1,2-Propylene Glycol: A Biomarker of Exposure Specific to e-Cigarette Consumption

Abstract

Over the past decade, new emerging tobacco and nicotine-delivery products have changed the tobacco landscape. Especially, electronic cigarettes (ECs) have been suggested to be considered for tobacco harm reduction, reinforcing the need to identify novel biomarkers of exposure (BoE) specific to the EC use as this would complement exposure assessment and product compliance monitoring. Therefore, a sensitive LC-MS/MS method for the quantification of 1,2-propylene glycol (PG) and glycerol (G), the main e-liquid constituents, was established. PG and G were analyzed in plasma and urine samples from a clinical study comparing five nicotine product user groups, users of combustible cigarettes (CC), electronic cigarettes (EC), heated tobacco products (HTP), oral tobacco (OT), and oral/dermal nicotine delivery products (used for nicotine replacement therapy, NRT) with a control group of non-users (NU). Data demonstrate significantly elevated PG levels in urine and plasma in EC users compared to users of CC, HTP, NRT, OT as well as NU. In addition, PG in plasma and urine of vapers significantly correlated with nicotine (plasma) and total nicotine equivalents (urine), biomarkers reflecting product consumption, emphasizing the high specificity of PG as a BoE for EC consumption. We therefore suggest the use of PG as BoE in urine and/or plasma in order to monitor EC use compliance in exposure assessments.

Assessment of nicotine delivery and uptake in users of various tobacco/nicotine products

“…A moderate to strong correlation was, however, found for vapers when the amount of consumed e-liquid was used as a consumption variable ( Table 3 ). Similar results were obtained, when 1,2-propylene glycol in plasma and urine of vapers was correlated with various dose markers ( Burkhardt et al, 2021 ). For the oral products (nicotine gum, OT), the usage time of the product in the mouth is regarded to be crucial for nicotine exposure dose per unit used ( Gale et al, 2012 ).…”

Comparison of urinary mercapturic acid excretions in users of various tobacco/nicotine products

“…18 The project aims to distinguish different tobacco/nicotine product user groups by either specific biomarkers or biomarker patterns. The results considering the intake/uptake of 1,2-propylene glycol, 19 nicotine, 21 and the exposure to tobacco-specific nitrosamines (TSNA) and minor nicotine alkaloids 22 as well as benzo[a]pyrene 20 and monophenolic metabolites of five PAHs 25 in this study have recently been published. In a recent review, which accompanied the research project, the intake and uptake of 38 chemicals of five user groups of tobacco/nicotine products (identical to those investigated in this study) and NUs was assessed based on literature data.…”

“…The project aims to distinguish different nicotine product user groups by either specific biomarkers or biomarker patterns. So far, targeted analysis from this study on 1,3‐propylene glycol, 19 3‐OH‐benzo[ a ]pyrene, 20 nicotine, 21 tobacco‐specific nitrosamines, and minor tobacco alkaloids 22 have been published. A manuscript on monophenolic PAH has been submitted for publication.…”

Assessment of the Exposure to Aromatic Amines in Users of Various Tobacco/Nicotine Products

“…In this paper, results for urinary biomarkers of four aromatic amines ( o -Tol, 2-AN, 3-ABP, 4-ABP) are presented. To date, results from this study for exposure and uptake of nicotine, 28 tobacco-specific nitrosamines (TSNA), 29 polycyclic aromatic hydrocarbons (PAH), 35 benzo[ a ]pyrene, 36 1,2-propylene glycol, and glycerol 30 have been published. Results for 15 mercapturic acids have been submitted for publication.…”

“…The “during-the-day” urine was collected between 7 am (after the first morning urine) and 5 pm of the same day. A collection scheme for the biological samples has been published previously. − …”