[mcguire]

What specific cancer risks are you referring to? The only serious reports I've run across are

https://www.sciencenews.org/article/vaping%E2%80%99s-toxic-v...

http://www.nejm.org/doi/full/10.1056/NEJMc1413069

which reports increased levels of aldehydes (formaldehyde, for example) from the breakdown of the propylene glycol and glycerin.