Critical analysis of the 2015 study on formaldehyde in e-liquids

The study led by the American searcher Paul Jensen was one of the most mediatised events for the vaping community in 2015. His work was published in the very serious New England Journal of medicine. It showed that electronic cigarettes were 5 to 15 times more carcinogenic than tobacco. But, Greek searchers have astutely proven that these conclusions were flawed.

According to this 2015 study, vaping is more carcinogenic than tobacco

Formaldehyde and cancer risks in e-cigarettesJensen and his team’s study was quite worrying for e-cigarette users. Their work focused on the quantification of the known-carcinogenic product called formaldehyde, which is most commonly called formol. The formaldehyde emission rate was measured depending on the voltage (V) of the vaping devices.

Their experiences showed that with a voltage set at 4V, 3g of e-liquid emitted 1 005.4µg of formaldehyde, namely one third of a cigarette pack. And at a voltage set at 5V, formaldehyde emissions reached 27 151.5µg. Which represents levels that are 18.5 times more important than smoking 20 traditional tobacco cigarettes. 

These figures that underlined the fact e-cigarettes were harmful seemed unequivocal. The impact of these findings was all the more important on the population since the press widely relayed them. And the consequences could have been terrible for the e-cigarettes industry. The articles were published at the beginning of the year, which is a period when many smokers switch to vaping as a tobacco cessation device.

Even if many scientists have challenged those conclusions since then, we had to wait more than 2 years and a half for another study to formally undermine them.

A new study undermines those conclusions based on real data

Docteur Farsalinos studies formaldehyde in e-liquidsThe Greek laboratory managed by Konstantinos Farsalinos reproduced the same conditions as Jensen. Namely, they took the same e-liquid, and a similar vaping device. The innovation of this protocol is that 26 regular e-cig users were included. And their role is key.

Each subject had to take 4-second puffs. The device was set to different voltage and they had to identify the “dry puff” phenomenon. This is a chemical phenomenon that is linked to an overheating of the e-cigarette. It leads to a very unpleasant taste. It’s therefore easily recognizable. The results were extremely instructive. More than one third of participants detect the “dry puff” at 4V and 88% of them detected it at 5V.

Konstantinos Farsalinos doesn’t actually challenge the raw data used by his colleague regarding the high formaldehyde emissions when devices are used with voltage settings superior to 4V. He challenges the conclusions of the study. It’s indeed unbelievable that vapers would use such voltage settings in real life, due to the sharp taste of the vapor produced. 

This study shows how important it is to analyze data in real life. Raw data obtained in laboratory with no links with the real usage of consumers have very little scientific value.


E-cigarettes emit very high formaldehyde levels only in conditions that are aversive to users: A replication study under verified realistic use conditions
Konstantinos Farsalinos, Vassilis Voudris, Alketa Spyrou, Konstantinos Poulas – 2017

Hidden Formaldehyde in E-Cigarette Aerosols
Paul Jensen, Wentai Luo, James Pankow, Robert Strongin, David Peyton – 2015


Pauline is known at BlogVape for her refined palate. An expert in rare e-liquids and the e-liquid marketplace, she is first and foremost a connoisseur of e-juice flavours.