Terpenes (general)

How Terpenes Can Cause and Prevent Degradation of Molecules in Cannabis Concentrates: A Conversation with Dr. Robert Strongin

Interview by Jason S. Lupoi, Ph.D.

There’s this common misconception in the cannabis industry that more fire leads to a bigger rip. Sure, you can dab at super high temperatures, and you may see a big cloud of vapor and smoke, but the real question is what’s in the cloud?

Dr. Robert Strongin of Portland State University and his research team have been investigating this question and have unearthed some pretty interesting results. I spoke with Strongin in what I hope is just the first conversation of many. I was curious how he got involved in cannabis product safety research.

“I didn’t start out with cannabis research,” Strongin began. “I actually got into it via tobacco vaping research, and that was by accident. A colleague came to me with an NMR [nuclear magnetic resonance] spectrum of a collected aerosol from an e-cigarette. After seeing this data, I became interested in the chemistry and a few years ago, I became intrigued by cannabis vaping because a lot of younger people were interested in it. The product chemistry had evolved to much higher potencies.”

Because of Strongin’s experience with tobacco vaping research, it was an easier set up to move towards cannabis vaping. “It’s hard to break into the field, however, because of the Federal laws,” he explained, “so, it took a long time to be able to get permission to work with cannabinoids. For me, dabbing was of interest because it’s unique to cannabis. We are so far behind as a scientific community, so it’s an exciting time to be looking at these things!”

Strongin’s group focused on their own formulations of delta-9-tetrahydrocannabinol (THC) and terpenes. Because of their Drug Enforcement Agency (DEA) license, they can only work with the cannabinoid standards from vendors. These are shipped as 1 mg/mL ampules of a cannabinoid standard in a solvent like methanol.

“We can’t look at the plant material,” Strongin explained, “and we can’t buy products from a dispensary. We thought we may be able to get plant material from Ole Miss, but that hasn’t happened. We didn’t realize how hard it would be to get DEA approval. The DEA, however, has been very supportive and they’ve inspected our lab.”

I was curious how Strongin’s team chose the temperatures used for dabbing. Typically, a scientist would consult the literature to see what’s been previously done, but with the cannabis industry, there’s so much that still hasn’t been explored.

“We looked in the literature, but didn’t really find any similar work on cannabinoids,” he answered, “so we had to go back to the 1970s to a series of papers out of the Netherlands. All they did was heat up cannabidiol and their temperatures were nowhere near what’s used for dabbing. So, we actually cite Reddit. By digging through social media, we can get a better information!”

Strongin got the idea for scoping out Reddit and other social media platforms from going to tobacco regulatory meetings. “That’s how they found out that Juul was advertising via social media,” Strongin added.

Strongin and his team are coming up with new ways to vaporize cannabinoids and terpenes. According to Strongin, they haven’t had much competition in this field. “We’re just crazy enough to try to stick it out,” he mused.

The interesting thing is that Strongin’s group didn’t know which molecules would produce toxins with heat. With vaping, because the formulations are simpler than the complexity of flower, they can better hone in on what molecules produce which toxicants. “We can trace back toxicants that form to specific ingredients and we can show how changing the formulations can affect the dosage,” Strongin explained. “If degradation products are forming, that means less of the main ingredients are getting into the aerosol.” (Which is ultimately a waste of money.)

In one of Strongin’s publications, both methacrolein and benzene formed from the degradation of myrcene, limonene, or linalool. [1] The concentrations of these health hazards increased with temperature. No methacrolein was detected at 322°C (612°F), but levels of methacrolein ranging from tens to hundreds of nanograms were found at 403°C (757°F), 455°C (851°F), and 526°C (979°F). I was curious how this compared to other products like e-cigs, cigarettes, or even baseline air levels.

“These levels are definitely above air levels, but they are really low,” Strongin answered. “There’s more acrolein in e-cigs than methacrolein. There are more toxicants formed from cannabis dabbing versus vaping. In every case, even at the highest power, and even during the dabbing conditions, we saw way less toxicant formation than you would from smoking cannabis. There’s fewer ingredients and less combustion.”

When Strongin’s team creates their formulations, they’ve targeted myrcene concentrations like 5% or 9%. A vape oil had 14% myrcene. I was curious if these levels were used to provide representation of an upper limit?

“We’re trying to stay within real world products that we’ve seen range between 2% and 20% terpenes,” Strongin answered. “Products seem to be naturally closer to 5% or less, but distillates seem to have closer to 10% terpenes. We do, however, want to know a failure point by doing extremes. The last thing we want is for someone to think that this work is not representative of the market.”

Strongin’s team also has considered caryophyllene, which gives similar but different breakdown products. Looking at these volatile organic compounds, or VOCs, are only part of the story. There are also non-gaseous particulates from cannabinoid breakdown. Particle sizes are something that people are just beginning to consider. “When you vape, you’re getting aerosols (liquid drop in a gas), and there’s a partition between the gas and liquid droplet phase to varying degrees,” said Strongin. “Just like in air pollution, the size of the particles determines where the chemicals will be deposited in the lungs, and nanoparticles are being found.”

A second publication considered the effects of myrcene during dabbing and also during vaping. [2] There’s a line in the article that reads “THC and terpene transfer occur with less degradation as terpene % mass increases, and that the vaporizer operates with higher overall efficiency at the highest terpene % mass tested, 14%.” (Emphasis added by me.)

Some cannabis vape cart manufacturers are looking to reduce viscosity by using myrcene, a terpene that’s often diminished due to the drying and curing phases of harvest as well as processing the extracts. What’s interesting and paradoxical in this study is that this finding is in direct contrast with the dabbing experiments in the paper, where more degradation products were measured with increasing terpene concentrations.

“There’s definitely a moderation of viscosity,” Strongin explained. “More THC gets into the aerosol and this could be considered a type of entourage effect. It’s may not be as exciting as other methods of an entourage effect, but it’s still there! Another explanation that could be operative is that a lot of terpenes are antioxidants. So much of the chemistry that goes on regards heating under oxygen. Most reactions involve oxidation, so terpenes may prevent molecular breakdown.”

So, what’s the overall take home message from the Strongin lab’s cannabis-themed research?

“We are so excited about these products to help palliative care, opioid addiction, pain — we’re really rooting for these products. Our big take home message, especially after the EVALI outbreak taught us all to be careful, is don’t get stuff off the street. We don’t understand what caused the outbreak. Smoking takes a lifetime for the bad effects to manifest. To see something that’s smoking related that happens within a week or a day is shocking!”

“Get your products from a licensed dispensary. We discovered pine resin in products! This was prevalent in Canada and pine resin creates the same fumes as solder fumes, which are a serious breathing hazard.” [3]

“Toxicant molecules are in lower levels compared to smoking, which is expected. Benzene is formed and carcinogens at any level above what’s in our air are obviously not good things to ingest. People who might be exposed over a longer period of time shouldn’t be using these products regularly. Be vigilant!”



[1] Meehan-Atrash J, Luo W, Strongin RM. Toxicant formation in dabbing: The terpene story. ACS Omega. 2017;2(9):6112-6117. [journal impact factor = 3.512; times cited = 34]


[2] Meehan-Atrash J, Luo W, McWhirter KJ, Dennis DG, Sarlah D, Jensen RP, Afreh IK, Jiang J, Barsanti KC, Ortiz AY, & Strongin RM. The influence of terpenes on the release of volatile organic compounds and active ingredients to cannabis vaping aerosols. RSC Advances. 2021;11:11714-11723. [journal impact factor = 3.36; times cited = 0]


[3] Meehan-Atrash J, Strongin RM. Pine rosin identified as a toxic cannabis extract adulterant. Forensic Sci Int. 2020;312:110301. [journal impact factor = 2.395; times cited = 3]

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Dr. Robert Strongin

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