Originally Posted by
MikeWMass
Not to detract from your achievement, but absence of proof is not proof of absence. The FDA is starting to look into this. It is almost certainly less bad than smoking, but (IMO) non- or ex-smokers would be ill-advised to take up "vaping", and vapers would be well advised to try to stop.
Getting back to your original question, when you say "trails" are you talking about MUT's, or rail trails, or gravel, or really off-road? If you are not doing single track, then a road bike (flat bar or otherwise) that will take 28 or 32 mm tires might serve you well. Suspension adds weight, low priced suspensions are not all that great, and may not add much value for your purpose.
Actually there have been studies in to the chemistry of what is in the liquids which stated there is more risk with the processed foods we eat then there is with the substances in quality juice for e-cigs. CAASA has a study they quote on that. Is there zero risk, well is there zero risk in riding a bike, of course not!
And as for the trails, I am talking bike trails around here which are all asphalt or concrete paved. No unpaved surfaces.