Dr Farsalinos' latest study again gives the green light on the safety of vaping as expected, however it tested a range of different flavours this time. One of these was a tobacco extract from House of Liquid (El Toro cigarello) that was found to be Cytotoxic. It's early days yet by it might have implications for all NET flavourings. House of Liquid claim to have their product tested for safety, however what they were testing for and the component that caused a negative result on the cytotoxicological (yep, I think I made that word up) test might be two different things. It could be that there's a component in NETs that is currently not known to cause a problem but which we should be testing for.
Evaluation of the cytotoxic potential of e-cigarette vapor on cultured cardiac cells: a new study
It sounds like bad news for NET vapers but to put it in perspective here: vaping NETs is still far, far safer than smoking cigarettes.