The study called, “Levels of selected carcinogens and toxicants in vapour from electronic cigarettes” further points to tobacco harm reduction when utilizing electronic cigarettes.
The study itself can be found HERE, but it appears you need to pay for it.
You can see a summary HERE
Results: We found that the e-cigarette vapours contained some toxic substances. The levels of the toxicants were 9–450 times lower than in cigarette smoke and were, in many cases, comparable with trace amounts found in the reference product.
Conclusions: Our findings are consistent with the idea that substituting tobacco cigarettes with e-cigarettes may substantially reduce exposure to selected tobacco-specific toxicants. E-cigarettes as a harm reduction strategy among smokers unwilling to quit, warrants further study.