Devilfish, glycerine is not toxic per se.
Glycerine is dangerous because @ 280 deg C it transforms in completely another chemical - acrolein - which is very toxic.
Our atomizers heat at about 200 deg, probably much more if you drag longer or if the filament has a bit lower resistance than the standard. This happens pretty often - that's why some atomizers die faster (lower resistance - higher temp) and others don't vape too well or they do it only if you keep dragging (higher resistance - lower temp). Also a proof for higher temperatures is that cotton burns at over 250 deg C, so if your cotton filament ever burned that's because it reached over that temp.