Baseline effects of non-flavored e-liquids in the in vitro micronucleus assay.

Introduction:
This article reports a study that aimed to characterize the baseline effects of six non-flavored e-liquids (NFELs) on Chinese hamster ovary cells under hazard identification conditions in the in vitro micronucleus assay. The study also sought to establish a reference point for assessing flavored e-liquids and the collected vapor of aerosolized e-liquids using the same approach.

Key Points:

* The NFELs induced cytotoxicity universally but differed in propylene glycol (PG), vegetable glycerin (VG), and nicotine content.
* Significant genotoxic responses were detected with the PG-predominant e-liquids NFEL-a, D, and F but not with NFEL-B, C, or E, which contained higher proportions of VG.
* all six NFELs induced extreme cell culture conditions, including increases in ph and osmolality.
* The NFELs exhibited nonbiologically relevant effects on mechanistic endpoints, such as cell cycle and phosphorylated histones h2aX and h3.
* The apparent DNa damage induced by the PG component of the NFELs was potentially misleading and of negligible biological relevance as a risk for DNa integrity.
* Data on adverse changes relative to this reference data set might indicate a possible genotoxic hazard and would prompt further investigations for exploring the extent of risk.

Main Message:
The study found that non-flavored e-liquids (NFELs) induced cytotoxicity and genotoxic responses in Chinese hamster ovary cells under hazard identification conditions in the in vitro micronucleus assay. however, the apparent DNa damage induced by the PG component of the NFELs was potentially misleading and of negligible biological relevance as a risk for DNa integrity. The study suggests that any adverse changes relative to this reference data set might indicate a possible genotoxic hazard and would prompt further investigations for exploring the extent of risk. Overall, the study provides valuable reference data for assessing flavored e-liquids and the collected vapor of aerosolized e-liquids using the same approach.

Smart DJ, helbling FR, Mchugh D, Vanscheeuwijck P. Baseline effects of non-flavored e-liquids in the in vitro micronucleus assay. Toxicol Res appl. 2019;3:2397847319887904. doi:10.1177/2397847319887904