Are they as safe as using smokeless tobacco? -Maybe.

We cannot be as certain of their safety range as we are with smokeless tobacco (ST) simply because they are so new.

With smokeless tobacco, we have evidence from decades and decades of use by many different populations. Evidence that comes only from examining substance effects on cells in laboratories, measuring constituents in blood or urine, or its effects on nonhumans does not provide enough information to know what the effects will be on humans over time.

There are some but not that many studies of the potential harms that might come from using electronic cigarettes. To date, there is no indication of anything substantial. So, all we can say at this point is that they could be as safe, or even safer, than using ST or pharmaceutical nicotine products but we cannot be certain of that.

There are studies that confirm the chemicals that the body receives from some e-cigarettes, but not all of them. There is some concern about quality control -- making sure they are only what they say they are -- given that many factories in China are producing various versions with little regulation or oversight. We recommend using major brands that have been well tested.
Unfortunately, the studies that we have are all about chemistry, and a chemistry study does not tell us everything about human health effects. Since nicotine seems to be the source of most, if not all, of the risk from using smokeless tobacco, e-cigarettes, like traditional pharmaceutical nicotine products, will likely have those same risks . To date, there is no reason to believe there is any substantial additional risk from the e-cigarettes, but we cannot be certain of that.