The present study was conducted to provide toxicological data on e-cigarette vapours of different vendors and to compare e-cigarette vapour toxicity to the toxicity of conventional cigarette smoke. Using an adapted version of a previously constructed cigarette smoke sampling device, we collected the hydrophilic fraction of e-cigarette vapour and exposed to human umbilical vein endothelial cells (HUVEC). After incubation of cells with various concentrations and for various time points, we analysed cell death induction, proliferation rates, the occurrence of intra-cellular reactive oxygen species and cell morphology.

Conventional cigarette smoke extract showed the most severe impact on endothelial cells. However, some e-cigarette vapour extracts showed surprisingly high cytotoxicity, inhibition of cell proliferation, and alterations in cell morphology, which were comparable to conventional strong high-nicotine cigarettes. The vapours generated from different liquids using the same e-cigarette showed massive differences, pointing to some flavours as an important source of toxicity. We detected a high variability in the acute cytotoxicity of e-cigarette vapours depending on the liquid and the e-cigarettes used. Nicotine as well as the formation of acute intracellular reactive oxygen species do not seem to be the central elements in e-cigarette vapour toxicity.