No one can say, because there are no long-term clinical trials or any other research that could verify or disprove such a statement. They were invented in 1995 and have only been widely used for a few years. This is one of those things on which you have to make your own decision. However, many people regard the decision to inhale a cool mist with half a dozen ingredients, none of which are known to be toxic or carcinogenic, or alternatively inhale a bonfire, as what is popularly termed a no-brainer, which is why e-cigarettes are taking the world by storm.