According to one of the researchers who published the study which has caused a lot of misinformation.
"Peyton acknowledges that he found no formaldehyde when the e-cigarettes were set at low levels’. But he says he thinks plenty of people use the high settings. Thinking and proving it are two different things.
He heated propylene glycol, glycerol and nicotine, in a nuclear magnetic resonance (NMR) spectroscopy at 5V before it registered any formaldehyde. One can the question the technique and methodology. This study has not been repeated by another set of researchers to confirm the results.