The deception of measuring formaldehyde in e-cigarette aerosol: the difference between laboratory measurements and true exposure
By Dr Farsalinos
A new trend is emerging in the e-cigarette research community of obtaining a variable voltage/wattage device, applying high energy to an atomizer and measuring aldehydes (mostly formaldehyde) released to the aerosol (vapor). The story started early last year, continued recently with a story from Japan, and is now followed by a letter published in New England Journal of Medicine.
This time, researchers obtained a variable voltage device, and applied 3.3 and 5.0 volts to an (unnamed) atomizer for 4 seconds per puff. At 3.3 volts they found no formaldehyde, while at 5.0 volts they found formaldehyde levels up to 15 times higher than in tobacco cigarette smoke. But there are major problems in this study.
For start, the authors did not find formaldehyde but formaldehyde hemiacetals. This is a combination of formaldehyde and alcohols (formaldehyde-propylene glycol or formaldehyde-glycerol). The authors characterized them as formaldehyde-releasing agents, providing a reference to a study evaluating contact dermatitis from such agents. However, looking at the study referenced, it is clear that those formaldehyde-releasing agents have nothing to do with formaldehyde hemiacetals found in e-cigarette aerosol. Moreover, there is absolutely no evidence that hemiacetals are toxic or carcinogenic. In fact, it is possible that the formation of hemiacetals might protect against damage induced by formaldehyde. Nevertheless, the authors considered the risk equal to formaldehyde and calculated the risk of cancer.
There are many other major issues in that study. The authors fail to realize that voltage levels provide no information about the thermal load of an e-cigarette device. It seems that both the researchers and the reviewers who approved the study for publication missed that energy should be expressed in watts. As a result, we do not know how many watts were applied to the atomizer. However, there is a way to approximate this, through the information provided about liquid consumption per puff. The authors report that 5mg of liquid were consumed at 3.3 volts. Based on measurements I have performed, such consumption is observed at about 6-7 watts at 4-second puffs. Thus, the atomizer resistance is probably 1.6-1.8 Ohms. This means that at 5 volts the energy was around 14-16watts. That would be an extremely high value for most commercially-available atomizers (excluding some rebuildables which can withstand such high wattage levels). Thus, it is more than obvious that once again the atomizer was overheated, which of course will result in very high levels of formaldehyde production. What the authors ignore is that these conditions, commonly called dry-puff phenomenon (which is explained in detail in one of my published studies), are easily detected by the vapers. In fact, overheating results in an unpleasant taste that none can withstand. As a result, no vaper is ever using the e-cigarette at such conditions and, thus, will never be exposed to such levels of formaldehyde. The story published in New England Journal of Medicine is similar to finding carcinogens in an overcooked piece of meat that none can ever eat. Of course the findings are true, but none will be exposed to the levels found.
I am concerned that we will very often see stories like this. The scientific community must realize that variable wattage devices cannot be used at any wattage levels with any available atomizer. Even for naïve users, the harsh taste of the dry puff phenomenon is unbearable. I would suggest scientists to try themselves an e-cigarette at dry puff conditions (it is very easy, just use an atomizer without enough liquid), and they will find out themselves. In fact, it is very easy to produce as much aldehydes as you want in the lab with an e-cigarette device. However, this has nothing to do with exposure from e-cigarette use.
Our team is currently working on identifying the temperature of the dry-puff phenomenon and evaluating the levels of aldehydes released at those temperatures as well as in temperatures associated with conventional vaping. We will have the results available in a few months, and we hope that this will end the speculation. Until that time, everyone should understand that measuring aldehydes in e-cigarette aerosol in the lab can be deceptive and is not necessarily associated with exposure of vapers to such levels.
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