Low-temperature (< 200 °C) degradation of electronic nicotine delivery system liquids generates toxic aldehydes

Abstract

Electronic cigarette usage has spiked in popularity over recent years. The enhanced prevalence has consequently resulted in new health concerns associated with the use of these devices. Degradation of the liquids used in vaping have been identified as a concern due to the presence of toxic compounds such as aldehydes in the aerosols. Typically, such thermochemical conversions are reported to occur between 300 and 400 °C. Herein, the low-temperature thermal degradation of propylene glycol and glycerol constituents of e-cigarette vapors are explored for the first time by natural abundance 13C NMR and 1H NMR, enabling in situ detection of intact molecules from decomposition. The results demonstrate that the degradation of electronic nicotine delivery system (ENDS) liquids is strongly reliant upon the oxygen availability, both in the presence and absence of a material surface. When oxygen is available, propylene glycol and glycerol readily decompose at temperatures between 133 and 175 °C over an extended time period. Among the generated chemical species, formic and acrylic acids are observed which can negatively affect the kidneys and lungs of those who inhale the toxin during ENDS vapor inhalation. Further, the formation of hemi- and formal acetals is noted from both glycerol and propylene glycol, signifying the generation of both formaldehyde and acetaldehyde, highly toxic compounds, which, as a biocide, can lead to numerous health ailments. The results also reveal a retardation in decomposition rate when material surfaces are prevalent with no directly observed unique surface spectator or intermediate species as well as potentially slower conversions in mixtures of the two components. The generation of toxic species in ENDS liquids at low temperatures highlights the dangers of low-temperature ENDS use.

Chemical Elements, Flavor Chemicals, and Nicotine in Unused and Used Electronic Cigarettes Aged 5–10 Years and Effects of pH

“…The data in Figure 3 are consistent with low concentrations being used in early EC products, but could also indicate that there was degradation or evaporation during aging. Hydroxyacetone, which was present in all products, was likely a degradation product of the solvents [ 48 , 49 , 50 ]. Although flavor chemical concentrations are low, some of these chemicals may be harmful.…”

Temperature dependence of emission product distribution from vaping of vitamin E acetate

“…Furthermore, a study by Jaegers et al [44] found that pyrolysis alone in an anaerobic environment was not able to induce thermal degradation of PG and VG at low temperatures (< 200˚C), despite previous studies observing degradation at temperatures as low as 149˚C during vaping [45]. However, when heated in an aerobic environment, thermal decomposition was observed at 133 and 175˚C, both without and with the addition of metal oxides Cr 2 O 3 and ZrO 2 [44], suggesting that oxidation is a key process during vaping. In combination with the results shown here, evidence highly suggests that pure pyrolysis alone may not be the only pathway for VEA degradation.…”

E-Cigarette Aerosol Exposure Favors the Growth and Colonization of Oral Streptococcus mutans Compared to Commensal Streptococci

“…tested, including S. gordonii ( 20 , 22 ). Oxidation and decomposition upon heating of the universal carrier components, glycerol and propylene glycol ( 4 ), can result in the formation of formaldehyde and acetaldehyde ( 29 ). It has been reported that these chemicals are bactericidal and have a negative effect on the oral microbiota ( 30 ).…”