There are several ways to look at this.
First, they claim your not getting enough to worry about (dilution of the flavoring it's found in)
Second, it's safer to make you own juice (DIY), since most of the flavor suppliers do list what's in it.
Third, If your worried about a juice your using, don't inhale.
The nic is absorbed by the linings of your mouth, throat, and sinus ... not your lungs.
The molecules in vapor (steam) are to large for you lung to use,
So .. take a puff, hold it in your mouth, roll it around like wine, and exhale through you nose.
And yes .. no matter what, ....
vaping is safer than smoking.