E-cigarettes, both with cannabis and tobacco oils in them, rely on additives to standardize the potency of oils and to change their viscosity so that their cartridges do not clog or leak.
There are several different additives that companies use including propylene glycol (PG), polyethylene glycol (PEG), vegetable glycerin (VG), medium-chain triglycerides (MCT), and even terpenes.
Complicating matters further, PEG comes in a nearly unlimited range of molecular weights, each with different known uses, risks, and consistencies; simply put, the bigger the number after the PEG the higher the molecular weight, and more solid it will be.
Most cannabis e-cigarettes that use PEG appear to use PEG 400.
Problems with PEG, PG and VG
A 2017 study published in the Journal of Alternative and Complementary Medicine looked into the amount of the carbonyls such as acetaldehyde, acrolein, and formaldehyde produced by vapes containing PG, PEG, VG, and MCT.
That study found PEG 400 produced the most carbonyls, followed by PG, and that MCT and VG produced comparably negligible amounts.
In an interview following up on his study, Dr. Matthew DiDonato discussed the gravity of his research, saying, “To my knowledge, this is the first study examining the byproducts of vaporized MCT, which is why, given its prevalence in vaporizable cannabis products, we felt it was important to determine its safety as a thinning agent.”
When speaking at the Institute of Cannabis Research Conference 2017, Harvard-educated physician, Dr. Jordan Tishler, expressed concerns that “PEG can become a carcinogen and PG can polymerize, coating the lungs in plastic and provoking an immune response.”
Dr. Jeffrey Raber, the CEO and CVO of The WercShop, echoed some of the concerns raised in the 2017 JACM article, saying “We do know that PEG, VG, PG ... produce formaldehyde and other deleterious agents.”
Some of the deleterious agents Dr. Raber spoke of could be acetals, which are the product of PG and certain flavor chemicals combining, which can happen even without heating.
Arnaud Dumas De Rauly is another important voice raising concerns about these additives.
Dumas De Rauly is the CEO and Co-Founder of the Blinc Group, a vapor products incubator; he is also the Secretary General of European and International relations at FIVAPE in France, the Chairman of the ISO/TC 126/SC 3 Vape and Vapor Products, and one of the world’s most renowned experts in vape technology.
After his years of working in the vape space, Dumas De Rauly feels that “PEG should never be used, and PG is the safest” thinning agent to use.
Despite that, in the U.S. “80% of the nicotine market uses VG and 20% uses PG, and that is reversed in Europe.”
Dumas De Rauly said the reason for VG's popularity is that “VG means a bigger cloud,” while on the other hand “PG means you have a better flavor.”
One thing we do know about PEG is that it can be used as a molecular “glue” to reattach severed nerves as part of a head/body transplant (which is currently being attempted).
Mixed Opinions About MCT
While Dr. DiDonato's research seemed to prove MCT oil as a safe thinning agent when compared to PG and PEG, that study just looked at the amount of carbonyls produced, not at the possibility of lipoid pneumonia.
Lipoid pneumonia is a condition caused by fat particles (lipids) entering the lungs.
Dr. Jeffrey Raber, the CEO and CVO of The WercShop, mentioned his concerns about it during his keynote at the 2018 Terpenes and Testing World Conference (TTWC).
“MCT oil can lead to lipid pneumonia,” said Dr. Raber, adding that “your lungs aren’t made to process oils.”
In a follow-up interview, Dr. Raber expanded on his TTWC keynote: “When we talk about lipid pneumonia, we don't know if it will happen with these lipids, so it’s best to err on the side of caution.”
The main issue he brought up was that “We don't have any data on the effects,” which means that “we don't know how much is too much when it comes to consumption.”
Without any research, there is no way to say if two grams of distillate a day is safe or if a safe amount is two puffs on a cannabis e-cigarette.
In the end, Dr. Raber's advice to manufacturers was straightforward: “Don't put things in there you weren't inhaling before.”
The Trouble with Terpenes
In his TTWC keynote, Dr. Raber said “Terpenes would be the best dilution agents, as they are natural,” they are something that was always inhaled when people smoked cannabis, not a new additive.
Terpenes are part of the essential oils of plants and are responsible for many of the aromas of cannabis and other plants.
While he advocated for using terpenes, Dr. Raber clarified in a follow-up interview that, “we still don’t know what safe consumption rates are for vaporized terpenes.”
He added that “like it or not, we are all in a running experiment, and we are the subject.”
Dr. Raber was clear that there is a “concern over when enough is enough, which is hard to tell.”
Dr. Tishler echoed Dr. Raber's concerns, saying: “Some companies are adding terpenes, but we have no research to show that super concentrated terpenes are any safer than PG or PEG.”
Concentrated terpenes may even have a corrosive effect on the device itself.
This is exactly why more manufacturers are moving away from plastic cartridges.
Justin Pentelute is the CEO of EvolutionZ Consulting, a group that owns the cannabis oil and cartridge company The Clear, one of the pioneers of the cannabis cartridge market who initially used plastic cartridges.
Pentelute discussed why they switched to using glass CCELL cartridges:
“In any plastic cartridge you will get leeching from the terpenes, even cannabis-derived terpenes, not all but most will have some acidic value.”
CCELL Cartridges are quickly becoming standard across the industry due to their higher quality.
He compared it to soda, “It is no different than coca cola, we drink it all the time but it will take rust off a nail, that is similar to how these terpenes work. They are good for you but they are acidic.”
Rene Suarez is a veteran of the e-cigarette space and the CEO of Orchid Essentials, a company that uses terpenes as the thinning agent in their CCELL cartridges.
Suarez also spoke of the potential leeching effects of terpenes.
“I know that in old vape cartridges we used to have plastic tanks and there were some flavors that were more acidic and they would leech the tank and could crack them,” said Suarez, adding one big example: “Cinnamon flavoring cannot go in a plastic tank.”
Beyond some terpenes being more acidic than others, some have been shown to have specific medical issues associated with them. The first terpene to attract attention for negative health effects was diacetyl, a butter-scented terpene which arises as a byproduct of creating cultured dairy products.
Diacetyl first came to attention as an additive to microwave popcorn, where some workers received toxic levels of exposure resulting in a condition called “popcorn lung,” which resulted in new FDA and OSHA regulations.
Diacetyl is not just used in microwaved popcorn anymore, and was found in 75% of e-cigarettes examined in a 2015 Harvard University study which noted negative health impacts from inhaled diacetyl.
In 2018, a study published in the American Heart Association's journal, Arteriosclerosis, Thrombosis and Vascular Biology, found that diacetyl and eight other terpenes impaired “nitric oxide production, which inhibits inflammation and clotting and regulates blood vessel enlargement in response to blood flow.”
Over time, that could contribute to heart damage and other health impairments.
Other than diacetyl, the researchers looked at acetylpyridine (burnt flavor), cinnamaldehyde (cinnamon), dimethylpyrazine (strawberry), eucalyptol (spicy cooling), eugenol (clove), isoamyl acetate (banana), and vanillin (vanilla).
While the study was looking at tobacco e-cigarettes, these terpenes are also used in cannabis e-cigarettes and, in some cases, like eucalyptol, they are naturally occurring in the cannabis plant.
So What's Safest?
It seems like every thinning agent out there has some potential drawbacks and health issues associated with it, but with all of them, we need more research to know the specifics.
Out of five additives looked at in this article, PG and VG seem to be the safest options to use, or possibly terpenes, as long as they are not terpenes shown to have negative health impacts.
Dumas De Rauly had some advice for regulators, “If there is one thing that should be tested for it should be an emissions test,” which means measuring what comes out of a used vape, rather than the oil that goes into it.
“No one is eating the oil, it is being vaporized, so that should be tested and an emissions study is required in both Europe and the US for nicotine vapes.”
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