[Margaret Pilkington]

You are at more risk from the chemicals released into the air from Diesel engines.
My understanding is that nicotine is taken up by receptor cells in the brain rather than being exhaled in water vapour.....but if you know different then OK. I will bow to your greater knowledge.
I would rather stand next to someone using an e cig than a real cig.....and it is bad to have to walk through the smoke at the doorways of some buildings(I'm thinking hospitals here) because smokers are banned from being inside(rightly so).

And how can air be 'laced' with nicotine if the quantity is minute?
If smokers are trying to quit and use these devices to help them, then they should be 'cut some slack' in order to help them ditch the tobacco habit.
Society has made those who smoke into pariahs......they are addicts, just as much as those who use illegal substances. They need help to manage and control their habits and you(and companies, government too - because of the mixed messages) are denying them something which is proven to assist in quitting.
I know some ex smokers who are now completely weaned off tobacco, but still use the e cigs without the nicotine.

Most of the damaging agents in tobacco are the tar compounds.
Second hand smoke(especially in confined spaces) is damaging to those breathing it in.

As for your colleague who goes on smoke breaks........this is something that can be tackled at appraisal.
If someone is a smoker then the employer can either help them to quit, suggest Nicotine replacement therapy or insist that smoking is only done at recognised break times, and in the appropriate designated space.
If your employer does not do this then that is their problem....it is they who are losing productivity.