• Anne Landmesser, Max Scherer, Nikola Pluym, Mohamadi Sarkar, Jeffery Edmiston, Reinhard Niessner, and Gerhard Scherer.
• ABF Analytisch-Biologisches Forschungslabor GmbH, Semmelweisstrasse, Planegg, Germany.
• Nicotine Tob. Res. 2019 Feb 18; 21 (3): 314-322.

IntroductionAn important basis for risk estimation for e-cigarette (e-cig) users is a well-founded dosimetry. The objective of this study was to assess the applicability of stable-isotope e-liquid ingredients for exposure studies in vapers.MethodsE-cigs with 10% of labeled propylene glycol (PG), glycerol (G), and nicotine was used by 20 experienced vapers under controlled (Part A) and free (Part B) conditions. In Part A, 10 subjects vaped at 10 W and another 10 subjects at 18 W power setting of the e-cig. In Part B, the same subjects used the same product ad libitum in their usual environment. Five smokers, smoking 10 non-filter cigarettes, spiked with labeled PG, G, and nicotine, served as positive control during Part A. PG, G, nicotine and its metabolites were measured in plasma, urine, and saliva.ResultsPeak nicotine levels (sum of measured labeled and unlabeled) in plasma were lower in vapers (15.8 to 19.6 ng/mL) than in smokers (36 ng/mL). The labeled plasma nicotine levels were ten times lower than the unlabeled, reflecting the ratio in the e-liquid. PG levels in plasma and urine also reflected the vaping activities in Part A, while G in these body fluids showed no association with vaping.ConclusionsThis proof of concept study shows that the application of labeled e-liquid ingredients allows the accurate quantification of the dose of nicotine and PG when other nicotine and tobacco products were used simultaneously. Unchanged G was not assessable by this approach.ImplicationsThis approach allows the investigations of the absorption of potential PG-, G-, and nicotine-derived vapor constituents (eg, aldehydes and epoxides) by vaping. Appropriate studies are in progress in our laboratory.© The Author(s) 2018. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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