Corruption in science is a big problem faced by ecig supporters.
In the 80's I was standing on Mt. Washington in Pittsburgh. That is where the skyline photos of the city are taken from. At that time, it was possible to look at a photo of that same skyline from the 60's. The 60's there was a black covering over the city from all the pollution but the early 80's Pittsburgh was listed as near the top of the list for air quality in a city of that size in the world.
My point - air quality since the clean air act of 1955 has actually been getting better overall.
Junk science was mentioned in this thread. One of the problems in the scientific community is allowing the degradation of what is presented as fact and the responsibility of scientists to set that straight. When scientists are questioned if they believe in man caused global climate change it is their responsibility to the purity of science to set the record straight when the layperson media weasel presents it as fact. Same goes when they present atheism as scientifically proven. Same goes when people claim ecigs are as bad or worse than traditional cigarettes.
I can back this. I live in LA and flying into LAX in the 80s and 90s we flew through a dense brown cloud of nasty. Its a lot better now.
IMO on the carcinogens, I think a big part of it is the synthetic chemicals. Not just in cigs, but everywhere. We have had a pretty long track record of co-existing and a symbiosis with the chemistry of our environment. It hasn't been really until the last hundred years or so that we've been heavily exposed to chemicals, and in quantities that our bodies were never designed to use for a biological function, or more than we can process and remove from our system.