Trigeminal Receptor Study of High-Intensity Cooling Agents

Coolants, organic acids, flavourings and other additives that facilitate inhalation of tobacco and nicotine products: implications for regulation

To inform regulatory policy, this article summarises findings on inhalation facilitation from the ninth report of the WHO Study Group on Tobacco Product Regulation. Some additives counteract the harshness and bitterness of tobacco and nicotine product aerosols, making them easier to inhale. Additives that promote inhalability may perpetuate and increase the use of inhaled tobacco and nicotine products, especially by young people. Thus, as a class, additives that facilitate inhalation are an important regulatory target to prevent tobacco and nicotine product uptake. We defined inhalation facilitation as modifications to products during manufacturing that enhance the sensory experience and (potentially) behaviours associated with inhalation (eg, deeper puffs, faster inhalation, larger puff volume, shorter intervals in between puffs and use episodes). Evidence review showed that: (a) menthol and synthetic coolants decrease irritation caused by aerosol constituents by activating sensory perception receptors (eg, cooling receptors) and may promote dependence in inexperienced users; (b) acid additives and sugars, which lower the pH of aerosols and shift nicotine from free-base to protonated salt forms, reduce harshness and increase blood nicotine yield; (c) e-cigarette flavourings perceived as sweet or fruity reduce subjective bitterness, increase attractiveness and may escalate use, although their effects on perceived harshness are inconclusive; (d) sugars in tobacco impart sweet sensations, but limited industry-independent data preclude strong conclusions for sugars' roles in inhalation facilitation. Given these findings, WHO policy recommendations suggest that regulators might consider banning ingredients that facilitate inhalation in all commercial inhaled tobacco and nicotine products.

Effects of 'Ice' flavoured e-cigarettes with synthetic cooling agent WS-23 or menthol on user-reported appeal and sensory attributes

BACKGROUND

This clinical experiment tested the effects of exposure to e-cigarettes with WS-23 or menthol cooling additives on user appeal and sensory attributes, and, secondarily, whether WS-23 effects generalised across base characterising flavour, nicotine concentration, or nicotine/tobacco product use status.

METHODS

In this within-participant double-blind experiment, adult tobacco/nicotine users administered standardised puffs of 18 different e-cigarette solutions in randomised sequences using a pod-style device. Each of three base characterising e-cigarette flavour solutions ('bold tobacco', 'mango,' 'wintergreen') in both 2% and 4% concentrations of nicotine benzoate salt were manipulated by adding either: (1) Menthol (0.5%), (2) WS-23 (0.75%) or (3) No cooling agent. After each administration, participants rated 3 appeal and 5 sensory attributes (0-100 scales).

RESULTS

Participants (n=84; M(SD)=38.6 (13.6) years old) were either exclusive e-cigarette (25.0%), cigarette (36.9%) or dual (38.1%) users. WS-23 versus no coolant products produced higher liking, willingness to use again, smoothness, and coolness and lower disliking, bitterness, and harshness ratings (|B|difference range: 4.8 to 20.1; ps<0.005). Menthol (vs no coolant) increased willingness to use again and reduced harshness and coolness (ps<0.05). Flavours with WS-23 (vs menthol) were rated as smoother, cooler and less harsh (ps<0.05). Coolant effects did not differ by base flavour, nicotine concentration, or tobacco use status.

CONCLUSIONS

Adding synthetic coolant WS-23 to e-cigarettes appears to make the vaping user experience more appealing, regardless of characterising base flavour. Regulatory agencies should be aware that the manufacturing process of adding synthetic coolants may increase the attractiveness of various e-cigarette products.Cite Now.

Ice flavours and non-menthol synthetic cooling agents in e-cigarette products: a review

E-cigarettes with cooling flavours have diversified in ways that complicate tobacco control with the emergence of: (1) Ice-hybrid flavours (eg, 'Raspberry Ice') that combine cooling and fruity/sweet properties; and (2) Products containing non-menthol synthetic cooling agents (eg, Wilkinson Sword (WS), WS-3, WS-23 (termed 'koolada')). This paper reviews the background, chemistry, toxicology, marketing, user perceptions, use prevalence and policy implications of e-cigarette products with ice-hybrid flavours or non-menthol coolants. Scientific literature search supplemented with industry-generated and user-generated information found: (a) The tobacco industry has developed products containing synthetic coolants since 1974, (b) WS-3 and WS-23 are detected in mass-manufactured e-cigarettes (eg, PuffBar); (c) While safe for limited oral ingestion, inhalational toxicology and health effects from daily synthetic coolant exposure are unknown and merit scientific inquiry and attention from regulatory agencies; (d) Ice-hybrid flavours are marketed with themes incorporating fruitiness and/or coolness (eg, snow-covered raspberries); (e) WS-23/WS-3 concentrates also are sold as do-it-yourself additives, (f) Pharmacology research and user-generated and industry-generated information provide a premise to hypothesise that e-cigarette products with ice flavours or non-menthol cooling agents generate pleasant cooling sensations that mask nicotine's harshness while lacking certain aversive features of menthol-only products, (g) Adolescent and young adult use of e-cigarettes with ice-hybrid or other cooling flavours may be common and cross-sectionally associated with more frequent vaping and nicotine dependence in convenience samples. Evidence gaps in the epidemiology, toxicology, health effects and smoking cessation-promoting potential of using these products exist. E-cigarettes with ice flavours or synthetic coolants merit scientific and regulatory attention.

Detection of the Synthetic Coolant Menthone 1,2-Glycerol Ketal in an e-Liquid and in Electronic Waterpipe Aerosols Therefrom

The presence and toxicological risks of synthetic coolants in electronic nicotine delivery systems (ENDS) have not been thoroughly studied. We identified the synthetic coolant menthone 1,2-glycerol ketal (MGK) in a menthol-flavored e-liquid at a concentration of ∼170 μg/mL. We also detected MGK in aerosols resulting from heating the e-liquid with an electronic waterpipe. MGK was initially detected in the e-liquid by two-dimensional gas chromatography-time-of-flight mass spectrometry. To avoid potential analytical artifacts that could result from heating samples in the injection port of the gas chromatograph, quantitation of MGK in the e-liquid was accomplished using a liquid chromatography-tandem mass spectrometry method. Following recent reports identifying other synthetic coolants in e-liquids, these results add knowledge about inhalation exposures from ENDS use and suggest the importance of future research to study the potential inhalation toxicity related to the use of MGK-containing e-liquids in ENDS devices. Furthermore, the results demonstrate the ability to quantify ketals in e-liquids using liquid chromatography methods.

Still 'Cool': tobacco industry responds to state-wide menthol ban with synthetic coolants

INTRODUCTION

In December 2022, California (CA) enforced a voter-approved regulation restricting the retail sale of flavoured tobacco products, including menthol cigarettes. Shortly after, new products emerged on the market containing similar blue and green package colours yet with 'non-menthol' descriptors. Using chemical analyses, we measured the content of menthol and 15 other cooling chemicals in Californian cigarettes with 'non-menthol' descriptors and compared concentrations to similar 'menthol'-labelled counterparts available in New York State (NY).

METHODS

A convenience sample of 10 brands and types of cigarettes in CA were purchased based on package colours suggesting a cooling effect and/or 'non-menthol' descriptors. The exact brand and type of cigarettes (with menthol descriptors) were purchased in NY. Cigarettes from CA were compared with equivalent cigarettes from NY on package design and colours, cigarette physical characteristics and the presence of cooling additives.

RESULTS

Menthol was not detected in any CA cigarette, except for Maverick-green box type, while its presence was confirmed in most NY counterpart products. A synthetic cooling chemical WS-3 was not detected in any NY cigarettes but was detected in four CA brands and types with implied cooling effect, ranging from 1.24±0.04 to 1.97±0.05 mg/cigarette.

CONCLUSION

While manufacturers have removed menthol descriptors from CA packaging and the menthol ingredient from cigarettes, synthetic cooling chemicals detected in several CA brands suggest that cooling sensory effects may still be sustained. Policymakers must consider both the chemical ingredients themselves and sensory effects in future regulatory approaches.

Disposable Puff Bar Electronic Cigarettes: Chemical Composition and Toxicity of E-liquids and a Synthetic Coolant

The popularity of disposable fourth-generation electronic cigarettes (ECs) among young adults and adolescents has been increasing since the ban on flavored cartridge EC products such as JUUL. Although the constituents and toxicity of some cartridge-based fourth-generation ECs, such as JUUL, have been studied, limited data exist for other disposable ECs such as Puff. The purpose of this study was to determine flavor chemicals, synthetic coolants, and nicotine concentrations in 16 disposable Puff devices, evaluate the cytotoxicity of the different flavors from the Puff brand using in vitro assays, and investigate the health risks of synthetic coolants in EC products. Gas chromatography/mass spectrometry was used to identify and quantify chemicals in Puff EC fluids. One hundred and twenty-six flavor chemicals were identified in Puff fluids, and 16 were >1 mg/mL. WS-23 (2-isopropyl-N,2,3-trimethylbutyramide) was present in all products, and concentrations ranged from 0.8 to 45.1 mg/mL. WS-3 (N-ethyl-p-menthane-3-carboxamide) concentrations ranged from 1.5 to 16.4 mg/mL in 6/16 products. Nicotine concentrations ranged from 40.6 to 52.4 (average 44.8 mg/mL). All unvaped fluids were cytotoxic at dilutions between 0.1 and 10% in the MTT and neutral red uptake assays when tested with BEAS-2B lung epithelial cells. The cytotoxicity of Puff fluids was highly correlated with total chemical concentrations, nicotine, WS-23, both synthetic coolants, and synthetic coolants plus ethyl maltol. Lower concentrations of WS-23 than those in the fluids adversely affected cell growth and morphology. Concentrations of synthetic coolants exceeded levels used in consumer products. The margin of exposure data showed that WS-3 and WS-23 concentrations were high enough in Puff products to present a health hazard. Our study demonstrates that disposable Puff ECs have high levels of cytotoxic chemicals. The data support the regulation of flavor chemicals and synthetic coolants in ECs to limit potentially harmful health effects.

Synthetic Cooling Agents in US-marketed E-cigarette Refill Liquids and Popular Disposable E-cigarettes: Chemical Analysis and Risk Assessment

INTRODUCTION

Menthol, through its cooling and pleasant sensory effects, facilitates smoking and tobacco product initiation, resulting in the high popularity of mint/menthol-flavored E-cigarettes. More recently, E-cigarette vendors started marketing synthetic cooling agents as additives that impart a cooling effect but lack a characteristic minty odor. Knowledge about content of synthetic coolants in US-marketed E-cigarette products and associated health risks is limited.

AIMS AND METHODS

E-liquid vendor sites were searched with the terms "koolada", "kool/cool", "ice", or WS-3/WS-23, denoting individual cooling agents, and relevant refill E-liquids were purchased. "Ice" flavor varieties of Puffbar, the most popular disposable E-cigarette brand, were compared with non-"Ice" varieties. E-liquids were characterized, and synthetic coolants quantified using GC/MS. Margin of exposure (MOE), a risk assessment parameter, was calculated to assess the risk associated with synthetic coolant exposure from E-cigarette use.

RESULTS

WS-3 was detected in 24/25 refill E-liquids analyzed. All Puffbar flavor varieties contained either WS-23 (13/14) or WS-3 (5/14), in both "Ice"- and non-"Ice" flavors. Modeling consumption of WS-3 from vaped E-liquids, resulted in MOEs below the safe margin of 100 for most daily use scenarios. MOEs for WS-23 were <100 for 10/13 Puffbar flavors in all use scenarios. Puffbar power specifications are identical to Juul devices.

CONCLUSIONS

Synthetic cooling agents (WS-3/WS-23) were present in US-marketed E-cigarettes, at levels that may result in consumer exposures exceeding safety thresholds set by regulatory agencies. Synthetic coolants are not only found in mint- or menthol-flavored products but also in fruit- and candy-flavored products, including popular disposable E-cigarette products such as Puffbar.

IMPLICATIONS

Synthetic cooling agents are widely used in "kool/cool"- and "ice"-flavored E-liquids and in E-liquids without these labels, both as a potential replacement for menthol or to add cooling "notes" to nonmenthol flavors. These agents may be used to bypass current and future regulatory limits on menthol content in tobacco products, and not just E-cigarettes. Because synthetic cooling agents are odorless, they may not fall under the category of "characterizing flavor", potentially circumventing regulatory measures based on this concept. Regulators need to consider the additional health risks associated with exposure to synthetic cooling agents.