Wow, real research! This is a pleasant change from status quo. Though small, study results are illuminating and potentially useful, though the impact seems overstated.
Study reports first evidence of biological changes related to e-cig use in never-smokers
...
Although the magnitude of change was small compared with a control group, the pilot data suggests that even short-term usage can result in inflammatory changes at a cellular level.
...
Participants were randomized to a four-week intervention with e-cigs containing only 50% propylene glycol (PG) or 50% vegetable glycerine (VG) without nicotine or flavors. (PG and VG are used in e-cig devices.) Results from these tests were then compared to a separate control group of never-smokers. Researchers did not see levels of inflammation higher than the controls, but there was an increase in inflammation among the users who inhaled more of the e-cigs.
...
"Human clinical trials can provide valuable information regarding actual toxicant exposure and risk for disease. Through the randomized clinical trial of healthy never-smokers over a month, we found that an increase in urinary propylene glycol, a marker of inhalation-e-cig intake, was significantly correlated with increased inflammatory response in the lung," says Min-Ae Song, first author of the manuscript and environmental health researcher at the Ohio State College of Public Health. "Future studies could be of longer duration, include an assessment of flavors, the effect by varying ratios of propylene glycol and vegetable glycerine, and examine randomization of smokers to e-cigs."