Any eliquid can't be guarenteed safe yet since we don't know about any unknown long-term effects of vaping flavoring. People like me will go so far as to say that it's probably safe, and I'm not concerned of the relatively small chance that it may be problematic down the road.
Tobacco is extracted in a few different ways, all involving tobacco leaves to get flavor. I believe the studies on some show very little to no carcinogens detected, but that may vary on extraction method. I don't think we can say for sure yet how more risky extracted tobaccos are, but I think it's safe to say the risk may be a little higher than synthetic flavors, but not nearly at the risk level of burning tobacco.
Most of the danger (from what I understand) from smoking comes from the tar and carcinogens of burning tobacco, so no worries about that part with vaping.
In the end, no one can say for sure yet if vaping synthetic flavors or extracted flavor is a health risk long-term, and if one is more-so than the other. I think the harm reduction either way is immense compared to smoking, so I vape the flavors I love, many happen to be extracted tobaccos.
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