Electronic cigarettes don’t burn and so there is no smoke. And no smoke means no second-hand smoke. And no second-hand smoke means no health worries for the non-e-cig public who happen to be in the vicinity.
Since e-cigs do not involve lighting tobacco, some argue, they should not be included in tobacco regulations—including smoking bans. Instead of toxic smoke, what e-cigarettes emit is a water vapor that contains propylene glycol (PG), the same substance used in nicorette inhailers. As to whether or not there are any other trace chemicals in that vapor that will harm bystanders, no one is sure yet