I've often wondered myself about the atomizers. The liquid itself I believe to be reasonably safe as long as it is EU sourced ingredients. The cheap chinese liquids were proved to contain certain metals that could cause all kinds of problems - cancer being the LEAST to worry about.
The atomizers have always concerned me. They burn out, which like most heating elements is due to physical breakdown of the materials or coatings they are produced from. If you ever run an atomizer dry - due to wicking issues or lack of fluid, then the taste that hits your throat is quite simply BLOODY AWFUL. It can't do any good.
I use to be a massive fan of ecigs - I even sold them! After a long stint of using them I ended up back on normal fags purely due to running out of liquid one day. I've thought about going onto them again, but there really is no evidence either way of their safety. Now I choose just to smoke and be done with it. Whether it's cigs or ecigs the chances are it's no good, so I might as well smoke and not vape! If I had the will power I'd stop altogether.