- Wednesday, 20 November 2013 07:46
Nicotine content in e-cigarette cartridges and in vapor: looking beyond the safety issues
By Dr Farsalinos
A new study was published yesterday in the journal “Addiction”, evaluating the nicotine quantity present in the cartridges of 6 cigarette-like devices and the amount of nicotine present in the produced vapor. The purpose of the study was to evaluate the efficiency of the devices in delivering nicotine to the users and to check the accuracy of the labeling. The main results of the study were that accuracy of the labeling was moderately good, while the amount of nicotine released in vapor (300 puffs was from 2 to 15mg.
The authors of the study correctly explained that nicotine at such levels could never become a problem for users. There is no risk of intoxication or even mild overdose. But there is some important information besides the safety issues: the efficacy of the devices in delivering nicotine.
The devices differed by up to 7 times in the amount of nicotine present in the vapor. This is quite impressive, but e must exploit the reasons for that. First of all, each device has different characteristics. However, the authors used the same puffing set, which in fact is not really representative of realistic use. It is extremely rare for vapers to take one puff every 10 seconds. Moreover, it is unlikely that each puff lasts for only 1.8 seconds (especially with these cigarette-like devices). They also used a 70ml puff volume which is quite high; however, they were probably forced to use such levels because some devices may not have been activated with a lower puff volume (it has to do with the amount of negative pressure applied to the cartomiser in order to activate the internal automatic switch of the battery). The authors described in the discussion section that each device would have been used differently by the consumers (vapers).
Therefore, does this study provide information about the efficacy (or not) of the devices)? Yes and no. The first and obvious impression is that the huge difference between devices means that some of them are completely inefficient. For example, when one device provided 2mg of nicotine with 300 puffs and another provided 15mg, the conclusion is obvious. This may probably be an issue with some devices. The authors reported that the levels of nicotine present in the cartomiser were not associated with the levels found in the vapor. Surprising? I wouldn’t say so. I have mentioned in my studies that the concentration of chemicals in the liquid are not similar their concentrations in the vapor. The main reason is that the liquid is a mixture of several substances. The evaporation temperature of each one of them is different. For nicotine, it is more than 240 degrees Celsius. Of course, we should take into account that e-cigarettes emit aerosol (liquid droplets) and not vapor, but still the temperature plays a major role in the composition of the aerosol because it is through heat that aerosol is produced (another method to produce aerosol is to have the liquid under pressure). This discrepancy between liquid and vapor contents shows why it is useless and mis-informative to perform any cytotoxic studies using the liquid in liquid form (like the cinnamon study performed lately by the Talbot’s group).
However, this is not merely a matter of efficiency. The puff setup is extremely important. For example, some devices have a tighter puff; in others the puff is more relaxed. Those devices will be used differently by vapers. So, the same puff duration and interpuff interval cannot be applied to different devices. In some devices you can see more vapor coming out, in others less. The user will adjust the puffing regime to his preference. Obviously, in a laboratory study it is almost impossible to avoid using the same conditions for all samples, but this is not the way used in the real world. The authors have acknowledged that in the manuscript. This shows why any regulatory efforts supporting that they will provide us with more consistent products are doomed to fail. The results of this study may provide misleading information to the regulatory authorities (although that was clearly not the purpose of the authors). It is not a matter of consistency between products; it is a matter of preference of use. Obviously, as I mentioned above, there are some efficiency issues which the companies should examine and resolve. In that case, it would be more appropriate to examine nicotine absorption in real use rather than perform laboratory studies or testing vapor in pre-specified conditions. The regulatory authorities should take this as a consideration before jumping to conclusions and rush for inappropriate regulations.
Dr Farsalinos is a researcher at Onassis Cardiac Surgery Center in Athens-Greece and at Medical Imaging Research Center, University Hospital Gathuisberg in Leuven-Belgium. He is actively involved in research on e-cigarettes’ safety and risk profile.