Negative view on e-liquids

[Smoky Jordan]

Hi peeps take a look at this on News 24 and give your thoughts:
This is why your vanilla or cinnamon flavoured e-cigarette is toxic

19:59 12/04/2018


The safety of e-cigarettes has been an ongoing topic for a while.

Research has shown how e-cigarettes can be bad for your health in various ways.

But a new study suggests that the flavourings used in e-cigarettes might potentially be the most toxic part of the vapour inhaled by users.

What makes the flavour so dangerous?

E-cigarette liquid contains dozens of different chemicals, and these vary widely from product to product, said lead author Flori Sassano. She is a research project manager with the University of North Carolina School of Medicine.

Many of these chemicals are toxic to human cells in the laboratory, but the most toxic appear to be those related to the flavourings contained in e-liquids, Sassano said.

These chemicals include vanillin and cinnamaldehyde, which respectively produce the flavours of vanilla and cinnamon.

The flavourings have been approved by the US Food and Drug Administration (FDA) for consumption, but that doesn't mean they are safe to inhale as vapour from an e-cigarette, Sassano explained.

The FDA's list of safe flavourings "is based upon studies that have been done on these chemicals when ingested, but not when inhaled," she said.

Not all flavours tested

There are more than 7 700 e-liquid flavours on the market from more than 1 200 different vendors, and most have not been tested for their potential toxicity, the study authors said in background notes.

For their research, Sassano and her colleagues tested about 150 commercially available e-liquids, and out of those identified 143 unique chemical compounds.

"What this tells us is these e-liquids are very diverse, and because they are diverse they are very hard to study as a group," Sassano said.

What the study entailed

To test toxicity, the researchers developed a system by which lab-grown human cells are exposed to e-liquid chemicals. The more toxic a chemical, the more it will reduce the growth rates of these cells, according to the report.

Most of the liquid in an e-cigarette is made up of propylene glycol and vegetable glycerine, and those chemicals on their own are toxic to lab-grown human cells, the researchers said.

But the flavourings added to e-cigarettes can be even more toxic, the investigators discovered.

The toxic effects of these liquids proved harmful to cells from human lungs and upper airways. And, overall, the more ingredients included in an e-liquid, the greater the toxicity, the findings showed.

The study was published online in the journal PLOS Biology.

Sassano said the process they've developed provides a fast and reliable way to evaluate the toxicity of the chemicals in e-liquids.





Image credit: iStock

 

[Spyro]

Interesting, thanks for this. Looking forward to more research on this topic.

 

[Silver]

Thanks @Smoky Jordan
Interesting

The part that worries me is this :
Most of the liquid in an e-cigarette is made up of propylene glycol and vegetable glycerine, and those chemicals on their own are toxic to lab-grown human cells, the researchers said.

I thought PG and VG were fairly harmless.

@RichJB, what are your thoughts on this? Seen anything on your radar about this study?

 

[Rob Fisher]

The part that worries me is this :
Most of the liquid in an e-cigarette is made up of propylene glycol and vegetable glycerine, and those chemicals on their own are toxic to lab-grown human cells, the researchers said.

That is the point that I lost interest in the article... yet another piece of shit journalism.

I know the difference in my health since I stopped smoking and started vaping and that is all I need... I do not even read these articles anymore.

 

[Alex]

Thanks @Smoky Jordan
Interesting

The part that worries me is this :
Most of the liquid in an e-cigarette is made up of propylene glycol and vegetable glycerine, and those chemicals on their own are toxic to lab-grown human cells, the researchers said.

I thought PG and VG were fairly harmless.

@RichJB, what are your thoughts on this? Seen anything on your radar about this study?

That's completely wrong

 

[Adephi]

Most of the liquid in an e-cigarette is made up of propylene glycol and vegetable glycerine, and those chemicals on their own are toxic to lab-grown human cells, the researchers said.

Its the same stuff that is used in beauty creams, shower gels, various medications, foods, and the list go on. Where is the studies on those products?

And as for the flavourings, they most likely put the cells in a petri dish full of liquid and the cells died. Yes, i do believe taking a bath in any concentrate will be hazardous but not at the concentrations we are vaping.

 

[Jordache]

Cigarettes are bad but it doesn’t mean vaping is entirely healthy ? There’s not enough case studies which are generated over a period of time.

There has to be a chemical reaction when you heat a coil substantially with ejuice? Surely some of the coil substance is transferred into the juice?

 

[Alex]

E-cigarette flavors and aldehyde emissions: another failure to verify findings from a previous study

• 
• 

Thursday, 08 March 2018 09:12
By Dr Farsalinos

More than 1 year ago, a study was published in the journal Environmental Science and Technology reporting that aldehyde emissions from e-cigarettes are derived from thermal degradation of flavoring compounds rather than the main liquid ingredients (propylene glycol and glycerol). The study found non-detectable levels of aldehydes in unflavored liquids, but up to 10,000-fold higher levels of aldehydes in flavored samples.

At that time, I uploaded a comment clearly stating that the results contradict previous research on aldehyde emissions. I also emphasized that the findings were NOT related to overheating and dry puffs, unlike other studies that had seriously overheated the devices. In my comment I was very careful not to mention anything insulting for the authors of the study, since I had no proof that something went wrong and I could not find any flaws in the publication. I did however mention that: “One of the fascinating aspects of science is the ability to replicate, and thus confirm or reject, the findings of a study… We also plan to use some of the liquids used in the recent study (same brand), if the author replies to my email requesting information on the brand used (there is no such information in the manuscript, and I still have not received any response to the email I have sent).” I also remind everyone that I submitted a letter to the editor of the journal presenting my views on the issue, obviously before the replication attempt was made.

The main author of the study responded to my comment in what I consider a clearly provocative and insulting tone. He mentioned: “Dr. Farsalinos revealed that (a) he is not up-to-date with the current literature, and (b) has not read our paper carefully”. I suggest everyone to read my previous comment and the comment by the main author Dr Khlystov in order to understand the difference in the context.

As I had promised, we were planning to replicate the study. After 2 emails I sent to the main author asking to report the brand of the liquids tested (the e-cigarette device and power settings were mentioned in the manuscript, but not the liquid brand), and after many public requests by myself and Prof Peter Hajek through PubMed Commons (unfortunately all PubMed Commons comments have been removed from PubMed), the authors NEVER reported the liquid brand they tested. In PubMed Commons, the main authors referred us to the cigalike brand they tested, which was useless because we could not use unflavored liquid in the prefilled cartomizers of the cigalike and thus could not compare flavored with unflavored liquids. Additionally, prefilled cartomizers are known for their inconsistent performance, making such comparisons difficult. In my opinion, this was an unprofessional behavior. Additionally, the main author NEVER responded to any of my emails requesting for such information. I have never experienced in the past such a behavior, and unfortunately I must say that this was unprofessional.

We were able to replicate the study due to a coincidence. One of the flavors used in the study was called “Dragon’s Café”. We could find only one company (a US company) which produced a flavored e-cigarette liquid with this name. We also found all other flavors from this company as they were tested in the original study, and chose the 3 flavors with the highest levels of aldehydes (Dragon’s Café, watermelon, blueberry). The liquids were available in standard and sweetened versions. Considering that sweeteners can be transformed to aldehydes when exposed to heat, we chose both the standard and most sweetened versions. The study was replicated using the same devices and power settings as the original study, while additionally we tested similar flavorings from a different manufacturer and a newer generation e-cigarette device.

For start, no dry puffs were detected with any of the liquids. This verified my original assessment as documented in my first comment and the letter to the editor. Our results were revealing in identifying a very small contribution of flavorings on aldehyde emissions. In fact, aldehyde levels were so low that consumption of 5 grams liquid per day would expose vapers to less formaldehyde and acetaldehyde than just staying at home and breathing air. For acrolein, exposure was orders of magnitude lower compared to NIOSH-defined recommended safety limits. To give you an idea of the differences in results, the authors of the original study found up to 7000 ug/g formaldehyde, while we found a maximum of 62 ug/g.

This is the third replication from our group which failed to verify previous findings. I should note that the journal Environmental Science and Technology has been involved in two of these replications, publishing 3 papers (paper 1, paper 2 and paper 3). The replication rejecting the findings of papers 2 and 3 can be seen in a previous comment.

In a recent review on aldehyde emissions from e-cigarettes, I stressed the need to replicate studies reporting unusually high levels of aldehyde emissions. For example, I reported that only 4 of the 32 published studies verified that no dry puff conditions were generated during the laboratory experiments. It seems that in this case there are more methodological issues, possibly related to false-positive results. The authors of the flavorings study are now presenting findings that e-cigarette use increases aldehyde levels in exhaled breath. Considering their previous publication on flavorings and aldehyde levels, I will be very reluctant to accept their results unless they are independently replicated. If they publish the results, we will try to perform a replication study. There is already a publication showing that the exhaled breath of vapers has the same level of aldehydes as non-smokers. So, everyone understands my concerns about another study reporting “peculiar” results. However, I am not going to rush into judgment, I will wait for their results and the replication (if we will be provided with details on the study materials).

source: http://www.ecigarette-research.org/research/index.php/research/2018/262-flavors

 

[KUDU]

All info is welcome, good or bad. The more I know the less I have to explain to the un-informed why I vape.

 

[Silver]

Its the same stuff that is used in beauty creams, shower gels, various medications, foods, and the list go on. Where is the studies on those products?

And as for the flavourings, they most likely put the cells in a petri dish full of liquid and the cells died. Yes, i do believe taking a bath in any concentrate will be hazardous but not at the concentrations we are vaping.

I hear you @Adephi
But for products that we ingest, its different to when inhaling
The stomach is a very different place to the lining of our airways and lungs

Im wondering if the lab grown human cells they used in their study were like the lining of the airways and lungs and whether their simulation replicatds what we do when vaping.

I sincerely hope their research is flawed - but it certainly warrants further investigation.

Also, when they say its toxic, we need to understand how toxic and get it quantified. So if the growth of cells were slowed down by 1% or 50% it would make a big difference to how bad or not so bad it is.

We need details!

 

[Alex]

Cinnamon flavours in e-cigarettes: how inappropriate research can misinform the public and the (amateur) professionals

By Dr Farsalinos

Considerable debate has been focused on the issue of cinnamon flavors after a study was published in a toxicology journal declaring that such flavored liquids are cytotoxic. Just one month ago, a study published by our group also found that a cinnamon-flavored liquid was slightly cytotoxic (although still 10 times less toxic that tobacco smoke). I have already sent a letter to the editor of Toxicology in Vitro raising concerns about the latest study they published on cinnamon, however due to significant misinformation spread throughout the social media, I decided to publish this comment.

First of all, it was surprising to see a vendor removing cinnamon flavors from his sales list. According to a well-known e-cigarette activist, “When a juice maker that fills thousands of bottles a day does this - you should listen.” My response to this is: “If the juice maker who fills thousands of bottles a day knew what he was doing, he should have found out about it before any research was published”. What I mean is that makers have no idea about the cytotoxicity of their products. They are doing no research, so how would they know? But it is even worse that they are making such moves (to remove cinnamon flavors) without even reading (or understanding) the research they quote.

Let me explain. The latest study by Talbot’s group discussed about the cytotoxicity of cinnamon flavors in e-cigarette. Interestingly however, IF SOMEONE READS THE PAPER, he will find that the researchers never used any e-cigarette. Moreover, they never produced vapor! They tested the liquids in liquid form, not in vapor. How can you support that the results have implications for e-cigarette users when no e-cigarette was used and no vapor was produced? However, there is a bigger mistake. The authors mentioned that they tested 8 refill liquids with cinnamon flavor. They mention the names of the liquids and the companies they got them from. After personally searching on the internet and communicating with some companies, I found out that 4 of the samples were concentrated flavors, not refills. The authors themselves found cinnamaldehyde (the substance giving the cinnamon flavor in the liquid) at levels that differed between samples by up to 100 times. This confirms what I found: some of their samples were concentrated flavors.

Finally, there is still another problem in their study. They tested the substance itself (cinnamaldehyde) to see how toxic it is. They found it toxic at levels 400 times lower than currently approved for food use. This is a very strange result and it is hard to explain how regulatory authorities have accepted cinnamaldehyde to be available at such high levels (of course, before the approval, several tests were performed and it was not found toxic).The authors have to explain why their findings contradict previous research.

As I mentioned above, a letter to the editor has been sent and is currently evaluated for publication. In short, the results of this study have nothing to do with e-cigarette use and are more applicable to cinnamon use in food (since they tested the liquid in liquid form and they used several concentrated samples). Besides that, the reactions from manufacturers show that, unfortunately, they cannot accept their ignorance and instead of asking an expert so that they get informed, they react in a way that produces panic to vapers, does nothing to protect consumers and only results in a game of public relations tactics. This is even more unfortunate than the mistakes in the research protocol. As a final note, let's not forget that research has shown cinnamon to have anti-inflammatory, anti-oxidant and maybe anti-cancer properties...

source: http://www.ecigarette-research.com/...07/2013/138-cinnamon-flavours-in-e-cigarettes

 

[Greyz]

Sorry to the OP but I disagree with that article. I don't need to read through @Alex source to know that since vaping I'm healthier than ever.

 

[RainstormZA]

Haha what a joke!

 

[RichJB]

@RichJB, what are your thoughts on this? Seen anything on your radar about this study?

This seems to be a continuation or parallel study of Maciej Goniewicz's work. He, too, concluded that flavourings are the most likely source of harm in e-liquid, more so than PG, VG and nic. Wayne has recently become very cagey about cinnamon flavourings and doesn't want to recommend that people use them anymore. He seems less worried about vanilla. I don't think he got his info from this study, cinnamaldehyde has been a concern for a while.

Goniewicz is concerned about flavours. I'm sure we all remember the section in the BBC Horizon doccie on vaping where he passes vapour over human cells in a Petrie dish and notes that menthol, cherry and some other flavours kill a lot more cells than other flavours do. Although all of them kill less cells than smoking do. Nevertheless we don't want vaping to just be less harmful than smoking. If flavours are doing harm and we can find a way to reduce or eliminate that harm, all the better.

As ever with these studies, we need to have some idea of scale. And, as usual, we get no indication in this report of scale or quantifying. It doesn't help to tell us that something "proves toxic to human cells". We probably breathe in fifty chemicals, just from living in a city, that are "toxic to human cells". How does the scale of vaping vary from that? Less toxic but still toxic? The same? Twice as toxic? Fifty thousand times as toxic?

When reports won't say, it's often an indication that the researchers want to generate media coverage but the figures wouldn't do it. So they resort to verbal descriptors instead. A statement that "The toxic effects of these liquids proved harmful to cells from human lungs and upper airways" sounds a lot more serious than "The toxic effects of these liquids proved harmful to cells from human lungs and upper airways, but no more toxic than just standing on a street corner and breathing in the the city air."

That's not to say that the study is bogus. But, as Dr Farsalinos has shown, when researchers decline to provide figures, it's usually because the figures aren't very dramatic.

 

[Silver]

This seems to be a continuation or parallel study of Maciej Goniewicz's work. He, too, concluded that flavourings are the most likely source of harm in e-liquid, more so than PG, VG and nic. Wayne has recently become very cagey about cinnamon flavourings and doesn't want to recommend that people use them anymore. He seems less worried about vanilla. I don't think he got his info from this study, cinnamaldehyde has been a concern for a while.

Goniewicz is concerned about flavours. I'm sure we all remember the section in the BBC Horizon doccie on vaping where he passes vapour over human cells in a Petrie dish and notes that menthol, cherry and some other flavours kill a lot more cells than other flavours do. Although all of them kill less cells than smoking do. Nevertheless we don't want vaping to just be less harmful than smoking. If flavours are doing harm and we can find a way to reduce or eliminate that harm, all the better.

As ever with these studies, we need to have some idea of scale. And, as usual, we get no indication in this report of scale or quantifying. It doesn't help to tell us that something "proves toxic to human cells". We probably breathe in fifty chemicals, just from living in a city, that are "toxic to human cells". How does the scale of vaping vary from that? Less toxic but still toxic? The same? Twice as toxic? Fifty thousand times as toxic?

When reports won't say, it's often an indication that the researchers want to generate media coverage but the figures wouldn't do it. So they resort to verbal descriptors instead. A statement that "The toxic effects of these liquids proved harmful to cells from human lungs and upper airways" sounds a lot more serious than "The toxic effects of these liquids proved harmful to cells from human lungs and upper airways, but no more toxic than just standing on a street corner and breathing in the the city air."

That's not to say that the study is bogus. But, as Dr Farsalinos has shown, when researchers decline to provide figures, it's usually because the figures aren't very dramatic.

Thanks for this @RichJB
Very helpful and much appreciated
Following this issue with much interest

 

[Hooked]

Thanks for the articles which you posted @Alex. We need two sides to the story.

Have we ever said that vaping is healthy? No. What has been said is that it's a healthier alternative to cigarettes. If one looks hard enough, there are unhealthy components to almost everything in the food world. First we are told that X causes cancer, then we are told that Y causes cancer.

 

[Hooked]

One more comment: On one of these hospital series on TV, there was an incident where two teenage girls swallowed powdered cinnamon as a dare. They were brought into hospital hardly breathing. Apparently cinnamon in large quantities is indeed toxic, but e-liquid does not contain large quantities of cinnamon.

 

[HapticSimian]

The entire study is available here, but after a tough week in retail I'm waaaaay too tired to read through it, let alone draw any inferences from it.

 

[RichJB]

First we are told that X causes cancer, then we are told that Y causes cancer.

In many cases, we are told that X causes cancer. And then, by a different study, that X prevents cancer. Foodstuffs which have been suggested to both cause and prevent cancer include eggs, coffee, wine, chocolate and several more. It is not necessarily indicative of an agenda, it is a function of science that while we are discovering things, we often get contradictory findings.

Vaping is still a very new thing, the science is very incomplete and mistakes will be made and wrong conclusions drawn as science finds its way. The important thing is that science keeps at it, studies are replicated and refined, and we keep moving forward in the quest to determine the truth.

 

[SmokeyJoe]

What a load of BS. I wonder how much BAT payed the "researcher"

 

[Steyn777]

Specifically, using an oak barrel to age the wine introduces vanillin, guaiacol, 4-ethyl guaiacol, ferulic acid, eugenol, 4-methyl guaiacol, 4-ethyl phenol and p-coumaric acid. Each of these exerts a subtle effect on the wine...so if vanillin is a problem I guess it's bad news for every single whiskey and wine distillery in the world?

 

[RichJB]

so if vanillin is a problem I guess it's bad news for every single whiskey and wine distillery in the world?

Again, there's a difference between ingesting and inhaling. DAAP isn't a problem if ingested. I don't know if vanillin is hazardous in vapour but we can't compare it to vanillin in food flavourings.

 

[RichJB]

Some interesting aspects emerge from the full study:

We have previously shown that vaped e-liquids exert similar toxicity as neat e-liquids [30]. However, during the course of vaping, e-liquids are heated to approximately 300°C before inhalation, which may induce chemical transformations that could alter their toxicity [5].

This is a reference to the work of Bekki, Lauterbach and others, who tested VG and PG to determine whether, during vapourising, pyrolysis (decomposition caused by high heat) induced the formation of carbonyl compounds (acetaldehyde, formaldehyde, acrolein) not present in the base liquids in their pre-vapourised state. It was experimentally determined, and is now widely agreed even by Farsalinos, that it does. Although the quantities produced are orders of magnitude lower than during combustion of tobacco. From Farsalinos's correspondence linked in the article quoted by @Alex:

A large number of studies have shown that aldehydes are formed due to thermal degradation of the main ingredients of e-liquids, namely propylene glycol and glycerol. Even more importantly, John Lauterbach reported in a 2015 conference that radiolabeled aldehydes were found in the aerosol of e-liquids containing radiolabeled PG and VG (abstract 188). This is definite proof that, at least part of, aldehydes are formed due to thermal degradation of the humectants of e-liquids.

And yet, in this study:

In agreement with our previous study [30], we did not find that vaping e-liquids changed their relative toxicity.

In other words, this study finds that pyrolysis has no effect on the potential toxicity of VG and PG, or such a small effect as to be irrelevant. That, if true, would be fantastic news for vaping and would contradict earlier findings of the production of harmful substances that even Farsalinos and other pro-vaping researchers have accepted.

I must confess, I find their methodology to be a bit odd. They emphasise that there is a vast range of juices available and the number is growing constantly. Their approach is to test retail juices, using gas chromatography-mass spectrometry (GCMS) to identify the constituent chemicals in the juice. While this may be helpful in determining whether a juice has high or low potential toxicity, and may be of value to consumers looking to buy that juice, it is of no value to the industry because other mixers do not have the recipe and don't know what flavours were used. Surely it would make more sense to test individual flavours because:
1) there are far fewer flavours than there are possible combinations of those flavours, which reduces the scope of the testing regimen required; and
2) information on which flavours are harmful, rather than which juices, would be of greater value to the industry.

Then we have this potential problem:

It is unlikely that PG/VG will ever reach 10% or 30% in the lung lumen during normal vaping. However, we wanted to perform a full-dose response in order to fully understand the upper toxic limit of PG/VG. Accordingly, we can now say that it does not induce cell death below 1%.

And this:

Furthermore, in addition to identifying vanillin as potentially highly toxic, we also identified—using this screen—3 e-liquids that contain diacetyl (2,3-butanedione), which causes bronchiolitis obliterans,

Yes but at what concentration was it found, and what dosage is required for it to become hazardous?

It appears that the nub of this study is that they used a new testing protocol of high-throughput screening (HTS) whereas most testing until now used nonmetric multidimensional scaling (NMDS). The authors contend that HTS is improving and growing in popularity:

Fluorescent-based HTS techniques have been used for decades for drug discovery screens, toxicity, and for genetic screens, and their adoption by the scientific community has increased following the development of better fluorescent dyes and better instrumentation both in the pharmaceutical industry and academia

And that it can provide different results from the more common NMDS testing:

Using an NMDS approach, we found only a weak correlation between the presence of flavorings and toxicity

But that it is more suited to certain types of cells and tests:

We used HEK293T cells for this screen because they are a cell line that is amenable to HTS and one of the favorites in the screening field

In our experience, vaping is more variable and less amenable to HTS.

KEH293T cells are drawn from the kidneys, not the airways. The researchers did run parallel tests on HBEC (bronchial) cells and concluded that the results show correlation.

This can be interpreted in two ways.

1) HTS is better/more accurate/more precise/more comprehensive than NMDS testing, and this is why they have found more alarming results than previous studies using different methodology. Or

2) HTS has acknowledged weaknesses, which might explain for example why they didn't find that pyrolysis increases the toxicity of vapour as opposed to neat e-liquid.

Their conclusions on this seem to indicate a desire to prove that vaping is hazardous:

Therefore, while we do not appear to observe a general increase in e-liquid toxicity after vaping as compared to liquid addition, the HTS data may not be representative of all pulmonary cell types.

Translation: when our tests show that vaping is more hazardous than other tests, we stand by the validity of our testing methodology. When our tests show that vaping is less hazardous than other tests, we readily admit that our methodology may be flawed or not fully applicable to the cell types tested. That strikes me as having their cake and eating it: that they only question the validity/accuracy/applicability of their HTS testing methodology when it doesn't produce the result they desire.

One positive aspect of this study is that they used a Fuchai mod with a Crown sub-tank and 0.25 ohm coil. So at least it is representative of the gear that we use, and not another frigging five year old cigalike with a 1ml cartomiser.

They do, however, end on a valid note:

However, HTS approaches for both e-liquids and their chemical constituents still have an important role in helping to shape future legislation for e-liquids and vaping. This is becoming all the more important, especially as researchers from the tobacco industry are now making claims that vaping represents a reduced risk of exposure compared to tobacco smoking [55, 56]. Therefore, it is vital that academic and government laboratories independently test as many different classes of these e-liquids as possible using multiple approaches and use evidence-based research as the guide for regulation. For example, when low-tar cigarettes were introduced and producers claimed they were a safer alternative to traditional cigarettes, these claims were later refuted.

This remains a stumbling block. The majority of vaping research is being conducted by tobacco companies, and the majority of pro-vaping findings are funded by and published by big tobacco. If the team that conducted this research can't have their cake and eat it, then neither can we as vapers. We cannot simultaneously claim that big tobacco lied to us about tobacco harms but is telling us the truth about vaping harms.

However, it is also true that anti-tobacco researchers like Dr Siegel are concurring with big tobacco's findings. And it is also true that non-tobacco research is divided, with some like PHE concurring with big tobacco and others refuting the claims of reduced harm. So overall, the consensus is in vaping's favour. But it is still a thorn in our side that big tobacco is fighting the battle for us, which automatically unleashes skepticism among a large number of scientists. Anyway, it is what it is, we can't do anything about the political divides undermining the science.

 

[CMMACKEM]

That is the point that I lost interest in the article... yet another piece of shit journalism.

I know the difference in my health since I stopped smoking and started vaping and that is all I need... I do not even read these articles anymore.

This right here

 

[Silver]

Some interesting aspects emerge from the full study:



This is a reference to the work of Bekki, Lauterbach and others, who tested VG and PG to determine whether, during vapourising, pyrolysis (decomposition caused by high heat) induced the formation of carbonyl compounds (acetaldehyde, formaldehyde, acrolein) not present in the base liquids in their pre-vapourised state. It was experimentally determined, and is now widely agreed even by Farsalinos, that it does. Although the quantities produced are orders of magnitude lower than during combustion of tobacco. From Farsalinos's correspondence linked in the article quoted by @Alex:



And yet, in this study:



In other words, this study finds that pyrolysis has no effect on the potential toxicity of VG and PG, or such a small effect as to be irrelevant. That, if true, would be fantastic news for vaping and would contradict earlier findings of the production of harmful substances that even Farsalinos and other pro-vaping researchers have accepted.

I must confess, I find their methodology to be a bit odd. They emphasise that there is a vast range of juices available and the number is growing constantly. Their approach is to test retail juices, using gas chromatography-mass spectrometry (GCMS) to identify the constituent chemicals in the juice. While this may be helpful in determining whether a juice has high or low potential toxicity, and may be of value to consumers looking to buy that juice, it is of no value to the industry because other mixers do not have the recipe and don't know what flavours were used. Surely it would make more sense to test individual flavours because:
1) there are far fewer flavours than there are possible combinations of those flavours, which reduces the scope of the testing regimen required; and
2) information on which flavours are harmful, rather than which juices, would be of greater value to the industry.

Then we have this potential problem:



And this:



Yes but at what concentration was it found, and what dosage is required for it to become hazardous?

It appears that the nub of this study is that they used a new testing protocol of high-throughput screening (HTS) whereas most testing until now used nonmetric multidimensional scaling (NMDS). The authors contend that HTS is improving and growing in popularity:



And that it can provide different results from the more common NMDS testing:



But that it is more suited to certain types of cells and tests:





KEH293T cells are drawn from the kidneys, not the airways. The researchers did run parallel tests on HBEC (bronchial) cells and concluded that the results show correlation.

This can be interpreted in two ways.

1) HTS is better/more accurate/more precise/more comprehensive than NMDS testing, and this is why they have found more alarming results than previous studies using different methodology. Or

2) HTS has acknowledged weaknesses, which might explain for example why they didn't find that pyrolysis increases the toxicity of vapour as opposed to neat e-liquid.

Their conclusions on this seem to indicate a desire to prove that vaping is hazardous:



Translation: when our tests show that vaping is more hazardous than other tests, we stand by the validity of our testing methodology. When our tests show that vaping is less hazardous than other tests, we readily admit that our methodology may be flawed or not fully applicable to the cell types tested. That strikes me as having their cake and eating it: that they only question the validity/accuracy/applicability of their HTS testing methodology when it doesn't produce the result they desire.

One positive aspect of this study is that they used a Fuchai mod with a Crown sub-tank and 0.25 ohm coil. So at least it is representative of the gear that we use, and not another frigging five year old cigalike with a 1ml cartomiser.

They do, however, end on a valid note:



This remains a stumbling block. The majority of vaping research is being conducted by tobacco companies, and the majority of pro-vaping findings are funded by and published by big tobacco. If the team that conducted this research can't have their cake and eat it, then neither can we as vapers. We cannot simultaneously claim that big tobacco lied to us about tobacco harms but is telling us the truth about vaping harms.

However, it is also true that anti-tobacco researchers like Dr Siegel are concurring with big tobacco's findings. And it is also true that non-tobacco research is divided, with some like PHE concurring with big tobacco and others refuting the claims of reduced harm. So overall, the consensus is in vaping's favour. But it is still a thorn in our side that big tobacco is fighting the battle for us, which automatically unleashes skepticism among a large number of scientists. Anyway, it is what it is, we can't do anything about the political divides undermining the science.

That was such an awesome write up @RichJB
Thank you so much
You summarised and commented on the salient points so well. Wow.
Thanks again