Nobody really knows because there have not been any reliable, comprehensive tests of vapor as yet. In any case, all that would show is what you inhale. Exhaled vapor will be very different.
The problem is that there is no known way to test exhaled vapor. Cigarette smoke tests cannot be used as the equipment would not work: the filters would need to be re-designed, as water-based vapor has a very different effect on the lab machinery from smoke. It would tend to clog filters much more.
All the published lab tests we know of have been conducted by people who did not know how an e-cig works, and who did not even perform complete tests of the mainstream vapor ingredients. The ecigs were tested upside down, which means they would have quickly dried out and melted the internals [1]. There is no known test of 100% of the vapor ingredients including water. So even 'mainstream' vapor has not been tested properly or fully.
In multiple sample tests, it was found that only the first test was accurate as the mist could not be cleaned out of the equipment, sticking to the inside, so that all subsequent tests were contaminated by the first. And after that is solved, nobody has even suggested how a filter to replicate the lungs could be constructed; but since all tests that used tobacco cigarette smoke protocols ended up faulty, it can be assumed that this much more complex test is beyond the capabilities of current lab technicians in this field.
You can make a rough estimate, with little basis for the evidence though. It goes like this:
1. Mainstream vapor probably consists of about 66% water, 3% PG, 1% glycerine, 1% nicotine, and the bulk flavoring. Yes, that is a lot of flavoring - but as everything else is accounted for, that's probably what it is (plus any flavor diluents such as alcohol).
2. After filtration by the lungs and mucous membranes of the mouth and nose; plus additional water since all exhaled air contains water; ignoring air gases such as nitrogen, oxygen, carbon dioxide and argon; the vapor could consist of about 90% water, 0.5% PG, 0.1% glycerine, 0.1% nicotine, and around 9% flavoring.
The water is harmless, as is the PG and glycerine. PG is likely to be found in the air in large buildings such as hospitals since it is used in the air conditioning plant to kill airborne pathogens such as Legionnaire's Disease (and as a harmless, non-toxic antifreeze) [2]. The nicotine is likely to be in such small quantities that it is much less than the amounts in the daily diet (everyone consumes nicotine in the diet, and everyone tests positive for nicotine as a result - it is neither an alien toxic chemical nor harmful). The largest ingredient of any interest is likely to be the flavoring. So far we think it unlikely that this is likely to cause harm on a wide scale, if at all.
Some people are intolerant to some flavors, and some flavors are known to be harmful if inhaled, although these are generally avoided now. It's basically down to whether or not you think chocolate flavor in minute quantities and often undetectable is likely to harm bystanders. There is reasonable evidence that room air fresheners would be worse in this regard, as some of the aromatics and excipients they use would not be safe for use in an ecig, and because the scent (and therefore the quantity in the atmosphere) is much stronger. Often, you can vape away without anyone catching the aroma of what you are vaping. A room air freshener though will always be easily detectable unless it has been exhausted (since that is its purpose).
Many of us would be happy to vape in a room with our children as the street air is likely to be far more contaminated. It's about the same as ultra-low amounts of disco fog. Individuals may feel differently of course, especially if they are mega-vapor producers, as some are. Using the average mini ecig probably wouldn't even be detectable. However I don't know if even minuscule quantities of certain compounds could affect pets, I'd imagine that fish and birds would be most vulnerable if so.
[1] Check the photos: there are about twenty or so tests, all incomplete; and all that included pics showed the device being used inverted, in a manner in which it could not possibly work correctly. An ecig is a gravity-fed liquid-feed device like an electric kettle.
[2] This is actually the follow-on from tests as far back as the 1940s that clearly showed PG mist in hospital ward air killed airborne bacteria and viruses, reducing infections by 95% in some wards tested. It was not necessary to take this further, since it became used in the aircon plant, and performs the same function. As pathogens clearly spread into building air from the aircon cooling/filtration water, it is assumed that PG molecules do exactly the same, since they are demonstrated to adapt to air dispersal so very well.
Don't know if you wanted the long version or not
