Presence of the Carcinogen N′-Nitrosonornicotine in Saliva of E-cigarette Users

Introduction:
This text analyzes the presence of the carcinogen N'-Nitrosonornicotine (NNN) in the saliva of e-cigarette users. The study compares the levels of NNN in the saliva of e-cigarette users, smokers, and nonsmokers, and also examines the levels of NNN and other related compounds in e-cigarette liquids. The study aims to understand the endogenous formation of NNN in e-cigarette users and its potential health risks.

Key Points:

* The study found that NNN is present in the saliva of e-cigarette users, with levels substantially overlapping between e-cigarette users and smokers.
* Nornicotine, a precursor to NNN, is also present in the saliva of e-cigarette users and is readily nitrosated to NNN in the presence of nitrite.
* E-cigarette liquids contain low levels of NNN, NNK, nornicotine, and nicotine, but nornicotine levels vary widely across brands.
* The study suggests that nitrite is not a limiting factor in the process of NNN formation in the oral cavity, as salivary nitrite levels are much higher than nornicotine levels.
* The analysis of urinary biomarkers confirmed that e-cigarette users were not smokers of regular cigarettes.
* The potential artifactual formation of NNN during sample processing and laboratory contamination were ruled out as alternative sources of NNN in saliva.
* The endogenous formation of NNN in e-cigarette users is a potential source of exposure to this known human carcinogen, and future studies should be based on salivary measurements.

Main Message:
The study demonstrates that e-cigarette users are exposed to the carcinogen NNN through endogenous formation in the oral cavity. While the overall exposure to NNN is much higher in cigarette smokers, the carcinogenic potency of NNN and its remarkably strong association with esophageal cancer risk in smokers highlight the need to better characterize factors that contribute to its endogenous formation in e-cigarette users. The study emphasizes the importance of monitoring salivary NNN levels in e-cigarette users and suggests that future studies should incorporate specific e-cigarettes/e-liquids used by the study subjects to better understand the factors affecting the extent of NNN formation in the oral cavity. Overall, the study underscores the need for continued research on the potential health risks of e-cigarette use.

Bustamante, Gabriela, Bin Ma, Galina Yakovlev, Katrina Yershova, Chap Le, Joni Jensen, Dorothy K. Hatsukami, and Irina Stepanov. “Presence of the Carcinogen N ′-Nitrosonornicotine in Saliva of E-Cigarette Users.” Chemical Research in Toxicology 31, no. 8 (August 20, 2018): 731–38. https://doi.org/10.1021/acs.chemrestox.8b00089.