This study provides some interesting data on what can happen to human cell samples when exposed to e-cigarette vapour in the lab. But the results can only tell us so much, as they weren't from studies in people. The number of different cell samples used was also very small (only 8 people) and we might have seen slightly different results if more cell samples had been used. The main limitation of this study is that it doesn't directly compare the effects of vaping versus the effects of smoking on the lungs.