The record shows that some components that have been used in e-cigs are dangerous or hazardous. To some degree, the industry has responded by improving the designs and materials of vaporizers. However, the industry has a major black market where anyone can produce cartridges, and horror stories have developed where people sought to make a buck by sacrificing safety.

But compared to cigarettes? We know what cigarettes do and those are deadly dangerous for most people. A true statistical comparison would be enlightening.

"current knowledge is still insufficient to say whether the effects of e-cigarettes are less than other tobacco products"

That's a very odd thing to say. I guess if you set your standards of evidence high enough then you can say this about anything. However from the currently available evidence e-cigarettes are thought to be far less harmful than regular cigarettes.

[gov.uk]