest in monitoring new products and chemical usages and in considering synthetic coolants in regulation to maximize the impact of flavor bans and protect adolescents and young adults.

© 2025 Science X Network