Using information on type of atomizer studied in the recent New England Journal of Medicine article which claimed that vaping produces formaldehyde levels that pose a greater cancer risk than active smoking, Dr. Konstantinos Farsalinos has confirmed that the conditions used in the study (at the 5 volt level) were implausible.
The study reported finding high levels of formaldehyde in the aerosol of electronic
cigarettes, leading the authors to conclude that the cancer risk
associated with vaping is higher than that associated with smoking. The formaldehyde was not detected at the low voltage setting (3.3V), but was detected in large quantities at the high voltage setting (5.0V).
It turns out that the atomizer had a resistance of 2.1 ohms. At a voltage of 5 volts, the power delivered would be about 12 watts. This is clearly in the red zone, where the atomizer coil may be damaged or burned and the e-liquid would definitely be overheated. This would create an extremely unpleasant taste, and no vaper could tolerate more than one puff under these conditions (known as "dry puff" conditions).
The Rest of the Story
The implications of this story are that the conditions used in the high voltage setting in the study were implausible. Thus, the cancer risk estimation in the study is invalid, as is its conclusion that vaping poses a higher cancer risk than active smoking because of the high levels of formaldehyde.
To borrow an apt analogy from Dr. Farsalinos, it is like totally charring a piece of meat, detecting high levels of carcinogens, and then concluding that people who eat meat are at a very high risk of developing cancer. While it is absolutely accurate that there are high levels of carcinogens in charred meat, no one eats meat under such conditions, so the cancer risk estimation is completely invalid.
If you overheat an atomizer, it is going to result in aldehyde formation. This is because at very high temperatures, propylene glycol degrades (is oxidized) to form formaldehyde due to incomplete combustion. This process is enhanced with the presence of metals.
While the high voltage conditions were implausible, the low voltage conditions were not. Thus, the only valid conclusion from the study is that at low voltage conditions, the atomizer tested did not produce any detectable levels of formaldehyde.
Unfortunately, the alarmist (and incorrect) conclusions of this study have already been widely disseminated in the media. Even if the information is corrected, it appears that the damage is done.
I believe that the damage is substantial because many smokers will now become convinced that there is no advantage to switching from tobacco cigarettes to electronic cigarettes. This will discourage many smokers from quitting. It also may cause some vapers to return to cigarette smoking, since they may be convinced that smoking is no worse for their health.
It is difficult to imagine even the tobacco companies of old disseminating such a false conclusion about the relative "safety" of smoking. What the authors concluded is that smoking is safer than vaping, at least in terms of carcinogenic risk. While the tobacco companies undermined conclusions about the hazards of smoking, I don't recall them ever stating that smoking was as benign as a behavior for which no serious adverse effects had been observed. Regardless, my point is simply to emphasize the magnitude of the fallacious conclusion of this study and the damage that it has already done to the protection of the public's health.