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The only unintentional exposures (i.e., not the nicotine) that seem to rise to the level that they are worth further research are the carrier chemicals themselves, propylene glycol and glycerin. This exposure is not known to cause health problems, but the magnitude of the exposure is novel and thus is at the levels for concern based on the lack of reassuring data.
And the results of these novel levels of exposure seem to vary widely from person to person. My own issues with vaping have nothing whatever to do with nicotine, and everything to do with PG and the thick viscosity of VG, and I have found exactly nothing written down online about the potentially uncomfortable and/or dangerous results of this several-orders-of-magnitude-greater exposure to these carrier chemicals -- though my own thread regarding PEG400 has generated a lot more interest than I anticipated when I started it with my own questions. A great deal more research really needs to be done, to see if there are other chemicals that might be of use in vaping, and to see if the existing ones can somehow be altered to make them less hazardous for what appears to be a pretty fair segment of existing vapers, and therefore probably a great many potential vapers as well It's beginning to be pretty widely accepted that vaping is harm reduction, but as a lot of us keep saying, that doesn't mean harm REMOVAL; everything you do to your body carries some price, and for some, the price of the existing carrier chemicals may be a bit too high -- but that doesn't, shouldn't mean, "give up" -- it means we need to investigate this further, for our (vapers) own benefit.
Andria