Another day, another study. Two actually. Though the first I was planning to cover is a meta analysis (which will have to wait), while the second is a vaping mouse study. As most of you will no doubt be aware, conducting experiments on mice is an age-old way of identifying possible links to humans.
However, in a large number of cases, the results identified in mice do not necessarily translate well across species to us homo-sapiens. Unfortunately, the fallout from this study is going to be the usual moral panic.
Professors John Britton and Peter Hayek have already seen, and commented on this paper over at the Science Media Centre and they make some valid observations. Reading the paper myself I spotted (with the aid of some additional research) a few other concerns.
A total of 85 male FVB/N mice (6 to 8 wk old; The Jackson Laboratory) were randomly placed into 3 groups.Tang et al 2019
Thanks to twitter user Caroline Orr I had a closer look at the specific mice used. According to Wikipedia (grain of salt) and other articles, this particular strain in general (FVB) they are susceptible to induced squamous cell carcinoma. So the researchers deliberately chose a mouse that is susceptible to cancer. When investigating whether e-cig aerosol causes cancer.
One group (n = 45) was exposed to ECS generated from e-juice (nicotine [36 mg/mL] dissolved in vehicle [Veh; isopolypropylene glycol and vegetable glycerin at a 1:1 ratio]). We maintained the particulate matter concentration in the chamber at 130 mg/m3 and the aerosol nicotine concentration at 0.196 mg/m3 (SI Appendix, Table S1). The second group (n = 20) was exposed to Veh. Aerosols for both groups were generated using an automated 3-port E-cig aerosol generator (e~Aerosols) set at a constant voltage (1.9 A, 4.0 V) (SI Appendix, Table S1), the same as is done in commercial E-cigs (12, 13). Mice were subjected to whole-body exposure.Tang et al 2019
Aside from simply saying they divvied up the mice into three groups, there’s no mention of how they were assigned, and why only 85 mice. Were the authors operating under the assumption that e-cig aerosol is highly toxic (how can that be with millions of users worldwide?) and that 85 would be a large enough sample to generate significantly measurable results?
Unfortunately, the paper makes none of that clear. I would suspect that this was a deliberate design, and a flawed one at that.
The exposure conditions were the same as previously described (12). Mice were exposed for 4 h per day and 5 d per week for 54 wk. The third group (n = 20) remained housed in the animal room, exposed to the ambient filtered air (FA).Tang et al 2019
The exposure conditions previously described are:
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. 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 (1 m3). Tanks were refilled with fresh e-juice at 1.5 h into the exposure period during the pause between puffs.Lee et al 2019
No mention of changing coils so the likelihood of dry puffs is significant. As I’ve mentioned elsewhere on these pages, the puff topography mentioned above lends itself “nicely” to the dry puff phenomenon.
Further, the length of exposure (bear in mind that it is full body exposure with no explanation as to why) is bonkers. 4 hours per day, 5 days per week for 54 weeks is in no way a resemblance of real life. Not to mention the simple fact that full body exposure to anything incorporates the epidermal layer (the skin), plus the eyes and so forth. There’s also another vector with rodents (or any other furry animal for that matter) and that is, the mouth.
Yep, rodents will lick themselves. All over. So any aerosol residue on the fur will get transferred via the saliva. Which, as you can guess, could lead to unexpected results.
During the 54-wk period, 3 ECS mice were found dead and 2 ECS mice had to be killed because of inactiveness. No lung tumor was observed in these 5 mice, and 1 was found to have a large intestinal polyp. One Veh-exposed mouse was found dead, and 1 was killed due to a paralyzed leg. Two FA-exposed mice were also found dead. No lung tumor was observed in these 2 Veh and 2 FA mice.Tang et al 2019
I’m not fucking surprised they found dead mice with that exposure protocol. Considering that it is 20 hours per week of aerosol exposure. How many humans are exposed to that, and at the levels detailed? Not many I would guess. After all, it works out as 0.000103 kg / m3 , but there’s no detail on the size of the chamber, but most of you have been to a vaping expo at some point. So you can probably guess how much aerosol was in those chambers.
At the end of the 54-wk exposure, 40 ECS-exposed, 18 Veh-exposed, and 18 FA-exposed mice survived. The average body weights among these 3 groups were similar (FA group, 34.4 ± 5.84 g; Veh group, 34.0 ± 2.78 g; and ECS group, 35.1 ± 2.99 g; ECS vs. FA, P = 0.67; ECS vs. Veh, P = 0.1998), and all mice appeared healthy. These mice were killed to examine tumor formation in different organs.Tang et al 2019
So aside from swamping the mice in aerosol for 4 hours a day, 5 days a week, those that remained were apparently healthy.
The results show that 9 of 40 (22.5%) mice exposed to ECS developed lung tumors.Tang et al 2019
In a species chosen specifically for the susceptibility of developing sarcomas.
None of the mice exposed to Veh developed lung tumors. Only 1 of 18 (5.6%) mice exposed to FA had 1 adenocarcinoma formed in the lung.Tang et al 2019
Surely this section would raise some alarms about the methodology used? If NONE of the vehicle only control developed a sarcoma, making it “safer than filtered air” shows that something is decidedly broken in the methodology.
Furthermore, there is no discussion or analysis of the actual aerosol itself, so these researchers would have absolutely NO IDEA if the ECS exposed mice were being heavily dosed with dry hits. Also, the authors merely express that they identified tumors, but at no point did they consider the possibilities of spontaneous tumors.
In summary, we showed that ECS exposure of mice induces lung cancer and bladder urothelial hyperplasia. These observations, combined with our previous findings (12) that ECS induces γ-OH-PdG and O6-methyl-dG adducts in the lungs and bladder urothelium and inhibits DNA repair in lung tissues in mice, and that nicotine and NNK induce the same types of DNA adducts and DNA repair inhibition effect and sensitize mutational and tumorigenic cell transformation susceptibility in the human lung epithelial and urothelial cells, indicate that ECS, as well as nicotine and NNK, is a lung carcinogen and a potential bladder carcinogen in mice. It should be noted that TS is a most dangerous environmental agent to which humans are commonly exposed and that ECS may or may not pose any danger to humans. The public should not equate the risk of ECS with that of TS. Our data simply suggest, on the basis of experimental data in model systems, that this issue warrants in-depth study in the future.Tang et al 2019
Why bother discussing tobacco specific nitrosamines when the science already demonstrates the absences of such agents in e-cig aerosol? There’s no mention in the discussion of any validation of the mouse grouping either. Nor any mention of why the small sample.
In contrast to the results showing that stream air-vaporized nicotine is not lung carcinogenic in rats (21), our results showed that E-cig nicotine induces lung adenocarcinoma in mice. The sources of this discrepancy are unclear.Tang et al 2019
I think we know why. You idiots didn’t perform any aerosol analysis so you wouldn’t have spotted it. DRY PUFFS. We know that dry puffs produce copious amounts of formaldehyde and other aldehydes which do have a link to sarcoma growth.
Idiots. Fucking idiots.