While some have cited the positive effects of e-cigarettes. An October 2014 study showed that six months of vaping led 21 percent of participants to quit regular cigarettes, there is also concern that more young people may be picking up the e-cigarette habit than would be starting traditional smoking. A CDC report late last year showed the number of teens using e-cigs has tripled over two years. And E-cigarette sales are projected to overtake cigarette sales in the next decade