Differences in “minty” flavor compound and synthetic cooling agent presence in US-marketed menthol-mint e-liquids and devices between 2019–2023

TL;DR

This study shows a shift from menthol to synthetic cooling agents in U.S. menthol/mint e-liquids from 2019 to 2023, especially in disposable devices.

Contribution

The study provides empirical evidence of changing chemical composition in menthol/mint e-liquids and highlights regulatory implications for TRPM8-activating compounds.

Findings

Menthol concentrations decreased from 15.6 mg/g in 2019 to 8.3 mg/g in 2023.

Synthetic cooling agents WS-23 and WS-3 became widespread in 2023, especially in disposable devices.

Label-based flavor categorization was unreliable due to overlapping flavorant profiles.

Abstract

Menthol and mint flavors consistently rank among the most popular flavor categories in electronic nicotine delivery systems (ENDS). While menthol/mint is often as a combined flavor category, different distinct “minty” flavors arise from a range of chemically distinct compounds to produce peppermint aroma (menthol, menthone, menthyl acetate, eucalyptol), spearmint aroma (L-carvone), and wintergreen aroma (methyl salicylate). In addition, the synthetic cooling agents WS-23 and WS-3 have gained popularity since 2019. This study analytically characterized menthol/mint ENDS products marketed in the United States in 2019 and 2023 for these compounds, alongside ancillary nicotine analysis.

A total of 104 refill e-liquids purchased from online vendors in 2019 and 63 products purchased from online vendors in 2023 (including refill e-liquids, disposable devices, and pod-based products) were analyzed. In 2019 samples, menthol was prevalent (87/104 products; mean content 15.6 mg/g), whereas synthetic cooling agent use was rare (WS-23: 1/104; WS-3: 11/104). 2023 products showed decreased menthol concentrations (mean 8.3 mg/g), while synthetic coolant use became much more widespread (WS-23: 43/63; WS-3: 23/63). Synthetic coolant use prevalence was largely driven largely by disposable devices, all of which contained WS-23 at higher concentrations (mean 28.7 mg/g). Mint-, peppermint-, and spearmint-labeled products frequently contained overlapping flavorant profiles in both test samples, indicating limited reliability of label-based flavor categorization. Nicotine content closely matched labels for pod-based products but deviated substantially for disposables.

Overall, results indicate a marked shift from menthol toward synthetic cooling agents in U.S. marketed ENDS products between 2019 and 2023, particularly in disposable products. This underscores the importance of analytical verification of menthol/mint ENDS products, but also suggests that regulatory efforts to limit the use of menthol due to its known cooling effect should not be limited to the compounds menthol, but should encompass all compounds that activate the relevant receptor TRPM8.

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