Terpenes in marijuana vaping products may produce toxic chemicals

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Terpenes, removed from marijuana during distillation, are often added back to e-liquids used for vape cartridges and other products for taste and smell. Photo by Bengoodwin15 /Pixabay

Dec. 10 -- Natural compounds added to marijuana-derived vaping liquid produce toxic chemicals in the vapor that users inhale, a new lab study reports.

The compounds, known as terpenes, are added into pure THC distillations to dilute the product and provide the vapor with aroma and taste, said senior researcher Robert Strongin, a professor of organic chemistry at Portland State University in Oregon.

Samples of lab-created e-liquids and "dabs" -- waxy pot concentrates -- produced a variety of toxic chemicals when they were heated, Strongin and his colleagues found.

Those chemicals included benzene, a known carcinogen, and an air pollutant called methacrolein, Strongin said. Others included xylenes, toluene, styrene and ethylbenzene.

There's concern that these toxins could harm users, particularly teenagers whose bodies and brains are still developing, Strongin said.

Terpenes are found in the essential oils of some plants, particularly conifers and citrus. They are the compound that "gives cannabis its very distinctive smell," he said, noting that pure THC doesn't have any scent.

Nearly 2,300 Americans have been sickened and 48 have died due to a lung injury that hampers and sometimes completely restricts a person's ability to draw breath, according to the U.S. Centers for Disease Control and Prevention.

The CDC has identified one compound, vitamin E acetate, as a chemical of concern in those cases. It's most often used as a thickening agent in vaping products containing THC, the ingredient in marijuana that causes intoxication.

But some experts have wondered whether terpenes also play a role, said Dr. Mangala Narasimhan, regional director of critical care medicine at Northwell Health in New Hyde Park, N.Y.

"That's what everyone is talking about now, that some of this might be the terpenes being burned at such high temperatures and us not knowing what the side effects are," she said.

The natural terpenes in marijuana are removed during the distillation process used to produce pure THC, Strongin said. Other terpenes are added back in to make sure the product smells like pot.

Manufacturers also use terpenes to thin the pure cannabinoids that are being distilled from marijuana plants, he added.

"THC and CBD are very, very viscous. It's really hard to use pure versions of those," Strongin said. "They're almost solid, very sticky and gummy and oily. Terpenes are more liquid, and adding them makes the cannabinoids more tractable and easier to manage."

RELATED Study links parental use of marijuana to abuse of drugs by children

To test whether terpenes would produce toxins when heated, the researchers created e-liquids and dabs containing 90 percent THC and 10 percent terpenes.

They then heated or burned their creations and captured the vapor for analysis.

Narasimhan said additives like terpenes are of particular concern because they have been linked to lung injuries.

Another organic compound called diacetyl is used to create a buttery taste. More than a decade ago, it was found to cause lung damage in popcorn factory workers who breathed in the chemical, Narasimhan said.

Her hospital has seen at least 40 cases of patients with vaping-related lung injury, and the vast majority were users of off-label THC e-liquids.

Narasimhan warns against using off-label vaping products.

"The off-label stuff can be mixed with anything," she said. "We have no idea what it's mixed with, and we have no idea what happens to the mixture at these high temperatures."

The new study was recently published in the journal ACS Omega.

The U.S. Centers for Disease Control and Prevention has more about vaping-related lung injuries.

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nyet-marionetka on December 10th, 2019 at 13:44 UTC »

The actual paper is interesting. They calculated hazard indices for vaping and dabbing which were less than 1, and excess lifetime cancer risks 10-7 - 10-9, compared to HI 200 and ELCR 4x10-4 for smoking. They state their calculated cancer risk for smoking cannabis seems inconsistent with observed cancer risks so probably an overestimate. The outcome is their cancer risks for vaping are calculated to be negligible.

They do say that methacrolein could cause noncancer health effects in dabbing, but were lower in vaping. Aerosol levels increased in vaping with heat, as you would expect, so lower temperatures are better to avoid breakdown products. Unfortunately they didn’t mention the amount of THC generated. There might be an optimum value that maximizes aerosolized THC while minimizing breakdown products, but I can’t tell from this.

MrTurkle on December 10th, 2019 at 13:24 UTC »

Does smoking the flower have the same Effect? I didn’t see a comparison in the article.

fredling on December 10th, 2019 at 12:23 UTC »

The important question is whether vaping creates more or less of those compounds than the traditional smoking of plant matter.