What is phytol and is it safe to vape?


July 19, 2021

On June 23, Canada’s cannabis regulatory agency, Health Canada, released a private document requested under the Access to Information Act (AIA), that country’s version of the US government’s Freedom of Information Act.

An alarming study of the vape additive phytol has rocked the cannabis vaping world.

The document in question was a 2020 safety study of the vape cartridge additive phytol. The study was conducted by Canopy Growth, one of Canada’s largest cannabis companies.

The data contained in that report has rocked the cannabis vaping world.

Phytol is a terpene that’s sometimes used to add flavor to vape cartridges, usually by adding it to a mix of cannabis oil and the common thinning agent propylene glycol.

The AIA request had been requested by David Heldreth, the former chief science officer of True Terpenes, a major phytol reseller. Heldreth’s friend Andrew Freedman, a Canadian citizen and vape expert, actually obtained the report.

CEO/founder of both Panacea Plant Sciences and Ziese Farms, Heldreth first grew concerned about phytol in August 2020 when Tokyo Smoke, the chain of Canadian cannabis stores owned by Canopy Growth, suddenly pulled all vape cartridges that contained phytol from its shelves.

Five months later, Heldreth became increasingly alarmed when the medical journal Inhalation Toxicology reported findings that indicated phytol was not as benign as propylene glycol. “Phytol, not propylene glycol, causes severe pulmonary injury…,” the study reported.

“I wouldn’t use a product that contains it.”
– David Heldreth, terpene scientist, regarding phytol

The Inhalation Toxicology article was based on research done by Canopy Growth scientists. The study sparked an alarming headline in the trade publication MJ Biz Daily: “Phytol cited as potentially dangerous cannabis vape ingredient.”

After filing an AIA request with Health Canada (which regulates cannabis nationwide), Heldreth finally received the full study in June of this year. Its contents floored him. The data was far worse than he imagined.

Phytol, according to the data in the study, appeared unsafe to inhale. When he spoke recently to Leafly, Heldreth made his opinion very clear: “I wouldn’t use a product that contains it.”

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Why is phytol a concern?

Since the 2010s, humanity has engaged in a massive, uncontrolled field trial of electronic drug-delivery systems known as vaporizers.

“This is something we should be sounding the alarm on.”
– Kyle Boyar, KB Consultations

People young and old are experimenting with liquid chemical mixtures never found in nature, aerosolized by cheap electronic hardware and misted directly into the body’s sensitive lung tissue.

“The science is just so far behind,” Robert Strongin, professor of chemistry at Portland State University, recently told Leafly. “We’re all guinea pigs now.”

In 2019, simmering quality control issues with illicit THC vape pens boiled over into a public health crisis. Vape consumers across America fell sick with what became known as VAPI, or EVALI, a lung distress that injured 2,807 people and killed 68 of them over a period of about six months. Leafly’s investigative reporting helped expose the culprit: vitamin E acetate, which had been added to illicit vape cartridges to boost profits.

Counterfeit THC vape and JUUL pods for sale in downtown LA. (David Downs/Leafly)
Counterfeit THC vape and JUUL pods for sale in downtown LA. (David Downs/Leafly)
Sickened lungs show up as cloudy on the left x-ray, and clear after treatment of one suspected VAPI patient in Utah. (Courtesy University of Utah)
Certain vape additives are associated with lung injury, which shows up as cloudy on the left x-ray, and clear after treatment of one suspected VAPI patient in Utah. (Courtesy University of Utah)

The vape lung crisis largely ended by February 2020, because consumers heeded media warnings, threw out their tainted vapes, and illicit pen factories stopped using heavy cuts of vitamin E acetate.

The Centers for Disease Control stated the number one thing state regulators should do to prevent future outbreaks was “ensure chemicals of concern didn’t enter the vapor supply.”

State regulators have not heeded the CDC’s advice. Few states have instituted any rules around the ingredients in cannabis or tobacco vape cartridges, aside from attempting to ban flavored carts—a move aimed at preventing minors from vaping, and not done out of concern for the health of adult vapers.

“It’s very risky, some of these ingredients,” said Strongin. “It’s just a shame we don’t know more about them.”

Given that cautionary experience with vape cartridge additives, Leafly asked experts to take a look at the raw phytol data from the Canopy study, and answer an urgent question: Is phytol safe to vape?

What is phytol?

Phytol is a diterpene alcohol that appears naturally in trace amounts in raw cannabis plants. It’s an aromatic plant oil, though it’s not a pleasant-smelling one. It can smell grassy in its natural state. Synthetic phytol, which is more commonly used in commercial applications, is odorless.

Outside the cannabis industry, phytol is used as a chemical in products like shampoos, household cleaners, and detergents.

In the cannabis industry (both legal and illicit), vape cartridge manufacturers can use phytol to dilute pure cannabis oil. It’s part of a class of cheap diluents that are most often used by vape cart makers in the illicit market, because illicit carts contain no lab-verified potency data on their labels.

Using phytol to cut cannabis oil in a state-licensed vape cart makes less economic sense, because licensed manufacturers are required to print their lab-verified THC levels on the cartridge package. Thus, a consumer can easily see that a cartridge thinned with phytol contains less THC than a competing product.

The chemical structure of phytol makes it a potential problem in the lung.
The chemical structure of phytol makes it a potential problem in the lung.

Phytol is not difficult to obtain. It’s a colorless or pale yellow liquid sold as a wholesale product to almost anyone who wants it on the internet. In fact, phytol is just a Google search away for anyone with a credit card and a delivery address. It sells for about $100 per liquid ounce, comparable to cannabis oil, but far more available. Phytol allows dealers to stretch their supply of THC oil further, experts said.

Dominic Black, lead account manager at Infinite Chemical Analysis Labs in San Diego, CA, explained, “For example, if someone has 50 liters of [cannabis] distillate and mixes it with 50 liters of phytol, they now have 100 liters of product to sell.”

In illicit markets, where lab-verified THC potency isn’t required, consumers don’t know they’re getting a diluted product—and one that may harm their lungs.

What did the Canopy Growth study find?

The Canopy report determined that certain levels of phytol inhalation hurt lung tissue in lab rats, and did not locate levels of exposure that could be deemed safe.

Results were so alarming that researchers ended the 14-day study after only two days.

A Canopy spokesperson said the company originally commissioned the study as part of its due diligence responsibility as a cannabis vape cartridge manufacturer and retailer. Canopy says it has never used phytol in any of its in-house products, but became both curious and concerned when officials noted the substance turning up in vape carts made by other manufacturers.

Until then, there was no data comparing the toxicity of inhaled phytol versus propylene glycol (PG). Propylene glycol is a commonly-used diluent in legally licensed cannabis vape cartridges. It’s used to thin cannabis oil and allow it to easily contact a vape device’s heating element, which vaporizes the mixture.

Canopy contracted with researchers in New Mexico, who gave lab rats a misted mixture of phytol and air, or propylene glycol and air, or just air. Researchers planned to run the experiment for 14 days, exposing the rats to phytol, or PG, for either 30 minutes or 1, 2, 4, or 6 hours.

A screenshot of the Canopy inhalation toxicology report from 2020, showing rat lungs filtering phytol from the test air.
A screenshot of the Canopy inhalation toxicology report from 2020, showing rat lungs filtering phytol from the test air.

But by day two, all the phytol rats had died or were suffering so badly—gasping, unresponsive—that lab scientists euthanized them. Directors halted the phytol arm of the trial. The PG rats finished their 14 days of exposure and all survived, with no lasting effects.

Among the findings from phytol-exposed rat autopsies:

  • There was “acute toxicity in all dose groups.”
  • Phytol caused “severely purple” lungs that were “hemorrhaging.”
  • The rats’ nose, throat, and lung tissue had melted away in a process called necrosis.
Canopy researcher's conclusions.
Canopy researchers’ conclusions.

The study results alarmed Kyle Boyar, head of KB Consultations. Boyar is also the vice-chair of cannabis chemistry for the American Chemical Society. “It’s pretty bad,” Boyar told Leafly. “It’s something we should be sounding the alarm on.”

Matthew Elmes is the director of scientific affairs at CannaCraft, a legal vape cartridge maker in California. He said phytol “appeared to have relatively high pulmonary toxicity. At the very least, based on these preclinical results, I think it certainly should not be considered for use as any sort of vape diluent!”

It’s important to make clear that Canopy Growth is not the villain in this story. By all accounts, Canopy officials practiced basic, responsible, and ethical drug development 101. And the scary fact is, that’s surprisingly rare in the cannabis industry.

What level of phytol inhalation is safe?

Nobody knows yet if any level of phytol inhalation is safe.

Experts generally agree there’s not enough research to conclude if the substance is safe to inhale in any amount. The Canopy report was the first to really detail the cutting agent’s potential harm to humans. Heavy users of vape pens in illicit markets—where exposure to heavily diluted vape carts is generally higher—are likely the most at risk of potential phytol lung damage.

The results were so alarming that in 2020, Canopy Growth immediately stopped selling all third-party vape cartridges containing phytol.

“For the safety of consumers, we do not believe [phytol] should be used in any vape products,” a Canopy Growth spokesperson told Leafly. “The findings of the study were clear that concentrated phytol resulted in adverse effects to the study animals.”

Is the Canopy study applicable to humans?

Experts say the amount of phytol the rats inhaled may not directly translate to vaping humans—but warrants real caution.

Imagine five vape carts, one-gram size, all completely filled with phytol. Now imagine that mixture misted into a one-meter cubic box, which is about the size of a large garage freezer chest. That’s the concentration of phytol these rats were getting.

But is that a little or a lot?

Marcu said it’s a typical concentration for an exploratory toxicology study. Menthol, for example, will kill 50% of rats exposed to a concentration of about 5,200 milligrams per cubic meter of air of it. Menthol has been added to tobacco cigarettes for decades. The US Food and Drug Administration (FDA) recently proposed a ban on all menthol cigarettes, but that ban was announced largely in terms of making tobacco smoking less attractive, and wasn’t so much about the harmful health effects of menthol itself.

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