Not that Innocent: Chemical and Toxicological Evaluation of Glycerin and Propylene Glycol Used in Vape Liquid Production

This work evaluated the elemental content and toxicology of the primary materials of the e-liquids without adding nicotine and other additives. Elemental content was determined through inductively coupled plasma mass spectrometry (ICP-MS) analyses, and biological effects were evaluated in Saccharomyces cerevisiae and H9c2 cells. Elemental analysis did not detect toxic elements above the limit of quantification (LOQ). Toxic concentration with significant difference (p < 0.05) between the samples and the non-exposed cells for glycerin (7.5% m/v) and propylene glycol (12.5% m/v) and at 70/30 proportions (12.5% m/v), 50/50 (12.5% m/v), and 30/70 (6.25% m/v) were encountered. Yeast toxicity presented a concentration-dependent relation with growth inhibition and lethality. Cytotoxicity tests in mammalian cells presented significant differences (p < 0.05) at low concentrations of glycerin and propylene glycol exposition (1.25 and 0.25% m/v, respectively). High concentrations of glycerin and propylene glycol induced increased reactive oxygen species/lactate dehydrogenase, decreased catalase activity, and interference in cell viability. On acute exposure, pure glycerin and propylene glycol are toxic for yeast and H9c2 cells, increasing with proportions of glycerin/propylene glycol and the increased amount of propylene glycol in the solution. No correlation between elemental content and toxicity was observed.