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. 2021 Jan 6;18(2):385.
doi: 10.3390/ijerph18020385.

An Unrecognized Hazard in E-Cigarette Vapor: Preliminary Quantification of Methylglyoxal Formation from Propylene Glycol in E-Cigarettes

Parham Azimi  1 , Zahra Keshavarz  1 , Marianne Lahaie Luna  1   2 , Jose Guillermo Cedeno Laurent  1 , Jose Vallarino  1 , David C Christiani  1 , Joseph G Allen  1
Affiliations

An Unrecognized Hazard in E-Cigarette Vapor: Preliminary Quantification of Methylglyoxal Formation from Propylene Glycol in E-Cigarettes

Parham Azimi et al. Int J Environ Res Public Health. .

Abstract

Up to 95% of the liquid volume in an e-cigarette consists of propylene glycol. Previous research has shown that propylene glycol can generate diacetyl and formaldehyde when heated. New research shows that propylene glycol can also generate methylglyoxal, an alpha di-carbonyl compound recently shown to cause epithelial necrosis at even lower concentrations than diacetyl, the flavoring chemical associated with bronchiolitis obliterans ("Popcorn Lung"). We analyzed chemical emissions from 13 JUUL pod flavors. Diacetyl and methylglyoxal was detected in 100% of samples with median concentration (range) of 20 µg/m3 (less than limit of quantification: 54 µg/m3) and 4219 µg/m3 (677-15,342 µg/m3), respectively. We also detected acetaldehyde (median concentration: 341 µg/m3) and propionaldehyde (median concentration: 87 µg/m3) in all samples. The recent evidence that methylglyoxal is more cytotoxic to airway epithelial cells than diacetyl makes this an urgent public health concern. Current smokers considering e-cigarettes as a smoking cessation tool, and never users, who may be under the impression that e-cigarettes are harmless, need information on emissions and potential risks to make informed decisions.

Keywords: e-cigarette; hazardous exposure; methylglyoxal; propylene glycol.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Proposed reaction mechanisms for formation of (a,b) formaldehyde, methylglyoxal, propionaldehyde, and acetaldehyde in e-cigarette puffs [11] and (c) diacetyl in e-cigarette liquids [13].
Figure 2
Figure 2
Schematic diagram of the experiment setup.
Figure 3
Figure 3
Concentration of selected carbonyls and di-carbonyls in e-cigarette puffs. LOQ: limit of quantification.
See this image and copyright information in PMC

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