One study done by the CDC confirmed that increased use in e-cigs in high schoolers did not translate to an increase in smoking rates. Another study was done by the University of Oklahoma Health Sciences Center, where 43 college students said an e-cig was their first nicotine product. Of those 43 students, only one of them said that they went on to smoke regular cigarettes.
The popcorn lung myth is centered around the idea that there is diacetyl in vape liquids which will cause the user's lung pathways to narrow. This was immediately debunked by vapors and scientists around the globe. This article will go into detail on the topic.