[melaniejs (OP)]

James asks:

Is the vapour exhaled by people vaping contagious? If so, should we be banning vapes?

Anyone know?

[chiralSPO]

The vapor by itself is NOT contagious--it's an aerosol of the active drugs (nicotine or cannabinoids, or...?) poteentially combined with perfumes/flavors and carrier (for nicotine products, my understanding is that propylene glycol and glycerol are common). This mix may well be a public health hazard (similar to second-hand smoke), but cannot be contagious, because it does not contain bacteria or viruses or funguses, etc.

However, if a person is sick with an airborne disease, I would not be terribly surprised if exhaled vapors would also carry contagions. How contagious this exhalate would be compared to a normal exhaled breath, I'm not sure.

It's possible that it could be more contagious, if the vapor increases the amount of contagion that is released, or if the droplets protect the virus particles (or bacteria, or whatever), or if the droplets increase the local concentration of virus particles by slowing down the dispersion.

It's also possible that it could be less contagious, if the substances in the vapor (or the high temperatures) destroy, damage, or deactivate the contagion.

At the very least, it could be easier to avoid than a normal breath because it's visible.

[Bored chemist]

The visible plume that vapers exhale contains a fine mist of  (typically) propylene glycol.
Propylene glycol vapor has been proposed as a way of killing airborne microorganisms.
The problem is that it kills bacteria, but I don't know if it inactivates viruses.
Apparently it sometimes does.
https://journals.sagepub.com/doi/abs/10.3181/00379727-48-13383?journalCode=ebma
so it's hypothetically possible that if the guy next to you has corvid, you are better off if he's vaping.

[set fair]

"Concentrations of 1 gm. of propylene glycol vapor in two to four million cc. of air produced immediate and complete sterilization of air into which pneumococci, streptococci, staphylococci, H. influenzae, and other microorganisms as well as influenza virus had been sprayed."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2135271/