Research looks at effects of irradiation on cannabis

The first study of its kind to look at the overall effects of gamma irradiation on cannabis

New research looking at the effect of gamma irradiation on dried cannabis is published in the Journal: Frontiers in Ethnopharmacology.

“Evaluating the effects of gamma-irradiation for decontamination of medicinal cannabis” looked at 4 separate strains of cannabis produced by Bedrocan BV in the Netherlands and tested samples before and after the irradiation process to test for changes in cannabinoids, terpenes and moisture content.

irradiation on cannabis

The results of the peer reviewed research showed no change in THC, CBD or moisture content, and minimal damage to a few terpenes present on the cannabis. While only a few terpenes were diminished, the exact ratio of terpenes in a strain is moderately changed. The overall profile is still clearly recognizable between the different varieties tested. The samples were compared before and immediately after standard gamma-irradiation treatment, and then evaluated visually and with GC and HPLC analysis methods.

Upon analysis, the main terpenes affected were the monoterpenes myrcene, cis-ocimene and terpinolene, and the sesquiterpenes gamma-selinene, eudesma-3,7(11)-diene and gamma-selinene. The study speculates this may be because these more volatile terpenes are more likely to evaporate when their molecules are ‘sped-up’ by the gamma irradiation.

Interestingly, the degradation was not the same for each strain. Myrcene, for example, was noticeably reduced in two varieties, but not in a third. The author of the research paper, Arno Hazekamp, speculates that this “indicates a protective effect that cannabis components may have on each other when present in specific proportions.”

“Some terpenes are reduced, but no new compounds are formed. This means terpenes are evaporated to some extent, but not degraded into new compounds. Gamma irradiation somehow accelerates the evaporation just a little bit, but does not kill or destroy your cannabis.” -Arno Hazekamp

This paper confirms similar research on other herbs like cilantro that has shown similar terpene damage from irradiation, while noting that the damage to/loss of terpenes was consistent with normal oxidation or evaporation after harvesting and storage.

In an interview with Lift, Hazekamp noted that while a handful of terpenes were diminished, it would be comparable to the amount lost by simply leaving a bud sitting out for a week.

“Everyone knows that terpenes can rapidly evaporate,” says Hazekamp, “because we can smell them. That means they are in the air, and therefore not in our cannabis anymore! Already in 1996 a study was done to quantify this effect (PDF) and it was found that after one week storage of cannabis a significant amount of terpenes were lost by evaporation.”

“In the case of gamma-irradiation we see the same pattern: some terpenes are reduced, but no new compounds are formed. This means terpenes are evaporated to some extent, but not degraded into new compounds. Gamma-irradiation somehow accelerates the evaporation just a little bit, but does not kill or destroy your cannabis.”

“Some terpenes are somewhat reduced in content,” he continues “because they somehow evaporate during the irradiation procedure. However, no new compounds, or degradation products, are seen. That means that the exact ratio of terpenes is somewhat changed, but the overall profile is still very recognizable between the different varieties tested. In other words: the difference between varieties is much larger than the smaller changes induced by irradiation, or keeping your cannabis stored for a week. Who would claim that a Purple Haze becomes a Northern Lights simply by leaving it in a paper bag for a week?”

​”Beyond looking at terpenes and cannabinoids, we also looked at water content and microscopic appearance. That is because we wanted to have a most complete picture of possible changes. It has been often claimed that gamma irradiation destroys cannabis, and this is the first time it is actually measured. I think there are many more topics regarding cannabis that should be measured instead of speculated. The laboratory tools to do so are currently there, so labs: get to work.​”

Terpenes are major components of volatile oils that exist in plants, from pine trees to oranges, lemons, lavender and more. Terpenes are known to have therapeutic effects: some acting as anti inflammatory, antibiotic and antimutagenic, among other applications. Terpenes are also believed to work in concert with cannabinoids to create what’s known as the ‘entourage effect’.

Many terpenes present in cannabis are also destroyed through processes such as smoking, vaporizing at a high temperature, or cooking, etc. “Whole plant” extraction processes like CO2 focus on preserving as many of these terpenes as possible, but any heating applied to such an extract (e.g. while ‘activating’ cannabinoids by decarboxylation) will inevitably also lead to loss of terpenes.

The study concluded that as long as medical-grade cannabis is required to adhere to strict pharmaceutical standards, as it is in places like Canada and the Netherlands, gamma irradiation remains the safest and most efficient method of ensuring a safe product, especially for the immunocompromised.

The use of gamma irradiation on food and herbal products has long been controversial. While dozens of countries allow the process to be used on foodstuffs to help prevent foodborne illness and preserve food, many activist groups have remained skeptical of the safety and efficacy of the process.

The medical cannabis market is no different. The irradiation process is used by several licensed producers under Health Canada’s Marihuana for Medical Purposes Regulations to ensure adherence to strict standards surrounding biological impurities in medical cannabis. However, some patients and activists have expressed concern with the process and its effect on cannabis and its medically-active components: cannabinoids and terpenes. Unfortunately, no other sterilization technique (e.g. UV light, steam or harsh chemicals) have been shown to sterilize cannabis, while leaving the active components intact.

The company who provided the cannabis for the study, Bedrocan BV, based in the Netherlands, is required to irradiate their cannabis as per the Dutch Ministry of Health. The author of the research paper, Arno Hazekamp, was a full time employee of Bedrocan BV,  the company that provided the medicinal grade cannabis used in the research, during the time of the study. Recently he has become an independent consultant on cannabis research.

Strains available for Bedrocan
Strains available for Bedrocan

Bedrocan Canada, a partner company of Bedrocan BV, also irradiates the cannabis they sell on the Canadian market, although Bedrocan Canada produces their own cannabis here in Canada.

The study used 4 different strains: Bedrocan, Bediol, Bedica and Bedrolite, covering the spectrum of sativa as well as indica type strains, and THC as well as CBD containing cannabis.

“It’s also important to remember that gamma-irradiation is not just done without good reason,” says Hazekamp.  “It is meant to prevent the potential greater harm of infecting a patient with harmful microbes, In my paper several sources are cited where this actually happened. It is weighing two ‘bad’ choices (risk of infection vs. irradiation) and picking the most sensible one.

"We should all hope for the development of new sterilization techniques for cannabis in the near future."

In this article

Join the Conversation


  1. Fonda Betts Reply

    This is a totally biased conversation because Bedrocan gamma irradiates their product.

    1. Eric Reply

      If there is a flaw/bias in the data, where is it? Which numbers are wrong?

  2. Alex Reply

    Fund all the studies you want and spin the results as you please. In the end, patients will always see a difference both in terms of optics and practical experience.

    Myrcene is far more important than most in the industry realize, as are the ratios. Messing with the entourage effect at a fundamental level, which could be good and bad.

    There are far better solutions for a clean product and producers who choose them will always have the advantage.

  3. Adam Greenblatt Reply

    It doesn't matter how much evidence there is that beyond the loss of some terpenes (which occurs during many other processes, like oil making, medible baking, hash making, drying, and so forth) people will cling to naturalistic fallacies, paranoid irrational fears, and confirmation biases.

    1. Alex Reply

      Sure other processes have impact on content. But what if the source material is already impacted by this process, would that not result in a further degraded/impacted end product?

  4. Burnt Eloi Reply

    Irrelevant, we'll all be vaping pharmaceutical grade concentrates within the next 5 years. Combustion is out, is not good for you, its dirty, strains and dosage problems etc, f$#k combustion.

    1. David Watson Reply

      What if you are a recreational user that prefers combustion? I know vaporization is cleaner but I do not like it, I get higher from smoking then vaping, also most concentrates do not have their full terpene profile as processing reduces them a lot. I like the terpenes and will not want to smoke low terpene products as you seem to favor? fS#k vaping for me, if people want to vape fine for them, I do not like it much, and will not stop smoking. Just because you prefer vaping does not mean all consumers will. I can assure you they do not, and will not. Different people like different products, herb, resin, extracts, WLD varieties, NLD varieties, there is no one that all like the best.
      Some people want CBD/THC at a given ratio, I can not stand CBD. You do not need pharmaceutical grade concentrates, unless you prefer them to dry sift that is 99.9% resin heads and over 80% THC and terpene rich. Your choice, you can choose what you prefer, so will I.

  5. MC Reply

    Is Arno available for questions? If so, how?

    Thanks for the article. Great work is being done all over the world, and this is forefront science!


  6. MARK LACKEY Reply


  7. Scott M Reply

    My wife is immunocompromised after a bone marrow transplant. Therefore mold is extremely dangerous and deadly to her. We need weed and concentrates that are completely mold spore free. Once the bud or concentrate is treated and then packaged, couldn't it turn moldy if spores were present or airborne during the process of packaging?
    Can I irradiate products at home to ensure they are completely safe for my wife to use?
    How would I treat or irradiate bud that I grow myself?
    How would I treat or irradiate concentrates like shatter to ensure there are no mold spores present?