It is a good article, and it exposes the central fallacy (or, if you prefer, scientific malpractice) of every study that claims to find hazardous/deadly things in e-cig vapor. The authors of those studies never bother telling us 1) whether the amount of the hazardous/deadly thing was substantial enough to constitute a health concern, 2) whether similar amounts of the hazardous/deadly thing were already present in the ambient air, or 3) whether (particularly in the case of formaldehyde) trace amounts of the hazardous/deadly thing are a normal byproduct of human respiration.