Flavors are widely used in electronic cigarettes.
Attractive in e liquids, they are often criticized for a possible toxicity by inhalation.
Scientific studies have been conducted and conclude with divergent opinions.

The flavors used in the electronic cigarette are food flavors
Doubts persist about their toxicity by inhalation exposure
The major danger is found in the aldehydes that compose them
Scientific studies multiply without reaching a tangible conclusion
Blend of flavors are not studied when they are the basis of vape juices

Dangerous vape flavors?

Since the beginning of 2018, articles on the dangerousness of flavoring for e liquid have been circulating in the media.

But are there more dangerous flavors than others when choosing a flavored e liquid or when making your own electronic cigarette e juice ?

We will try to see more clearly about DIY vape safety and the potential harmfulness of certain flavors and unravel some nodes of this vape question, by addressing these major points :

  1. Studies on flavoring used in electronic cigarette products
  2. The University of Rochester studies
  3. The danger of flavors
  4. Should we be afraid of flavors in e-liquids?
  5. Study methodology
  6. And what about cigarettes?
  7. Eliminate the dangerous vape flavors
  8. What about cinnamon and menthol ?
  9. Last studies on vape flavors

Studies on vape flavors used in electronic cigarette products

Sure, you could not miss the catchy titles on many sites evoking a new study alerting on the possible harmfulness of the ecig flavors.

Since 2015, studies on the toxicity of ecig flavouring have been increasing.

 - The Harvard University researchers tested 51 flavors for diacetyl, acetoin, and pentanedione.

As a result, they detected the presence of at least one of these substances in 47 of the 51 products.

The alert was thus given in 2015 regarding diacetyl and its potential involvement in triggering severe respiratory diseases ... far from proven as you can find in our article on diacetyl.

  - In the same year, a study from the University of Rochester concluded that some e cig liquid flavors damage the mouse's epithelial cells, with special mention for cinnamon, fruity and sweet aromas.

The endless alert relayed in the media is thus launched: the electronic cigarette damages the lungs.

  - In 2017, the University of Kentucky tests 55 flavor components on cardiomyocites, cardiac muscle cells, and this time points to citrus, cinnamon and clove flavors to conclude that they are potentially harmful to the heart, posing a serious question on methodology.

  - Then the University of Virginia publishes a new study on the effects of six electronic cigarette scents on tadpoles, concluding that some had developed a cleft lip and palate, also known as a hare's beak.
We then learned that 20% of tadpoles exposed to raspberry, almond, caramel, vanilla, biscuit and Viennese cream flavors had a hare beak, and up to 70% for those having been subjected to cereals, berries, cream and lemon flavors.

I leave you free appreciation on this study very useful for the tadpoles!

  - In 2018, the University of Rochester publishes a new study in which researchers note a significant inflammatory reaction on monocytes (white blood cells), specific cells of the immune system, in contact with vanilla, cinnamon and butter flavors as well as certain mixtures.

The University of Rochester studies

We don't want to underestimate the conclusions of the studies mentioned above, but we can only be surprised when we make the list of studies carried out by the University of Rochester on the electronic cigarette.

A simple research tells us that this university has a pretty amazing record in the field.

To date, and as each of the studies has been conducted, researchers at this university have come to the conclusion that:

      - the electronic cigarette and its flavors damage the gums and teeth

      - the electronic cigarette and its flavors damage the lungs

      - the electronic cigarette and its flavors have an impact on the immune system

      - the electronic cigarette and its flavors have an impact on wound healing

One may legitimately be surprised by so much interest in research on this electronic device.
But not that much ...

Looking deeper, we learn that in 2014, the University of Rochester received a budget of more than $ 2 million to conduct a series of studies on the e-cigarette and its products.

Such an investment could be welcomed to ensure the safety of this alternative to tobacco if this budget had not been allocated by the US Food and Drug Administration (FDA) for the purpose of place a regulation based on scientific research.

From there, to understand that Dr. Irfan Rahman, who has been doing most of these studies for the last 4 years through his Rahman Lab, is somewhat biased when he concludes:

" Currently, these are not regulated and alluring flavour names, such as candy, cake, cinnamon roll and mystery mix, attract young vapers.

Researchers said tighter regulations are necessary to reduce the risk of 'inhalation toxicity' due to exposure to vaping flavouring chemicals.

E-juice bottles must have a descriptive listing of all ingredients. We urge regulatory agencies to act to protect public health."

To superimpose Dr. Irfan Rahman's statements and the strict regulation that the FDA wants to impose on eliquids by banning sweet, candy, cinnamon and coffee flavors, which are considered too attractive for the youth, would certainly be somewhat insolent!

We will not allow it, but we can only emphasize the fact that the two major studies on flavorings published in one year come from an FDA-funded university that continues its program of regulation of the electronic cigarette in the United States and seems to find the support of the mandated scientists.

On the University of Rochester website, Dr. Irfan Rahman's team is delighted with the impressive sharing of their latest study in the media around the world, even publishing statistics:

"Currently, the article has been viewed more than 16,500 times (in one day) and several news sources have written articles and reported around the world.", we read.

Mission accomplished.

junk science

Are e-cig flavors dangerous ?

If we have the right to do some "slips" on the studies emanating from the University of Rochester, it remains that the alerts on certain flavors really existed.

In 2013, the Clearstream Life study conducted by Dr Romano and Farsalinos for Flavour Art revealed a mild cytotoxicity of maximum concentration coffee flavor.

Today, Dr. Farsalinos, cardiologist invested in research on the electronic cigarette, although fervent defender of the diversity of the flavors available to allow the majority to switch to vape, puts all the same cautions and invites the vapers to measure their ejuice in moderation when they do it themselves and do not overuse the power of their electronic mod until the flavor data is supported.

Diketone free vape juice

Is e juice safe ?

To tell the truth, at the moment scientific studies are not sufficiently documented to be formal and allow to exclude this or that flavor.

But the little we already know sheds light on how to handle apprehensions.

What these studies highlight about flavors are not the tastes themselves.

It does not make sense to say that vanilla, coffee or cinnamon aroma is potentially harmful to the vaper.
In fact, it would be more accurate to determine which component constituting a vanilla, cinnamon or coffee flavor can be potentially harmful.

Take, for example, the first The Flavor Apprentice vanilla custard flavor.
Its exact composition revealed by the manufacturer is:

  • propylene glycol
  • vanillin
  • ethyl vanillin
  • piperonal
  • benzyl benzoate
  • maltol
  • acetoin
  • acetyl propionyl
  • butyrin

Today, we know that in this composition, acetyl propionyl and acetoin will be eliminated as a precaution, part of the diketones family, just like diacetyl previously removed to reach a safe vape juice.

This is what Perfumer's Apprentice (and most manufacturers, see the Vanilla Custard v2 Capella flavor) has done by proposing a second version without these two components to reach a diketone free vape juice.

Now, if scientists need to warn about the potential danger of a vanilla flavor, should vanillin, ethyl vanillin and piperonal be mentioned here as they give this aroma its vanilla taste ?

In the same way, if scientists should warn about the cinnamon flavor in eliquids, should not they rather evoke cinnamaldehyde?

The possible concern of the ecig flavoring is in the aldehydes which compose it.
And the results of studies submitted to date can not be limited to stipulating that creamy or fruit flavors must be eliminated, but which specific aldehydes contained in vape flavors display a real toxicity, at what dose and according to which use.

With the exception of Dr. Farsalinos and Flavour Art, no study has come to specify what are the undesirable aldehydes to remove to make a safest e liquid.

aldehyde in flavors

Electronic Cigarette Study methodology

In addition, most of these studies show a questionable methodology.

Most are conducted on mice, sometimes even tadpoles (!), exposing them to steam produced by smoking machines.

They want to be alarmist while not reproducing the real conditions of the use of the electronic cigarette.
And when we know that overheat resistance or wick improperly wetted denature an e liquid and produce toxic substances, we can question the scientists on the veracity of their claims.

As for the latest study from the University of Rochester, cells are exposed to diacetyl, cinnamaldehyde, acetoine, pentanedione, o-vanillin, maltol and coumarin at different doses.

We are not even in an e-cigarette environment until unidentified flavored and nicotine-free juices are tested in the process.

This simple test allows the authors to conclude that some flavored eliquids have a potential harmful effect.

Does this mean that the food flavors we regularly face without even being vaping are dangerous for health at high concentration?...

food flavors

And at the same time, in March 2018, Dr. Farsalinos published the results of his latest study on the presence of aldehydes in ecigarette vapor in real test with flavored and non-flavored e liquids and concluded:

" The e-cigarettes tested here emit very low levels of aldehydes. Some flavors may contribute to aldehyde emissions, but the rates are minimal. Validated methods should be used when analyzing e-cigarette emissions."

His study has shown that flavored eliquids produce an emission of formaldehyde, acetaldehyde and acrolein 79 to 99.8% lower than cigarette smoke and also lower than the rate of aldehydes in the air we breathe when previous alerts denounced the presence of these potentially carcinogenic toxic substances.

No media has echoed this study to date, not even those who have claimed worldwide "the electronic cigarette is carcinogenic".

What's in a cigarette?

The flavors of the electronic cigarette are pointed out. They are dangerous. They are toxic. They risk triggering irreversible diseases. The electronic cigarette is dangerous!

Well but, are there such alarms when we know that the cigarette so generously made available to all to the delight of the tax administration contains:

- fruit, rum, licorice, menthol, vanillin, caramel, ethyl maltol, ethyl vanillin, vanilla, coffee, lemon, coriander, nail cloves, orange, cinnamon, cumin, ginger, nutmeg, lemon...

297 flavors identified in tobacco. No alerts in sight ...

Safe vape juice

Once again the alerts are not a definitive argument.
In the absence of in-depth studies on the impact of certain aldehydes on health, we can not eliminate this or that taste.

And even if we know which aldehyde is problematic, other elements such as its dosage in the flavor, its dilution in the e liquid, temperature threshold not to cross ... should also be specified to obtain an assessment of its actual toxicity threshold.

Of course, we strongly advise moderation.
Do not make a liquid by adding 40 or 50% flavor! Have a light hand, avoid overheating, in short, caution.

Are cinnamon and menthol bad for vapers?

Following the publication of a new study in the Journal of the American College of Cardiology in May 2019, highlighting the cardiovascular risk of e liquids on endothelial cells especially caused by cinnamon and menthol, Dr. Farsalinos publishes a counter argument.

It highlights a problem of methodology of this study since the e liquids were tested in their liquid form and not vaporized.

This slight detail poses a problem because only the degradation caused by the heat of the vaporization could have potential adverse effects.

It also lists the benefits of cinnamaldehyde, a component of cinnamon, for human health, including its protective effects, anti-oxidant, anti-inflammatory, anti-cancer, antiseptic.

He notes that in cardiology (his specialty), cinnamaldehyde is a protector by its anti-oxidant, vasodilator, blood thinner and anti-inflammatory effect. It is also beneficial in the treatment of other pathologies such as rheumatoid arthritis or Alzheimer's disease.

He concludes by once again insisting on the methodology of this study and the use of e liquid in its liquid form, insisting that cinnamaldehyde found in an electronic cigarette liquid is no different from that found in food and that the conclusions of these researchers could be applied to cinnamon in food if the virtues of this spice were already known.
cinnamon and menthol in vape

Scientific studies on e cig liquid flavors multiply

A study conducted by Konstantinos E. Farsalinos - Department of Cardiology, Onassis Cardiac Surgery Center, Laboratory of Molecular Biology and Immunology, Department of Pharmacy, National School of Public Health, Greece - and George Lagoumintzis - Laboratory of Molecular Biology and Immunology, University of Patras, Greece - published in Harm Reduction Journal on 25 July 2019 evaluates the main flavors used in electronic cigarette e liquids available in Europe.

This latest study echoes another analysis by Constantine Vardavas, a medical epidemiologist specializing in research methods for tobacco control and published in the European Respiratory Journal under the title of:

"Respiratory irritants in e-cigarette refill liquids across nine European countries: a threat to respiratory health? "

In this study, Dr. Vardavas concluded, after analysis of 122 samples of European e juices, the presence of numerous irritating additives, such as methyl cyclopentanolone, acetyl pyrazine, ethyl vanillin, menthol.

The last study by Dr. Farsalinos that interests us here was conducted in opposition to the methodology applied by Dr. Vardavas to reach his conclusions.

Conduct scientific research in the context of vaping

Dr. Vardavas' methodology is to have assessed the toxicity thresholds of the substances based only on the pre-established classification of the European Chemicals Agency and a simple analysis based on a single flavor and its maximum dosage.

However, vapers know that they use most of the time mixtures of flavors that make up an e liquid recipe.

Dr. Farsalinos' study therefore relies on mixtures of flavors diluted in propylene glycol and vegetable glycerine to obtain a vape juice with maximum dosage of each aromatic component.

The chemicals tested are:

- menthol: mint taste
- ethyl maltol: caramelized taste
- linalool: woody taste
- methyl cyclopentenolone: nutty caramel taste
- β-Damascone: fruit taste
- ethyl vanillin: vanilla flavor
- β-Ionone: fruit taste
- acetyl pyrazine: roasted taste
- α-Ionone: fruit taste
- ethyl hexanoate: fruit taste
- 2,5 dimethylpyrazine: hazelnut chocolate taste
- α-Damascone: fruity taste
- 3,4 Dimethoxy-benzaldehyde: vanilla taste
- Limonene: lemon taste, citrus

All these chemical compounds are classified safe for human health but irritating, some for the skin, others for the eyes or the respiratory system.
Environmental toxicity is also noted for some.

flavor chemistry and side effects

The analyzes conducted by Dr. Farsalinos and his team show that only methyl cyclopentenolone has a real toxicity at very high concentration.

Methyl cyclopentenolone is a broad-spectrum flavor and food additive, with a dominant caramel odor that adds notes of maple syrup, raw sugar, or a caramelized taste with nutty nuances to a preparation.

It is commonly found in pastries, ice cream, beverages, cosmetics and tobacco. It is also used to flavor coffee or chocolate.

How to evaluate ecigarette e liquid?

Dr. Vardavas' previous study noted the presence of 246 different flavors and additives in the 122 e liquid samples.

But Dr. Farsalinos notes that without specifying on their concentration, it is impossible to evaluate them correctly.

In the end, he emphasizes that simply using the regulatory framework on product safety does not allow to affirm that the electronic cigarette is or is not harmful, that it must be evaluated within a framework specific to its actual use.

The research must especially study the production of vapor and the possible thermal degradation of the products during their vaporization and not test products in liquid form.

Conclusions of this study on flavors

" In conclusion, a risk assessment analysis based on the EUCLP regulatory framework identified that only one of the reported flavouring chemicals found in e-cigarette liquids was present at levels sufficiently high to classify it as toxic based on the EU regulatory framework.

For the rest, the concentrations reported were by far lower than those needed to classify them as toxic.

Even if a liquid contained all the chemical compounds at the maximum reported concentration, still any toxicity classification would be associated with the use of only one compound at the maximum concentration.

It is important for a proper regulatory framework to continuously monitor the composition and quality of e-cigarette products available in the market and ensure that appropriate standards are used.

Such toxicological surveillance of e-cigarette liquids can be valuable in identifying, removing or adequately diluting potentially harmful compounds as part of standard regulatory practice.

The relative simplicity of the chemistry of e-liquids and e-cigarette aerosols makes this method practically feasible, whereas it is totally implausible for combustible tobacco products. "

What's the safest vape juice?

The ongoing studies of flavors today are not viable at the time the FDA is trying to remove them from the US market, claiming they are attractive to youth.

Of course, it is best to let a young person smoke rather than tempt him with a taste of strawberry candy in an electronic cigarette eliquid!

Unless it is even smarter to remove the flavored e-liquids so that smokers never hear again about this mysterious electronic device that can possibly replace the cigarette...

To go further :

  - A complete evaluation of electronic cigarette in 2022

  - What about diacetyl in e liquid ?

Ressources :

Toxicity classification of e-cigarette flavouring compounds based on European Union regulation: analysis of findings from a recent study
Dr Vardavas study

Rochester University 2015 https://www.urmc.rochester.edu/news/story/4253/e-cigarette-vapors-flavorings-trigger-lung-cell-stress.aspx
Rochester University 2016 https://www.urmc.rochester.edu/news/story/4667/first-ever-study-shows-e-cigarettes-cause-damage-to-gum-tissue.aspx
Rochester University 2018 https://www.frontiersin.org/articles/10.3389/fphys.2017.01130/full
Kentucky University 2017 https://www.ahajournals.org/doi/abs/10.1161/circ.136.suppl_1.20782
Harvard University 2015 https://ehp.niehs.nih.gov/15-10185/


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