Let me illustrate what I mean:
> "The estimated lower limit of a lethal dose of nicotine has been reported as between 500 and 1000 mg."
The highest commercially-available concentration of nicotine in ready-to-vape e-juice is 36mg nic/ml. This is considered extremely high nic, and is rarely purchased anymore. So, if you drank 14-28ml of this juice straight from the bottle, that might be a lethal dose (typical bottles are 15-30ml). I can think of several substances you likely have in your house today that have similar levels of toxicity.
My e-cig is loaded with 1.5mg/ml or 0mg/ml juice depending. I vape ~3ml/hour at full-bore. If I absorb only 50% of the vaporized nic, I am releasing 2.25mg of nic into the air over an hour. At 2 puffs per minute that's 0.02mg per puff, distributed over the volume of the vapor cloud.
If you walk through my vapor cloud on a sidewalk, your nic exposure is truly insignificant.
I -- and all friends I have who also vape -- make it a point to not subject others to our habit, out of simple human decency. But let's be real: you're far worse off walking by an idling car than you are walking through a single vapor cloud.