Where's the proof that e-cigarettes are harmful?

We have mountains of evidence that cigarettes are one of the most harmful habits one can do.

Do we have proof e-cigs cause lung cancer, or other types of cancer? COPD? asthma? no, we do not.

edit: people seem to be very downvote-happy on this site when they disagree with something.

Combustion of tobacco produces polycyclic aromatic hydrocarbons (PAH) which are heavily carcinogenic. Vaporization of nicotine does NOT produce these compounds.

Additionally the UK Government claims that e-cigarettes are 95% less harmful than tobacco cigarettes, suggesting they are less damaging than junk food, soda, or car exhaust. Why not ban coca-cola and real cigarettes besides ecig?