Most of us here who are vaping aren't doctors, therefore, I don't know how you expect the vaping community to deliver what you are looking for. A few here on VT are nurses. Though I'm not one of them, I am a teacher, and I do teach my students how to research. While Wikipedia may not have had the best marks in the past for their reputableness (yes, I'm aware that's not a word, but as an English major I make words up like the Bard), this information on nic toxicology is quite good.
If you scroll down a bit after Toxicology, there's some very interesting insight into nicotine's (gasp) therapeutic uses.
Links provided at that entry led me to an entry on electronic cigs. While ambiguous and not as thorough as I would like, it does have decent information.
If you are so worried about it, I'd talk to your doctor, not some folks on an internet forum. The vendors are not practicing bad business, in my opinion, by not suppling this information. It is up to the end user to do what feels comfortable for her/himself. The FDA is not (yet) regulating these devices. And I hope they don't, ever. They really turned cigarettes into quite a debacle.
Best of luck and I hope you find what works for you.