E-Cigarettes and DNA Damage
Leaving aside the fact that I haven’t posted for a while (almost two months), it isn’t particularly surprising to find that a) the media are at it again, and b) tobacco control researchers are at it again.
We have seen this kind of study before, at around the same time of the year, where some ‘research’ makes some claim about how e-cigarettes are “worse than originally thought”. We’ve recently seen a report from the National Academies of Sciences, Engineering and Medicine (NASEM) in the US which largely mirrors the findings from the UK’s Royal College of Physicians; I do plan to go over that at some point - time permitting.
Of course, there’s always more research to be done, nothing is ever 100 percent conclusive, so it is unsurprising to see more DNA research.
E-cigarette smoke damages DNA and reduces repair activity in mouse lung, heart, and bladder as well as in human lung and bladder cells
A mouse study. Again. Poor little bastards. A brief Google for the phrase “the problem with the mouse model” should give you some idea why using mice is somewhat useful, but not an entirely accurate predictor of effects in humans.
Mice were exposed to ECS (10 mg/mL), 3 h/d, 5 d/wk, for 12 wk. ECS was generated by an E-cig machine, as previously described
Aside from the irritating reference to “E-Cigarette Smoke”, the total exposure - 3 hours per day, 5 days a week for 12 weeks - is relatively low. Most vapers are exposed to the aerosol far more often and for longer. Although the concentration (10 mg/mL) is excessive for mice, also a factor why this particular study isn’t really applicable to humans. A concentration 10 mg/mL in mice would be far in excess of anything a vaper would ever use if scaled upwards correctly - at a guess, it’d be above 54 mg/mL.
An automated three-port E-cigarette aerosol generator (e-Aerosols) was used to produce E-cigarette aerosols from NJOY top fill tanks (NJOY, Inc.) filled with 1.6 mL of e-juice with 10 mg/mL nicotine in a propylene glycol/vegetable glycerin mixture (50/50 by volume; MtBakerVapor MESA). Each day the tanks were filled with fresh e-juice from a stock mixture, and the voltage was adjusted to produce a consistent wattage (~1.96 A at 4.2 V) for each tank.
Interestingly, there is no mention of coil replacement and, as vapers know replacing a coil is necessary after varying time-periods; depending on the flavour being used.
The puff aerosols were generated with charcoal and high-efficiency particulate filtered air using a rotorless and brushless diaphragm pump and a puff regime consisting of 35-mL puff volumes of 4-s duration at 30-s intervals. Each puff was mixed with filtered air before entering the exposure chamber.
Pretty standard puff topography, although a 4s puff every 30 seconds will lead to higher than average liquid consumption (not measured, or mentioned in this paper), and an increase in thermal degradation of the coil and liquid. This topography probably did reach the dry puff condition, especially given the following:
Tanks were refilled with fresh e-juice at 1.5 h into the exposure period during the pause between puffs.
Taking a 4-second puff, twice a minute for an hour and a half? A quick calculation suggests that would generate ~6300 mL of aerosol which would also suggest the tank would be empty, or almost empty by the halfway stage.
As any vaper knows, when the tank starts running low on liquid a couple of things happen:
- the coil retains a lot more heat
- the wick doesn’t get replenished as quickly
Under a consistent usage regime, this will, very quickly, lead to overheated liquid, drier wicks, and hotter aerosol which will end up containing higher levels of aldehydes and other nasties.
As for causing DNA damage, as usual instead of analysing the effect of the aerosol on the various respiratory cells available, the researchers deliberately exposed cell cultures to specific nitrosamines and nicotine, which will - of course, result in cell damage.
As succinctly put by Prof Hajek:
Human cells were submerged in nicotine and in off-the-shelf bought carcinogenic nitrosamines. It is not surprising of course that this damaged the cells, but this has no relationship to any effects of e-cigarettes on people who use them.
“In the other part of this study, animals were exposed to what for them are extremely large doses of nicotine and this also generated some damage, but this too has unclear relevance for effects of vaping.
“No comparison with conventional cigarettes was made, but in the text of the article, the authors acknowledge the key bit of information that is of crucial relevance in this story: Vapers show a reduction in these chemicals of 97% compared to smokers. They should have added that this may well be the level that non-smokers obtain from their environment.
Quite. While somewhat useful, this paper doesn’t cover the most basic of comparisons - e-cig aerosol vs tobacco smoke. It does compare with “filtered air”, by which they mean ‘clean’; not the usual environmental air we humans breathe.
(image credit Marc Bruxelle/shutterstock.com)