Assessment of the potential vaping-related exposure to carbonyls and epoxides using stable isotope-labeled precursors in the e-liquid

Abstract

The formation of carbonyls and epoxides in e-cigarette (EC) aerosol is possible due to heating of the liquid constituents. However, high background levels of these compounds have inhibited a clear assessment of exposure during use of ECs. An EC containing an e-liquid replaced with 10% of 13C-labeled propylene glycol and glycerol was used in a controlled use clinical study with 20 EC users. In addition, five smokers smoked cigarettes spiked with the described e-liquid. Seven carbonyls (formaldehyde, acetaldehyde, acrolein, acetone, crotonaldehyde, methacrolein, propionaldehyde) were measured in the aerosol and the mainstream smoke. Corresponding biomarkers of exposure were determined in the user’s urine samples. 13C-labeled formaldehyde, acetaldehyde and acrolein were found in EC aerosol, while all seven labeled carbonyls were detected in smoke. The labeled biomarkers of exposure to formaldehyde (13C-thiazolidine carboxylic acid and 13C-N-(1,3-thiazolidine-4-carbonyl)glycine), acrolein (13C3-3-hydroxypropylmercapturic acid) and glycidol (13C3-dihydroxypropylmercapturic acid) were present in the urine of vapers indicating an EC use-specific exposure to these toxicants. However, other sources than vaping contribute to a much higher extent by several orders of magnitude to the overall exposure of these toxicants. Comparing data for the native (unlabeled) and the labeled (exposure-specific) biomarkers revealed vaping as a minor source of user’s exposure to these toxicants while other carbonyls and epoxides were not detectable in the EC aerosol.

Electronic Cigarette Solvents, JUUL E-Liquids, and Biomarkers of Exposure: In Vivo Evidence for Acrolein and Glycidol in E-Cig-Derived Aerosols

“…17 We did not measure the formation of 13 C-parent compounds in the e-cigarette aerosol as Landmesser et al did wherein they show abundant formation of 13 C-acetaldehyde, 13 C-formaldehyde, and 13 C-acrolein yet not 13 C-glycidol. 40 The lack of detection of 13 C-glycidol in aerosols may result from it being potentially less stable in the presence of acids and metal catalysts. 22 The high concordance between abundant levels of urinary 23HPMA in both e-cig aerosolexposed mice and human e-cig users in our current study may be a consequence of the generally lower temperatures reached in e-cig devices (<300 °C) than in combustible cigarettes (up to 900 °C).…”

“…43 Recently, Landmesser et al used 13 C-PG and 13 C-VG to detect sulfur-containing thiazolidine carboxylic acid and thiazolidine carbonyl glycine metabolites of formaldehyde in urine following inhalation exposure to cigarette smoke or to e-cig aerosols, indicating a potential biomarker of form-aldehyde exposure, while a similar biomarker of acetaldehyde inhalation exposure is still needed. 20,40 5. CONCLUSIONS Our data provide further evidence for the formation of toxic compounds (glycidol and acrolein) in e-cigarette aerosols and support a hypothesis that the glycidol metabolite 23HPMA may be useful as a relatively specific biomarker of e-cigarette use.…”

“…Landmesser et al . recently show that combined 13 C-PG and 13 C-VG in e-liquids lead to 13 C-enriched metabolites, yet their results preclude definitive assignment of each 13 C-enriched metabolite to either PG or VG degradation . In contrast, our results show that 3HPMA and 23HPMA metabolites are both derived directly from the degradation of VG alone.…”

Electronic Cigarette Use Promotes a Unique Periodontal Microbiome

“…The use of e-cigs is often perceived and promoted as a safer alternative to cigarette smoking due to the absence or reduction of harmful combustion products ( 4 , 8 – 10 ). Yet e-cigs produce some toxic compounds shared with cigarettes in addition to unique products ( 11 – 16 ). E-cigs work by aerosolizing a liquid that contains nicotine, propylene glycol, and glycerol (flavoring chemicals are common) that is then inhaled by the user ( 17 , 18 ), whereby the mouth and oral microbial community are the first exposed.…”

The Effects of E-Cigarette Aerosol on Oral Cavity Cells and Tissues: A Narrative Review

“…Other research has supported these results, with an emphasis on their potentially harmful effects for human health [27,28]. Nevertheless, multiple potentially harmful components, toxic metals and trace elements, e.g., aluminium, lead, mercury, zinc, carbonyls, epoxides, policyclic aromatic hydroxycarbons (PAHs) and pesticides were found in e-liquids and aerosols [29][30][31][32][33]. New methods used to estimate toxic metal-containing particles in e-aerosols of various pod-type systems are permitted to detect metal-containing particles such as chromium, zinc, iron, cooper, tin, and lead in various concentrations [34].…”