Humans have been igniting tobacco and inhaling the resulting smoke for a long, long time. Well before the advent of modern medicine, microscopes, blood tests, and decent knowledge of biology and chemistry. If cigarettes were introduced today, we'd know they were bad before 20-30 years, paladinx.
While that certainly doesn't give e-cigs a clean bill of health, it looks a whole heck of a lot safer. That's really the key word here. Wouldn't you agree they're safer? If so, I don't see the problem. If they help get people off of cigarettes, they're a plus in my book.
As for far-reaching health problems, it's unknown. I'd love to see a medical test of small amounts of e-juice vapor exposed to lung tissue over 10-30 years. Given the chemicals involved, it's unlikely there will be major problems, but as always, it can be hard to tell with the human body.
I'd believe that the largest unknown factor would be the flavorings used. PG has been used for quite some time without major problems. We already know most of the negatives of nicotine. As for inhaling flavorings that are usually ingested, there's our unknown.
The true test for all e-cig users out there is whether you're willing to risk the possibility of problems far down the road to known immediate and future health concerns.
