The formaldehyde scare came from a letter about a study at Portland State University in which a group of scientists heated some cheap clearomizers to the point where they burned off the liquid and delivered unvapeable dry hits. Their conclusions have been soundly debunked.
We breathe and eat chemicals every day, but most of them don’t affect us. It’s true that there are a lot of scary-sounding chemicals in vapor, but they’re present in tiny concentrations. Everything we eat, drink, or breathe has chemicals that might be risky to consume in large quantities. But we don’t consume them in large quantities.
The Royal College of Physicians agrees. In its comprehensive review of e-cigarette science, the College concluded, “In normal conditions of use, toxin levels in inhaled e-cigarette vapour are probably well below prescribed threshold limit values for occupational exposure, in which case significant long-term harm is unlikely.”