The major component of the secondhand vapor would be glycerin and/or propylene glycol. In extreme cases you might inhale entire milligrams of the stuff. Both su

The major component of the secondhand vapor would be glycerin and/or propylene glycol. In extreme cases you might inhale entire milligrams of the stuff. Both substances are safe enough to be in the FDA's 'Generally Recognized as Safe' list and you could drink liters of them without any ill effects.