A Device-Independent Evaluation of Carbonyl Emissions from Heated Electronic Cigarette Solvents

Abstract

ObjectivesTo investigate how the two main electronic (e-) cigarette solvents—propylene glycol (PG) and glycerol (GL)—modulate the formation of toxic volatile carbonyl compounds under precisely controlled temperatures in the absence of nicotine and flavor additives.MethodsPG, GL, PG:GL = 1:1 (wt/wt) mixture, and two commercial e-cigarette liquids were vaporized in a stainless steel, tubular reactor in flowing air ranging up to 318°C to simulate e-cigarette vaping. Aerosols were collected and analyzed to quantify the amount of volatile carbonyls produced with each of the five e-liquids.ResultsSignificant amounts of formaldehyde and acetaldehyde were detected at reactor temperatures ≥215°C for both PG and GL. Acrolein was observed only in e-liquids containing GL when reactor temperatures exceeded 270°C. At 318°C, 2.03±0.80 μg of formaldehyde, 2.35±0.87 μg of acetaldehyde, and a trace amount of acetone were generated per milligram of PG; at the same temperature, 21.1±3.80 μg of formaldehyde, 2.40±0.99 μg of acetaldehyde, and 0.80±0.50 μg of acrolein were detected per milligram of GL.ConclusionsWe developed a device-independent test method to investigate carbonyl emissions from different e-cigarette liquids under precisely controlled temperatures. PG and GL were identified to be the main sources of toxic carbonyl compounds from e-cigarette use. GL produced much more formaldehyde than PG. Besides formaldehyde and acetaldehyde, measurable amounts of acrolein were also detected at ≥270°C but only when GL was present in the e-liquid. At 215°C, the estimated daily exposure to formaldehyde from e-cigarettes, exceeded United States Environmental Protection Agency (USEPA) and California Office of Environmental Health Hazard Assessment (OEHHA) acceptable limits, which emphasized the need to further examine the potential cancer and non-cancer health risks associated with e-cigarette use.

The toxic potential of a fourth‐generation E‐cigarette on human lung cell lines and tissue explants

“…These include the variable device settings, i.e. voltage, current, temperature (Geiss, Bianchi, Barahona, & Barrero‐Moreno, ; Wang et al, ), composition of E‐liquids, i.e. the type and ratio of humectant and whether they contain nicotine or flavourings (Kosmider et al, ), and the type and age of the coils (Sleiman et al, ).…”

“…However, this cannot be confirmed, as measuring the actual real‐life temperature of the heating coil was not possible. Using a device independent methodology, much higher levels of acrolein, formaldehyde and acetaldehyde have been reported at a known vaporization temperature of 318°C (Wang et al, ). This suggests that the E‐cig device used in our study probably did not reach this temperature, but would have been above 270°C, where acrolein formation is detectable (Wang et al, ).…”

Electronic Cigarettes: Their Constituents and Potential Links to Asthma

“…In a recent study, Wang and colleagues heated PG and VG under precisely controlled temperatures to determine whether common vaping temperatures are capable of pyrolyzing PG and VG into toxic volatile carbonyl compounds. They reported that significant amounts of formaldehyde and acetaldehyde were generated at temperatures ≥ 215 °C for both PG and VG, and heating VG to temperatures in excess of 270 °C resulted in the formation of acrolein [28]. Numerous studies have implicated exposure to reactive carbonyls, including formaldehyde, acetaldehyde, and acrolein, in the pathogenesis and exacerbation of asthma [29–32].…”

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

“…In order to have a good balance of flavor intensity, throat irritancy, and vapor density, the majority of e-liquids contain a solvent mixture (which works as a carrier) with different proportions of glycerol (most commonly of vegetable origin, VG) and 1,2-propylene glycol (PG), rather than either alone (17). However, this kind of solvent mixture has been reported to have matrix effects on the signals of the analytes by interfering with the ionization process and causing a reduction of the accuracy (18).…”