Correlation of volatile carbonyl yields emitted by e-cigarettes with the temperature of the heating coil and the perceived sensorial quality of the generated vapours

Abstract

E-liquids generally contain four main components: nicotine, flavours, water and carrier liquids. The carrier liquid dissolves flavours and nicotine and vaporises at a certain temperature on the atomizer of the e-cigarette. Propylene glycol and glycerol, the principal carriers used in e-liquids, undergo decomposition in contact with the atomizer heating-coil forming volatile carbonyls. Some of these, such as formaldehyde, acetaldehyde and acrolein, are of concern due to their adverse impact on human health when inhaled at sufficient concentrations. The aim of this study was to correlate the yield of volatile carbonyls emitted by e-cigarettes with the temperature of the heating coil. For this purpose, a popular commercial e-liquid was machine-vaped on a third generation e-cigarette which allowed the variation of the output wattage (5-25W) and therefore the heat generated on the atomizer heating-coil. The temperature of the heating-coil was determined by infrared thermography and the vapour generated at each temperature underwent subjective sensorial quality evaluation by an experienced vaper. A steep increase in the generated carbonyls was observed when applying a battery-output of at least 15W corresponding to 200-250°C on the heating coil. However, when considering concentrations in each inhaled puff, the short-term indoor air guideline value for formaldehyde was already exceeded at the lowest wattage of 5W, which is the wattage applied in most 2nd generation e-cigarettes. Concentrations of acetaldehyde in each puff were several times below the short-term irritation threshold value for humans. Acrolein was only detected from 20W upwards. The negative sensorial quality evaluation by the volunteering vaper of the vapour generated at 20W demonstrated the unlikelihood that such a wattage would be realistically set by a vaper. This study highlights the importance to develop standardised testing methods for the assessment of carbonyl-emissions and emissions of other potentially harmful compounds from e-cigarettes. The wide variety and variability of products available on the market make the development of such methods and the associated standardised testing conditions particularly demanding.

Fate of pyrazines in the flavored liquids of e-cigarettes

“…AcP represented well the behavior of the pyrazines in the commercial samples since it was the most abundant in the tested liquids. We observed complete evaporation of AcP from the sample holder at 130 °C, which was considered a lower temperature than the reported temperatures in the vicinity of the ECIG heating element (Geiss et al 2016, Talih et al 2017). …”

Practise Patterns and Perceptions of Chest Health Care Providers on Electronic Cigarette Use: An In-Depth Discussion and Report of Survey Results

“…volatile carbonyl compounds) has been shown to increase significantly with higher temperature and electrical power applied to the e-liquid. (Bekki et al, 2014; Geiss, Bianchi, & Barrero-Moreno, 2016; Kosmider et al, 2014; Talih, Balhas, Salman, Karaoghlanian, & Shihadeh, 2015) Consequently, since ECs and EC use patterns vary significantly with respect to product characteristics, it is inappropriate to think of ECs as a single entity with a given level of risk, and it would be more appropriate to view this as a class of products with a continuum of risk.…”

Analysis of Nicotine and Nicotine-Related Compounds in Electronic Cigarette Liquids and Aerosols by Liquid Chromatography-Tandem Mass Spectrometry

“…When the applied powers for cartridges were increased from 5 to 20 W, the yields of myosmine were dramatically increased (as shown in Table 8). A possible explanation for this is that when the 5-W output power was applied, the energy supplied by the battery was probably primarily consumed on the evaporation of the e-liquid mixture and less for further heating up of the generator (23). Accordingly, the detectable levels of nicotine-related compounds in the aerosols might originate directly from the evaporative transfer of minor impurities present in the e-liquids.…”